The Knowledge - Velocette Owners Club

1
The Knowledge
Being a compendium of eGroup discussions compiled from:
http://autos.groups.yahoo.com/group/velocette/
and,
http://groups.yahoo.com/group/velonorthamerica/
January 2002 - June 2005
Complied and Edited by:
2002 Les Carman
24 January, 2003
2003-2005.5 David S. Liebl
July 2005
Provided courtesy of the VOC and VOCNA

Table of Contents
A. Diagnosing Troubles
1. Hard Starting, Poor Running .................................................. 3
2. Poor Gearchange ......................................................... 25
3. Faulty Electrics ........................................................... 29
B. The Engine
1. Bottom End & Crankcase ................................................... 34
2. Cylinder & Piston ........................................................ 50
3. Cylinder Head & Valves .................................................... 59
4. Timing Gear & Pushrods ................................................... 81
5. Oiling System ............................................................ 96
6. Crankcase Breathing ..................................................... 122
7. Racing & High Performance ................................................ 131
C. The Electrics
1. Ignition & Timing ......................................................... 137
2. Sparking Plug ........................................................... 144
3. Battery, Dynamo & Magneto ................................................ 148
4. Lights & Horn ........................................................... 157
5. Electric Conversions ...................................................... 161
D. The Carburetor and Fuels
1. Carburetor.............................................................. 174
2. Fuels .................................................................. 189
E. The Drive Train
1. Primary Drive, Chainwheel and Clutch ........................................ 193
2. Gearbox ............................................................... 212
3. Final Drive, Chains & Cases................................................ 228
F. Running Gear
1. Steering Head, Forks & Shocks ............................................. 245
2. Brakes, Wheels and Tires .................................................. 260
G. The Frame and Ancillaries
1. Bodywork, Paint & Polish .................................................. 270
2. Cables & Controls & Instruments ............................................ 293
3. Exhaust Pipe & Silencer ................................................... 300
H. Manuals & Spares ............................................................ 305
I. Miscellaneous ................................................................ 312
[Editors Note: These contributions to http://autos.groups.yahoo.com/group/velocette/ and
http://groups.yahoo.com/group/velonorthamerica/ have been organized according to the general
subject under discussion. The apparent beginning of discussion of a new topic is indicated by:
L While the eGroup message # has been retained, the messages are no longer strictly
consecutive. The full text of the messages, in chronological order, can be found in the eGroup archives.
Terminology and spelling is multinational, reflecting the membership.]
Disclaimer: The opinions expressed herein are those of the correspondents. No claim is made regarding the
validity of their assertions. Please enjoy and benefit from them nonetheless.
2

A Diagnosing Troubles
A.1 Hard Starting and Poor Running -
L #223 At last year's Stanford Hall Rally my Venom did not want to start. After I had exhausted
myself a volunteer from the inevitable crowd that were watching finally managed to get it going. On
kicking it over, it had now developed a habit of spitting back enough neat petrol for it to be seen
running down the oil tank. It got me home OK and ran well at higher revs. After repeating this
performance a couple of times I tackled all the obvious things, plug, BTH manual magneto points,
pickup etc. with no joy. I then changed the carburettor, from monoblock to concentric. This was easier
to start but ran lumpily at low revs and this time spat a small quantity of neat petrol back through the
carburettor on each firing stroke; again it seemed to be OK at higher revs. Getting more desperate I
have removed the cylinder head to find no problem with the inlet valve or seat. I have taken off the
timing cover and found the cams, followers and gears all to be in apparently excellent condition. What
next?
#225 I had the same problem on my 58 Venom, after fitting a new Monobloc. Spitting back at low revs
indicates richness, which is controlled for the first quarter of throttle movement by the Pilot Air Screw.
Try screwing it out a little at a time (to weaken the mixture) until the spitting stops. You may have to
adjust the throttle stop afterwards to obtain a satisfactory tickover.
#228 One of the major reasons for a Venom spitting back is due to the large amount of valve overlap
that a M17/8 cam gives. If you check out most Venoms after a run, you will find petrol and oil debris on
the oil tank that has been jettisoned from the carbs. A MSS with a softer M17/7 doesn’t suffer from this.
Check your valve timing, remembering to use the increase valve clearances. You will find that the
timings will not be spot on mine were 65–39–50–55 rather than the 65-35-45-55 as specified. If yours
are out you can spread the error by moving the cam a tooth either way to see if it helps.
L #431 Since the main bearings failed in my `54 MAC after getting back from Bavaria last year I
haven't been able to get the bike to run properly. I've had a number of problems including nipping up a
piston since, possibly unrelated. I have discovered, in the course of investigation, that the bike has an
M17/7 cam and followers as fitted to MSS and early Viper. Has anyone else got an MAC with this cam?
If so is the cam set up according to the marks on the wheels? I've checked the cam timing with the
valve clearances set to 30 thou inlet, 35 thou exhaust (as specified for the MAC). The results are as
follows (M17/7 spec in brackets) [Inlet opens 25deg BTDC (19deg) - opens early Inlet closes 50deg
ABDC (49deg) - closes late Exh Opens 50deg BBDC (49deg)] opens early Exh Closes 16deg ATDC
(19deg) - closes early I've tried taking cam lobe centre readings but as I haven't got a dial gauge it
proved to be difficult to be accurate enough to perform the check. Can anyone comment on whether I
have the valve timing right or not? Should I get a dial gauge and do the cam lobe centers? This is
driving me mad. My MAC used to be an easy starting good performer. Now it doesn't start well and
coughs back through the carbs.
#431b Just a further thought - the MSS with a M17/7 cam has ignition timing 36deg BTDC fully
advanced. Does the ignition timing follow the type of cam i.e. if I'm using an M17/7 cam (MSS type) in
my MAC in place of the M17/5 (MAC type), should I change the ignition timing from 38degrees to 36
degrees? I have a sneaking suspicion that I should. This is most perplexing. Before the recent
problems the bike ignition timing was set by the roadside, after yet another ATD spat its fibre teeth,
using a piece of stick found at the roadside with a rough estimate of about 11mm for the piston crown
distance BTDC. The bike has been running fine ever since:-)) I've never used a degree wheel until
recently. Precision measurements ain't what they are cracked up to be. Going to get a dial gauge and
check the cam lobe centers.
#434 You might check your ATD to make sure that the springs are still okay, I had one break once, the
ATD went into full advance. Velos are very sensitive to ignition timing, less so to cam timing. But the
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timing at full advance won't affect starting much. If you want to check the cam timing on a /7 with
VM/MSS followers you should use 50 thou clearance as specified for the cam. This should yield
numbers closer to the spec. Also, it is not well documented but there is more lift on the 86mm cams, a
/8 has 20% more at the lobe than a /4. I don't have the others handy to measure, but I'll bet the /5 and
/7 also have different lifts.
#435 Thanks for the note. I had already tried checking the cam timing with the 50thou gap and ended
up with crazy readings. Last night I read the MSS Maintenance Manual I have and it said check with
30thou gaps (the MSS used the M17/7 cam). I tried this and the cam timing came out to within one
degree of spec as I have it set up. I also got hold of a dial test indicator and checked the dwell and
calculated the cam centre point. That came out to within half a degree. I doubt that it could be adjusted
closer than that. At least that’s one thing sorted out. The bike won't start at the moment. It has good
compression (for a re-ringed motor) and a fat spark at the plug. I am beginning to suspect that the fuel
has gone off. Its possible that it could have been there the best part of a year. When the bike started on
Tuesday it was coughing/spitting back through the carbs a lot, particularly on small throttle openings
(i.e. while trying to start) indicating, I think, that the mixture is weak. I blew out the idle drillings
yesterday but now it won't fire up at all. If the fuel has separated and/or the volatiles have evaporated
then surely that would make the fuel calorific value lower hence the mixture would be weak (higher air
to fuel energy ratio)? Does that make sense? Maybe the small amount of fuel in the float bowl was still
good and once that had been used up the remainder was bad? Anyway, tonight’s job is to get some
fresh fuel, drain the tank and carbs and try again. I hope that’s what is causing the problem but I've
never experienced petrol going off (although I've heard others talk about it). The ATD springs are OK.
The ATD was overhauled a few years ago with a new fibre wheel and springs. I have set the mag
timing to 38deg BTDC fully advanced. The MSS manual says 36degrees BTDC. I wouldn't have
thought that this would make too much difference to whether the bike would start or not.
#436 I have had similar problems with my Venom recently ( see earlier posting on 'spitting' ). After
repeated checking of valve and ignition timing, cleaning out of carbs jets etc. without benefit, I changed
the carburettor to an old spare. Hey presto the damn thing ran as well as ever. I suspect that the float
height was wrong.
#442 Well, I found the reason the MAC wouldn't start - the ATD had come loose. Idiot!! I had checked
that there was a spark at the plug and it seemed fine. Anyway, now the bike is running again there
seems to be a lot of noise from the timing chest of the engine. My Haynes says that if the intermediate
timing gear is only in shallow mesh then the symptom is a mechanical clacking noise. If I turn the
engine over by hand this is what I hear. Has anyone else experienced this? I plan to check the mesh
tomorrow evening and if necessary adjust the intermediate timing pinion..
L #501 anyway I cleaned up the points and gapped them and checked out tappet clearances and
generally checked the bike over, primary adjustment, etc etc. I cracked the bike up and went for a run.
it was quite tall geared with a close box and a 19 tooth gearbox sprocket. it went like the wind and
pulled 105 on a chrono clock absolutely no problem. I thought wow this is some motorcycle. I went out
and about on it for about a week and I was batting down a dual carrigeway doing about 80 when a
fiesta xr2 passed me, I thought not having that and changed down and followed, they hit just over the
ton and slowed and I thought lets get passed. I was just about to pass them when BANG a noise like
a shotgun then nothing, the motor just died. I costed to a halt. I kicked the bike over and plenty of
compression, I then checked the spark, seemed ok, no noise when I kicked it over, I thought weird. a
couple of friends pulled up and asked what was wrong, I told them what had happened and they
offered me a push. the bike would fire but not start. investigation showed that it had blown a
condenser, I had the mag rebuilt and the bike ran fine. next job I did was to take off the oil tank and
wash it out. it was sparkling, very clean. I put new oil in and went for a run, it ran great. a week later I
was out on the bike and it tried to seize up, I came home on tick over and stopped the bike and put it
on its side stand and oil poured out of the chaincase. I thought what’s going on. I looked into the oil
tank and there was no oil. I scratched my head. investigation revealed that the tube in the oil filter was
blocked with debris. something at the time that I was unaware of. apparently if the bike has had a
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automatic mag fitted at sometime in its life and stripped the teeth, the remains go down into the motor
and the oil pump will pass it and it will lodge in the cross drilled hole. this is what I had happened to
mine and it cost me a set of main bearings because after the event they whined like hell and they had
to be changed. I got the work done at Criterion and they advised to leave out the tube which I duly did,
and no problem.
L #515 I have a 1961 Velocette Venom Clubman 500. It starts fine when cold but if it stalls it will
not start up again when hot. I have recently had my magneto (Lucas KF1) overhauled (about 2 months
ago,) but it still will not start when hot.
#516 Same thing happened to me who ever did your magneto didn't do it properly, I would ditch the
whole thing and go electronic,
#517 I have a Thruxton which also will not start when hot. The magneto was done by Dave Linslay and
I am totally confident he did a great job because it flies when I get it started, regardless of how hard I
ride it and how hot it gets. Before the mag. was reconditioned the motor was inclined to missfire under
load and was down on power. When we had leaded fuel (oh no, not the unleaded fuel saga again!!)
available in Australia, I never had this problem of hot starting. The odd thing now is that when the motor
has been running and then stopped, there is a white vapour which 'curls' out of the Concentric MKII
and if I open the throttle and get the inlet valve open (it's easy to look down the carbs throat on a
Thruxton) until the white vapour clears, it fires up readily - the same thing happens if I remove the
spark plug and kick it over a few times - it starts easily. It is definitely not flooded and the NGK B8ES is
dark brown to black and not wet or fouled. This may sound like I have been out in the sun too much
but I can assure everyone that this is always the case when the motor is hot.
#526 Try fitting a quarter or three eights inch heat insulating spacer between the carbs and head.
Although I agree that just because a mag has been rebuilt does not mean that it is working. This
happened a few months ago to someone in our VOC center, replacing the mag with a good old one
cured the problem. Additionally if you are running a NGK B8ES or equivalent spark plug with a
compression ratio of about 8 :1, try going down a grade to B7ES, this helped in three cases I know of.
L #883 I was out on the MAC (1951) the other day when the engine unusually stopped when I
closed the throttle at a junction. It started again first kick and I carried on. It did the same thing again a
minute or so later. Again, it started OK but this time I noticed it wasn't pulling so well. After a short time
the engine started to run very rough and then just stopped. I pushed home - not very far, fortunately.
Now, the engine is firing early, during the compression stroke I think, and pushing the kickstart back up
against my foot. I also get an oily-smelling blowback through the carbs. I know it's a timing problem,
but haven't had to deal with this before so I was wondering if anyone could advise me on what probably
went wrong so I know where to start.
#884 It sounds like you have stripped the fibre gear wheel on the magneto. when you take off the
timing cover, and if this is the case, remember to flush out the lower end of the motor to get rid of all
the bits of fibre teeth. I believe there is a firm that now make replacement auto advance units in alloy.
#892 I had the same problem once, & suggest you check your mag timing gear which is probably fibre
& may have stripped a tooth.
#888 Another word of advice - DO NOT use an alloy replacement for the fibre gear. These will wear
quite badly and deposit alloy shards in the sump, which will do rather more damage in the long term
than the bits of fibre. If you are going to replace with anything then use a steel gear.
#889 I'm a fan of the John Hales modified ATD's, superb, and in my MSS. BUT Those nice people at
Criterion have been supplying very good adjustable ALLOY pinions for years ( NOT for ATD's ) and I've
never had any problem with shards filling up the engine.
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#890 I used an alloy replacement pinion on my ATD after the fibre one did the disintegrating thing many
years ago, and when I stripped the machine quite a few years but not so many miles later the pinion
was showing signs of quite severe wear and there was a fair amount of alloy around, mostly little bits
but all about the length equivalent to the width of the timing gear - it didn't take much deduction to see
where it had all come from! I replaced the pinion again about two years ago with one of John Hales'
steel gears and so far so good, no sign of wear at the last inspection when I had the oil pump
overhauled earlier this year.
L #977 My 1959 Venom exhibits poor hot starting. I'm fairly new at Velocette set up (I had my last
one about a third of a century ago). Cold it starts almost first kick. When hot it is very unreliable. I am
using a Champion N8 plug. Is it set up or starting technique? When I remove the plug after a non
starting episode it can be wet, sooty and hot. There is a good bluish spark. Ideas anyone?
#983 In almost all cases of this sort, the magneto capacitor and/or coil is responsible. They degrade
with heat. What model magneto do you have? The Lucas are more susceptible to this malady than
BTH.
#985 My '57 Venom had exactly the same problem with a reluctance to start hot. Try a Champion N4C
spark plug. Get the points in the magneto exactly right. I replaced mine. Don't flood it, not much throttle
either. If you think it is flooded. Hold the valve de compressor in and swing the starting lever about 12
times. Try starting again without flooding.
#987 Just a few points which may help with poor hot starting - excuse any that you find pb obvious: For
a magneto to work decently it of course has to be in fair nick. The points gap is 12 thou. Plugs should
have a gap of 18 thou (not 25 - that’s for electronic ignition) The usual plug cap is a resistor type and
that is not what you want with a mag. Don't use a resistor type lead either - solid copper is the only one
to use and forget resistor type plugs. In case you are worried about interference, my Mk ! has no
suppressors of any kind fitted and it causes no interference (as far as I know!) although I know it
should. In the past I have had trouble with Champion plugs playing up when hot, they always seem OK
cold. I have used NGK for some years and they seem to cope well with hot or cold starting.
#994 If there is a good spark when hot, you are flooding the engine on hot start. Just grab a fistful of
throttle (open it about ½ to 3/4 or so) and kick. The greater throttle opening will reduce venturi effect in
the carbs and pull less fuel and more air on the start, evaporating excess fuel accumulated in the
carbs and getting the mixture correct. A hot motor will also cause a slight expansion of the fuel in the
fuel bowl, possibly pooling fuel in the carbs (this varies by carbs type), causing flooding at hot start.
Comments about the magneto are applicable if the spark is weak when hot. Magnetos are velocitychallenged
at kickstart speeds, generation of the correct primary current requiring everything to be in
good order for a hot spark. Resistance in the secondary will limit their performance at start. Get rid of
resistance plugs, caps and wires.
#1035 when I purchased my MAC. it was a poor hot starter until I found it had the wrong projection
type plug BP6ES instead of the standard B6ES .I know the MAC has a lower compression ratio etc
than the viper & venoms and that the magneto resistance should be reduced to a minimum. But the
reduction of the gap to 18 thou instead of the Velocette’s recommended 23 thou, would in the 50s &
60s be asking for whiskered up plugs. but that said we did have Cleveland Driscoll 101 octane petrol
in the UK that any old biker, will tell you made your bike go like a rocket. Are you saying that the
demise of lead in the petrol fouling, the plug is not a problem now?
L #1201 I recently overhauled my Venoms top end with Omega piston and Total Seal piston ring
set (gapless second and 3 piece oil ring) and head is overhauled too. Now it`s real pig to start, The new
rings are very tight and it`s hard to get good enough kick to get motor spinning, it will bang once to
three times then spits back and dies. The ring gaps are ok so is the ignition. I got three different carbs
Amal Mk1,5 Amal MkII and Mikuni round slide 32. Which is best one in your honest opinion to get good
gold start. And do anyone have general settings for these carburettors? My garage is quite cold, under
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10celsius and only oil I could get my hands to is Silkolene 50 which is too thick in these conditions. Two
days ago it fired in first kick but wouldn’t idle but spits to carburettor, yesterday it did`t start at all...oh
what a cursing...and my friends got a good laughter and advice to look some 350 or 250 for the next
bike!
#1203 I'd rank order the ease of starting and idling as MKII, MKI. I've little experience with Mikunis on
English bikes. I can share with you that I recently bought a 75 Bultaco Alpina 370cc fitted with a MKII.
The previous owner had great difficulty starting the bike. He told me the carbs had been cleaned
several times and that the 370 cc was notoriously hard to start. It would take 40 or 50 kicks some times.
A brief study of the idling circuit disclosed the float bowl was dirty and the small drilling at the bottom of
the bowl was plugged. After cleaning the bowl and the idle jet, the bike now starts 1st or 2nd kick in all
weather. It idles and performs wonderfully. Part of the starting problem I had on the Alpina was my
wanting to open the throttle while kicking. Once I had the carbs clean, leaving the throttle closed results
in a reliable start every time. My '60 Gold Star has a 1036 AMAL MKI which has a removable idle jet.
"IF" tickled just right, kicked thru 2 or 3 times with the compression release pulled in, the bike starts in 1
- 3 kicks every time. Again, like the Alpina, the carbs must remain closed till the bike fires. This bike
likes a 25 pilot quite well, but loads up quickly with a 30 pilot. In conclusion, I believe the idle circuit on
the MKII, with its enrichner circuit, makes it superior technically to the MKI or Monobloc. It seem each
bike has its own combination. I'd suggest you look carefully at the idle circuits and starting "drill".
#1207 Could be that you have some oil in the crankcase, this will slow the flywheels enough to stop it
starting up. Drain the cases and try again. You are making life hard enough with straight 50 if its cold!
#1211 I drained the crankcase first thing but there wasn’t much oil. I must clean the carburetor, it has
been standing for few months. The cold certainly makes things difficult, oil is so thick it hardly drains
from crankcase, ah it`s so nice to live here in cold Finland... And kicked enough the oil starts to leak
from primary chaincase under the crankshaft, is that normal? I believe that it is...
#1212 If the ambient temperature is well down (as I believe Finland is at this time of year) straight 50
grade oil will cause a huge amount of drag - the stuff is like glue at low temps. Try changing for a
multigrade 20W50 such as GTX for the winter and revert to 50W if you feel the need in the warmth of
summer.
L #1637 A wet morning to be sat at this gizmo & ponder a little. As a first time Velo owner, and
unfortunately bus pass owner, with only a certain allocation of kicks left in me, I was looking at
message #1588-'normal starting drill'. I can start this machine (a std. MAC),but I'm aware that it's
usually more by luck than judgement. I'd appreciate a proper table of events to obtain the easiest
possible start. Spark, Timing & petrol supply are all good.
#1638 To start my MAC I turn on the petrol, close the air slide, find compression, lift the piston over
TDC, release the valve lifter, long swinging kick with no throttle. Usually starts OK hot but can be
reluctant when cold. Tickling the carbs just wets the plug. The secret is the lifting the piston just over
TDC and the long swinging kick.
#1639 This works for me: turn on the petrol. Wait a few seconds. Pull in the valve lifter and turn the
engine over a couple of times to draw in some mixture. Release the valve lifter. press down on the
kickstart until you feel compression, hold your foot there while you pull in the valve lifter and turn the
engine a little further, beyond compression. Release the valve-lifter, let the kickstart return to the top
and give it a long kick all the way down. From cold, my MAC usually starts first or second kick this way.
Mine doesn't like any throttle while starting and you find out by trial and error how much choke (if any) it
likes. The Velo instruction book suggests flooding the carbs a little, but mine doesn't like that and will
invariably flood big-time so I leave the carbs alone. Hope this helps.
#1648 The only thing I would add is to grip the brake lever when you have the throttle at the
appropriate setting (for me about one sixteenth open). This stops you inadvertently opening the throttle
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when you swing your boot (and the rest of your body) downwards. My Venom was always a first time
starter, until during an enforced lay of I completely forgot to hold the brake lever, it became a pain to
start. When I remembered to hold the brake lever again it started first kick. Finally flooding, a lot of
individuals drown the carbs rather than flood it. Try lifting your finger off the tickler immediately you see
first signs of petrol emerging
#1645 I too am a first time Velo owner (though unable to claim a bus pass for many years yet!). I have
a 1953 Alloy engined rigid MAC. The best way I have found to start it is to 1. Turn the fuel on. 2. Flood
the carbs. 3. Close the air leaver fully 4. Gently turn the engine over with the Kickstart until it comes
onto compression, 5. Allow the kickstart to return to the top of its stroke 6. Pull the decompressor. 7.
Gently kick the kickstarter until it is at the bottom of its stroke. 8. Let the kickstart return to it upright
position. 9. Kick as hard as you can blipping the throttle as you do it. It usually needs between 1 and 3
kicks to start. For some reason contrary to the other reports I have read here I have never got it to start
without flooding the carbs.
L #1742 After much searching have just acquired 1968 Thruxton with one previous owner from
new, alas now deceased. Only 36K certified miles from new and meticulous documentation. It starts ok
but will not run cleanly without cutting, coughing and refusing to rev properly most of the time. Vibration
also seems excessive. Mag/points are fine, timing is correct and plug (NGK) is new. GP carbs is on
recommended settings for needle/slide although slide does look a little worn. Surely a carbs overhaul is
not warranted at this mileage?. Compression is good and records show recent Seymour bottom end
rebuild. I am using an octane booster. Clearly, consultation with previous owner is not possible, but I
doubt he would have accepted such poor running. I would appreciate guidance on how to proceed
logically, apart from selling it quickly for a profit!
#1743 Obvious things first (as I found with mine when I bought it after it had stood unused for a few
years).
Take the carbs apart and make sure all the jets are clear of evaporated residue. New petrol.
Put on a new HT lead (but not a resistor cap). You say it doesn't run properly "most of the time". If it
runs well sometimes I would think around bad electrical connections. I had a badly crimped LT feed at
the coil which wasn't obvious because it was under an insulated crimp. Misfires/cutting out until I found
it. If it starts well but misfires when hot, what about insulation between the cylinder and the carbs? or
faulty coil? Sorry if these are too obvious and you've tried them, but if it's starting well I wouldn't have
thought it was too serious a problem. The only concern I'd have would be why it had needed a bottom
end rebuild after only 36k miles.
#1752 Resleeve the carbs. GP slides wear at an alarming rate. Mine was consuming a new slide per
year until I took the most recently worn out slide and the carbs to a carbs resleever near Sydney
Australia in 1982 and it came back with what appears to be a SS sleeve on the slide and a good fit in
the body. I then set it up as per the book (except some versions of the book say No3 slide and it
definitely has to be No4 to run crisp and clean on the midrange) and didn't have to touch it until last
year when I couldn't get a sensible static float level after an engine overhaul. That problem is being
addressed using a Keihin float needle and seat conversion screwed into the original matchbox float
chamber seat (as written up by VOCNA Pres Cory Padula in a recent FTW article). One other problem I
now have, which doesn't appear to be implicated with your VMT, is excessive wear of the cam ring
housing of the K1FC mag. There is so much slop after many years trouble free running, that poor Ol'
Faithful ended the Cape to Cape Grape Rally here in Western Australia with the cam ring supported
between a couple of beer can shims to provide some semblance of a consistent points gap and hence
a steady advance setting. Tried another cam ring but it was just as sloppy so the wear is definitely in
the housing, as you would expect. Took some tracking down but eventually got to the crux of the
problem. However two months later, the beer can remedy lives on. So, don't give up in despair, don't
sell it for a profit, just keep tinkering and using the beast until you develop a deep and meaningful
understanding and you should find it becomes the easiest starting of Velos which defies the Classic
motorcycle press generated image of being only suitable for hairy chested musclemen. If it won't fire by
the second kick after a generous tickle (very hard to get at unless you can lift the rear of the tank
8

enough to slide the left hand in above the battery box) then something else is amiss. And don't forget to
use two fingers on the front brake when you crack the throttle a whisker to be sure it fires and runs, so
that the vigorous body action of the long swinging kick doesn't end up translating to vigorous but
unintentional rotation of the twistgrip.
L #1845 Some time ago, when rebuilding the engine of my Venom Clubman (now 1200 miles), I
got a new concentric, the old one being worn out. It was fitted with 30 pilot jet and 270 main, as
specified, but valve cutaway is 3 instead of 4. Being supplied by Nick Payton, I suppose it is not too
wrong, and it works well at mid throttle. Problems occurred at tickover and full throttle. First, I used to
have a very irregular tickover, very weak mixture, even with air screw fully in. It then needed flooding
and closed choke even for starting when stinking hot. I checked everything (level, channels...), to find
the base of the body, supporting on the bowl, where is the paper gasket, was not flat, and the pilot
system was sucking air instead of fuel. So I turned it flat on the lathe, getting about .2 mm off. Then it
worked very much better. It is even better now without pilot jet.
An other problem remains : full throttle, even on 2nd or 3rd gear, it hardly goes over 5000 rpm. Just
releasing the throttle gets 200 extra rpm. That's not enough, and indicates it is still weak. Will I fit a
larger jet, larger than the specified 270, or look for another cause in the carbs, or elsewhere, or throw
the whole stuff away, and get a Monobloc ?
#1847 I've got exactly the same full throttle problem with my Clubman fitted with a new concentric.
I've tried main jet sizes 270 -300 and settled in the end for...270. Then I began experimenting with
needle position. In position 2 the bike runs well except at full throttle and doesn't rev over 5000. In
position 3 acceleration is improved but doesn't go above 5000 and at constant rpm the bike has a
tendency the run irregular. Also pick up is worse as you snap open the throttle I'm also considering
going back to a monobloc! Hope someone knows more about concentrics than we do.
#1848 I wonder if the float needle is passing enough fuel at WFO and 5000 rpm? Sounds like they are
running out of fuel. Did they run ok at WFO and 5000+ rpm with the monobloc? If so, higher float level
or larger bore float needle and seat may be needed.
#1849 Can’t add much to this except maybe a few more things to try/consider - systematically:
I) exhaust system is strangling performance a bit - is it original silencer ?
ii) check fuel taps are passing sufficient fuel etc.
iii) performance will drop off if cyl head is getting sooty
iv) obviously - carefully check ignition timing
v) check for other air leaks (e.g. exhaust system / carbs to head etc.)
vi) try changing sparking plug
#1851: 1. it is the original silencer. 2. fuel lines are ok. 3. the bike did have a decoke 500 miles ago. 4.
and I did check ignition. it is spot on. 5. I don't think there are air leaks, but will check again. 6. I tried
champion n4, ngk B8ES, ngk B8EGV. No difference in full throttle running. Although the last seems the
best!
The bike is a 99% standard Venom Clubman mk2, except for carbs and alternator (alton).
#1858 Regarding the slide needle, it doesn't matter at full throttle. But I will check the level needle flow,
even though you can hardly modify it.
#1865 I think you will find that the float seat will need adjustment. I do know that most of the new carbs
have the float seat set too high. a friend of mine who runs a bike shop always has to adjust the float
seat. he uses a brass drift to lower the seat. I seem to remember 80 thou being used somewhere. also
on the triumph/bsa three cylinders, the racers had their float bowls modified to give extra fuel. I have
details how to do it. it involves a small milling job. if you want the info, give me a shout. cheers.
#1863 If the float level is set too low the float needle may not open enough to allow the fuel to reach its
proper level in the float chamber causing a lean condition at WFO regardless of the main jet size. In
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this case the restriction of the inlet needle is acting as the main jet, that is, it is limiting the amount of
fuel going in to the carburetor air stream. And yes, weak 50 year old valve springs can cause valve
bounce. But 50 year old strong ones will not.
L #2002 If I leave my bike running on tickover ,it has periods of about five seconds (a long time
when you're wondering whether it's going to stall) of running at varying speeds. Adjusting the air screw
seems to have minimal effect. I'd guess that it's something to do with carburettion but exactly what I'm
not sure. Plug looks OK so don't think it's that. It's got to be something to do with the pilot feed because
at full whack it makes me feel like I was seventeen again (Ariel, I have to admit -But Hartley tuned)
#2004 Could be a worn slide taking a little time to settle into place and leaking a bit of air until it has.
#2075 Have you checked the face of the carburettor where it bolts to the manifold ? It is quite common
for this to bow (warp) if over tightened. If so either reface using a piece of glass and fine grinding paste
or fit a soft cork or similar gasket with a smear of silicon sealer to see if that effects a cure.
L #2047 I have spent an inordinate amount of time trying to prevent my newly rebuilt Viper basket
case from pinking once the engine was hot and under load at low revs (even when gently feathering the
throttle). Eventually after lots of experimenting with timing without real success( it is coil ignition so the
base plate of the contact breaker can be moved to advance or retard the ignition easily), a friend
suggested the mixture may be too weak ( needle position 2nd groove from top). I raised the needle to
the bottom groove to establish if any change and the problem was instantly cured. I have since fixed
the needle in one groove down from middle and the engine will only pink if severely provoked now. I
have never known an engine to be so sensitive to mixture strength under load before to result in the
degree of pinking I was experiencing.
L #2285 HI everybody on the list, Pete here, have recently joined the forum and have read
eagerly the discussions about all things velo. I myself have a Venom veeline clubman and have
recently ripped off the electronic system in order to go back to the original mag. However, even with the
assistance of friends, one of whom has had velos for many years, the correct timing is eluding us. I
understand the timing should be 38 degrees before top dead centre, although that is certainly how we
are setting the timing up, every time we go and start the bike the timing seems to be out, this has varied
from being 34 degrees before to being so far out the bike is just kicking back. So what is happening, it
could possibly be that the bike is on the wrong stroke. What I am not sure of is what happens if the bike
is on the wrong stroke, what are the symptoms? Although nothing seems to be moving with respect to
putting and tightening on the auto-advance retard unit, the timing remains out. I am now wondering
whether there is something so obvious that I can't see it. Have checked to make sure the timing disc is
not moving, the points are not moving during the instalment of the auto-advance retard unit, etc. Any
suggestions would be greatly appreciated, the bike is my main form of transport for work and therefore I
am keen to get it back on the road asap. In advance of any suggestions thanks, Living in the Essex
area if there is anybody nearby who might be able to help.
#2286 If the bike will start, you are obviously on the right stroke of the cycle, or the bike would not run,
nor would even fire. You do not state which magneto you are using, but do mention auto advance. I'm
sure you realize the timing spec, 38 degrees is full advanced, which requires the auto advance
mechanism's bob weights to be "locked" in the out or advanced state, when setting the timing. Rubber
blocks or small wood wedges work well for this.
L #2565 How slow a tickover can you achieve on a Clubman ? And do you tune it fully advanced,
or fully retarded, or in between ? My engine is in very good general condition, fitted with a newly rebuild
BTH mag (really excellent job done by Dave Lindsley) and a concentric (pilot jet 30). The best even
tickover I can achieve is in slowing down the carbs at full advance to about 1200 rpm, and then retard
ignition to slow to 1000rpm, about half way. Under 1000 it will run quietly for a while, and then stall,
usually as the traffic lights turn green, with 50 cars waiting in the lane behind, as you know. Do you
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think I could expect better? I remember a mate MSS idling at some 500 rpm or so.
#2567 If you want a really slow tick over on a VM fit multi rate coil springs. The difference is amazing.
The valve is pulled straight back onto the seat hence sealing is better and the lower seat pressure
means less internal resistance throughout the motor. Having said that with a M17/8 cam you'll be lucky
to get slower than about 900rpm . The MSS has softer cams and heavier flywheels (well some do) and
that really makes the difference.
L #3054 I've completed the winter rebuild which included new mains, big and little ends, piston,
valve guides (used old valves as they were OK). When I started it up today there was lots of smoke,
which I expected from the oil I'd used during the reassembly. I went for a ride of about 15 miles and
was really pleased with the way the bike felt. BUT, when I got back home and left it ticking over while I
had a listen to the engine, the exhaust smoke reappeared. I'm not talking about the odd wisp of smoke
here, it's really smoking badly (enough for me to think the neighbours might not be happy) and seems
to get worse the longer it ticks over until the engine finally misfires and stops. The plug is oily. I can't
believe this is still "assembly" oil. My logic is that if it's not "assembly" oil, it can only be getting into the
combustion chamber down the guides or up past the piston, all of which are new. My options now are
to try another ride to see if it will clear, or to take off the head and cylinder again to see if I can see a
problem. Any suggestions would be welcome. I feel as though I might be missing something obvious
but can't think what it is. The only thing I've done any differently building this engine is that I got a local
machine shop to ream the new guides to suit the valves and it came back with the valves fitted and
lubricated with "assembly fluid". I felt the valves for fit (they were fine) and then assembled springs etc.
I've never used "assembly fluid", just an oilcan, could this be the cause? I'll speak to the machine shop
on Monday. I really would welcome any advice or suggestions, the bike was running so well I really
don't want to start to take it apart again, but if I have to, so be it.
#3055 Was the bike on the side stand when it was ticking over? If so the top of the guides will be
submerged in oil, with the throttle closed the guide acts like a drinking straw.
#3056 Either your oil pump is not returning the oil to the tank and you are wet sumped (do a careful
monitor of the oil level in the tank), or you oiled the rings and piston during assembly. Modern oils are
so good that the rings will refuse to seat if not assembled dry. The good news is that if you clean all the
oil off of the rings and piston and reassemble, they should seat just fine. If you used the one piece cast
iron oil ring, your engine will use more oil than if you used a modern three piece ring. I get all my rings
by size from Hastings (800) 776-1012
#3057 If it's any help, I was riding my venom between Portsmouth and Derby about a million years ago
when all of a sudden it started to spew smoke out of the silencer. Investigating the problem showed
that the rocker box was full of oil. It turned out that a small piece of gasket material had found it's way
into the rocker box drain pipe, blocking the return. Once it was winkled out and the top end
reassembled all was fine then and for years after that. I guess that I may have had some wear in my
valves/guides but it won't have been terribly bad.
#3058 The one mistake that a lot of people make after a rebuild is that they put quality oil into the
motor. have you used running in oil. very preferable after a rebuild. needs to be in about 500 miles and
then dropped and then a good quality oil added. millers do a running in oil to break in new or rebuilt
motors. if you put in quality oil at the start you can glaze the bore, as the oil is so good, it wont let the
rings bed in. this could be an answer as to why the motor is smoking. also check the cross drilled hole
in the return in the oil tank, the one that the tube goes over in the filter chamber. make sure that there is
no debris in there, as this can restrict return flow and up the level in the motor. this can also contribute
to the motor smoking, as the oil level gets higher, the flywheels will fling it up the bore. hope this info
might be of some help.
#3059 Thanks for all the replies. Here are answers to the questions you posed and where we're up to:
The bike was on the centre stand not the side stand when ticking over and making smoke. There was a
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good oil return flow to the tank. Compression feels fine. I had oiled the barrel and piston/rings using
Silkolene 40. I'm using the same oil in the tank. I understand what's been said about rings not bedding
in but I'm sure the amount of smoke it's producing is more than would be caused by this alone. If it were
a 2-stroke the amount of smoke would indicate a problem. About 24 hours after being used and making
smoke I drained the crankcase and got around 100cc of oil. Thinking about drain down from inside the
engine over 24 hours I don't think this is excessive. This and the good return flow is inclining me away
from wet sumping as being the cause. This pointed me more at the top end and the suggestion of
blocked oil drain from the rocker box. I removed the oil drain pipe (head to pushrod tube) and this was
clear. I was half hoping for a gush of oil from the rocker box but there was only a drip. Poked into the
drain holes with a cable tie and I'm certain they are clear. So where now? I won't be able to do any
more until next weekend so please keep thinking. What about the fact that it seems to get worse the
longer it ticks over and is more pronounced on the overrun? My current plan is to go for another run in
the probably vain hope it sorts itself out, then, if it doesn't, start by removing rocker box then head then
barrel and checking as I go. I have a nagging feeling that the cause might be really simple and might
just be very embarrassing - in a way I hope it is!
#3060 When you take the head off - and it's looking like you are going in that direction - unseated rings
will give you a fairly even deposit of soot on the outside margin of the piston crown. You'll have oil on
the stem and tulip of the intake valve if that guide is at fault and lots of soot in the exhaust port if that
guide and valve are letting oil by. I've tried knurled guides a few times and sometimes it worked,
sometimes it didn't. I'd suggest valve guide seals with knurled guides, but that may not be an option
here. Hope you don't have to dig this deep.
#3062 I have had a think about this, and it might be a guide going up and down with the valve. I have
seen it happen before. velocette idea of putting guides in without a landing is not a good idea in my
book. hope you sort it out. cheers.
#3061 My experience is that a lot of oil getting by the rings will keep the top of the piston clean at it's
circumference with the carbon growing like a weed just 1/4" away from the bore
#3063 The oil surely comes from the head. The smoke development will get worse during a long tick
over period because the head gets hotter and hotter and this might increase the gap between guide
and head. When checking for loose valve guides, make sure to do it when the head is hot because it
might be that they are a tight fit when cold. If the guides are really loose, you probably have to bore out
the guide holes because of the action of the rocker they will not be round anymore but somehow
elliptic. Then you need to buy/make oversize valve guides and re-cut your seats afterwards.
sorry mate, hope this is not the case.
#3064 I had an appalling amount of smoke from my MkI a while ago. It was expensive to buy all that R!
The cause was a cracked oil ring which had fallen into four pieces. New ring = no more smoke; no rebore
etc.
#3116 Sorted the smoking out and, as I feared, it was something I'd done and am duly embarrassed
about. So here it is, just to complete the story and prevent anyone else doing the same. The ideas
about oil covering the guides as a cause pointed me in the right direction. I took off the rocker cover
and poured oil into the recesses on the top of the head to see how much needed to be in there to cover
the guides. The drain rate was slower than I'd expected but the exhaust side was significantly slower
than the inlet. When I had fitted the rocker cover I had used what I thought was a very small amount of
silicone sealant on the gasket. The fixing screw just in front of the pushrod tube had taken some
silicone down in front of it and squeezed this into the exhaust side rocker drain drilling, partially blocking
it. I hadn't realized that the two rocker drain drillings are just broken into by the fixing screw holes. The
drain was reduced to maybe two thirds of its full diameter. Anyway, cleaned it all out, refitted the rocker
cover with no sealant, started it up and it still smoked but by no means as badly. Went for a ride, maybe
10 miles, no sign of smoking afterwards so think that what there was just burning off from inside the
exhaust. There we are then, Ian with red face but relieved.
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L #3777 My 1938 MSS has an old AMAL 276, with the remote float. It has been running a bit off
for the last 500 miles or so. The bike will run fine when opening the throttle from idle through wide
open. But if I hold the bike at 3/4 throttle, it will cough every 2-3 seconds. If I open the throttle a bit
more, the bike runs great. On my last two rides, I've just kept the throttle opened a bit more, or a bit
less, than the trouble spot, and everything has been fine. I'm guessing that the slide is slowly wearing
out, but shouldn't that affect the carburation at lower rpm levels? Maybe the needle jet is wearing out... I
guess I'll pull it apart and look inside.
#3779 It's quite possible the slide is worn after many years - you can bore out the body and re-bush,
but it's a fiddly business. Before that I'd take it apart and clean out thoroughly - try the easy things first.
Is there a leak on the carbs flange joint -? this would affect slow running worst. Needle worn - probably
the jet it runs in is more likely . The fact that it's only happened in the last 500 miles suggests a
blockage etc rather than wear which would take many 1000's of miles to show up, and happen so
slowly you'd hardly notice.
L #4281 Hello all, this past weekend was the first shakedown run for the new MAC on our fall club
ride. Things didn't go too well. After getting about 10 miles from home, at an intersection, it quit and
refused to start again. After waiting for about 20 minutes it did start, and I continued, but it wasn't
running very well. The further up the canyon I went the worse it ran. It seems to run really well as long
as the road is flat and I don't push it too hard. Does this sound like a magneto problem? Does anyone
know about Kirby Rowbotham engineering in England that offers an electronic ignition conversion
inside the existing magneto? Coming down the canyon it was backfiring and spluttering all the way. I
think it felt like ignition trouble. Anyone on this list have any thoughts?
#4286 Does it still have the fibre mag wheel? If so check the teeth for wear. I had a problem years ago
where the timing kept altering by itself. I fitted a steel wheel and ran with ignition fully advanced, no
problem with a MAC.
#4282 Poor hot starting is classic magneto trouble. While you could go electronic I'd suggest that you
just get the magneto rewound by a reputable company and it should be fine. I had the same problem
with my 1954 MAC when I first got it and the rewound mag transformed starting and has been good for
8 years now.
#4283 Most likely the magneto, but first make sure the petrol can get into the carbs quickly. I changed
the mag ( which meant lifting the barrel to remove it, and just how are you meant to get to those 3
nuts?) only to find that the tap filters only passed a dribble that run the bike fine until you tried to go
faster!
#4284 Do you have the proper heat proof gasket on the carbs / cylinder head joint? (K180/3). I had
similar problem with poor hot running /starting performance. When I replaced the paper gasket with the
proper one the problem went.
L #4689 I have just purchased a restored 1956 Venom and can't get it to run other than with the
choke open (air slide closed). As this is my first ever Brit Bike ( or indeed any bike that did not run as a
starting point!) I am at a bit of a loss where to start with changing the settings. The previous owner
indicated that the jetting is standard so I am guessing I need to play initially with the pilot air adjusting
screw. Is there such a thing as a standard setting from which I can then twiddle ( similar to the
procedure on my Airhead BMW's Bing Carburettors) ?
#4690 Look at: www.croesus-consultants.co.uk/v-tec (the Group owner’s) and a treasure trove of Velo
info (including carbs settings). For guidance on checking the settings try:
www.hitchcocksmotorcycles.com which has the AMAL hints and tips for setting up your carbs.
#4699 Assuming an Amal Monobloc is fitted. I'm not sure what you mean by choke open/air slide
closed. Choke open usually means the air slide is not obstructing the choke of the carbs (the air slide is
13

in the up position in the body of the carbs). However if the choke has to be used (closed/down) to make
to make the engine run once warm it is obvious the mixture strength is far too weak. Firstly check all
the jets and slide are as per the manual and that there are no blockages obvious in any of the jets.
Check that the needle valve is clipped in the middle position or one groove up or down from this. The
pilot valve should be one and a half turns out from fully screwed in as a starting point. (Screwing out
weakens the mixture and enrichens it)
#4702 sounds like the pilot jet is blocked.
L # 4835 Just got my Velo from UK. Its got a good spark and fuel to the carb but won't even
make a pop. Followed the Velo startin drill from my books as well. The only thing I can think of at this
point is that when I got the bike all the cabling was disconnected. Is it possible that the exhaust valve
vacuum release is not properly hooked up? it seems unlikely because I seem to be getting
compression but I’m out of ideas at this point. And I am quite certain it did run before being shipped.
# 4837 After kicking was the sparkplug wet? One thing that works on my velo's is to give several
priming kicks with the decompressor pulled in. (this may be my imagination but...) Flood carbie well
(turn off petrol if you don't know bike as in this case for safety), do my primary kick thing as above, then
kick gently to compression, decomp, push kick starter slowly to bottom of movement, then give a good
kick. If valve and ignition timing is OK, Maggy has spark, and carb is wet and in good nick, it must go!
# 4838 I think that you need to experiment with old bikes until you find out what the particular
machines likes. For example, reading your note, my MAC will not fire if I flood the carb. Absolutely no
way. I close the air slide then follow the standard Velo starting procedure (ease over compression etc.)
and after one or two kicks it either fires or starts.
#4846 Tickle carb till finger wetted, close air lever 3/4 way, turn engine till compression felt, then with
kickstar at top, operate exhaust valve lifter, kick slowly to bottom of kickstart stroke, release valve lifter,
and kick manfully over compression, with throttle opened only the merest amount, avoiding the
tendency most people have of snatching open the throttle as you kick. Repeat this several thousand
times cursing loudly. My '47 MAC sidecar outfit refused to start after I added a lead substitute ( Redex)
but was fine again after drained out and refilled with standard lead free, which I have used ever since
leaded became unavailable. Some many years back, I was asked by Phil Bleasey (ex Fishtail editor) to
help him pick up a Venom he had bought from a chap who had done quite a good job of rebuilding the
bike, but eventually gave up on the machine as he had never managed to start it. Everthing seemed
OK till we realised that it was timed to exactly 38 before top dead, but on the exhaust stroke. 10
minutes later we were flat out on the by-pass! Good luck, you'll love it once you've got it going.
# 4836 Sometimes a good hill does the trick.
L # 4848 I recently took delivery of my 1960 Venom that has been expertly restored by Dave
Smith in Chicago, fitted with a 10.5:1 compression piston, squish head, and a new BTH magneto and
twin plugs. Because of the minimum RPM required to light off the BTH I was learning all sorts of new
words trying to get it started. I'd been aware of various "mobile starters", i.e. the Foxley, that use a
rubber tire powered by a gasoline engine which one positions against the rear tire. Definitely a two-man
operation and expensive also. I finally found a chap who makes a battery-powered starter that consists
of a pair of parallel rollers mounted in a fabricated steel structure, each of which is powered
independently by a Ford truck starter motor. A folding steel plate on each end allows the rear wheel to
be rolled onto the platform where it contacts both rollers. A foot switch supplies power to the starters
through a HD starter relay. In practice the bike is put into third gear, the front brake is applied, the
decompressor lever is pulled in, the unit is engaged, and when you release the decompressor lever the
bike is instantly running. You can then roll the bike off the starter and motor away. Not only is this
useful for starting the bike, but I've also used it to thoroughly purge the oiling system of the old oil when
changing oil. I've also learned that AMAL used to make a device they called the "Easy Start" for the
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Monoblock carburetors, which replaces the slide stop screw. There is a little "toggle" in this device
which when actuated, raises the slide by .030", the ideal amount to provide excellent air velocity across
the idle jet and get the bike running quickly. Once it warms up a bit you can deactivate the toggle and
motor away. I certainly can't take credit for this idea, an acquaintance in England came up with this idea
and is making a couple of these for me for the AMAL Mk I Concentric fitted to the Venom and if there is
enough interest I suspect he will offer them generally for sale. Those interested in the roller starter can
contact: Mr. Art "Doc" Zimmerman Doc Z International Ltd. 24220 Bruce Road Bay Village, OH 44140
Phone: (440) 841-7112 email: docZ01@... Current price is probably around $600.00, which doesn't
include a battery or the battery cables, but this thing really works well and saves beating the kickstart
mechanism to death.
# 4851 George, If you need rollers to start a Venom, there's something wrong. A good BTH mag will
put out a super spark even at low revs; that's not the problem. A sump full of oil with close ratio (TT)
gears may be. Maybe the technique too?
# 4853 I have a '60 VM clubman with a Dave Smith supplied squish head, 10:1 ratio, BTH TT mag,
and a 1 1/4" TT carb, and have no trouble starting whatsoever. Check mag output and carburation, the
BTH should give a fat spark at almost no revs, with hand turning of the mag shaft, or a slow kickover.
But, if the idle circuit isn't right, even a docile beast like an MSS will be a difficult starter. Will it idle
slowly, once started?
# 4854 My '51 MAC was once hard to start for a while, but the problem eventually came to light when it
also began idling poorly or stopping completely when the throttle was closed. Tracked it down to the
idle- jet having a tiny bit of 'something' stuck in the hole-almost too small to see with the naked eye but
once removed everything was back to normal- ie 2 or 3 kicks at worst and usually a first-kick start even
after several weeks of storage.
#4859 My definition of “hard starting” is having to kick twice. If we do not fire up on the first kick a look
of surprise spreads across the face. Is it not more particle to have the thing set-up right and avoid the
problems?
# 4855 I used to think I could no longer run fast enough to start my bikes via bumping off....my sons
showed me up! Actually the magneto may be the culprit....was it rebuilt? As an aside....a lot of us
AHRMA guys used starting rollers both powered and driven but IMHO they are a waste of bucks ($) if
all is properly tuned.
L # 4867 Can anyone clue me into how to get a Venom started again once it's hot? The Mag is
fine I have spark and I have fuel and compression. Starts like a champ cold. Runs great. But if I stop
and let it sit longer than 5 minutes I might just as well fine a pub and wait an hour.
# 4868 Gees. Most people look forward to a good excuse to sit in a pub for an hour. Seriously,
though... do you have a phenolic thermal insulating washer to isolate the carb? That helped me.
# 4873 I agree, but we need to help him solve the problem because there are times when the hapless
Velo rider is stuck with a beast that won't start and there's no pub within cooee. So, the procedure
according to JJ is as follows: 1. If spark, compression and fuel are confirmed, find a hill (or if flat ground
enlist the help of a bike pusher) and bump start. I despair to see Velo riders wearing out their right knee
joint (and less importantly, the kickstart ratchet) with a beast that clearly has no interest in firing and
continuing to run after that single shot we get, courtesy of that low geared kick starter. The second best
starter in my shed is Li'l Speedy, the '39 MAC racer - and it doesn't even have a kick starter! 2. Nearest
I can get to help the Venom problem specifically, is a problem we had with Kamahl, the Concentric
equipped Mk2 Clubman. When almost hot, it fires, then spits back and won't run. A timely hint from my
old mate Richard (who has the world's best and much ridden Mk2 Clubman) prevented me and PD'O
from setting fire to this bugger. A smidgin of choke to get started when almost hot solved the problem
completely. It doesn't appear to be related to jetting or float level (because I know Richard's would be
15

spot on - he's that type of bloke). It's just what experience and a period of getting to know you
determines is the answer for this specific "starting when almost hot" problem when running a
Concentric. Like yours, if you get to it in the first 5 minutes of stopping, just kick once and ride off. But
after that period ....... 3. By the way, the best starter is Old Faithful, GP equipped VMT457. Correct carb
settings and 30 years of "getting to know you" explain this behaviour. Not that you need 30 years - it
only took about 18 months for me to wake up to the need to get carb resleeved and float level spot on
in order to turn it into a pussycat with respect to starting.
# 4874 I had a hard starting problem when my Venom was warm and discovered that if I killed the
engine by letting out the clutch gently while in gear it started easier if I had to start it while still hot or
even just mostly warm. I think maybe it has something to do with the engine not sucking in several
chugs of gas with no spark. I know there are probably lots of reasons not to stop this way and that if the
bike is spot on (as mine has seemed to be lately) it should start regardless or engine temp, but it's a
tactic to be tried with a taciturn Velo.
# 4880 The position of the piston has a lot to do with it.
# 4876 Well now , there is one problem about setting off down hill with a reluctant starter - What do
you do at the bottom of the hill when the dear little thing has failed to start? In good order a Velo will
start easily. If you are involved in racing you will have noted that two or three steps and bump will see
the thing burst into life (one good thing against clutch starts!) So; no hills or rollers will rectify a machine
in poor nick, and that is what the problems are, be it mag or carburretion. Look after those knees!!
# 4872 First, Re. the little gadget that clamps on to the slide idle adjusment screw. Maybe my memory
is defective, but I can remember that the very first MSS that I rode prewar, brand new & belonging to a
very proud mate, had that little accessory, & so did other MSS's of the time, (those that I remember
anyhow !) Of course I only rode my 1930 KSS normally. Further to this, I have a 37 MSS, as original as
you could possibly expect, except for the caburettor that was used as a target for a child's hammer
attack, long before I found it sitting up in a mallee pole thatched cow barn. This fact, & the wet cow pat
carpet had ensured that the bottom had almost completely rusted off the rear stand, upon which it had
stood for many a year, after the sidecar had been taken away around 1948. - & it was still standing
believe it or not, some 20 years later ! The stand was repaired, & the carb. replaced from the spares
box. This bike still has that satin chromed throttle stop clamp, & also the sudden death throttle twistgrip
set up. The point is, I was always of the view that this easy starting gadget was standard on the MSS's
of those early years ? I have to say that the hard starting thread has given me many a chuckle to start
out the New Year, especially the starting rollers ! I am left wondering how the Hell we ever started our
bikes back in the pre historic times ? One thing I do remember was that it was a point of pride that your
Velocette started while your mates were wrestling & wiggling levers on their 'Other Makes ! One clue
has to be pointed out, -- the bikes had brand new magnetos ! - everything else was new also, so my
advice is to add to what has already been said many times, - have your magneto checked out by a
RELIABLE magneto man of good repute ! As to general hard starting , - especially when hot, common
sense , - assuming that all else is in good fettle, points the finger at over generous flooding, a sure way
to upset a Velo, - especialy a MSS, or Mk. 2 KSS in my experience, -- but I still have no real idea why
some Velos at odd times, can sense a gathering crowd, & absolutely refuse to fire, but I think we would
all agree that Veloce's unique kick start gearing has something to do with it. I do know that a big bloke
with Velo starting experience can kick a reluctant Velo into life, (probably first kick), when smaller
mortals have given up, but are not prepared to swallow their Velo pride, & ask for a push, - select a low
gear, - lift the decomp. lever, & the motor will spin over, clear out the rich mixture & burst into full song
immediately ! We Velo owners are a strange breed, but we have to accept that we ride a very spirited &
proud machine. Neglect to change it's worn shoes, forget to curry comb it's fine coat, & worst of all
forget to give it a bucket of oats now & then, -- & while it will tolerate this for a while, - it will eventually
decide enough ! I really feel for these new owners who have eventually found their first Velocette, & all
the baggage that can sometimes come with it. ---- Unfortunately Velocettes are particularly prone to the
after effects of an uncaring owner.
16

L # 4946 I'm having difficulties with my 1969 Clubman, specifically getting the darn thing to start.
I got the bike about two years ago, my first Velocette. After I learned the standard starting routine, I
could always seem to get the bike started... one or two kicks if it was hot, or 10 or 15 kicks when cold. I
never really figured out exactly where to set the spark retard lever, relative to the conditions, just fiddled
around with it until I got the thing going. Now, I've stupidly let the bike sit for I don't know how long...
probably since last August or so. I couldn't get it started for quite a while. So, I checked the plug, and
yes a little moist, and got some carbon off with a paper towel. Put the plug back in and it started first try.
Then three days later, it was cold and rainy... then the sun came out, an it tried it again. Wouldn't start.
Thinking I knew something, I took out the plug and wiped it clean. Put it back in, still wouldn't start.
Finally gave up exhausted after an hour or so. Since then I have not been able to start it... Yesterday it
fired off for a few seconds, but I was so surprized by the noise of a running motorcycle, I couldn't keep
it going. Then it wouldn't start again after that. So, my question is sort of "what do I do?" Or rather, what
is the sequence of things I should start checking out, so that I don't go and adjust something that
doesn't need adjusting, and make matters irretrievably worse?
# 4950 Are you using the same old fuel that has been in the tank all this time? I have had problems
with fuel going "off" if left more than a week or two.Try draining and using a drop fresh fuel and at least
its reatively easy to try first!
# 4951 Sounds like a sparks problem - and since you've found cleaning the plug helps, it might be
worth fitting a new one. From there it's worth going through the HT stuff - leads and plug cap, decent
rubber boots at each end of lead. If the bike runs OK ( you should be able to get 90+ out of a clubman)
when started the timing probably isn't far out. At the worst the mag may be weak - clean / new points,
correct gap, brushes, needs new capacitor, remagnetising, rewinding in that order of difficulty. But try
the plug first - it's cheap and easy regards.
# 4953 I once had an occasion on my MAC when the pilot mixture adjusting screw spring was too
weak which allowed the screw to work out on a trip. On attempting to restart, it wouldn`t. Checked the
spark which was OK along with all the usual roadside checks like fuel at the carb, compression there
etc. Eventually thought it may be mixure and found the pilot screw well out from the 1 1/2 turn starting
point. Adjusted to 1 1/2 turns out and he presto it was a runner again. Maybe worth a check.
# 4954 Thanks for the initial help. I appreciate it. I need to take the carb off anyway, because I've
noticed that the throttle sticks when it's wide open and the spring can't move it back down. And while
I'm at it, I'll drain out the old gasoline. When I checked for spark, it didn't really look that strong to me. I
don't really know what it ought to look like though, and it was a bright day. Again, thanks for the input,
and I'll be sure and report back after I check a few things out.
# 4958 Eric, a good mag should make a spark that will jump a 1/4 inch gap when turned by hand. My
Venom can sit for months with stale gas and still fire after a few kicks. Don't blame the condenser too
quickly for poor cold starting. Make sure the plug insulator is not cracked (try a fresh one) and that the
cap is in good shape. The plug gap should be 0.018". Take the ground brush out (gently, the spring is
hair thin) and check for oil on the slip ring, that would mean a bad seal. And make sure there you've
tickled the carb until your finger is wet to the first knuckle; when my Velos are being difficult lack of
sufficient fuel has been the problem 90% of the time.
# 4960 You didn't mention using the valvelifter/decompressor lever, I found my Viper starts a lot easier
with correct use of it. Also oil could have drained down into crankcase causing excess drag when
kicking over. Try a new plug and fill with fresh fuel,good luck and let us know how you get on.
# 4965 No, I didn't mention it. I think I'm doing the right thing. During my sessions of unsuccessfully
trying to start the bike, I like to have a contest to see who gives out first, my left forefinger, or my right
leg... Anyway, I've got two shiny new B8ES plugs, and reasonable weather predicted for the weekend,
so I'll report back. Just need to pick up a little fresh gasoline and something to clean up the carb.
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# 4991 I promised to report back. It lives! I did the easy thing first and put in a new spark plug.
Replaced the tired looking N3C with a new B8ES. I won't lie and say it started first kick, but it almost
did. I didn't bother cleaning out the carb or replacing the old gasoline. I'll purge that out with my fresh
tank. Thanks for the helpful suggestions everyone! On my ride, I stopped at my neighbor's place. As my
primary chain case left a few drops on his driveway, he asked me if I knew why the British were never
famous for manufacturing stereos.... because they couldn't figure out a good way to make them leak oil.
# 4993 This is no consolation to you but I am having exactly the same problems with my 56 Venom. I
guess all these years of push-button starting from German and Italian (!) bikes has just lulled me into a
false sense of security. The Venom has punctured all that.... Regards Ian PS: My earlier problem with
the "choke" was solved when on removing the Carb I realized that I was operating the choke lever in
reverse i.e. when it was closed I thought it was open, and vice versa. No wonder it was difficult to start !
L # 4985 I have just replaced my GP carb (temporarily) with an Amal Mk1 1000 series 36mm with
all settings as per factory so I can enjoy a motor that idles. My bike is an early 1968 so no coil. The
motor has recently been rebuilt and is running on BP 98 octane premium unleaded here in Australia.
The problem I'm trying to solve occurs at any speed where the throttle position is constant the motor
hunts almost like a four cyl motor on three cyls with the forth firing occasionly. However the motor feels
very comfortable under acceleration and wants to rev. There is some pinging but I can remove this by
retarding slightly so not a problem. My mechanic has suggested that its a combination of the fuel being
set for injection motors rather than carburettors and the larger inlet valve in the Thruxton head causing
the problem?? All suggestions welcome.
# 4992 Try to boost the octan by 2%. I had severe problems when the engine was hot with too low
octane. What are the settings used by You for the GP - slide, needle end jets You use ( I have a early
1968 too running on the GP).
# 4999 I can confirm that I have the correct throttle needle, needle jet and discharge nozzle for a 4
stroke as per your email. I haven't tried drilling out the air correction passage and will sit on that one for
a while, as you say there is no going back once done. I'm starting to wonder if the velocity of fuel/air in
the inlet manifold is too slow under constant throttle and if I might solve the problem by fitting a venturi
inside the manifold to speed things up. As the problem goes away under throttle.
L # 5515 anybody have any advice ? My dad’s Venom is a 1st kick starter when hot and runs
beautifully,but trying to start it from cold is a nightmare! Recently rebored,new concentric carb and coil
ignition, my brother’s Venom set the same starts readily hot and cold! We have tried flood/not
flood-choke/no choke and every available combination! It rarely fires when kicked and then will
eventually just burst into life and then start fine for rest of day.It does seem to wet plug easily and
sometimes the front of oil tank is wet with fuel,
# 5521 Don't use too heavy a grade oil and check oil not draining down into crankcase causing excess
drag when kicking.
L # 5537 Here’s one for the experts. A Venom,well set up & running well but runs out of go at 70
mph. Check all settings, all to spec but still runs out of puff at 70.Valve timing checked & found to be
ok, still 70mph.Valve timing RETARDED one tooth, we now get 70 mph & engine still pulling!I have
even seen 90! Any theories?
# 5538 Hi, Have you checked valve timing with disc? You will be aware that the sleeve on which the
cams are formed has a taper interference fit into the cam wheel. Has this assembly been dismantled at
any time and reassembled incorrectly in relation to the timing mark?
#5539 With the cam an interference fit in the wheel, it can move and retard the timing. You need to set
the cam up with a degree disc and turn the cam in the wheel till you get the cam timing corresponding
to the marks on the wheel. It’s not a bad idea to weld the cam to the cam wheel when you have dialed it
18

in. With the cam timing right, these motors can fly.
# 5540 Please note my original text, all settings were to spec.The only way to time valves on a Velo is
with a deg disc, you can use the old valve rocking technique, but you need the disc to check the angle.
# 5541 I once had a very reluctant Viper. I found the petrol tap filters totally clogged. Cleaned them & it
flew!
# 5542 Fuel starvation was my bet, the obvious. Do the simple things first.
# 5549 Don`t forget the breather hole in the fuel tank cap. I have seen an occasion where when the
cap was turned to fasten it something inside the cap moved, or didn`t move, and covered the breather
hole.
# 5547 Did you change the ignition timing after moving the valve timing? You may have retarded the
valve timing and advanced (?) the ignition?
L # 5636 I have a few questions for Mac owners out there but I will start with what I have got so
you have the info. 1949 Mac m17 cam set to marks and confirmed to be good ( valve timing check
done) 276 pre monoblock carb ( new ) Advance set at 4* ( fully retarded, has BTH mag with ATD)
running 91oct. new valves and guides, new cam followers, fairly fresh bore ( @1000mi ) 18T sprocket I
suspect no exhaust baffle Now on to the symptoms Started with book specs for carb ( middle groove on
needle, 130main ) and was lean at WFO and at the top of the needle range ( white B7HS plug), put
needle up one notch and now get dark plug in low to middle range, still white at middle to top, kept
going up on the main jet with the same results only to get a VERY little color at a 160 main ( color was
around the base of plug and very bottom of electrode ( cap side)), suspecting float level I went WFO
and held down the tickler and did not get any adverse effect, even seemed to go better ( maybe
because I was hauling down the road with one hand wedged between the tank and motor). This lean
condition with such a large main jet vexes me, all I can think of is float level ( float is without leaks ). I
have a float needle from what I think is a velo 276 that sets a higher float level and I have installed it,
have yet to run it though. Could it be something that simple? When I look at a parts diagram from
hitchocks I see only two float needles ( top and bottom feed ) but I know that amal made different ones
( as evidenced by me having one with a higher float level). Has me scratching my head. as an aside I
was able to reach 60mph and a pitmans book I have states that as the max speed for the Mac but with
the white plug I think I will wait until I get the bike sorted before attempting to sustain a speed over 55
for any length of time, what kind of speed are you getting out of your Mac and how did you get there?
My goal with this bike is to be able to at least cruse at 55 for the portions of highway I am forced to take
to get to the B roads that I like to ride. Seems strange that I can easily hit 65 on my mostly stock Enfield
g350 and hold that speed for quite some time before worrying about the motor and this bike seems to
hummingbird out at 60, 55 seems to be pushing it right now. Sorry about the long post but this one has
me scratching my head.
# 5637 Not sure I can answer your questions. First, can you check that the new fuel level is the same
height as the top of the mainjet? If it was originally lower then that would weaken the mixture. Too high
and the carb will flood continuously (and it'll be richer). I have a 54MAC and use an NGK B6ES plug
with no problems. These are longer reach than an HS I think. My MAC will happily sit at 60mph with
plenty of go left. It has an M17-7 cam though. I have clocked it at 82mph before. An exciting (and
worrying) speed for an old 350. Yours is probably stopping at 60mph because its not getting enough
fuel. An old chestnut but you have checked the tank cap breather, haven't you?
# 5638 Look out! Regarding the plug question, NGK plugs with an "HS" designation are 1/2" reach -
i.e. thread length. Those designated "ES" are 3/4" reach. They are NOT interchangable. 1/2" plugs are
most commonly used on iron head engines, 3/4" on alloy heads, although I must admit to not knowing
which variation should be used on a MAC, whether iron or alloy. Easy enough to tell if you've got the
head off though!
19

# 5641 I think it is impossible to check the fuel height in a pre monoblock carb due to the way they are
put together, I am sure that the level will go up as there is more fuel in the float chamber which would
put more fuel into the mixing chamber so maybe it will be that, I will try the new float level soon. I think
the b6 is a hotter plug so that would tend to make the plug chop even worse and I am stuck with using
the shorter plug due to clearance. Your speed sn encouraging and I think you are correct about not
getting enough fuel, I have mains for that style carb going up to 210 but as it is was I think I could keep
going up in jet size without making much difference in the top mixture, If the new float level dose not
work I think I may try stuffing a concentric carb on it just to see if that makes a difference. fuel cap
seems clear ( can blow thru the breather ). again thank you.
# 5642 you are correct about the plug reach, in an iron mac the plug would stick into the chamber far
too much and could even cause clearance problems due to the location.
#5647 The iron MAC should be good for about 75 MPH. I have a '47 MAC with a sidecar attached. it
cruises happily all day at 55, and will do 65 at a push. It is geared down 2 teeth. Early MACs had 19
teeth on engine, and 22 on gearbox sprockets. This was later changed to 22 engine, and 19 on
gearbox. This made the clutch turn faster, and therefore less likely to slip. If you have 18 gearbox, and
19 engine you are undergeared and my just be running out of revs. With 22 engine, I have found one
tooth down an advantage, as they are slightly overgeared as standard. Without taking my carb apart to
check, i think it has 180 main jet. I get around 45-50 miles per (UK) gallon. It does tend to cook plugs if
pushed hard for long periods. Unlike Venoms and Vipers, the bigger cutaway on the piston goes to the
front (exhaust valve). I would check ignition timing fully advanced, at 36 - 38 BTDC, and also check
cam timing with timing disc, as the marks can be out, if sets mixed, or the cam has turned in its
gearwheel. If it falls between 2 teeth, err on the side of the cam timing being advanced. The MOV head
is identical except that the inlet port is smaller, I think 7/8 as against 15/16 ? The MAC was set up to
run on 76 octane fuel, if you feel brave enough, shortening the barrel by 1/8" will usefully improve
compression ratio.
#5650 I am wondering if the leanness you are seeing could be due to an air leak? Take a look at the
carb mounting points, did you use some sort of sealant there? I have checked for air leaks on other
motorbikes using a spray lubricant around the carb/manifold joints with engine running. This may not be
foolproof, but if you get a change in rpm , it is an indication of leakage. I'd agree with the other good
advice to double check ignition timing especially. I've seen people chase a lot of "carb problems" that
were actually ignition related.
# 5654 My personal preference is not to use sealants on intake port joints but to ensure that the faces
are flat and clean. Use a paper gasket between the heat insulator and the head, and between the carb
and insulator unless you have a later carb fitted with an "O" ring. Consider the conversion to "O" ring on
both sides of the insulator to be a worthwhile mod if you have the facilities to do it. Leaks at these joints
will manifest themselves as fast or uneven idle. When the throttle is opened by any degree the
influence of manifold air leaks is pretty well negated, certainly at wide open there will be no effect at all
(unless the carb is literally hanging off its studs!). From what you've said about your timing being
checked at full retard I think I would go along with Bob's suggestion of checking at full advance, this
being the critical factor as far as performance is concerned.
# 5668 Timing, gearing, and float are likely culprits. Timing---Make sure to check your timing at full
advance. You can jam a small stick of wood into the advance unit to do this. Timing at fully retarded
setting is only good for idling. If the advance unit is faulty, you won't know it by checking the retarded
timing position. Next thing is, is the advance unit sticking? Maybe the timing isn't advancing with
increased rpms.... That would be very bad. Gearing---I'll suggest counting the teeth on all 4 sprockets.
If one or more of them is not the standard size, your gearing can be way off. If they are incorrect, I can
show you how to calculate your final drive ratio. It is simple math. Float---Finally, you can check the
float level, but it's not easy. Try to remove the lid of the float chamber. You can then drop a stick down
from the top edge to measure the level. Transfer that line around to the main body of the carb, and see
if it is close. Alternatively, you can drill and tap a hole in the float chamber, and add a barb fitting and
20

clear fuel line. Fill the float chamber, and the fuel in the tubing will raise to the float level. You can move
the tubing to be near the carb body to check the height. You can cut new slots in the float needle. I
have a carb or two that came with home made cuts, above or below the factory locations. Just use a
small file and work your way around the needle slowly. Spark Plugs---Also, you may want to try a colder
plug. NGKs can be very sensitive. For a few bucks, it's worth a try on a sparker from the next heat
range. best of luck!
# 5652 As a lark, I have cams M17/3,5,6,7,8 you could try to see if there is any difference with cam
timing. Also, perhaps your 'baffle-less' cam has in fact a baffle but blocking the exit slightly? Have you
tried your mag OFF the bike to see how it sparks at higher revs? Just casting around for all the
possibles. Your MAC should be faster.
L # 6033 I have a 1956 venom, Have fitted new inlet and exhaust valves and guides, clearance
on the guides as per the book. Compression is excellent, no ring or bore wear. The pump seems to be
scavenging OK, the right amount of oil in the crank case after a run, no wet sumping after leaving for
any period of time, the bike goes really well one of the best I have ridden. However it uses large
amounts of oil! 200 miles to approx half litre. Any ideas would be welcome. It does not appear to smoke
from the exhaust, maybe just a little on over run I put this down to clearance on the exhaust guide (
three thou).
#6035 Unless the VM is leaking a bit (!) I suggest that the bore is worn. Or, the oil control ring is either
broken (I have had this happen) or not working. Is the combustion chamber/ piston crown very oily? Is
the exhaust black? 3 thou is not a lot of wear on a guide and should not cause this problem
# 6036 If the oil return pipe from the head to the push rod tube gets a bit of sealer stuck in a banjo bolt
the head will fill up with oil and over oil the guides. I may or may not have personal experience with this
:-). You mention smoke on the over run possibly from the exhaust guide. I have wondered about this
myself but never verified. Most blame smoke on the intake guide. Does oil in fact pull through an
exhaust guide on over run and does it burn (either in the combustion chamber or in the hot exhaust
port) and show up as blue smoke?
# 6038 The smoking on the overrun is more likely to be from the inlet guide than the exhaust, it's from
oil being pulled through the guide due to the increased vacuum in the inlet port when the throttle is
closed. If oil is getting down the exhaust guide it will be mainly due to sloppy guide clearance coupled
with excessive oil level in the head (due to your blocked rocker box drain!) and poor breathing allowing
case pressure to build up and force the oil through. I can also confirm that this does not only occur on
the overrun, but under power too, and is likely to cause very heavy smoking - it really doesn't take
much oil in the exhaust to create a massive smoke screen!
# 6051 Make sure that the valve guides are tight in the head. I've had one that felt tight, but the hole in
the head was oval. When it heated up, the guide spun around in the head, and allowed oil to pour past
it. The oil is going someplace, is it leaking out? Maybe out the breather? Is the primary chaincase filled
with your missing litre of 50wt?
L # 6079 Hi Folks, A few questions from a bloke who remembers the good old 60s wanted a velo
when all he could afford then was a BSA! Just bought a 1959 Viper with a documented 30,000miles
and about 95% original. No known work on the engine. It starts ok and clears to a smoke free exhaust
in less than a minute. Oil seems to be circulting with a steady stream in the tank. It runs quite well on
the road but is perhaps a bit flat until the revs pick up. No trail of smoke. There is a rattle from the top of
the engine which might be the small end??? It's not there all the time. Any thoughts on what usually
rattles on a Viper? The thing that I am quite concerned about is that the engine oil level was low when I
first tried the bike. I filled it up to the higher level and took the bike for a 3 mile run. On stopping I notice
oil spewing out of the breather and this stopped after a couple of minutes of ticking over. I remember
Velocettes always used to have a long breather pipe and a few drips of oil would find there way to the
chain but this seems a big pool of oil. Any thoughts? I was also given with the bike a new alloy viper
21

arrel with liner. Is this an aftermarket bit or could you get vipers with alloy barrels? I expect I will have
to strip down the engine eventually but would like to have a few rides on the bike first. Are there any
recommendations for places to get work done like new valve seats/guides , rebushing the con rod etc
etc. All thoughts and comments gratefully received.
# 6081 You'll probably get some extra advice on the rattle, but your oil problem might be that some oil
has seeped past the non-return valve into the sump whilst the bike has been standing. When the oil
pump scavenges this oil and returns it to the tank it's added to the bit you've already topped the tank up
with and the tank is then over-full and blows out the breather. Try checking the oil level in the tank after
the pump has had a chance of clearing the cases. Some Velo's wet sump a little, some don't. If the bike
has stood a while before you fired it up this could be your problem. If wet sumping is a problem then the
ball in the non-return valve can be re-seated. The normal method would be to give the ball a slight tap
against its seat, but some prefer to machine the seat flat giving a 'knife edge' for the ball to seat
against. An alternative method, but definitley not for the forgetful is to put a quarter turn stop valve in
the oil feed line (I personally wouldn't trust myself to remember to turn it on). As you have noticed
Vipers are supposed to perform better if you keep the rev's up. This isn't from my experience, but from
other friends who own or who have previously owned them.
# 6087 Vipers had alloy barrels - with an adapter plate to the crankcase mouth- until about 1960. The
barrel is the alloy MAC one with a bigger bore. The oiling sounds like a bit of wet sumping - as the other
replies have suggested. The oil return on a VR should be in spurts; a continuous flow indicates too
much oil. I would guess that it 'spurts' when it has been running for a few minutes? The rattle could be
anything. Small or big end, bore/piston wear, wrong ignition timing.... etc. The VR is known to like
revving a bit. The top revs are 7200 and its not really a 'slogging' engine. However; my first Velo was a
VR that had the fuel tap filters clogged with gunge. When that was cleared it flew! As far as work goes it
depends on where you are (and of course what needs doing)
# 6090 Had another go on the bike and no oil pouring out of the breather at the end of the run so it
looks as if I have expelled all the surplus oil. Oil level is now just under the top mark on the oil tank
transfers. Top end rattle is still there and I think it is probably the small end as it is quite high pitched
and only there on revs just above minimum idling. Thanks for the info on the alloy barrel. My bike is a
1959 and is supposed to be original so it must have been on the change. The question will be whether
to fit the alloy barrel or rebore the existing caste iron one. I guess the change to caste iron was to even
out the temperatures around the barrel. I'll try and enjoy the bike a bit first but will definitely be stripping
the engine to have a look. I'll ask again about who to trust for things like rebore and rebushing later. But
although I'm near Reading and Henley On Thames I'd rather get the bits to the right people no matter
how far away they are.
# 6092 Another thought re the top-end rattle is wear on the rockers & their bearings in the rocker box.
The alloy barrel will give no trouble; if it's OK on bore size & not up to max. oversize it could be used. I
suggest Nick Peyton or Ralph Seymour's for bits & work - both reasonably close. Of course it may not
be too bad when you look inside.
# 6099 Check the end float on the cam shaft and idler gears. My Venom had rather excessive
clearance and was much, much quieter when this was corrected.
# 6101 Piston slap is quite common, you say it is noticeable just above tickover, this would also fit
piston slap especially on light load. .
# 6104 I think it's a bit too high pitched for piston slap and perhaps not regular enough. The only way
to find out for sure will be to strip it down. As soon as I get the manual I'll have a go at it. My curiosity
will get the better of me! The problem will be that I'll probably end up restoring everything.
# 6105 An "Old Dogs" trick is to use a screwdriver as a stethoscope. Jam the handle into your ear and
probe the running engine with the blade. You'll soon identify what area of the engine the noise is
22

coming from (top end, barrel, bottom end, timing chest etc.). It can be quite revealing. I wouldn't advise
getting too close to the HT lead!
L # 6179 My Venom makes an irritating intermittent squeak while riding. Of course, as these
things go, I can't reproduce it in the garage. While poking my head around while riding, I think it may be
coming from the Lucas Dynamo. Does anyone know if the bearings in the Dynamo require periodic
lubrication, some other form of attention, or is my Dynamo on the way out?
# 6186 Ah, the Intermittent Squeak! Shortly after buying my first Velo, it seemed certain that a mouse
had taken up residence in old and crumbling foam inside the seat of the Venom, as every time I took
the bike out for a ride it squealed in terror, especially when I wound on the throttle. I even went so far
as to take the cover off the pan to release the hapless vermin, but the foam had crumbled honestly
without rodent help. Anyway, after putting the bike on the stand and running her up and down the rev
range, it was clear that the squeak was coming from the cylinder head. How had the mouse survived in
there? Removing the head and annealing the copper head gasket got rid of the mouse for good.
# 6193 I'll try additional diagnostics when out on my morning ride this weekend. I know it is an engine
generated noise, as pulling in the clutch, letting revs drop to idle at speed stops the squeaking. This is
still a very new bike (612 miles from new so far), and was built quite casually it seems in 1970, so
anything is possible. By the way, how does the head gasket potentially make this noise?
# 6194 Loose head hold down nuts allows the head to lift when hot, creates leakage past head gasket
# 6195 I had a similar problem and the beauty with singles is you can give the head a little lap against
the barrel. Problem solved, tightened me nuts and me head's not loose either.
# 6188 While your noise could of course be one of any number of things, it might be worth checking for
something mysterious which gave me a bit of grief lately on my own VM .. . symptom was a weird
screechy sort of noise (almost like that sick rattle that accompanies a partial nip-up of the piston). The
cupped dust cap over the lef tside front wheel bearing is meant to be a press-fit onto the narrow
shoulder of the collar/spacer that sits on the end of the bearing spacer around the axle. In my case it
had become slightly loose (dunno how) such that it could move enough to longer be aligned axially with
the axle ~ & consequently the inner edge of the cup could pick up on the face of the ali hub underneath
it, & it would start or try to spin despite the efforts of the axles clamping effect to stop it .. . . so hence
the horrible screeching noise as it argued with the two opposing faces/forces . .. The solution was to
dismantle the assy &, after pressing the cup back onto the (far too) narrow shoulder in carefully
squared alignment, a couple of spots of TIG have hopefully secured it permanently. BTW, the collar it
sits on was extra tight on the hub/bearing spacer so I relieved that fit slightly while all was apart.
L # 6301 Has anyone any idea why an engine that has a strong tick over, accelerates well with a
good handful and has a good top speed should always cut out when the throttle is opened a fraction off
the throttle stop? The carb is on a standard setting with a good plug and ignition.
# 6303 blocked idle jet?
# 6304 Sounds a little weak - is the slide worn?
# 6307 Try raising your needle one or two notches! douglas.
# 6308 Try a bigger pilot jet. If it wont start anymore then the pilot jet is too rich, go back one size and
that is the right size. Pick up should then be clean and responsive.
# 6311 Go back and review the AMAL tuning instructions and study the pictures. Throttle openings up
to 1/8 = pilot circuit throttle 1/8 to 1/4 = cut-away 1/2 - 3/4 = needle position 3/4 to full = main. If the bike
starts fine and idles well, the problem is the transition between the pilot system and the slide cut-away.
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The four metering circuits in the carb have a slight transition from one circuit to the next. I.E., the pilot
does not stop its control exactly at 1/8 throttle, it simply diminishes its effects as the cut-away begins to
take control. That being stated, you can make a small correction to the pilot mixture to help the
transition to the cut-away. Assuming an AMAL, Monobloc, Concentric, or Standard, with carb settings
including size of cut-away specified for your bike, alter the air screw 1/8 turn increments to see if the
condition can be corrected. Small patient changes are encouraged only after the bike is fully warmed.
L # 6349 I have just bought a Viper 1960 model one owner it looks as if all the right bits have
been looked after the only thing I am unsure about I get a bit of pinking under load and I am wondering
if this can be caused by the concentric. I have plenty of 376 carbs and wouldn’t mind going back to one
of those but I am unsure what to expect of the Viper it seems to want to be revved not as mellow as say
a MAC, also how can you tell a Venom top end from a Viper without stripping is it possible?
# 6352 First, make sure you are running a high enough octane rating fuel - Super Unleaded at least,
either Shell Optimax or BP Ultimate being my preferences, NOT Premium Unleaded under any
circumstances. LRP is a poor substitute and should be avoided. Have no worries about using Unleaded
in a Velo - the valve seats were almost made for it! A little bit of pinking is almost inevitable and could
be tuned out by richening up slightly in the throttle region in which it occurs, but I find usually that by
opening the throttle a little further it usually passes through the affected region. I really wouldn't worry
too much about the problem so long as it is only a bit of pinking (or audible knock, as it is commonly
known in automotive engineering parlance). Dropping a gear so the engine is revving a little harder with
less load is another way of getting past it - no engine likes being slogged in a low gear with high throttle
openings and I believe the Viper is no exception. A Venom has a 1.2" or 30mm (approximately) bore
inlet port - someone please correct me if I'm wrong, but I suspect the Viper port will be significantly
smaller, perhaps around 1" to match with a 376 carb..
#6355 I have just put a new concentric on my Viper as the old one was worn. It is a 26mm, has a 210
main jet, 25 pilot, 3 1/2 slide(although the book reckons a No.3) and the needle is in the central
position. I get no pinking at all, but admit I am running Super unleaded.
# 6358 The easiest way to spot a Viper is that the cylinder studs are fully exposed for five fins on a
Viper and only the last fine on a Venom.
# 6381 Thanks for all those kind souls who sent in their suggestions in answer to my bike's problem of
cutting out when I just opened the throttle a small amount. I tried them all, but it turned out to be broken
and perished O-rings on the throttle-stop and mixture screws, simple when you know how. The moral?
try the simple things first.
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A.2. Poor Gear Change -
L #3 I have a 1969 Thruxton which is very difficult to change from 1st to 2nd gear.
#4 Having just stripped and reassembled my gearbox ten times to try to eliminate a non-returning gear
leaver I have become very familiar with the selector mechanism. Firstly I would suggest you try to
isolate where the problem lies i.e with the selector mechanism or with the sliding gears and dogs.
Firstly reassemble the gearbox with the selector mechanism only i.e. camplate, forks, rods, etc leaving
out the gears. Use a new gasket but no jointing compound and just three bolts. Try the mechanism to
see if the fault is with the selector mechanism. If all is OK, just add the layshaft and associated gears
and try this. Then try it with just the mainshaft and associated gears. Hopefully by now you may have
isolated the area in which the problem lies. A few tips on the selector mechanism, I compared three
different camplates and the notches were a different form on each. On two of them they looked as if
they had just been quickly ground out on a hand grinder. With an oilstone make these notches a nice
smooth transition, I found you could safely “round” the edge of the notch to half depth. While the cam
plate is out just polish the circumference with the oilstone. Saying all that I don’t think the camplate is
your problem, as you have tried two different ones. Next look at the striking pawl GC23/2. Two possible
problems here. This may make contact with the cam plate pivot on full travel, stopping the cam plate
from fully engaging. The solution is to grind a small amount from the hole, making it slightly larger at the
contact point. Next culprit could be the centralizing lever BK99/2. The solution is to grind a little from
either side of the crescent shaped cut out i.e. having done that you may need to grind the back of the
crescent to maintain clearance.
L #786 Rebuilding a '69 Velo Clubman I've had an early introduction to the wondrous clutch. Took
it apart, fitted new inserts, and put it back together again. Great, except that tightening everything up
now leaves the clutch springs almost fully compressed with no movement to allow the clutch to
disengage. I've read all the technical notes on the web, pulled it apart ten times, but still no joy. As best
I can see, relining the plates should make no difference. The sandwich of plates is no doubt thicker, but
the spring holder is independently adjustable to accommodate this. What happens when I try to screw
the sleeve nut on is that the springs compress until they are virtually bound (i.e. about 20 mm) before
the sleeve nut can tighten against the boss in the back plate to secure the clutch assembly. Winding
the spring holder further in simple presses it against the thrust pins and starts to disengage the clutch.
Incidentally, in case it might be relevant, the chain wheel is well out of alignment with the engine
sprocket. The wheel would need to be 4-5 mm closer to the gearbox for alignment, although the tooth
wear suggests it's been running out of plumb for a good while. All very odd. The clutch was together
and operating properly before disassembly and only the spherical thrust washed has been renewed,
because of pitting.
#787 Sounds like you have fitted the chainwheel, back to front?
#800 Many thanks for your reply. It would certainly put the chainwheel in alignment, but unless I've
misread every reference I can find, there are four plates between the back plate and chainwheel, and
only two plates between chainwheel and front plate (which is why the chainwheel has a shallower rim
on this side). In other words it's not possible to fit the chainwheel back to front.
#803 I think you've misread the references. There should be two plates between the backplate and
chainwheel, and four between the chainwheel and front plate. The later clutch was (as is normal with
Velos) a development of the earlier clutch whose basic design was the same, but which had two fewer
plates. These were added on the outer side of the assembly to cope with the extra output of the later
engines, but without having to change any more components than necessary, so the inner side of the
clutch remained the same with only two plates and the original chain line was kept. The shallower rim
therefore fits to the inside (towards the backplate). Contrary to what you say, it IS possible to fit it the
wrong way round, but you would also have to stack the plates wrongly too. One other thing to watch for
is that the bend on the tabs of the plates is in the right direction. From the top of my head and without
reference to the books, the bend is away from the chainwheel on either side. Should be obvious with
25

the bits in your hands - things will touch if you get it wrong!
#805 Who has misread the references? With backplate fitted to a disused sleeve gear held in the vice.
And quoting directly from the red book: "Fit the first clutch plate in position followed by a spacing plate,
second clutch plate and second spacing plate. Note that the external tongues on the clutch plates and
internal tongues on the spacing plates must all point away from the chainwheel, i.e. downwards." It
goes on to say centralize all the plates then fit the chainwheel with the deeper slotted rim underneath. It
continues "With the chainwheel fitted put on the third spacing plate and clutch plate in that order and
with their tongues pointing upwards." It says centralize the plates and fit the front plate. Personally I
agree with Chris Wood and message 787.
#816 Sorry everyone, I stand corrected. Just checked the books and Tony is of course correct. That'll
teach me to jump in feet first without checking my facts! Can't see how the chainwheel can be fitted
back to front with all the plates in the correct order though. The only other thing I can think of is that the
plates have become displaced during fitting to the sleeve gear splines.
#827 Are you sure you haven't fitted the thicker 7 plate inserts in error?
#829 Many thanks for your suggestion. The inserts I've used came with the bike, amongst a batch of 25
year-old spares. I soaked them in oil to soften them and fit them more easily. Maybe they've swollen?
They are about 9/64ths thick, say 3.5 m.m. Forgive my ignorance of the 7 plate clutch. Do my inserts
sound like the wrong ones?
#833 New VM style inserts are 1/8" thick. The earlier type are close to 3/16". Is it possible that when
you put the clutch back onto the sleeve gear you forgot to fit the loose sleeve on the sleeve gear first?
Maybe also, even though you used the old one, is it the correct nut? They came in two lengths, the
longer one being used for the 9-plate clutch. Are you using the correct length pins for the release
mechanism? Or did you use 'new' big-end roller without shortening them?
L #4006 Why does my venom jump out of first gear just after setting off ?
#4007 I would guess that the engagement dogs have rounded off somewhat after countless clonks into
first. The same happened on my thruxton after 27000 miles. The cog material proved too hard to
re-dress with tools available to me at the time and was regretfully remedied by a new pair of cogs.
#4008 It is also possible that the dogs are not fully engaging. This situation would also, over time,
promote rounding off of the dogs as previously described. A lack of full engagement can arise from
several factors [or a combination of these factors]. Having now rectified a similar situation, I
encountered the following: 1) worn shifter fork faces; ii) the figure-8 shaped hole in the actuating lever
internal to the transmission needing to be ground slightly at its extrema, thus allowing the cam plate to
fully rotate to the required index detent; iii) the camplate indexing pawl having it's point worn off so as to
not accurately engage the detent with the necessary force and/or precision; and iv) excessive wear in
any part of the camplate ratcheting pawl, the pin that drives it, or the indexing hub itself. Polishing the
edge of the camplate results in smoother and more precise shifting.
#4009 Another possibility, on older boxes the 1st gear cog could get knocked along the bronze bush
after years of clunking into bottom, thus reducing the depth of engagement of the dogs. Later boxes
overcame this by having a 2 piece bush, pressed in from either side.
#4010 Your first gear is located by it's bushing too close to the right side of the box, allowing only partial
engagement of the sliding dogs moved by the shift fork. The fix is to make up a new pair of flanged
bushings for the gear with a thicker flange on the right side (or a one piece bush that is a press fit in the
gear with that thick flange on the right ) such that the gear will allow full engagement with the dogs. This
flaw was widely discussed in the English Fishtail some years ago and I remember the recommendation
being made that the gear should be moved left by .055". Sounds arbitrary to me. Every gearbox that I
26

use gets shimmed as tightly as I can do it such that the outer gears on both sides of the sliders get the
most engagement possible and so that the sliding rings or gears engage equally in both directions.
British boxes were all designed with 'assembly tolerances' which can be usefully closed up for more
precise engagement, and the VM/MSS box seems to have had the first gear flaw designed in.
#4011 I hope you did not scrap those gears. After a similar experience with my Venom: jumping out of
gear on drive then eventually jumping out on coast, I had to stop holding the gearchange pedal with my
toe and do something about it before my selector fork was worn away. Not only were my 1st gear dogs
rounded off; some amateur mechanic had tried to hand grind them straight again - bad news. I was
guided to an engineering firm that could cut the dogs back until the rounded part was removed then
re-harden the faces; ditto the sliding gear that the first gear mates with. They used a spark erosion
technique and they ensured that each drive dog was cut back to the same angle. Otherwise, the drive
load would have been unevenly spread between the dogs, with the prospect of consequent failure. The
'one off' charge for this work was prohibitive but, between us, a friend and I managed to find four sets of
gears which required salvation. This brought the cost down to £60 per pair of gears. At first, I thought
that the thinned down dogs might shear but after comparison with the simple round pegs/holes on the
first gear of an AMC box, one of the toughest in the business, I had no worries. Increased backlash was
indistinguishable, no doubt because it was insignificant compared with that already in the gearbox,
primary and final drive chains. Between us, we have ridden 5,000 miles on these refurbished gears with
no problems.
#4013 Had this problem years ago on my thruxton. The dogs were rounded as expected. Careful
undercutting with an angle grinder did the trick - never jumped again.
L # 4989 The gear change peddle on my 1956 Venom type 12 box would not centre after every
gear selection resulting poor to no gear selection. Easing the rear cap bearing on the selector pivot
shaft (it runs across the top inside of the gearbox end cover) immediately restored free movement. I
fitted a thin fibre washer "shim" to keep the cap out the necessary amount and the box now works fine.
# 4990 During a rebuild of my Venom it was pointed out by someone wiser than me that the incorrect
shorter camshaft followers had been fitted.
L # 5144 Can anyone shed light on the problem of false neutrals, usually when going up the box.
The problem manifests as not getting the next gear, and usually staying in the presently selected gear.
The problem is cured by lightly tapping the gear lever in the opposite direction and then having another
go. All 'slap' has been taken out of the linkage and the "big bore" pipe replaced with one of smaller O.D.
(in case the pedal was bottoming out on the pipe before the next gear was selected). I have replaced
the ratcheting pawl, spring and cam plate central boss with new items; although there was no visible
difference between the new parts fitted and the parts removed.
# 5148 Sounds like your pedal is not returning fully to the centre position between gear changes. This
can be caused by a weak return spring or by something in the operating linkage being too tight. You
mention that all the slop has been taken out of the linkage, this might be your problem - you've
tightened things up just that bit too much! Otherwise, if the problem occurs only when going up through
the box it could be that the previous gear change isn't pushing the cam plate fully into gear. This could
be accounted for by insufficient clearance between pedal and exhaust at full depression (but you say
you've checked this) or by something fouling inside the box. I replaced the bent tin link inside my box
with a pair of rose joints, but these did need slight modification to ensure they didn't foul the case during
operation. Might be worth checking? If you've used rose joints you should be using the bronze bushed
type. The fibre or plastic bushed ones really aren't suitable for this application and also could be
causing your problem by having too much drag. Make sure all your joints are free and smooth running,
without any slack, for the best operation.
L # 5525 This morning I took my thruxton out for a run round, it being a nice day and an
opportunity to start running in the new Avon tyres I have fitted. All went very well until turning into the
27

oad where I live, I changed down into first gear and there it remains, it refuses to change up at all, I
cant even select neutral, engine running or stationary, only way I can move the bike is by pulling in the
clutch. I have tried rocking the bike backwards and forwards in gear and trying to select and upward
change of gear all to n o avail. Disconnecting the linkage I find that I can move the gearbox lever arm
backwards from the vertical but no movement forward of the vertical. It feels absolutely solid trying to
move the lever forward and I have no wish to use force or damage anything. Can any of you guys out
there help?
# 5526 Although you'll probably get better advice to follow - so hold on a bit, but if it were me I'd have
to strip the box to examine the internals - linkages, strike plates, pawls, camplate, selector forks etc.
Although you may free it off without stripping the box, there's something in there not quite right and it's
a bit of a pain if it sticks again (or worse) when you're out on a run. I know it's a real pain to have to do
this at this time of year, but It's not a bad job. The box can be stripped whilst still in the frame, it can't be
to difficult as I've managed to strip and re-build the box before now.
L # 5628 I thought that one could only get slip and drag from a lack of free play on the clutch
cable: i.e. with the operating mechanism "partially operating" the clutch (through no cable free play) and
the spring carrier wound up tighter to compensate. I however, have a clutch slipping under the modest
acceleration of a running in Thruxton and yet dragging so much that it stalls on engaging first - one has
to set off down a hill and keep moving. I have free play in the cable when measured as it exits the top
of the box. Notching up the spring pressure to cure the slipping will surely make the drag worse - even
when I take the extra cable play that will result. I am a little stumped. The bike has only done 90 miles
in this incarnation and has just come back from Goodman Engineering with "one of those new clutches
c/w 20 spring carrier". Will it improve with a bit of bedding in or am I missing something? Kind regards
in anticipation.
# 5630 Suspect you may need to adjust the clutch TO THE BOOK several time to clear this as
everything is so new.
# 5640 Did you check that the plates were not buckled? If you fitted new friction plates with insert
(rather than the bonded type) then it will tend to drag until they wear in. The slightest drag will make
first gear hard to engage, a good blip of the throttle does help by making the clutch spin and "free up" a
bit then a good press on the0 gear lever. The "slipping" clutch makes the plain plates heat up and
distort making the drag even worst so you should adjust the clutch to stop the slip. Think about bonded
plates and chainwheel with the new slotted plain plates if your problem continues, they are not too
expensive and I found themn well worth it to get a clutch that works nicely.
28

A.3. Faulty Electrics -
L #1 I have a Viper which has no battery connected - it has 6V electrics and a Lucas E3L
Dynamo. It has a LUCAS regulator - on the mudguard - although not taken this apart to see if std or
something like JG conversion underneath/ How do I know whether to use positive or negative earth -
some manuals say negative some positive - any tests before connection? If I get it wrong and run the
bike - what damage if wrong polarity - could I be looking at? If the battery is connected and the lights
turned on - I assume ammeter would show '-' when lights on if right way round - if connected wrongly
'+'? is this feasible? Anyone know a source ok KIF magdrives - are these fibre or steel?.
#2 You've worked out the best quick test - checking which way the ammeter swings. However, if you
have an electronic regulator then it can indeed be damaged if you connect up the battery the wrong
way round. So either look into the "Lucas" regulator can or simply disconnect it for the test. Another
way, if the ammeter had been disconnected, is to see which direction the dynamo motors in; but that
takes longer and isn't 100% reliable. Or the colour coding of the wires will indicate what it was
originally.....but an owner may have reversed everything. It depends if you have an autoadvance unit or
manual. If manual, it is a simple steel wheel. The Owners Club can supply top-quality drilled and
lightened versions of these. If autoadvance it originally was fibre, that could strip, so steel conversions
are available. I believe Dave Lindsley has everything for K1F magnetos, he's at 0706 365838 196
Pilsworth Road, Heywood, Lancs OLI0 3DY
L #724 If you have ignition trouble, make a two foot stick with a small damp sponge attached to
the end and also a wire between the damp sponge and the other end of the wire (grounded) with a 12
volt neon lamp somewhere in series. Start the bike and slowly wipe the HT lead from pickup to spark
plug cover. Any flashing of the neon lamp indicates a crack or leak and the whole assembly should be
replaced and reevaluated.
L #3305 Hi I need help please how do I check to see which part of the charging system is faulty,I
have a 1955 MAC with a Miller dynamo 36w and a K- tec regulator, the label on it states that it is a
(K-tec dynamo reg +ve earth 199931006p) the battery is a positive earth and all the lights work when
battery has been charged.When the the lights are on the ammeter shows an approx 5amp discharge.
With the lights off and the engine running the ammeter does not move, with the lights on and the
engine running the same 5 amp discharge, all relative connections have been checked.
#3349 This may get long-winded but I will do my best! The first thing is that the K-Tec is designed for a
lucas dynamo, but don't despair, the miller dynamo is fine but needs to be modified. The cut-out under
the cover needs to be removed, and the resistance windings are not required. One end of the field coil
connects to the brush that is earthed to the body, the other end becomes the 'F' terminal. The other
brush becomes the 'D' terminal. Assuming this has been done, remove the drive belt, and the wiring
from 'D' & 'F' to K-Tec. With another length of wire, join 'D' & 'F' on dynamo together, and touch it briefly
onto the -ve battery terminal. The dynamo should motor in the direction that it will turn on the bike, ie
anticlock looking at the pulley. If it does not motor there is a problem with the dynamo, possibly you
have connected the resistance coil, not the field coil. If it turns in the wrong direction, simply swap the
two ends of the field coil. Motoring the dynamo like this will ensure that the residual magnetism is
North/South the correct way round, (possibly all that is wrong with your setup). The dynamo is self
exciting, that is that a small voltage is generated by the residual magnetism in the dynamo body, this
voltage is fed back into the field coil which makes the body more magnetic, which generates more
voltage which makes the body more magnetic etc etc ... the regulator simply cuts supply to the field coil
when the output reaches the required level. If so far all seems OK replace the belt, connect the wire still
on 'D' and 'F' to a sacrificial bulb (the good 1/2 of and old back light bulb) the other side of the bulb to
earth, and start the bike and rev it quite hard, when the now unregulated magnetic runaway starts, the
bulb will light, and almost certainly blow the other half of the bulb. This will prove conclusively that the
dynamo is ok and that the fault is elsewhere. Check all connections, and that the K-Tec itself is
earthed.
29

#3358 Have done as you suggested and dynamo motors in an anti clock wise direction. I have also had
an output from it and a system output but the charging is intermittent.....I have a field resistance of 4.6
ohm's I have hard wired the k-tec to earth on the battery which is +ve earth. I've come to the conclusion
that the k-tec is shot.....will try to get another one. Do you know who makes them, also is they a way of
testing the k-tec to prove it functionality.......
#3361 Sounds like your reg may be shot. I don’t know where you would get another K-Tec. A few
people I have spoken to don't rate them too highly, but I have no personal experience of them. I have
got V-Reg units on 2 of my bikes and (touch wood) have had no problems. They are available pos or
neg earth, and can be made 6 or 12 volts. I got mine from AO Services. 01953 884681.
L #3872 I switched the sidelight on and smoke appeared from headlight shell. The brown/white
wire cover from the light switch appears to have melted slightly. I do not know where to start looking for
the fault. Brake light and horn work. Any advice greatly appreciated.
#3873 Tracing an electrical fault in a vintage motorcycle or car is a comparatively easy task, -
especially if there has been smoke & a melted wire ! treat the problem as if the electricity is water
running through a pipe, (the wires) - smoke /melted wire equals a leak somewhere to the frame/tinware
of the machine, - that is where the water is running out on to the 'ground' Work away from the ammeter
power source, in this case it has come as far as the main switch without problems, - but somewhere
from there on, & PAST the melted wire, there is a 'leak' to ground, (earth) most probably a wire rubbed
bare or even a wire broken & fallen off a connection & sitting on the surrounding metal work. In your
problem it has to be somewhere along the 'side light' (?)/ taillamp wiring, but there is also the possibility
that an instrument panel illuminating globe, (speedo, ammeter illumination etc.) has a wire touching
metal . If you have been 'servicing' your machine in a major way immediately before the 'fire' occurred,
go straight to where you have been working, it quite often happens that a wire gets 'pinched' under a
bolt head, or between 2 adjoining pieces of metal work, - this happens all the time ! Circuits
(waterpiping) vary, & in quite a lot of cases have been modified over the years to the owner's choice &
extra fuses installed, but certainly not in your case, as a blown fuse would have been the result instead
of the outpouring of smoke. One would have to conclude that you are not proficient in the use of an
electrical 'multi meter' tester, but certainly in your case, a pair of good eyes should solve the problem !
let us know the result
#3896 Thanks for the advice. The problem was on the tail lamp wiring, under the tank, not in the
headlight where the smoke was coming from and where I was looking. I insulated the bare bits of wire
in headlight and still had a problem. I had forgotten about the tail light being on the same circuit. I
insulated a wire under the tank and the system seems ok now.
L #3904 My dynamo won't charge, it was o.k. till couple weeks ago and just suddenly stopped
charging, I sprayed the rotor with WD40 and it started charging again for 2-3 miles then stopped again
sprayed WD40 again and it charged again did this several times then stopped charging completely, I
fitted new brushes and it worked ok for a few minutes then stopped charging again, any ideas what it
could be? I have recently had a transistorized regulator fitted as it was over charging I have checked all
of the connections and they are sound.
#3906 Dave, make sure that the commutator is clean (rub with fine emery cloth and rinse w/contact
cleaner) and that the brush holders are smooth and clean inside. If playing with the brushes helped,
that's probably it. They are probably just sticking. I wouldn't blame the regulator. My 60W Lucas has
done the same thing. Stuck brushes.
#3907 It's better to use sandpaper because emery is metallic! Well, that's what I learnt when I was an
apprentice motor-fitter.
#3912 I concur with Tom. If I don't use the Venom for more than a couple of days I always have to take
off the dynamo end cover and "waggle" the brushes, WD40 helps. When I use the bike every day I
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never have the problem.
#3909 First thing to check is whether the dynamo motors when connected across a battery? If it does,
then the problem is almost certainly not with the dynamo. What sort of electronic regulator have you
fitted? That would be my first suspect! Is it a Miller or Lucas dynamo? I don't think WD40 would be
good for the armature.
L #4813 I Have put new bearings in and new brushes and eureka the dynamo's charging again 10
miles later it's stopped charging. Running it with out the end cover there is no arcing around the
brushes(it is going round) no movement of the ammeter.It has a good battery fully charged am only
measuring 0.52v+ at the field and output terminals with the engine above tick over ...as this is a bike
that is in daily use any suggestions on the best way to go for the least amount of pounds would be
greatly appreciated.........
#4815 In order of probablity.. are the brushes free or have they jammed? Is the wiring in good order? is
the regulator OK? Try 'motoring' the dynamo - if it goes OK then its almost certainly OK. 0.52 volts
seems a bit low - if you've got an electronic regulator this may not be enough to fire it up - transistors
need at least 0.7 volts. Give the engine a really good blip ( 4000+rpm) and see if things burst into life. A
bit of detective work required!
#4816 Dirt on the commutator? Are the brushes contacting? I would see if the dynamo motors and/or
disconnect the dynamo from the regulator and see what voltage you get to earth. If the battery is fully
charged then you shouldn't see any current at the ammeter unless you turn on the lights or depress the
rear brake pedal.
#4817 Hi, If it passes the motoring test, I would also try leaving F and D connected together (as for
motoring test) and ,without the regulator connected, run the engine and measure the output wrt to
ground. There should be a sudden increase from near zero to 6volts or more as revs go up to say
1500-2000. Dont exceed this rpm or do it for longer than it takes to get a measurement or you could 'fry'
the dynamo. Also I find that an 'old-fashioned' moving-coil (needle) type meter is best as the
electronic/lcd meters often respond to all the interference from the ignition and commutator sparking
and you cant get a meaningful reading from them.
L # 4813 I Have put new bearings in and new brushes and eureka the dynamo's charging again
10 miles later it's stopped charging .Running it with out the end cover there is no arcing around the
brushes (it is going round) no movement of the ammeter. It has a good battery fully charged, I am only
measuring 0.52v+ at the field and output terminals with the engine above tick over ...as this is a bike
that is in daily use any suggestions on the best way to go for the least amount of pounds would be
greatly appreciated...
# 4815 In order of probability: Are the brushes free or have they jammed? Is the wiring in good order?
is the regulator OK? Try 'motoring' the dynamo - if it goes OK then its almost certainly OK. 0.52 volts
seems a bit low - if you've got an electronic regulator this may not be enough to fire it up - transistors
need at least 0.7 volts. Give the engine a really good blip ( 4000+rpm) and see if things burst into life. A
bit of detective work required!
# 4816 Dirt on the commutator? Are the brushes contacting? I would see if the dynamo motors and/or
disconnect the dynamo from the regulator and see what voltage you get to earth. If the battery is fully
charged then you shouldn't see any current at the ammeter unless you turn on the lights or depress the
rear brake pedal.
# 4817 If it passes the motoring test, I would also try leaving F and D connected together (as for
motoring test) and, without the regulator connected, run the engine and measure the output with
respect to ground. There should be a sudden increase from near zero to 6volts or more as revs go up
to say 1500-2000. Don’t exceed this rpm or do it for longer than it takes to get a measurement or you
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could 'fry' the dynamo. Also I find that an 'old-fashioned' moving-coil (needle) type meter is best as the
electronic/lcd meters often respond to all the interference from the ignition and commutator sparking
and you cant get a meaningful reading from them.
# 4834 I would suspect you have a 'dry' joint somewhere. John
L # 6325 Hello, for the last couple of weeks, my electrical circuit has been going crazy. I've
blown two rear bulbs, and a couple of fuses isolating the battery, and every time that happens the
engine labours massively: I guess either the alternator loads up the engine or the electronic ignition
(Rita-type?) system doesn't like having the battery out of the circuit. Anyway: I've gone over the whole
system and there's no shorts anywhere, so I checked the voltage, and it's reading almost 17v at high
revs. This means the regulator's failed, yes? So, expecting it does, I've been searching the interweb for
help identifying this regulator, and I've drawn a complete blank: My velo has a belt-driven alternator
(unbranded, unidentifiable), and a regulator mounted under the seat with 'repco' cast into the aluminum
casing. The contents are sunk into epoxy, on the underside and it's secured, off the rear mudguard, by
two bolts (one at either end). The casing has shallow heat fins on it. There are three spade
connections: AC, Output, and AC (that order). There are also two insulated nut and thread fittings on
the top which are continuous with the AC connections. I've seen pictures of Lucas, Podtronics, JG,
V-Reg II, and Boyer Powerbox regulators, and it aint none of them! The previous owner fitted this
system, so I don't know what it is. Ideally, I'd like to replace it, like for like, so as to spare the rear
mudguard from my drill-bit. However, I wonder if it would be acceptable to merely fit a zener diode
between the output of this device and the bike? The rectifier in this unit obviously works well enough.
Any suggestions appreciated.
# 6329 I missed the reference to the blown battery fuse. Sometimes an older battery will short out cells
from sulphide accumulation, I would still try a new one before blaming the regulator. Also some Yuasas
had a documented problem with bad internal welds, an intermittent contact could also produce current
spikes that would blow the fuse. That said, my old Ducati 350 (now there's an electrical system that
made Lucas look mil-spec) ended up with a home made rectifier - two diodes in a half wave
configuration, and a zener from a H---a 450 twin. It worked.
# 6330 I'm already on that track! I bought a new battery, but that failed totally, at speed! (with engine
braking problems thrown in, so it wasn't drivable) Just went from full charge to zero in a second: must
have been a contact breaking inside... Luckily a seven year old kid sold me a yb9 there and then. I
don't even want to know why he had one of those... this was in east london. I'll cary a large capacitor
about from now on, to get me home! Would that let you start a bike with no battery? Few swings to
charge it... So I exchanged the failed one, and the replacement is sitting in the hallway charging right
now, and will go on tomorrow evening. You reckon 17v is acceptable in the charging circuit with a fully
charged battery at high revs, then? I'm no electrical engineer, but I reckon a 20a 12v fuse can take
240w. So at 17V, this is 14A...Yes, I don't think my circuit's putting this out (ammeter goes up to about
+9 at really high revs, although I don't rev it that hard very often. I guess it's within the realms of the
possible...), although it's always a good few miles into a ride the fuse gives out (like 40-50), so it might
be a cumulative load/melt type problem. Also, I'm a little worried this might have had something to do
with the battrery failing: too high a charging voltage? I don't know. I'll put the new battery in, test the
voltages up to max revs, and if this is okay (17V?), I'll go over the harness again, trust the regulator,
and assume the blown battery fuses must be due to a short somewhere. Damned if I know where,
though...
# 6333 I would not be happy with 17volts, 14.5-15V would be more acceptable. If you are getting up to
17volts then maybe you should look towards the Zener, if you have a high output alternator you are
normaly expected to use two Zeners in parrallel to keep the voltage to more acceptable limits. Just my
thoughts.
# 6389 Quite agree - 17v will boil the battery a treat - and blow your bulbs when the battery is dry. The
zener approach is terribly wasteful - even if you're using no power you're dumping 120 or 150 watts in
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the zeners as heat - and using 1/4 horsepower for the privilege.
# 6390 I now have an external zener in addition to the one integrated into my regulator, and
everything's a lot happier. 15V in the charging circuit, and the zener's not too hot. Whilst some people
might tune their engines to get that extra 1/4 hp, and bolt anything on in order to get it, I'm pretty happy
with a working, reliable bike. The only bits that can't break are them wot aren't there! Besides, I can't
believe this drains more power than a V-belt, dynamo, and mechanical regulator.
L # 5025 After trying to get the band chaincase on Dad's 53 MAC to seal and painting a couple
of parts, we put everything back together, once the clutch was adjusted correctly it fired up well and
everything is working properly except the charging. The generator was not apart except the end cap
was changed for a better one. The D and F wires were hooked up in their correct positions, but there’s
no charge. Is there any way to check the voltage coming out of the generator with a multimeter? Or
does anyone have any other suggestions?
# 5027 Have you tried polarizing the dynamo? Long piece of wire. One end on the live battery terminal,
touch the other end to the dynamo body (you should see sparks). Just a quick touch. You can check
the charging by taking the D and F connections out of the end plate. Insert two wires and connect the
other ends together and attach to one side of a voltmeter. Earth the other side to the bike frame or
battery and start the bike. If you are charging you will see a voltage. An analogue voltmeter is better
than digital one for this test.
# 5036 Are you sure? ( "Have you tried polarising the dynamo? Long piece of wire. One end on the live
battery terminal, touch the other end to the dynamo body (you should see sparks). Just a quick touch.")
I agree you certainly will see sparks, you will be shorting out the battery! You would be better off
"flashing it" on the F tag, thereby energizing the field coil and restoring the residual magnetism in the
field.
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B. The Engine
B.1. Bottom End and Crankcase -
L #198 Tony described the correct way to fit an oil seal to stop oil exiting the main bearing – now
I will describe a “bodge”, that a fellow club member used to fix the same problem. Clean the inside of
the sprocket with alcohol or some other solvent, place a circular bead of silicone around the part of the
sprocket that abuts the main bearing boss. Smear light oil on the main bearing boss, slide the sprocket
on and rotate at least one revolution. Lightly screw on the shock absorber, spring and nut. Leave it for
24 hours, before reassembly.
L #264 What methods have members of this group used to overcome slack oil pumps in
crankcases? I have just come across this with an engine I am building out of autojumble parts and I
am thinking of having the main oil pump body hard bearing chromed, anyone any comments .
#281 The only method I have come across but never used, is to sleeve the crankcase – a skilled
engineering job.
#364 You can use grinding compound on a plate glass plate to remove the wear on the oil pump base,
but I would expect a surface grinder to do a more efficient job. The only other problem I could think of,
was if the pump was slack in its bore then when the crankcase warmed up the differential rates of
expansion may allow air to be sucked into the pump. However I feel this would be unlikely.
L #369 Anybody know how to get the flywheel off a two stroke? The engine freed off in my U last
night, but that now means I can't lean on the stuck piston to undo the flywheel nut. My reading of the
engine section drawing on www.Velocetteowners.com is that the nut acts as an integral puller - or am
I way off the mark? Also discovered that the Mag appears to have automatic advance - hence no cable
for it. Despite standing for 50 years it still gives a (feeble) spark.
#370 I am not familiar with the model U but I did own a GTP. I believe the nut is separate from the
pulley/flywheel/sprocket assembly. If the engine is in the frame and the transmission is still intact, try
putting it in gear and applying the back brake while trying to remove the nut. It may work but no
guarantees.
#380 Thanks for the reply. I discovered that the pulley was just bolted onto the flywheel - a home mod I
think! The nut does however act as a puller for the flywheel, and I was able to both undo the nut and
break the taper fairly easily by jamming the crankshaft against the conrod with a block of wood.
Unfortunately I think I moved the flywheel round, so now have no idea where the Mag was timed at,
but I am sure there must be a fairly easy way to re-time it when it comes to rebuilding the engine.
#512 Here's my nightmare, from yesterday, which began when I followed the 'red book' instructions for
fitting the oil pump back into the crankcase. "Heat up the case around the oil pump housing using a
blow torch." Heat up? How hot? The BMS manual talks about "considerable heat". How considerable? I
broke a corner off the oil pump's cast iron base plate, by hitting it off axis with a hardwood drift while
trying to drive it back into the housing. A Good Samaritan, an old-time Velo expert, took pity on me,
heated the case, withdrew the pump, cleaned up the abuse, replaced the base plate and refitted the
whole thing. Now I know, having watched him, what considerable heat means. Blowtorch? Propane
gas flame? Forget it. He used a 'cool' oxy flame. Here's the drill as I'd now write it. Heat the crankcase
until it will easily char-grill a thick fillet of steak in thirty seconds. Continue heating until it is barely
possible to remain in the same room as the crankcase. When the sound of racing fire engines can be
heard, and the jaws on the vice are starting to melt, drive the oil pump into the housing. If it doesn't
drop in with one gentle tap, you need more heat. Iif the manuals had hinted at the very considerable
temperature needed, and given the hint that very little force is needed to insert the pump when the
temp. is correct, I might have saved myself a lot of grief and my mate a lot of time.
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#523 I can't remember where I learnt it from, but the answer to "How much do you heat the crankcases
to remove the oil pump or main bearing races" is an easy one. You can use any reasonable heat
source from plumber's blowlamp through to an oxy-acetylene torch - nowadays I've found that a good
electric hot air gun works well with a little patience. Heat the case until spit sizzles off as soon as it
touches the metal and the pump or race will drop out or in perfectly. I've used this method as a guide
for many years and it's never failed yet. If you don't get the cases up to this temperature you will really
struggle to move either component.
#525 Regarding heating crankcases, I wait for my wife to go out for the day and use the kitchen oven
when rebuilding an engine. The RHP catalogue says, “Do not exceed 120 degrees C or the bearing
hardness will be effected.” I have found elsewhere that the maximum temperature is 160 degrees C. At
this temperature the bearings knock out when brought down sharply on a piece of MDF and the pump
slides out of the bore with a very gentle tap. Ralph Seymour used soap turning brown when rubbed on
an ali head to indicate the right temperature for fitting valve guides.
L #513 Throwing my Venom engine together at the last minute before the rally, I finally got in a
test ride the day before the start and half way to Washington. Got it hot and realized I didn't get the
preload right on the mains and could wiggle the crank when hot. Damn! The bike was noticeably
smooth though, smoother than I'd ever recalled it being. Just rumbled a bit at idle. I had all but given
up on using it for the rally then suddenly came up with a bodge extra ordinaire. With it still hot I pulled
the primary and drilled 3 holes in the case around the periphery of the outer race and tapped it in with
a punch. I was then able to slide a .002 feeler gauge between the race and the case, so it moved in
about that far. I squirted some green loctite in the gap, tapped the holes for 8-32 set screws to butt up
against the race, went to bed and prayed. The bodge worked great but I noticed right away the engine
felt rougher. Paul D'O told me years ago that his tapered main Velos always felt rougher when cold
then smoothed out when the cases heated up. I wonder how much the .004 spec pinch on the crank
affects smoothness. I suspect I may have preloaded my mains even more with the bodge. Also was
told by longtime Velo guy Dee that the tapered mains are very forgiving and I probably could have just
left it alone for the rally.
#518 I have to say it's brilliant clever, but I would have done it with the engine cold if I had the nerve to
do it at all, then you have a better idea of what the preload is relative to the standard. How did you get
a feeler gauge in there? But on the subject of preload on taper roller mains, I think they are indeed
very forgiving. If you read the Bible of Bodges, i.e. the compendium of tech articles, there are stories of
everything from zero to 12 thou preload on the taper rollers. The fellow using 12 thou reckoned his
engine was extremely smooth! Go figure. All I know is that when I set up my VMT mains 13 years or
so ago, I went according to the book with no problems to report so far. And re cush drive taking out the
drive side mainshaft, it's too bad the factory didn't use the KTT style cush drive which sits on a taper
and doesn't pull on the shaft at all. All those years of hammering/pulling away on the shaft can do it no
good. And re torque and oil on the threads; how on earth do they stay together at all, knowing all the
ways in which it's possible to get it wrong. Perhaps ignorance is bliss after all..
#522 I've had both of the problems mentioned here at different times in my Venom's life. The drive side
mainshaft pulled out of the flywheel not long after I'd had the big end replaced by an engineering firm
who I suspect didn't really know what they were doing. This can be rectified permanently by pressing
the shaft back into position, making sure that the breather holes line up and are clear, and fixing the
shaft in position by a spot of weld or by pegging the joint. So far mine has lasted over 20 years and is
still going strong! The broken drive side crankcase was a much more recent problem, occurring only a
couple of years ago. This time I sent the case to Seymour's who machined out the damage and
manufactured a new top hat bearing support in Dural which was then screwed and Loctited into the
case. This is apparently an old method of strengthening the cases used by racers in the past, which is
totally invisible until you remove the engine sprocket or split the cases, and is very neat. One of the
great beauties of this method is that you continue to fit bearings in exactly the same way as before,
since the expansion rate of the repair and the original material are to all intents and purposes identical.
I've done quite a few miles on the machine since and can honestly say that it's never run smoother!
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#514 however they do have problems and the one that is number one in my book is the crank axle
pulling through the flywheel on the drive side. they have a taper but its not enough. I mention this to
other owners and I usually get the answer its years old and if it was going to do it, it would have by
now. my answer for what its worth is never assume anything. my mate had his vm rebuilt and I timed it
up for him and it ran great, and sounded really sweet, 600 miles later he was out on a run and it
developed a bottom end rumble, he asked what I thought, I had a quick listen and said that is mains,
he said it cant be its only just been done. I said I reckon the crank axle has started to pull through, take
off the primary and have a look. he did and the end of the case had come off and there was all the
shims as well. you couldn’t have cut it off neater in a lathe. the problem is that having a spring under
constant tension acts as a puller and sooner or later it will come out. I had my motor down and sure
enough it was on the move. I had mine welded up but I have since learned that this is not really the
way to go. the trouble is that when you weld it, it tends to distort. the best way is to go to Nick Payton
in London my mate did and he machined the flywheel and put in a flanged shaft and pinned it. game
over as regards problems in that area. I intend to have mine done that way as well. he also made and
machined a crankcase half and paired up the cases for what I considered a very reasonable price.
L #708 A friend who wants to build up a 1959 MSS from a pile of parts has two pairs of flywheels.
The dia/thickness of one pair is 209mm/20mm and the other is 196mm/18mm. Is the smaller pair from
a Viper maybe? Is the larger pair correct for an MSS?
#714 Technically they are both for the MSS (or Viper for that matter). Velocette changed the
dimensions of the flywheels to reduce oil drag as the larger set are a very tight fit in the crank cases.
This took place in approximately 1958. Additionally the smaller flywheels give the main bearing housing
an easier time, particularly if your MSS has the small bearing housing. The MSS with the heavy crank is
supposed to be a super bike to ride due to the heavier flywheels and softer cam, so the choice is up to
you,(although Veloce must have had a good reason for reducing the flywheel size). Just one check, I
am assuming you are talking about a spring frame MSS engine number 10001 onwards, as the iron
MSS also has the larger flywheels with a 96mm crank and bolt up big end. I am about to build a spare
engine for my 1937 MSS sprinter, and cannot make up my mind whether or not to turn down the
flywheels to the smaller size or leave them as is to benefit from the greater flywheel effect off the line.
Is there anyone who has any experience of this?
#720 Flywheels size: I had the large MSS wheels in my 86mm stroke Venom for years and finally put
the smaller wheels back in this year. About the only advantage I could notice was it's a bit easier
getting the clutch out leaving a stop sign with the larger wheels. Once under way, first gear
acceleration is better with the light wheels. My other swingarm Velo has 96mm stroke. I had occasion
to do the big end a couple years ago and while I had the wheels split I carved them down to the
smaller size as well, removing four pounds of metal in the process. Same result as the Venom, quicker
in first gear. I don't believe the large flywheels aid vibration much. Given the same balance factor, the
only benefit the larger wheels have is smoothing out the power pulses, and in the case of a Velo the
size of flywheel compared to the power pulse is enormous.
L #862 Can someone tell me the length of the Venom conrod please?
#864 According to the technical site, the rod length is 6.875" centre to centre.
L #952 Are Mk 1 KTT flywheels common to any other model (i.e. Mac)?
#955 Mk I flywheels. These are basically the same items used on Mk I K models from about 1931 up to
the Mk VIII. The size of the crankpin changes in this period and earlier versions can be modified. The
main thing is that the wheels are steel in place of cast iron as used on the earlier K type motor. The
mainshafts are the same of course on all the above motors with the tapered drive side shaft. The MAC
wheels are similar but different. You may be better off starting from scratch and machining up new
wheels and shafts, the drawings are available.
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L #1042 Was hoping someone could recommend Engine Balance percentages for an Iron MSS
(1946) and an Alloy MAC (1960). Both bikes are used as regular rides, not racing if that makes any
difference.
#1044 The only information I can find for the MSS comes from P88 of Burris's latest book. "The balance
factor was altered from 70% (iron MSS) to 55% (alloy MSS / VM/VR heavy flywheel) influenced by
changes in mounting methods. The bad vibration in the long stroke engine was reduced. Later 65%
was adopted as the balance factor for the lighter flywheels" Unfortunately I cannot discover the source
of this information to validate it. Based on my experience of the long stroke MSS, it doesn't vibrate
badly.
#1047 Stick to 70 percent. I once rode a friend's Clubmanized Venom, set up to 55%, and it was the
hardest shaking single I've ever ridden - worse than a KTM Duke! My Venom was in bits at the time,
and I remember thinking, "If this is as good as it gets, my Venom is staying in the boxes." But once he
rebalanced it to 70, it was fine. Don't know where Mr. Burris got his info, but it sounds like bullpucky to
me. Another Veloist, one with more mechanical ability than most, told me that he has measured several
86mm engines and has found that Veloce used 70 percent on all. My experience with overweight
pattern pistons (which reduce the factor) indicates that you don't have to stray very far from original to
ruin high rpm smoothness. Finally, I have a 1953 Cycle magazine with a 1000 mile test of the
swingarm MAC that quotes a 70 percent factor.
#1048 Remember the MSS in question is an Iron MSS, different frame, stroke etc. all affecting the
balance factor, so 55% may be OK.
#1052 I have just heard (second hand from Dad) that Phil Irving in 'Tuning for speed' suggests 66%. It
may be tin tacks in the end, but is it possible to get a British single running smooth across most of the
rev range with only primary balance to play with?
#1054 regarding engine balance there is a firm in holland called Dymo Track. they are second to none
as regards balancing. they are the only firm I have ever met who can balance a triumph and you end
up with no vibration. they have very sophisticated machinery to do the job, plus they understand
motorcycles as martin the owner has a Norton commando which he balanced and he uses regularly. I
don’t know if they have ever balanced a velo but I do know that they have done goldstars. triumph
cranks can be up to 100 grams out of balance plus the wrong balance factor. he told me that sixties
triumphs used 85% balance factor on the 650's and he told me that it is wrong and the balance factor
should be 74% add that to up to 100 grams out on the crank and you get a vibro massager.....as they
do. there is also the way in which the engine is installed into the frame....i.e. in a different frame. twin
downtube like featherbed or hung in the frame...i.e. Seely. the engine balance has to be altered to suit
the frame..i.e. the harmonics. check out Dymo Track www.dymotrack.nl/ you might be glad you did.
plus they also heat treat conrods as they work harden and become brittle. he told me that the ceiling
for rods was 100,000kms about 60,000 miles, after that you are in the red zone. after heat treatment
you are back to as a new rod and you can start again. cheers.
L #1056 I have good condition MOV flywheel ,big end ,etc. but the main shaft is rusty. I would like
to change the shafts from MAC flywheel I have, which main shaft is good condition but mess in the big
end. Question is how it could be done , and what I have to be careful to do this?
#1059
If you look at the inside of the flywheel you will see what looks like a pin between the main shaft and
the flywheel. It is in fact a threaded stud. Drill it and try to extract it with a broken stud extractor. If it's
tight drill it out. Press the shaft out using a hydraulic press from the drive shaft side, take care not to
damage the thread on the end of the main shaft. Try to line up the two halves of the stud holes and
press the pin through from inside the flywheel. Press the pin in until it is flush with the flywheel. Odds
on you will have to re drill and re tap the stud hole a larger size as the hole / threads will not line up.
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#1345
I confirm about pushing out the main shaft from flywheel again. It is linguistic problem, I think. "a
hydraulic press from the drive shaft side" Means both flywheel main shaft pushed from drive side?(
timing-side one from pushed from flywheel side and drive-side from end of shaft?) Or both shafts
pushed from end of shafts into flywheel ?
#1358
The drive shaft has a taper on it, so having removed the threaded peg press the shaft from the outside
of the flywheel towards the inside.
L #1213 Does anyone have any useful advice on crankshaft balancing?
#1214 Having some practical experience in static balancing in twins and singles, I can provide some
small details if desired. It is well established that single cylinder engines can not be balanced to
completely eliminate vibrations. The annoying vibrations a rider may feel are generally caused by a
harmonic resonance caused by the reaction of a given engine in a given frame at a given RPM. The
annoyance can not be eliminated, but the period of greatest vibration can be moved to a RPM that is
less annoying to the rider and depends on the intended use of the machine. Thru much testing,
manufacturers have found that a specific imbalance can be applied to a given crankshaft to move the
vibrations to an RPM that best suits most riders for the intended use of the bike. In simple terms this
imbalance can be specified as a balance factor, a percentage of the actual reciprocating weight. The
balance factor, I.E. the percentage value differs for each engine, but for singles, generally lies between
50% and 68%, with numerous exceptions. In most cases, the factory got the "compromise" right and
unless you are making drastic changes in reciprocating weight, you can either ignore attempting to
rebalance the crank, or alter the new reciprocating parts to have the same weight as the original parts.
#1217 I have found that reciprocating weight is far more important than actual balance factor (within
reason). Velo's have very heavy rods, pistons and pins. A standard Venom reciprocating mass is about
800g. In my Thruxton with Carillo rod, lightweight pin and hand carved piston it's about 600g (and that's
with 97mm bore vs 86m). I also have ten ½" grub screws installed radially in my crank shaft with
access holes at the front of the engine. I can add or remove enough weight to change the balance
factor from 65% to 75% in about 5 minutes. The difference in minimal. It is a very smooth machine,
much smoother than my bone stock Venom. I won't do another crank with a stock Venom rod as the
reciprocating end of a Carrilo is over 100g lighter. Try grinding that off a piston.
L #1326 I am looking for MOV big end pin or assembly. VOC spare lists the M192 nold stock
pattern component without nuts-one piece component So what is the difference between pattern and
genuine? How quality different? What I am looking for is good quality (cost as well) Do you know any
recommended place I could ask for the part? genuine pin is still obtainable? Or may be pattern one is
higher quality? What does one piece component means? ( My old one looks one piece )
#1335 Two piece big end pins have a pressed on hardened sleeve over a pin that has a parallel
centre. It is most likely that the pin that the VOC made came from Alpha Bearings, so is probably OK.
The only way to tell would be to have it tested. At GBP20, my counsel would be to buy it, as I am sure
Bob Higgs would not have stocked it if over the many years the VOC has sold them, there have been
any complaints regarding the pin quality.
L #1939 I have just heard the distinctive nock of the big end from my 58 Viper. I hope it's the small
end but won't know until I remove the barrel. I've ordered a new big end bearing and small end bush
and gudgeon pin plus circlips in anticipation. May be able to pass on some dimension if it is the big
end. However I may as well check the main bearings at the same time. Does any one know what the
designation number is on the main bearings in order to confirm the correct ones are fitted? Also, how
does one lap in the big end?
#1950 You can find the designation on the main bearings under "bearings" on
38

www.croesus-consultants.co.uk/v-tec/ If anyone need dimensions of main bearings I have access to
some of the original works drawings including big end and outer race. As per 's post I suggest you read
"Tuning for Speed" on how to lap big ends.
L #2027 I've managed to find a pair of flywheel webs machined for the mainshafts but not for the
crankpin (venom). Could someone give me a measurement for the gap between flywheel halves
(conrod + .008" ?), and measure the distance from the flywheel boss to the end of each mainshaft (i.e.
how far does each mainshaft protrude from the crank web)
#2040 If it helps the shoulder to shoulder measurement of the pin is 0.8125 + 0.002. All flywheels I
have seen have the mainshafts flush with the inside of the flywheels.
L #2154 Anyone know what the crankshaft side float should be for an all ally engined MAC? Got a
feeling that I read `less that 1 thou' somewhere. This seems pretty tight to me.
#2157 According to the BMS generic Velo workshop manual, side (end) float is 0.0015" for all engines
except for the MSS which has tapered bearings. e
#2162 Thanks for the reply. 1.5 thou seems pretty tight to me. Isn't the MAC the only Velo single that
doesn't have taper roller mains?
#2163 The Velo singles that had taper roller mains were VM, VR, Alloy MSS, Late iron MSS. All the
others have ball or roller mains. If you set up the mains with 1.5 thou., i.e. nothing, there will be much
more at running temps. With the design of the timing gears etc this is the only correct clearance. It is
normal to set up the OHC Velo engines with no clearance at running temperature. This gives a slight
nip when cold which disappears when near running temp. After some running there is then a free but
not loose bottom end. The same applies to all 'non-taper roller' Velo bottom ends.
#2184 I've done it this way on a number of bikes with success (end play adjusted for the current victim
of course) so I am going to once again quote the BMS Velo manual:
"With main bearing outer rings correctly shimmed and in the crankcase, the timing side half can be
threaded over the shaft. Set the connecting rod in the cylinder opening and turn the half assembled job
over to fit the drive side crankcase. Check all crankcase oilways and freely lubricate all bearings. Fit the
bolts and tighten up the nuts gradually all the while checking the flywheel assembly for freedom of
rotation. At the first sign of tightness, stop work and measure the gap between faces with a feeler
gauge. If it is less in some places than others than the bolts have not been tightened evenly. Correct
and check again. MSS engines with taper-roller bearings must be shimmed so that all side play is
removed with the faces apart 0.005" and no more. The shimming is then correct and the drive side
case can now be again removed, and the face lightly smeared with "gasket goo" and reassembled. If
the crankcases meet, or in the case of the MSS engine, the faces come closer than 0.005" before the
bearings are nipped, extra shimming may be required. All engines except the taper rollered MSS
should have the flywheels perfectly free to revolve when the engine is cold with side float of not more
than 0.0015.
L #2385 I had a fairly dramatic failure (in terms of disconcerting noises) at about 80 mph last
week and, after stripping the engine, the drive side main bearing has broken through the end of the
bearing housing, the result being a thin disc of aluminium + shim that use to be attached to the
crankcase. Although relatively new to Velos, I understand why it has happened (I didn't build this
engine, so I don't know how well or badly the crank axial float was set up, nor whether the bearing
housing was damaged at some previous time in it's 40 year life). Anyway, the obvious option is to find
another crankcase half or pair and rebuild. However, I've spent the afternoon taking measurements of
the whole bearing housing and crankcase around that area and it seems to me that a repair in the form
of an aluminium "top hat" could be turned and tig welded to the crankcase. The crankcase walls are
around 0.4 in. thick in this region ...not exactly over generous, but sufficient to attach aluminium of ~ 1/4
- 5/16 in. thickness. The primary chain back piece of tinware will need a few mods, but that's trivial. Has
39

anyone ever heard of such a repair being undertaken?
#2391 Nick Payton - 0208 540 2118 - can solve your problem as he gets reinforced drive side
crankcases made and machined to match your surviving timing side case. Seymour's at Thame -
01844 212277 - did, and I believe still do a top hat conversion. This involves fitting a steel insert -
similar to a smaller version of the type fitted to a Matchless G.50. Criterion Engineering - 01793 790219
also manufacture a strengthened drive side case.
#2392 Send it to Seymours - they did this conversion (which I understand to have been a "racer mod"
in the past and stronger than original) for me recently and a beautiful piece of work it is - invisible after
the engine is rebuilt and treated exactly the same way as a standard case when it comes to fitting new
bearings etc. No need, and probably unadvisable due to the distortion that could take place, to weld in
position. The conversion is simply sealed with an appropriate grade of Loctite and held in place with
screws.
#2393 Just to offer a small correction Tony, the Seymour conversion uses a Dural Top hat, not a steel
one. Steel would be unsuitable since the different expansion rates would give problems in
fitting/removal of the bearings - i.e. the bearing and ring would have similar expansion rates making it
necessary to use a press to remove the outer ring - impossible due to the semi blind nature of the hole.
#2394 I had a set done in the early seventies and was advised to drill three small holes to "drift" out the
outer race if necessary. I still have the cases with the steel top hat. I can understand that they have
obviously changed the material over the years. I am intending to use my steel hatted cases for a
road Venom I'm building out of all the spares I have acquired since I took my original Venom onto the
race track and 'tile o'man. Incidentally did you know that Veloce were obviously aware of the
weakness? Some of their engines for the Island were fitted with a split steel top hat around the bearing
outer, but they appeared to be retained by interference fit as the "brim" of the hat wasn't very wide. I
won't name names, but there is a member of the club who has the afore mentioned engines and I've
seen them. I used to have my reinforced crankcases (both sides) made locally, that source has now
ceased, but they may become available in the future. I will advise anybody who is interested in due
course as they become closer to a reality. No it's not me making them. A final comment, I used some
larger parallel roller bearings in my latest engine which survived this years Manx. When they have been
stripped and examined, if all is well I will be altering my other "Manx" engines accordingly.
#2397 I'd like to ask about using roller bearings: What about crankshaft end thrust? Is it so small it can
be ignored?
#2400 Plan B may not be such a good idea - if the MSS cases are numbered 12078 or earlier they will
have the small driveside main bearing boss. Based on your experience you can work out why Veloce
beefed this area up. Also will need new chaincases, to accommodate the smaller boss.
#2402 Not quite sure what you mean by a "split steel top hat" and can't understand how such a
conversion can be held in position by interference. A solid item, yes, but a split sleeve will change
dimensionally quite dramatically due to the pressure of interference. If I were to use a steel top hat
conversion I would make a solid sleeve a good tight interference fit in the bored out case and make the
bearing outer race a push fit in the fitted sleeve. I'd like some additional security for the sleeve - either a
screw or two or at very least an appropriate engineering adhesive. Honda (and others) have used steel
sleeves on the main bearings on a number of their single cylinder machines for many years but the
sleeve is cast into position so is unlikely to move. Personally I prefer the Dural method since expansion
rates between case and sleeve are very similar, and you have the advantage of improved material
properties in the critical area. My original cases lasted through almost 40 years of use and abuse - not
raced but seen a lot of very hard road use - before the drive side did the usual trick and had to be
sleeved. Ask me in another 40 years whether the sleeve lasted the pace!
#2408 I have read with some interest about the crankcase failure and the suggested remedies. no one
40

has mentioned the probable cause and the solution. for my money, I would say that the crank axle is
pulling out of the flywheel and I would fix that before I did anything else. by putting in a top hat and
strengthening up the crankcase is not solving the problem of the crank axle. if the crankcase has
popped the end of the case off, you have to ask why. if the crank axle is coming out it will take the main
bearing with it which will push on the end of the case and pop off the end of the case off. I would have
the flywheel split and have the flywheel modified and a flanged main shaft fitted and pinned before I did
anything else. Regarding a top hat fitted into the old case, I myself am not keen on having three screws
in there that could back out and go into the motor. in my opinion that is poor engineering. a new
crankcase half that is thicker and paired up to an existing half must be the better and more logical
solution. the design of the original cases is ok provided that the pre load is right and the flywheel axle is
modified. I have heard people say to me that if the axle hasn’t moved in years, then why should it in the
future. well I would say that with a spring wound up on it for years on end and acting like a hammer drill
and an inadequate taper on the crank axle, sooner or later it will fail. modify and forget, that’s my way of
thinking. its like running a three cylinder triumph/bsa with alloy rods, you know that someday they will
fail. I hope you can use this info. cheers.
#2418 Another way of removing the outer race is to put the crankcase half in the oven and then crank it
up to full power. it’s a good way of uniformly heating the case and all you have to do is wait for a clunk
as the outer race drops out. it will usually do this as the oven approaches full heat. I regularly used to
do this with bsa victor cases and it works every time. just for a bit of history, neil kellys bike which won
the tt in 1967

#2416 I think I can now visualize the construction and your explanation of the purpose of the split helps
my understanding. However, I think that the reason for the split is in fact to compensate for the
difference in expansion rates between the two materials. The split, as you say, allows the case to hold
the bearing under the same pressure as if it were set in the aluminum case. The alternative conversion
which utilizes a dural top hat does not of course require a split since the expansion rates of dural and
the original alloy case are very similar. I much prefer this method since this also means that there will
be very little differential movement between top hat and case in service as well as permitting the
"normal" method of bearing fitting and that Dural has superior properties to the original alloy casting. To
me the use of steel in this application presents more problems than it cures. Which brings me on to
Tony Ainley's suggestion that the use of a puller is a preferable method of extracting the bearings to
heating the case and dropping on a block of wood. The cold extraction of an interference fitted bearing
in an alloy case will result in some galling of the hole walls, eventually leading to a poorly fitting bearing.
If the case is heated to a similar temperature to that required to remove the oil pump, the outer race will
all but drop out of its own accord with no risk of galling. Dropping on a block of wood is only really
required if the race is gummed up with old oil, and little more than a light knock should be enough to
shift the race. I suppose that on really stubborn examples a combination of heat and bearing puller
might be the way to go!
#2421 I have always favoured the 'spit test' when heating alloy bits such as crankcases. Heat them up
and spit at the heated surface. When the spit forms a ball which hops around on the surface that's it -
no more. This is around 120C I would reckon. I cannot claim originality for this. It came from Stan
Johnson, who new a thing or two about building motors from many years ago!
#2425 Shimming the mains out is a piece of cake. use an old outer with the outer ground so that it a
push fit in the case and then shimming is easy. I am shocked that you wouldn’t reuse the bearing after
welding it to get it out. a bit of wet and dry and a scraper and its as good as new, takes about half an
hour. if you are heating a crankcase in an oven, always be near it so you can hear the bearing drop out.
as soon as it does I remove the case and leave it on a concrete floor to draw the heat out of it. I
wouldn’t have thought that heating a crankcase up would affect it in any way. dymo track in holland
heat up alloy rods until the molecule structure is altered to stress relive them and they must get very
hot. you are better heating up something uniformly rather than in one area because the cool alloy on
the rest of the part will draw heat away from were you need it. boiling water isn’t enough in the heat
stakes, the oven is the answer, or acetylene works well. we all have our different ways of approaching
things, just a few of my ideas. My comments are based on the heat applied. An oven can and does go
way over the heat required which is safe for the heat treatment applied to the cases (or head etc)
Exceed that and you spoil the material. The same goes for using acetylene to heat castings - its too
much heat. Overheat the cases and they will fail in the future is my guess. Also bearings are a pair - the
inner and outer races are not interchangeable. Hence you cannot shim mains up unless you use the
bearing inner and outer that are going to run together, the difference may be small but so is the
clearance you are setting. This applies to taper or parallel roller types. The 4 thou preload is a figure
given in a manual. Its not the absolute right figure as you say; its not what the works used on their
motors either!
#2433 It wasn’t my idea to shim bearings up using a slave outer but dodkins, because that’s how they
used to do it. when a machine is turning out bearings by the thousand my guess is that they are the
same. I have bought timkims that had the outer made in one country and the inner made in another
country, so they have to be the same. as for excess heat ruining a crankcase, I just don’t buy it. when
dymo track stress relive alloy con rods they heat them up to a very high degree and the forces on them
are enormous, and they don’t fail. alloy is a malleable metal that work hardens with use and heating it
up wont do it any harm at all. but I will check it out, here where I live we have a shipyard and I will see if
I can talk to a metallurgist about this. if I am wrong you can have my profound apologies.
#2442 What preload do you recommend, and what did the works use? Also, I wonder what SKF and
Timken say the tolerance on bearing pair width is? It would make sense that the tolerance should be
insignificant, but wonder what the manufacturer(s) says
42

#2445 The way to set the shimming for the lower end, is to shim the crank to nil clearance with the
cases heated to normal running temperature. I believe that the 4 thou pre load was ok on a new motor,
but as they work harden with use it is preferable to set the crank at zero with a warm motor. That’s what
I was told by a very good authority. Regarding the timkin bearings, when the timkin bearing company
learned that velocette were preloading their motors, the refused to give any sort of warranty on them
and if they did fail under warranty, it was down to velocette to stand and failure on the bearings. I
believe that they never had a claim regarding timkins under the bikes guarantee. if you are shimming
out, I would go with the slave bearing outer race idea. it will save you no end of time.
#2430 Holes in the cases to remove bearings come in very handy, especially if you have to remove
those Japanese (Club supplied) taper bearings. Even the grand master Geoff Dodkin always had two
holes in his "split" steel top hat bushes to aid removal of the outer race. In service those holes are
easily covered up by gasket goo. I like them. I combine heat and slight taps through the holes to free
the races. I guess I know why my parallel main rollers failed : they were definitely not of the C3 variety
which means increased clearance. I am happy if I can get here Imperial bearings at all, beware to ask
for C3 ! And in all roller bearing cranks the mains are C3 type. Thus combined with a much smaller
bearing area, plus a crank which flexes probably a lot when thrown around at 6000 revs all contributed
to their failure after 2000 kms. Although I had two drive side cases separated from the bearing boss, I
never had the tragedy of a moving mainshaft. God thanks. One reason for the cracked boss I know
today : I adjusted the primary chain, and did not tighten up the gearbox bolts enough. When I tried to
escape a thunderstorm on the motorway I trashed the engine very hard. The rear chain pulled the
gearbox backwards tightened the primary chain and too much stress was put on the (small diameter)
main bearing boss. End of game : rumble, rumble......Why my Thruxton with flanged shaft and heat
treated cases had the boss popping off, I do not know.
#2434 If a bearing is coming out and staying out then the welding method is the easy way to remove it.
to shim out the motor a slave timkin outer ground so it is a push fit in the crankcase makes shimming
easy. I read about doing it this way from an article that geoff dodkin wrote years ago. it makes sense to
me. you say that your motor blew the end off the case with a flanged shaft and thruxton cases. its
possible that it might have been wrongly preloaded in the past which might have weakened it.
#2403 It seems some people are interested in end float of parallel roller bearings and therefore intend
to use them. here are my experiences with parallel roller bearings, maybe well known facts for the
enthusiasts in this group but not for me when I rebuilt the engine... To prevent a pushed out left main
bearing seat I used one side lipped parallel roller bearings intended for a 500cc Ariel single (w = 5/8")
with the end float set to 0,01mm when cold. When warm this increased to 0,1mm. After 2000km noise
developed from the region of the drive side main bearing. The engine was dismantled, the bearing
showed severe pitting on the inner race. As the pitting was spread over the whole area of the race I
don't think the end float has been critical. It also turned out that the outer races on both sides turned
inside the (unmachined, no top hat bush etc.) housing. The reason for this is that the timken taper roller
bearings have a slightly larger outer diameter than standard parallel roller bearings (+ 0,01 - 0,02mm).
This, taken together with the fact that the housings are at least 30+ years old and worn accordingly,
gave this rather unhappily result.
I don't know whether this problem has been caused by a manufacturing failure or if the load applied to
this kind of bearing by the engine is generally to high. Maybe a wider bearing will eliminate this problem
but then there is still the risk of the turning outer race. I will now revert to taper parallel bearings in
conjunction with strengthened drive side housing from Nick Payton.
#2411 After a collapsed drive side main bearing boss in my Venom, I thought to bring this problem to
an end with parallel rollers. I guess I used RHP bearings- very expensive ! End float was set to 0,02mm
which increased to 0,08mm when hot. A dural top hat bush was used, but its inner diameter was
machined to accommodate that minimal smaller outside race of the lipped parallel roller bearing.
Everything was fine, when after 2000 km the evident roughness of the engine was felt. Upon
inspection, a worn outside race was identified which has turned in the top hat bush as well. I did not
inspect the inner race which was probably worn as well. My conclusion why Veloce fitted taper bearings
43

is that the bearing area of the taper version is appr. 25% greater than of the parallel roller bearing,
which is quite substantial. Although I play round with VM and VMT engines for a long time, I really
never had failed taper main bearings, "just" broken drive side casting bosses. In reference to the top
hat bushes I want to mention that I have an unslotted steel top hat bush in my VMT secured with 3 M5
counter sunk allen screws. No problems since 20.000km. The story of the slotted steel top hat bushes I
can confirm, having in my stock two of them, and both are originating from Geoff Dodkin. This grand
master of Velos obviously had some thought behing this slotted version. However the technical reason
for the slotting I have not found yet. When buying taper rollers be careful before fitting and measure the
outside diameter and the inner one of course. Some (Club supplied) are Japanese made, with
fractional larger outside diameter. No problem to fit them in hot cases, but a pig (or near impossible) to
remove them again !
#2414 Hello Johann, so it seems that the parallel roller bearings are generally overloaded. I also
noticed the noise from the bottom end after a 80+ mph blast. Nevertheless I would like to know the
exact specifications of the bearing you used. Width, type of cage, number and diameter of the rollers,
play etc. to compare this with mine. I used bearings of 5/8" width, steel cage and on the outer race is
written "c2". When I ordered the bearings I clearly stated to get them with increased play. I know that in
the metric system a "c3" means increased play but I am not sure what c2 means and if this annotation
is the same for the imperial system. Maybe anybody from the island can help me with this?
#2417 Regarding removing an outer race from a blind hole or crankcase or steering head etc, the last
thing I would ever do is drill holes to try and drive it out. an easy way to remove the outer race without
heating the case is to go round the inside of the outer race with an electric stick welder. run a weld
around it and then let it go cold and then it will fall out, easy peasy lemon squessey. when the weld run
cools, it contracts taking the outer race with it and it will fall out, or at the very most a light tap on wood
and out it comes. but hey, you knew that. tar ra a bit.
#2422 Great idea - so long as you don't want to use the bearing again! No good if you are going
through the procedure of shimming up a set of bearings which involves fitting, measuring, removing,
shimming and finally refitting the outer race! I'm with you on the oven idea though, so long as her
indoors doesn't object to the Sunday roast being tainted with oil fumes! Personally I find the use of a
hot air gun played over the case works very well - just don't keep it directed continually at the one spot.
A gas torch should be used in the same way to ensure as near even heating of the case as possible.
#2437 I used the following parallel roller bearings : RHP LRJA1J (RR), steel cage, 11 rollers, lipped on
the outer race. Because they are slimmer than the taper rollers, a distance shim of 4mm thickness was
used between flywheels and inner race. Although I got 53% discount, those two bloody bearings still
cost me 54 Pounds. Expensive experiment. For the bearing abbreviations : C2 means tighter clearance
then standard, in our case between 0,001mm and 0,011mm. Standard clearance, which I used is
between 0,006 and 0,020mm, C3 means clearance between 0,015 and 0,033mm, C4 between 0,028
and 0,046mm, C5 between 0,030 and 0,053mm. If you used C2 type (nearly a precision bearing for
armatures etc.) and I standard ones, and both failed, and even precise Japanese single cylinder
engines use C3 and C4 bearings, we should go at least to C3 or C4 or even, if available at all, to C5.
Would be interesting to know what type of bearings Ralph Seymour used in his conversions.
#2453 I fully agree with you regarding the costly experiment.... If you are right, there is no need to
waste anymore thoughts about why the bearings failed. What puzzles me is the fact that the bearings I
used were intended for an Ariel 500cc engine and I don't think that the crank assembly of those
engines is stiffer than that of the Velo. Are you sure that in the imperial system c2 means the same
than in the metric system? Nevertheless, to be on the safe side I will use the taper roller bearings. They
are also much cheaper... keep it between the hedges, taper roller.
#2455 I just looked up an English bearing catalog as well and they have the same explanation for C2
like the FAG one. C2 has smaller clearance than standard. Maybe you got yours by error. C3 should be
the right ones. But again with parallel rollers you loose a lot of bearing area, and therefore they will not
44

last as long as tapers. I also went back to tapers with all the preload labor, and knock on wood, no
rumbling noises till today.
#2480 Phil Irving in various books confirms, C2 is designed for tight outer race, push fit inner race. C3
is for tight inner and outer race.
#2440 Well, I set up the mains on my Thruxton about 12 years ago according to 'the book', using a
propane torch to gently heat the cases (until my spit danced on the surface) and slamming them on a
big flat block of wood to remove the races, then shimming to 4 thou as measured at the crankcase gap
before bolting it all together. It has survived many, many hours of flat out running in these years. Is it
me, or are there too many ways to skin a cat? Peter, what was the pre-load the works used with a taper
roller main setup?
#2446 I hinted at the way Veloce assembled flywheels into the cases previously. This is how they did it
for special cases: 'shim the outer bearings to a point at which the flywheels will just stop in any position
yet spin freely when the crankcase reaches working temperature. This can be checked by carefully
warming on a gas ring' (Advice from Jack Passant) The same method is the one I use for setting up K
type bottom ends too. The pre-load is there to ensure that the flywheels cannot hop about when the
cases expand. That degree of expansion will differ from case to case to some extent. Hence the 4 thou
as a production standard which is still a good guide. Hands up who wants burnt fingers?
#2447 Finally a definitive concise 'how to do it' on setting up c/cases ! While I cannot claim to have
worked on any post WW 2 Velos, apart from a 46 & 48 KSS, I did set up & assemble a few early KSS
engines, & I found out from good advice of that time what really worked ! Yes, we did carefully drill the 2
small holes & a small pin punch was always at the ready in case the races didn't come out at the first
bang on 'the big block of wood' usually a solid timber bench that most of us possessed back in those
days, but there were times when the races just fell out as the cases were heated, - & yes we also
watched the spit bubbles do their dance ! Also when the arc welder came into use, we soon 'invented'
the ring of weld in outers method, although for my part, I used it in my daily workplace on bearings the
diameter of which, rivalled the outer diameter of Velocette c/cases! I have to mention that we never
aspired to reuse 'outers' after, 'careful use of scrapers & wet & dry' ! Yeah, I know ! The flywheels just
sticking at rest at working temperatures was aimed at, but not always religiously accepted, you sort of
knew your engine, & what you intended to do with it, & trusted the new, (& sometimes inspected &
found to be worn bearings) & then you went out & rode & raced your Velocette as the maker intended. I
can only talk of the Mk1 KSS really, & never considered that the motor was being 'thrashed', but I sure
as hell rode mine hard, & over long distances interstate at high speed, certainly 80 MPH & faster if
possible at times. One thing I can truthfully claim, & that is that I never had a bottom end failure of any
kind back in those years, & only in recent times did I experience a broken big end with the Mk.2, & that
was explained by a batch of badly manufactured replacements, with an inbuilt stress spot. It's a well
known experience thing that 'M' series derivatives suffer when used hard, as did the very first MOV's &
MAC's but failure has virtually always been the result of racing, (road or track !) & is one of the facts of
life for a Velocette racing enthusiast, & most of the modifications & 'cures' have their merits, but the
facts are, that the designs are quite old now, & it is of great credit to Veloce that these machines
continue to be successfully raced by enthusiasts. Good luck to you all, but bottom ends will continue to
fail, possibly more frequently as time goes by !
#2449 Since some people are drilling three 120 degree spaced holes behind the mains outer to aid its
removal, would it not be possible to tap these and fit set screws? It would then be possible to set up the
crank end float on a fully assembled engine at normal running temperature. The drive side case seems
to fail on those engines assembled with too much pre-load, rather than because of the shuttle loading
of the crank, so the screws should be able to withstand axial loading.
#2456 In the last year I've renewed mains in 2 different machines and found in both examples that the
original shimming gave the correct nip when cold (4 thou as near as I could gauge it, which wasn't all
that near. You know the routine - 6 thou here 3 thou there add them all up and make the average
45

answer equal 4, even if it ain't quite.). This lends support to Billy B's assertion that the bearing cups are
close enough in thickness to use a slave to get the setup right if you are starting from scratch - it would
certainly save a lot of time otherwise spent heating and banging. As a precaution the final setup could
be checked for freedom without radial play at operating temperature, whatever that is! Maybe in the
oven, or in my case the hooded gas barbecue (a less controversial place to hide an assembled bottom
end) at 80 to 100 deg C?? When VMT457 was first stripped down in the late 70's I found it had been
converted to parallel roller mains for racing purposes - standard practice for serious racers of the post
war M series here in Oz. I have heard the tapered mains referred to disparagingly as trailer wheel
bearings by old time racers. However since racing wasn't on the agenda for me and VMT457 and the
tapered mains were readily available and affordable, I converted back to tapered rollers and my
fledgling attempt at Velocette engineering led to over 20 years of trouble-free performance - I only
renewed them last year because I had it apart for other reasons and didn't fancy having to get back in
there within the next 10 years or so for mains maintenance. Speaking of VMT's, if I remember rightly
their cases are heat treated to deal with the greater power output and likelihood of sustained high
speed work. Does this then theoretically make them more susceptible to weakening by the inexpert
application of heat? As far as optimum nip goes, Paul Z has posted stories of trials with 10 thou nip,
and reported that it gave a smoother engine. So just how much latitude is there in the recommended
nip? It seems to me a fair bit, since the normal operating temperature must vary considerably. Just say
you ride south from Alaska and then travel through the Arizona desert, as some of our North American
Velo owners have done. More nip in summer, less in winter? In practice I think not, but if the theory
requires a precise level of nip, shouldn't we be doing this? Finally, if Paul D'O's infamous Courgette still
has no top hat in the drive side crankcase after all these years, then I rest my case. With a crank set up
so it is properly supported (whether by parallel or tapered rollers) the majority of Velos will stand up to
sustained hard road use over long periods of time.
#2457 Just to add another tip which might be useful to all who might want to take on the job of
shimming main bearings, I too have found that the method of measuring the gap between cases with
feelers to be rather hit and miss, even though it is the technique recommended in the red book. Having
pondered on the problem I came up with this method which I'm sure others have also used judging by
some of the other posts on the matter. First, remove the outer races and shims from both cases and
refit the races. Ensure that the mating faces are thoroughly clean and free of any residue of gasket
compound, then assemble the crank into the cases and bolt them together all round. Then, either fit the
timing gear steady plate, clamp your magnetic stand to it and mount your dial gauge so that the probe
is pressed against and in line with the end of the crank, or fit your timing cover with dial gauge adapter
fitted in the oil jet hole as per Tony Ainley's photo. Rest the assembly on the bench on the drive side
crank end so that the mainshaft is vertical and take a reading from the dial gauge. Raise the assembly
off the bench and take a second reading. The difference between the readings is the end float, which
should now have 0.004" added to it, the result halved and shims equaling this final amount should be
fitted behind each outer race before final assembly. I found that this method took a lot of guess work
out of the process and has given me a sweet running bottom end.
#2466 I am interested to hear the suggestion that the red book preload value is an approximation, I
think it was suggested, and that a better way is to shim to zero play at operating temperature. Would
someone who has done this explain how they accomplished it? It would seem to me that determining
operating temperature, getting all the bottom end parts to that approximate temperature and
assembling would be near impossible. Also, perhaps it is just me, but I always assumed the reason that
the drive side broke out of some velo engines was due to the loads applied by the tapered roller design.
These bearings resolve the loading applied by the combustion and compression pressures into a radial
and axial component, the axial is a result of the tapered design, and this put an outward force into the
assembly which, in some cases found the weakest point at the drive side bearing housing perimeter. I'd
really like to hear more discussion on this subject if everyone can stand more.
#2468 Putting top hats into crankcases is a bit like having a thorn in your hand and taking aspirin for
the pain. do you continue to take aspirin for the pain or do you pull it out and effect a cure. i.e. most
crankcases fail because the crank axle is pulling out. modify the flywheel and have a flanged axle fitted
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and pinned and the preload set up correctly, i.e. zero clearance at working temperature. the use of a
slave outer bearing is invaluable for doing this, as you don’t have to keep trying to get the outer bearing
out as a normal interference fit. dodkins used this method, and if you think it through, it is the most
sensible and logical approach. if I bought another velocette the first thing I would do is to have this mod
done. if I bought a thruxton and because of their very high prices, I would fit a modified crankcase half
supplied by nick payton and use the bike with that fitted. the price is so cheap, its almost a joke.
tremendous value for money. the original half could always be put back on the motor, if ever there was
a time to sell it. going back to the taper bearing set up, one outer race is the same as another. a
machine does not spit them out at different sizes, cnc programmed machines just don’t that.
L #2654 What's best to use for sealing the crankcase halves? Don't want any crazy colours!
Unfortunately the motor wasn't sealed properly and it's leaking from the inside into one of the back
mounting lug holes and coming out at either end, took me ages to trace it!
#2656 Two products are in my quiver. If the mating surfaces are in excellent condition and I have no
reason to suspect a problem, I use Hylomar Aero Grade. If the surfaces are otherwise, I use Three
Bond 1014. Depending on your location in the world, Honda Bond or Yama Bond may be more readily
available and are comparable in quality and characteristics.
L #2862 When I dismantled my engine for a re-build on the main shaft up against the main
bearing and behind the front sprocket somebody had put an eighth washer. This you could see had
been done to stop the primary chain from rubbing the case behind you could see where it had taken
chunks out before. with regard to this mod the engine worked fine and the clutch worked fine. with the
washer in place the two sprockets were in line but remove the washer and the primary chain starts
taking chunks out of the crank cases and primary chain case
#2865 Veloce seemed to have various offsets for the front sprocket, on a selection I have they vary by
anything up to .060". Dependant upon which front sprocket I have on my Venom racer, I also use a
washer .100" thick to provide correct chain alignment and also ensure that the inner face of the
sprocket clears the main bearing boss. Obviously the thickness of washer (if necessary) can vary
according to the shimming behind the main bearing outer race and the relative position of the crank
within the cases. As you say, the washer helps to line them up correctly in your engine and it works
satisfactorily. I only replied to make you feel better and to let you know that you are not alone!
#2870 After running my VM for over 10, 000 miles with obviously misaligned sprockets ( you should see
the scuffing on the outboard side of my clutch chainwheel!), I eventually got them to line up by making
a spacer out of an old main bearing inner race ground to about 0.10" thick. Before you shoot: yes, I've
got the chainwheel in the right way round and there are no weird spacers behind the engine/gearbox
mounting plates. The gearbox final drive ball race is fully home in its housing (except it's not truly the
final drive bearing on a Velo, of course) and the gearbox is a standard Prefix 12. Everything works fine
but my primary chaincase "pants" or, if you prefer, "oilcans" when I pull in the clutch and this would
explain why my downshifts are a bit rough. So what is causing the complete clutch assembly to be
offset towards the primary chaincase outer cover by what appears to be one tenth of an inch? I do not
accept that this could be the result of cumulative wear on the original Veloce jigs.
#2871 Seems to me that you would cure both the misalignment and the flexing of the case by reducing
the length of the spacer behind the backplate of the clutch, no?
L #3709 I am in the process of rebuilding my 53 MAC engine. However I am finding it very difficult
to set up the end float. The book says there should be no more than 0.0015in of movement. However
the best I have managed is 0.002 at BDC and very slightly tight at TDC. Is this likely to cause a
problem? I cant understand why the end float should vary with crankshaft position?
#3711 Difficult to diagnose at a distance, but I think I'd strip the engine and check the complete flywheel
assembly for truth.
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L #4164 Does any one have the specifications for ramp height for the engine shock absorber and
sprocket? If assembled without the spring should there be room for the two ramps to turn over the
peaks? mine can and has about 25 thou clearance as well. I believe this unit to be the cause of my
"clutch slip". Everything seems to be in order with other used items I and my friend have to hand. Can
any one shed some light on this assembly? Has anyone had their unit fail. I’ve heard about broken
springs but mine is intact though again I don’t know what the free length should be. I stripped the clutch
down and found the outer friction plate tangs were fouling the clutch cover plate, (new bonded plates
used)I straightened the tangs and reassembled with confidence. Ran the bike without the outer
chaincase and found that it seems to be the shock absorber is spinning at mid revs on full throttle. At
this engine speed you don’t get the machine gun noise which is why the clutch became prime suspect
in the first place. Your experiences will be appreciated.
#4166 I don't believe that the ramps should be able to clear each other. Sounds like your drive side
shaft is pulling out of the flywheel, a common failure corrected by installation of a 'nail head' shaft.
#4167 I'm not sure, but I don't think it matters... if the spring breaks it will still be too wide for the ramps
to pass each other. I had the spring break once on my Thruxton.. at low throttle openings it made an
awful racket and vibrated a lot, but once opened up things smoothed out. Fortunately only 15 miles
from home and I had a spare spring. Had the 'nail head' mod done by Dodkins when my big end went
some years ago as a precaution. Apparently the old shaft had pulled out some 20 thou or so.
#4172 The factory drawing show the ramp height to be 0.250" +/- .010" above the face, or 0.406"
trough to peak. I am referring to the shock absorber - the sprocket from peak to face is 0.375". From
peak to trough on the sprocket is 0.406". The factory drawing show the ramp height to be 0.250" +/-
.010" above the face, or 0.406" trough to peak.
#4168 Can't be that the shaft is pulling out, I had the flanged mainshaft fitted. Checked the free length
against one of the original shafts and it appears about the same, well within a few thou. So does if it
rides over the peaks like mine., is it worn? or has the spring suddenly lost it's temper?
#4179 I have experienced shock absorber clutch slip, the symptoms of which where not so much
machine gun as gear teeth stripping noise. my problem was caused by drive side main shaft slowly
eating its way though n/side flywheel causing extra clearance in shock absorber assy. The engine ran
well still!! the way to check is looking down onto big end, both end of main shafts should be flush with
inside faces of flywheels, my drive side one was 3 to 4mm below.
L #4479 Hello group, is there anybody who has used a carillo rod in a venom/viper engine? I'm
just in the process of lifting a venom engine to it's next tuning level and as the con rod seems to be
damaged after 90k miles of (hard?) service it might be worth a try. However, there is no Velo rod in the
Carillo catalogue but I remember somebody mentioned to use one in his (racing?) engine. Any
information appreciated.
#4480 Still got one in my racing Venom, contact Nick Payton and he can identify/ supply it.
L #4723 Does anyone known what the right size crankshaft oil jet is for a Venom with the early
type crankshaft fitted? There seem to be 2 different bore dia. in my collection of parts. One is bored
approx. 2.3 mm and the other about 3.3 mm. Which one to use?
#4743 0.078" with a tolerance of +0.003
L # 6353 I am in the process of rebuilding an old MOV engine, and needed to replace the main
bearings (Both roller bearings). I removed the inner races by teasing out the rollers, lifting off the cage,
and slotting a large open ended spanner over the roller channel, placing a fulcrum in the form of a 3/8
stud under the spanner as close to the bearing as possible, and whacking the spanner. Both came
straight off a lot quicker and easier than grinding through them as the last time I did this operation. ( I
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know, - this is no help with a Venom!) Then I was faced with removing the outer races, and like the
Venom, they are a bugger, as you can't get to them to encourage them on there way. I have seen
engines that have had holes drilled so a small pin punch can be employed. I put the cases on to cook
to a point where they spit back at you when you spit on them, and went for the gardening gloves to hold
the case while I whacked them on a plank of wood. A couple of hefty whacks and nothing had moved.
Thinking that they go in so easy when the case is hot and the bearing is cold, what it needs is the
bearing cooling to get it out, so I took an old face flannel, soaked it, folded and rolled it up to about the
inner diameter of the race, held the case bearing side down, and plunged the rolled flannel up into the
bearing. Both of them fell straight out much to my amazement. I guess this would also work for the
steering races, and would not need a welding set that the 'ring of weld' method needs..
# 6356 I have seen the whacking the crankcase on the piece of wood trick done before but it resulted
in breaking off a piece of the mating lip around the crankcase, so be careful.
# 6367 I've read of a similar trick in an old workbook. The book suggested heating the crankcase, then
touching the bearing race with a large piece of dry ice. As it is very very cold, it will chill the race.
# 6370 When I replaced the main bearings in the Thruxton, I made up a dolly from a large bar of
aluminum. I machined a taper, not quite the depth of the bearing, then a lip just wide enough to catch
its outer edge. I used aluminum, thinking it would be kinder where it came into contact with the bearing.
It turned out to be too kind. Being over cautious with the oxy, the cases were not quite hot enough and
a tap with the hammer was absorbed by the dolly rather than transferring it to the bearing. Next time
round, I propose to use 60mm solid steel and will make it in such a way that it can be used for removal
and insertion. If the taper is “just right” after being in the freezer all night, and the case is heated to a
more accurate temperature than blow lamp or oxy will allow (kitchen oven at say 150ºC) then as
observed, the bearing should just fall out when the cold dolly is applied to the inverted bearing. A minor
amount of machining will see the same dolly used to insert the new bearing, with both bearing cup and
dolly in the freezer overnight. With luck it should just slip in like a you know what, and be easily held
hard against the inverted hot crankcase till the bearing grabs. I had earlier replaced the steering head
bearings in the swing-arm frame with so little drama that I quite forget how it was done. There is no
internal radius in the headstock, so the new bearings go straight in. The tapered rollers were over the
counter bearings from an automotive trailer kit, cheap and easy to come by. The rigid MAC frame still
awaits conversion to tapered rollers. As Geoff has implied, this is also relatively easy and has
apparently stood the rigors of racing. However, I won’t be happy unless I see the bottom of the bearing
hard up against the headstock, and the internal radius here remains an irritant.
L # VOCNA 3 Have any of you had experience with the thicker heavier flywheels used in
Venoms from 1956 to about 1958. If so, disregarding balance factor, can you detect a difference in
engine running smoothness and throttle response compared to the later thinner and smaller O.D.
flywheels used up to end of production?
# VOCNA 4 I can tell you from experience that if you mix up earlier and later flywheels, there is a real
problem! Someone, no names please, built up the crank on my '61 Viper with thick and thin wheels on
each side, and even though the crank was set up/balanced perfectly, there was vibration above 4000
rpm which I just couldn't trace. It wasn't until the crank was out for rebalancing that John Prideaux
noticed that one was 1/8" thicker than the other. But they were the same o.d., so perhaps it was just
factory variance. I would say its difficult to detect any difference attributable to flywheel changes. The
smoothest Venom I've ever ridden was a '69 Special. Snappiness of response? Hard to compare, but
general engineering principles apply. My mk IV KTT has a few pounds taken off the flywheel, and by
comparison all early KTT's are slow to rev. Its my understanding that larger flywheels were used early
on to help with a reliable tickover and smooth low and mid-range running. Lighter flywheels were used
later when higher revs and snappy acceleration were valued over plonking, and as the Venom was
tuned further for racing.
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B.2. Cylinder and Piston -
L #101 My white Venom Veeline - is running great. It has an Aussie piston now, after problems
with Omega ones, and the Total Seal rings (first time I ever saw a 2 piece second ring!) give it the best
compression I can remember. The only time it has stranded me in 13 years and 30000 miles (since its
long sleep and reassembly) was when the infamous fiber gear stripped. It now has a steel geared ATD
like yours
#116 I'd love to know more details about the Aussie Venom piston and ring set you mention. Can you
forward me details re-manufacturer etc.
#119 Aussie pistons because of problems with Omega ones ? Sounds interesting. I dislike too a great
extent those primitive Omega cast iron piston rings. Easily identified by its charcoal black color. Just
changing the oil ring to a modern 3 piece design cut oil consumption to zero on my VMT. Modern
chrome compression rings create then the required healthy compression. But in recent times it proved
impossible to convince the local automotive parts dealer to sell ring sets for just one piston. So where
can I buy modern rings for Velo pistons, and if a complete piston is needed, where can I buy them
already fitted with rings of 2000 technology, not 1930ies ?
#120 A couple of you have asked, so here is everything I know about Velo pistons and rings. I include
the history so that you don't repeat my mistakes. A.k.a. one rider's experience Based on advice and
experience from other local owners, when I reassembled the Venom back in '88 I decided to scrap the
original one-piece oil ring and use a 3-piece one. This seems to be a requirement when using modern
oils. I found a Toyota pickup motor (22R?) with the "same" ring dimensions and bought a set. When I
tried to fit them (not an easy task, the oil ring's expander is very stiff) I soon discovered that the third
ring land (groove) was too narrow by a few thousandths. That's how I met Mike Parti, an incredible
restorer and collector (his favorites are pre-war - as in WW1) who turned the land wider for me. This set
worked fine until the top ring broke at the "top" punch mark and destroyed the original piston. This
happened 50 feet from the end of a 1000 mile VOCNA ride, I coasted in so it doesn't count as a
breakdown! After that I went through 2 Omegas in the original cylinder, each set to 6 thou or more, and
both seized repeatedly. I used the supplied top and second rings and the Toyota 3-piece oil ring. With
the cylinder now beyond last overbore, I had another sleeved (the original was not cosmetically perfect,
remember this was a Veeline) and installed a used standard piston (Wellworthy), same rings again.
This lasted a couple more years until I got tired of the poor performance caused by leakage behind the
pushrod tube. Apparently the sleeved cylinder would not stay round when hot. Honing, new rings,
changing oil grades, nothing helped. On conversation with Ed Gilkison I found that the VOCA (down
under) had arranged for some pistons to be produced. Unfortunately, gentle readers, the one I was
supplied (.060" oversize, for a mighty 517 cc) turned out to be the very last, and I have heard that no
more will be produced. Dunno about MAC ones. There is an alternative, however, so read on. The
advantage of the Aussie item is that it is made from a very low-expansion alloy. It came with
instructions to set up at 5 thou at the top of the skirt! This gave a clearance of only 3 thou at the
bottom, the normal measurement location. It nipped up slightly when I gave it a bit too much stick
during break-in, but a quick pass on the Sunnen and at about 4 thou at the bottom of the skirt it is fine. I
didn't even change the rings, just filed the high spots on the piston. 90 mph sitting up is no problem,
and blow-by is minimal. Ah, the rings. They are made by Total Seal, and the part number (remember,
these are 87.5 mm) is #C 3445 047 059 157 (TS1). My set was made under license in Oz, but I
suspect that a good racing equipment shop (check out Streetfighters!) can supply them. They came
with a hard chrome top, 2-piece 2nd, and 3-piece 3rd . Compression is amazing, cold or hot. You DU
types (Mr. Tesser) should contact your Tech Secretary if you need more info. I turns out that many
SoCal Veloista have ordered pistons from a local firm called Venolia. They make pistons to order, and
have copied the Venom design (I think they have drawings for a MAC one, too). This is also done in
low-expansion alloy, and can be furnished with whatever style rings you desire. Cost is not prohibitive.
Their website is at www.venolia.com. Again, I have not had personal experience here, but they come
well recommended. And they have not caused their riders any Summer Ride mishaps, to my memory.
This is the current crucible of Velo reliability, and quite amusing to watch when it's not your bike!
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L #458 I've just got a +60 piston for my MAC from Founders Day today. I measured the skirt and
compared it to 68mm +60thou which gives approx 5 thou skirt clearance (or about 2 thou per inch).
Does this sound OK? Too big? Its an all alloy engined 1954 MAC. I was wondering if it is possible to
use an iron cylinder in an alloy motor.
#459 I have a MAC from 1952, rigid, AL-engine, but with an iron barrel. The engine sounds very good.
I didn't know if this was original or something put together later. Then I found in Fishtail 264, page 30-
32, "Useful information for rigid MOV & MAC", where it was said under "Engine, no. 6: Alloy engine
with either iron or alloy cylinder introduced 1951 (from MAC 15982). This engine had split skirt piston."
So that's the point, either iron or alloy cylinder. It works. When Velo introduced the AL-engine they
obviously worked up all the stocks of iron barrels.
#460 Give Tony a call at Hartlen engineering, he should help you. Tony has been reboring motorbikes
for many years including doing a lot of work for Geoff Dodkin. I took my MSS barrel and piston to him,
and before I even spoke he correctly identified what it was. He also does cylinder sleeving at what I
think are reasonable prices. His number is +44 (0) 1483 202540.
L #701 Has anyone got a Venom with Venom(Omega)piston and Viper-head?. I have a -56
Venom endurance with .040 Omega Thruxton piston and head from Viper. I have opened up the
combustion chamber to make room for piston and calculated the CR to be 8.9. I`m going to fit one
more decompression plate which should lower the compression to 8,4. Criterion said that I should use
the MSS-flat crown piston with machined Viper head but then the compression have to be too low I
think... What's the point with Mss-piston? I don't think that the 8.4 is too much or is it (we have 98octane
fuel here in Finland).
#707 You may want to look at articles on squishing in Fishtails 294 and 304. In the UK using 4* LRP
with compression ratios above 8.0 will cause pinking. The only other issue I can think of regarding the
MSS piston is being flatter is there will be less of an obstruction to flame travel (improved flame travel is
the main benefit of squishing). There is always a compromise to be made between increasing the CR
and obtaining the best combustion chamber shape.
#720 For the fellow who mentioned using a Thruxton piston with a Viper head, this would be a mistake.
The reason Viper heads are used on 500s was to take advantage of the smaller chamber size, use a
flatter piston dome (MSS) to aid flame travel and incorporate some squish area as well. Opening the
Viper head out to take the high dome Thruxton (same as Venom) piston would negate these
advantages. My squish head bike runs 10.5:1 compression on 92 octane unleaded with only 28
degrees total advance.
#726 Bloody hell, so I ruined the Viper head because I made the combustion chamber to full
hemispherical shape... So is it now same side as Venoms combustion chamber or is the Venoms
chamber more deeper than Vipers? So you use unmodified Viper head and MSS-piston or what?
Because Criterion-people said that you must machine the edges of combustion chamber to match
cylinder bore edges, but then it is the same shape as Venoms I believe or is it? If I now put MSS-piston
I don`t have compression at all..
#732 I'm afraid by cutting the Viper chamber out to fit the Venom piston all you have now is a Venom
head with smaller valves and ports (which some would argue is not all bad). The chambers are the
same depth. I believe the general way it's done is to machine the Viper chamber just enough for the
MSS piston to clear around the circumference by whatever you desire for squish band, in my case
.035. I am not one who believes a 500 can run up top with the small Viper intake port and valve, so I
have a Venom head with the sides welded in for a 'bathtub' chamber.
#734 So, I ruined a perfectly good Viper head, great job. I just understood wrong the method to convert
the head. In my case the bike came with just bored cylinder and new Omega Venom piston but
without original head. With the bike came a Viper head which naturally don`t fit with Venom piston so I
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went on and opened up the chamber so I can use the new Omega piston. The head has bored out (to
30mm) intake port but smaller valve. I have also a new Venom intake valve. So if I change the seat
and valve do I then have basically a standard Venom head? And is this job to be trusted to normal
automotive workshop or is there danger that the seat can drop when engine heats up? I heard that the
head must be heated up before installing a new seat. Otherwise the head is in very good
condition...The bathtub-welding sounds interesting, I saw the same in Commando-head with D-shaped
exhausts ports and that was very effective indeed. Is your welder interested doing any more these
heads to some foreigner abroad perhaps...:-) P.S. How can you use such a high compression ratio
(over 10) because in previous messages some said that over 8 cr causes pinging at least with English
petrol? Is that squish band so effective that you can use higher compression ratio?
#735 At this point in your shoes since you have a new piston, matching fresh bore and a new valve I
would put in the Venom intake valve, shim the cylinder for whatever compression ratio guys who burn
your petrol get away with and call it a day. Nothing wrong with a good running Venom spec engine. I
probably have twice the horsepower of PdO's Velos and he still passes me. I think he leaves his brake
levers at home. If you are interested in high speed hunting down of Norton Commandos or modern
machinery (one of my favorite pastimes) you can get more umph but you'll need to work up to a
Thruxton size carbs and intake. I have a Venom head ported out to 34mm with no welding (go up with
the port, don't lower the floor) and it works well with 36mm carbs. I think the factory claimed 5hp
increase with the few Thruxton squish head engines they built, sounds a bit much to me. The squish is
good for about 1 point increase in compression ratio in my experience. You could run twin plug (I do in
both my squish and non-squish Velos) and get some of the benefit of squish that way but don't expect
more than a hp or two. I run 35 degree advance instead of 38 in the non-squish motor with twin plug.
Can't do it with a mag though. If you do twin plug, put a 10mm plug in vertically, you can get it out on
the same side of the bike and without taking the tank off. More details on how to if needed. Valve
timing, particularly the point at which the intake valve closes during the compression stroke, has
everything to do with effective compression ratio. Just last week I changed cams in the Turd ('59
Venom). With the /8 cam I had in it, the intake valve was closing late (I couldn't use factory timing,
valve hitting piston), the engine was sluggish in the mid range but not a hint of detonation. I replaced
with a /5 cam (I have high ratio rocker arms for .5 inch lift so don't really need all the duration of /8 cam
in a 500cc) to close the intake valve about 10 degrees earlier on the compression stroke. Mid range
power went way up, no loss on top however a bit of pinking now due to the increase in effective
compression ratio. When degreeing in your Velo cam, the spec you are most interested in is the
closing of the intake valve, it is by far the most important of the four valve events. I have trusted
automotive machine shops that have experience with VW or other air cooled engines with Velo seats,
so far no failures.
L #745 On another VMT I blew a hole in the piston I did read about another soul who had the
same problem ...Should I strip the engine to find the bits in the oilways etc.....what is the main cause of
this in velos....is there a filter of any kind that can prevent the oil pump from getting ruined.....it seems
that it was an Italian piston is this a possible
#746 A friend of mine blew the piston in his venom earlier this year. Although he had only owned the
bike for a short period it had been running fine prior to the problem. He checked the ignition timing and
that was ok. The only thing he could attribute the problem to was that he had replaced his petrol tap
and when he examined it he found that the flow of petrol through the tap was restricted. This may have
caused a weakened mixture leading to overheating. He took the safe option and completely stripped
the engine to remove the bits of his piston - it would be a pity to rebuild the top end only to have
engine failure due to restricted oilways or a pump problem. There is a suction filter plug in the bottom
of the crankcase that stops debris from reaching the pump, but I'm not sure how effective this would be
in stopping fine bits of alloy, from the holed piston, reaching the pump? The Velo owners club do quite
a nice conversion kit that replaces the fabric oil return filter in the oil tank with a more efficient
cartridge type filter. The kit also allows return oil to bypass the filter if it becomes clogged. However,
this is on the return side the oil having already returned through the scavenge side of the pump which
would not help in this case. I would also be interested in any body else’s comments regarding holes in
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pistons.
#747 If you've melted metal in your engine, doesn't it sound like a good idea to clean it thoroughly
before you run it again? I know someone who's on this list who didn't strip after a piston became a
breather pump, and he sheared his oil pump shortly after rebuild, seizing piston #2! As aluminum isn't
magnetic, it's really hard to drag the little bits out. At the very least, take the engine out and flush
everything very thoroughly, and blow it out with compressed air. You just might get away without taking
the cases apart... Petrol vapor/spitback is a function of valve timing, and is normal at low rpm's with an
M17/8 cam and Thruxton followers. It's part of the compromise for high rpm performance.
#748 While I haven't holed a piston, I did buy an engine with a holed piston. On striping the engine I
found "blobs" of ali in the crankcase, which had wedged between the crank and cases. Aluminum was
crushed in the main bearings. It also lodged Aluminum in the pump which seized the pump, striping the
oil pump drive worm and cracking the pump housing. The oil pump requited stripping to clean out all
the contamination.
#753 I have never holed a piston or got anywhere close, and I'm not known for treating the machine
gently. The main reasons for holed pistons are weak mixture, over advanced ignition timing or low
grade fuel, all of which I would expect to produce an horrendous amount of audible detonation (pinking)
long before any damage occurred. However, if an engine is run at certain speed/load conditions where
it is close to the pre-ignition limit, coupled with any or all of these factors, failure will be extremely rapid.
One other possible cause could be the use of a spark plug of the wrong grade (too hot or soft), creating
a hot spot in the combustion chamber. Couple this again with any of the factors above and the same
disastrous consequences will result.
L #964 I have freshly bored Venom with Omega piston. Piston rings are those "black" ones. Is it
better to change these to chrome rings and three piece oil ring? And can you get those rings anywhere
to suit Omega?
#965 Standard Velo-sized rings should fit the Omega piston. Modern oils prefer a three-piece oil
control ring. IMHO, the best rings are made by Total Seal, they include a chromed top ring, two-piece
"gapless" second ring, and three-piece oil ring. Your "black" rings are plain cast iron. Total Seal has a
website (www.totalseal.com) and dealers in many countries. Their HQ and manufacturing facilities are
in Arizona, the phone number is 800 874 2753. They should be able to give you appropriate part
numbers, or even sell directly.
L #1093 My venom has never behaved like what it oughta, and I have spent many long hours
trying to find out why. The bike looks cobbled together from other models, but all the bits are right
according to the parts catalogue, for a standard venom. I've stripped and rebuilt, but still not good
performance and too much vibration. Current theory is that the piston is too tight in the bore. Existing
piston is stamped VM STD, and is solid skirt (no split). So does anyone know correct gap between
piston and bore for this type of piston in iron cylinder. Currently it is about 2.5 thou if memory serves me
right It's a bit odd that a bike of this age is going around on original bore and piston without any
apparent wear, so presumably the previous owner (or builder) never solved the bike's mystery.
#1094 Is that `per inch of bore' or the clearance between skirt and cylinder? If it’s the former then its
OK, if it’s the latter then its way too tight.
#1095 The conventional wisdom is for new Omega pistons to have .006" clearance in iron bores and
.004" in alloy bores, as measured 90 degrees to the crank centerline. It sounds as if a curmudgeon was
in your bore, doing as PO's all over the world are wont to do. A piston this tight will be busy turning
friction to heat and wasting your power, trying its darndest to seize.
#1114 I have some original fitting instructions as supplied with the piston for Hepolite pistons. The
information is as follows: Air-cooled (doesn’t state whether iron or alloy barrel) - solid skirt, .0015 inch
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per inch of bore at the bottom of the skirt, .0025 per inch of bore at top of skirt.
#1118 As I am currently building an iron MSS engine using a JAP speedway piston which requires the
barrel to be shortened and sleeved, therefore I have been investigating piston clearances. I spoke to
Tony at Hartlen engineering who did all the boring and sleeving work for Dodkin, Roy Smith and
currently Nick Payton. His knowledge of Velo pistons, barrels, clearances etc is exceptional. He
confirmed roughly the figures in Fishtail of between 4 to 6.5 thou, however he did say it is not so strait
forward as it sounds. He also stated that Veloce did more experimental work on pistons and barrels
than the other manufacturers.
L #1419 This may be a daft question, but I have a new Hepolite piston for my '35 MAC any it
doesn’t have an orientation arrow on it. One of the valve flats is larger than the other, which I take to be
the inlet side even though the valves (iron head) are identical sizes - can anyone confirm this please?
#1420 Good question, I've been trying to find that out for the MSS. I believe inlet and exhaust valve lift
is the same on the MAC cam, and as the exhaust valve is heavier it tends to float first. Therefore this is
how I set it up in my MSS. The other thing to consider is using plastercine or Blue Tac work out which
valve is closer to the piston
#1421 So you have the larger flat towards the exhaust then? As the valves are identical sizes, how
does the exhaust valve float first? I was tending towards having the larger flat by the inlet to give
greater clearance around the new inlet charge when the piston is close.
#1422 As the exhaust valve is significantly heavier than the inlet on the MSS due to the difference in
the 5/16 to 3/8 stems it tends to float first. If you use a cam where the inlet lifts more than the exhaust it
is a balancing act. As long as you have 0.080" clearance on the inlet and 0.115" on the exhaust you
should be OK as these are the recommended racing clearances.
#1423 I have been occasionally proved wrong in the past, but EVERY engine I have ever put together
(and I've done quite a few in my time) has ALWAYS had the larger cutout towards the inlet valve. On
most machines the inlet valve is larger than the exhaust, or in some instances there are more inlet
valves than exhausts - viz 5-valve Yamahas or 3-valve Hondas. The piston may be the same spec
used in a number of different models, some using differing valve sizes, some not. I would still fit the
piston as above as a matter of course unless otherwise dictated by the manufacturer.
#1424 Logically I would agree. The MAC and MSS have the same valve sizes, so I'm just going on
experience and what my selection of scrap pistons tell me. Also the proximity of valve to piston is
influenced by cam timing, so you work it out for your own particular situation.
#1426 On the MAC the larger valve pocket goes to the exhaust side. Don't know why though!
#1427 Just a point in your reply re the MAC piston. I always build engines using .25" valve drop at
TDC. This was Veloce practice and Ralph Seymour was insistent too. Besides which it works!
#1429 Thanks - my information came from David Holmes, Brian Giles et al. with the plasticine method
the valve is closest to the piston prior to TDC. I bet that if you calculate both methods they would
probably work out similar.
L #2596 Im rebuilding my '58 Venom and have a few questions. Is the oil groove in the small end
bushing essential? As my more modern bike don’t seem to have this anymore.
#2597 Regarding the small end bush oil grove, I would stick with it. if you are having problems turning
the spiral oil groove, cut a straight grove through the oil hole.
L #2632 Could anybody please confirm the standard bore size of a 53 alloy MAC? The figure I
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have is 2.677 inches. However this does not seem to add up with what I have measured on my bike:
The bore measures 2.821 inches with the piston 2.803 inches (has + 30 stamped on it). This seems to
be nearer +126 thou from standard? It just does not seem to make sense.
#2633 68mm is the standard bore size with plus .020 ro.040 oversizes.
#2634 Maybe you've got a Triumph piston in there. I've heard that this is a common substitute for a
MAC piston. Can't remember exactly what the bore for a 500 Triumph is but 71mm would match what
you have. Anyone know the answer? More importantly from my point of view as the owner of a 1954
alloy MAC, have you used the bike with this bore size? If so it gives me a lot more scope as I'm still on
a rather rattly +40 at the moment and was wondering how big I could go.
#2639 Grove lists mac pistons up to +60, give them a try.
#2641 I am running a 71 mm piston intended for a unit 650 Triumph twin (std bore) in our '56 MAC. I
wrote an article about this for FTW. I know you Brits like your homegrown parts but the cheap
Taiwanese piston has half the thermal expansion and is lighter than the Hepolite. I am running it at 3.5
thou clearance, try that with a Hepolite or Omega! An original MAC std bore piston (Wellworthy), with
rings and pin, weighs 316 g; the import 71mm assembly is within a gram. The Hepolite weighs 327 g.
My experience with O/S Hepolite and Omega pistons is that they weigh considerably more than std;
this produces more vibration at higher rpm unless you are willing to rebalance the flywheels. Our '51
iron MAC has a +40 O/S piston from Oz and shakes mercilessly above 55 mph, it will be next. By using
pistons from the Triumph twin range one can accommodate bore sizes from 68 to 73 mm (the limit for
the thickness of the liner). The bad news is that the pin is larger, requiring boring and/or replacement of
the small end bush. I was not successful in getting perfect alignment when I replaced this "in situ", it
really needs the cases and flywheels split and the job done on the bare rod. With an increase in
compression ratio and a slightly bigger carbs this offers a considerable increase in performance. 71 x
96 = 380cc.
#2635 A 500 Unit Triumph has a 69mm bore, but I heard a piston of a 750 would match...
#2636 Yeah, 69mm was ringing a bell but I can't help thinking that some of the 500's had a 71mm bore
(maybe the pre-unit 500's?). 650's are much bigger. I'd need to consult a Hepolite catalogue or one of
Bacons Triumph books. Is your piston a Hepolite? If so, what’s the number?
#2637 The pre unit 500s have a longer stroke than the unit twins (I think 81mm respectively 65,5mm).
The 650 unit construction uses the same bore than 500 but has a longer stroke. This may explain why
they are not considerably faster... I don't know the dimensions of the pre unit 650 twins. they had nearly
the same stroke than the pre unit 500s so the bore should be considerably bigger.
#2640 I had exactly the same problem on my MAC no 2 and with a bit of help from Nick Payton found
out I had a Triumph Daytona piston the little end is sleeved as the triumph has a smaller gudgeon pin
and she is using BSA rings this apparently was a fairly common substitution for a +60 piston, the only
real problem is the increased compression ratio (roughly 10.5) and valve clearances have to be
watched, but she runs very well and has a nice kick back every now and then just to remind me who is
the.
L #4152 I had a big-end failure recently that resulted in a bit of swarf scoring the bore and piston
on my Venom. The piston is serviceable but the cylinder bore is a bit too badly scored to reuse. The
obvious solution is a +.060" piston (Mike at Grove has these in stock) and a rebore. I'm already at
+.040". However, I'm wondering if anyone has tried Nikasil plating the bore and if so what their
experience is. I think there is enough material to skim about .005" to .010" off the bore to remove the
scoring and this would be the depth of the plating. Would you run the same clearance as cast iron? Will
the standard rings be OK ?(I know you can't run chrome-chrome , but Nikasil?). The cost of new
piston/rebore vs Nikasil seems to work out about the same.
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#4153 A friend of mine had his iron VMT barrel nikasil plated from worn .040 back to standard! He went
through Dave Smith. It seemed to work fine.
L #4177 Dose anyone know what the inlet bore for a 49 mac ( iron ) should be? I have a head that
I think is for a mac but the carbs inlet seems small by comparison to the head I have on my mac now,
although it may be nothing because the head that is currently on my mac has been changed a lot.
Someone put in bigger valves ( from god knows what ), and has ported it nicely but it is not preforming
well and I suspect that it was set up for the kind of driving that I do not do. looking thru the parts book
many items are shared between the mac and mov and I want to make sure that I do have a mac head
and not a mov head so any help on what the differences between the two would be helpful. just trying
to save myself a lot work if the spare head is not for this bike.
#4204 Mov 7/8", MAC 15/16"
L #4375 I recently bought a 1936 rigid mac which had not been standing for too long after getting
it running and 200m of trouble free riding it seized up while riding up the wendover bypass I left it a
while to cool down and it freed itself, got it home and took the head and barrel off it had only minor
scores on the skirt of the piston , I thought I had found the cause of the problem when I noticed one of
the holes on the skirt of the barrel was blocked after unblocking and reassembling and a new
concentric carbs I took it for a spin yesterday and after 10 miles it did it again! it seems like a heat
seizure but I don’t know why any ideas?
#4376 The simple answer is that the piston got too big for the bore. The real question is, Why? The
variables are cold piston clearance established by whomever bored the cylinder, and the amount of
heat buildup in the piston during use as the piston will expand in tandem with it's temperature. The
place to start is to measure the piston clearance and compare to specification (which I do not know). If
within spec, you are simply running too hot and the piston is expanding with the heat until seizure.
Excess piston heat is generated most often by lean carburetor settings, although incorrect spark timing
or high compression ratio can be the culprit. Unfortunately, the maker's recommendation for carburetor
settings cannot be relied on today due to changes in fuel chemistry, so you are looking at a sometimes
long and agonizing education as you learn how to work with the beast. A useful and easy assist is a
cylinder head temperature gauge, using a sender that is a ring held under the spark plug. These can be
bought from www.westach.com and many other suppliers.
#4382 Hello all, I would be very much interested to hear what other listeners have to say about this new
engine seizure problem. Over the past 5 years I have been working restoring a 1956 Ariel VH Red
Hunter- 500 single. This bike has an aluminum head, aluminum piston, and cast iron cylinder. The first
engine rebuild I used a 7.5-1 compression ratio piston, per the piston manufacturers suggestion I bored
it to 4 thousands clearance. During the shakedown ride, about 20 miles from home, going about 45
mph the thing seized, locking up the rear wheel. Ill tell you, a full power slide at 45 mph, in traffic, on a
bike that you have spent two years, and many thousands of dollars restoring, is not something I would
recommend to anyone faint of heart! After getting to the side of the road, and waiting to stop shaking,
amazingly it started again and seemed to be running fine. Off down the road I went again, about a mile
or two and it seized again! Two full speed power slides in one afternoon was enough for me. The bike
seemed to run fine after that. After putting about 100 miles on it, I crashed it head on with a car in an
intersection. It was the classic car making a left hander in front of me as I entered an intersection. Of
course the whole front end was mangled. Not to mention my own person. The bike sat for nearly a
year. When I started to fix it again, I decided to have a look at the cylinder to see what had become of
the seizing issue. The engine thankfully was not damaged in the crash. The piston and cylinder wall
had light score marks just as Dave described. I made the decision to fit a new 9.0-1 piston this time; I
thought it could use a little more power. This was a different manufacturer of piston than the first rebuild
I did, but the recommendation was still 4 thousands clearance. After a very long rebuild period, and
much searching for parts, painting, etc., etc., the bike was finally finished. I was very careful with the
break in period; never more than half throttle, never more than 50 mph, etc. After about 500 miles of
this kid glove treatment, I took the bike on its first real club ride. Riding up Wolf Creek Pass here near
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my home, I started to push it a little hard, and I'll be damned if it didn't seize again! No wheel lock up
this time. As it started to loose power I immediately pulled in the clutch and it promptly quit. I waited for
about 20 minutes and tried to continue up the hill, I got about 200 yards, and it started to seize again. It
was as if the old Ariel was saying how tired she was and refused to climb the canyon road anymore. I
rode it all the way home, mostly downhill and flat, about 125 miles, with no problems. I did receive the
Bent Valve award for this club outing, the equivalent of a DNF. From that time I have ridden it only
sparingly, 10-20 miles at a time, and really taking it easy. Once again the fall Oil Bath club ride was
scheduled for September 25th. I again decided to take the Ariel. I mixed in about 12 oz. of Slick 50 with
the oil. The climb up Wolf Creek Pass went fine, no problems. It seems to be running great, good
compression, good power for an old 500. I am not advocating exclusive use of Slick 50, but it sure
seemed to help.
#4377 What clearance do you have between the piston and the barrel?
#4383 got the barrel off and I can just squeeze a 4thou feeler gauge between the piston and the bore
the piston says 1.d:10 and +20
#4386 For my money that sounds too tight. I'd be erring towards a piston skirt to barrel clearance of
6thou rather than 4. It might rattle a bit but it won't nip up on you.
#4388 The problem with lots of clearance is that while the piston is rattling, it's also tipping. When
tipping, it's wearing the corners off of the rings and rounding off the rings on the surfaces contacting the
bore. When the rings don't seal well, hot compression gasses heat the skirts, thereby expanding them,
sometimes into seizure. Far better IMHO to set the pistons to specified clearance and keep them cool
with mixture and timing. An EGT and a CHT gauge will allow you to monitor temperatures as you make
the tuning adjustments. You'll spend about $150 US, about the price of one piston, to say nothing of the
several that you might ruin while tuning in the olde fashioned manner.
#4389 True enough. The maximum wear recommended by Velo was 0.008" so 6thou clearance (which
would include the design clearance) would be well within that. I guess that the real answer should be to
bore the cylinder exactly to size so that you get the correct manufacturers clearances as the piston will
have them built in. Sometimes it doesn't seem that simple though.
#4381 Regarding seizures: I had a similar problem with an iron MSS recently. After a rebore to the
'correct' clearance for the piston supplied (thanks VOC Australia!), it seized up lightly several times,
with gentle riding, on the way to a rally. As I had further to go still, it seemed the best solution would be
to raise the carbs needle a notch; result, no more of that sudden slowing down!
L #4730 could any one tell me how far it is possible to bore out a 350 mac 1960 approx. i.e. cc
and what they use piston and so on.
#4742 I wrote a detailed article for FTWest about our "BigMAC" conversion. We fitted a Triumph 650
piston, 71 mm gives 380 cc. 72 mm (391 cc) leaves 2mm at the (thinner) barrel skirt, but this is close to
the point where cracks can occur at the rod notches. Your later MAC barrel will have round notches
which resist cracking, but clean them up with a Dremel. If you are willing to resleeve, 73mm might be
safe. You'll have to make a special small end bush, as the pin is a bit bigger than the Velo one. And,
depending on the piston top shape, the barrel may be shortened to raise the compression ratio. I also
have a MAC barrel with a BSA B series piston fitted, but have no further information. This came from
the collection of Ed Arnold, once a well-known racer here in California. This is a well-traveled road, and
can make a MAC quite a bit quicker. How are your main bearings?
L # 4828 Hello, A quick one - which way round should a split skirt piston be fitted? Split to rear or
front of cylinder? I think that the split should be to the non-thrust side of the cylinder ie. The front. Am I
correct?
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# 4829 Correct, split to the front.
L # 6041 I Have just purcased what looks to be an original, plus .020 oversized piston for my
iorn barrel 1937 MSS 500. This piston (81.5mm)from the Goodman Co. has the conventional ring set
up with two compression rings and an oil control ring on the top but also has a fourth ring near the
bottom of the skirt. The piston is very solid with no expansion slots at all. I have been told that iron
barreled MSS bikes had a lot of seizure trouble with "stock" pistons and were sometimes fitted with up
to .012 thou clearance to prevent seizing up though this seems like way too much. The book says
maximum wear on the cylinder is .008. My question is how much clearance ought I allow for when
reboring the cylinder?
# 6056 As standard the bore is 3.189" with clearances of: Top land .0178" to .0185 Top skirt .0092 to
.0105 Bottom skirt .0052 to .0065 but if you’re worried you can go up a thou or so on this without any
worry. I leave off the orphan ring on the bottom of the piston, but it's your choice.
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B.3. Cylinder Head and Valves -
L #6 Recently we have had two different makes giving problems with seizure of inlet valves. The
Velo, a late Venom, fairly new to us, is almost certainly because the machined boss on which the
M38/4 valve spring bottom holder sits was badly cast, and is off centre. Late heads are called "diecast"
but in fact, the ends are formed possibly by a die, but the central part is a core as in sandcasting. The
boss is off centre laterally, and does not support the M38/4 properly on one side. We welded and
remachined, and hopefully this will cure the problem. The spring tended to tilt the valve laterally when
pressure was applied. Hairpin valve springs are probably prone to the problem of different pressures
between the two individual springs. One answer might, at the top of the valve stem, to make two demispherical
parts to allow the springs to tilt a little without transmitting lateral thrust to the valve. Or fit coil
springs, but make sure the seating for the spring, and the top collar, as well as the spring, have
perfectly parallel faces.
L #201 I have a 1955 MAC which I am building at present and as some bits were missing: rims,
mudguards, seat etc, I am doing it as a street scrambler with 21" front wheel and 18" rear, stainless
guards and Thruxton seat. Looking at the inlet valve guide yesterday and being slightly bemused by
the fact they are straight sided. Obviously another Velo idiosyncracy. I started to think about valve
guide seals. I also happen to own a Armstrong MT500 with the Rotax 500 engine. Believe it or not the
Rotax valve guide seal fits the MAC inlet guide. Anyone got any reason that this might not be a good
idea.
#202 I have never had a problem with burning excess oil via the guides on a pushrod velo. Restricting
oil to the guides (particularly the exhaust) may cause the valve to seize.
#203 I had an intake valve seize some years ago, it was a Manley SS intake in a silicon-bronze guide.
The clearance was per the Red Book, and no seal was fitted. It just picked up some guide material on
the stem, which was removed with emery cloth and the Venom took us home the next day. Methinks
there is precious little oil in a pushrod Velo rocker box to begin with...and it has a hot, brutal life.
#205 Contact The Cylinder Head Shop. They have a technique of swaging a centre into the guide. The
guide has lateral corrugation which hold the oil and allow finer valve stem/guide clearances to be used.
L #233 Do I win a prize for spotting that the desmo setup on the front cover of Fishtail 323 shows
that the exhaust cam follower appears to have a roller on the rear follower instead of the usual "slipper"
I have an article from Motorcycle Mechanics 1962 which shows ALL to be slipper type. Does anybody
have any knowledge about this apparent variation. Does anybody have the fitting instructions or a copy
as supplied by BMG. Is there anybody out there still alive from the BMG days who could give some
advice/clarification? Lets hope so on all counts!! There was a firm in California called "BHB Cyclery" Do
they still exist? They used to advertise BMG desmo stuff and were advertising as recently as August
2001, but alas not desmo gear, but a Thruxton so equipped. Do any of our American friends know the
answer
#234 I have seen two sets of BMG kits here in the USA outside of a bike, and know of one VMT with a
kit installed. The two I've seen had the skids not rollers, and I'm not sure rollers would work due to
space considerations. Remember, they follow the cam on both top and bottom, in a 'c' shape. One of
the uninstalled desmo kits was very interesting, as it had broken a pull-rod and wreaked havoc; the
diameter of the rods was quite small, only slightly bigger than a GTP oil pump rod (there's your Velo
memory test). From what I've heard, there was essentially no difference in performance between the
BMG kit and standard. BUT the Thruxton locally with the kit installed held a speed record at
Bonneville, and I think I recall seeing a period road test showing a BMG-kit Thruxton lofting its front
wheel(!). Ed Gilkison has a kit which he's studying for possible reproduction; bug him about it if you
want one!
L #489 has anyone had any problems with venom/viper thru studs, that hold the head and barrel
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down. I just bought a venom off a guy and when he fired it up it started to blow slightly at the head.
this confused me a bit as velos don’t do that. the holding down method is excellent and I have never
known it happen. I got to thinking about it and I asked the guy if he had used stainless instead of the
originals, he replied yes he had. I have seen this before with guys with triumphs and BSA's the
stainless application doesn’t seem to be up to the job. I would guess that the original material would
be a good grade tool steel and the stainless would be an unknown quantity. could anyone please give
me any feedback about this. I took out one of the studs to examine it and I noted that the nut was
direct on the head. Should
#492 Stainless engine studs are known to work loose. There should be a washer under the Nylock
nuts, and normally (but not always) there should be an “O” ring underneath.
#493 Would you recommend using the original studs instead of the stainless items, ?. I have zinc
plated the originals and was considering putting them in. what do you think.? does the stainless studs
require a bit more tightening ? I believe that they were pulled down to 24lbs originally.
#494 The original studs and one hopes the Velo replacements would have been calculated to "do the
job". Stainless steel used id free machining, normally A2 and one would suspect the UTS (Ultimate
Tensile Strength) would be up to 50% less than the original steel studs. People automatically think
stainless steel is stronger. Change them.
#496 I wouldn't recommend exceeding the factory torque specs for stainless or other studs, the
consequences are a lot more vexing than re-torquing the head or replacing the studs themselves. I've
found that a Velo, or any other bike, left sitting long enough in conditions where there is a cycle of
heat/cooling, like normal daytime/nighttime cycles, will loosen its nuts up. This is most dramatic in hot
climates, obviously not as much of a problem in England! It sounds like the bike in question with
stainless studs is more in need of the proper nuts and washers than new studs.
#497 There is very little difference in elasticity and thermal expansion between various grades of steel
(including most "stainless"), so torque specs should not vary either. A higher tensile strength only
allows more torque, not needed here. The failure mode would be a broken or stretched stud, which I've
never heard of in a Velo. Stripped, yes. Make sure you oil the threads. The key is using the correct
washers, they are thicker and hardened. The O-rings help against leaks, as do Nylock-type nuts. If you
kept the C.R. down maybe your nuts would stay tighter,
#498 316 by which Ron probably means 316 S16 is a very superior stainless to the commercial A2
which is more a kin to 304 S31. 316 S16 has good strength and creep factors. It is also the material
used extensively by us in ships. So if you drive your Velo into the sea the bolting will be OK.
#499 Agreed, The thread in the Aluminum is the weakest part of the equation. A clean lubricated thread
will produce up to 25% more squeeze for the given torque. Lubricate the threads with oil. Grease is
used to prevent rusting.
#500 I have read all the comments and take on board what was said. I think that putting oil on the
threads is a no no as it tends to send the torque settings haywire. as regards the stud pulling out of
the crankcase, this is possible and the cure is 4 helicoils which are two and a half times stronger than
a thread tapped into alloy. the o rings are another must, and the later breathing setup is another must
if the engine is to become more oil tight. also a one piece pushrod tunnel is a very good mod, one that
I would recommend. does anyone know the thickness and od of the washer on the holding down stud,
these were omitted when someone built the motor. I thank everyone for the response. I was told by Mr
Dodkin to pull the head down to 24lbs, is this right ?
#503 The literature says 20lb./ft, remember Aluminum expands more than steel. I set mine to this and
have no problems.
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#509 I cant agree about oiling the threads, in a manual it says torque settings and in brackets if
it was to be lightly oiled it would say lightly oiled, not dry. my mate went to an engineering seminar and
they got talking about torque settings, and something that always sticks in my mind was that the guy
doing the talk said, if you tighten a bolt to 40lbs dry and then add oil to get to the 40lb dry torque with
oil would be 5lbs. that has always stayed with me. when torqueing a bolt or nut I always check that the
thread has no tight spots. dirt or uncleanliness is not an option. the problem that I have found is that
adding oil makes the bolt skid and it cant click off until a much higher poundage is added. I once
tightened the rocker oil feed domed nuts on my rocket three and forgot to clean out the threads with
brake cleaner, what happened was the torque wrench wouldn’t click off at 22lbs and it pulled out the
threads in the domed nut. and that was due to oil. I am not Mr perfect when building motors but
sometimes things are logical.
L #665 I have a venom with alfin barrel. I have adjusted the tappet clearance to .006 and .008 iaw
the owners manual. On other classic bikes I have with aluminum barrel and iron liner the clearance is
adjusted to 0. You only verify that the pushrods can easily be rotated by hand when engine is cold. On
my bike there is clatter from the tappets when the engine gets warm. I am considering to adjust the
tappets as described above. Will I have a problem
#667 You will probably burn out the exhaust valve and seat. You say there is clatter from the tappets
when the engine gets warm, usually tappet noise reduces when the engine gets warm.
#668 Well it's easy enough to check your tappet clearance hot. On my alloy barrel Velo the clearance
typically increases .002" or so when hot (check your own as I'm using aftermarket cylinder and studs).
By the time I get the tank off the cylinder head temp has dropped to 200F or so (400F during full flog)
so it's probably even a bit looser at times. BTW, I quit using feeler gauges to check clearances along
time ago (especially with one piece pushrods). Since one turn of the adjuster is .038", it's an easy
matter to turn the screw to zero lash (pushrod won't spin), then back off 1/6 or 1/4 turn to get .006 or
.008. Not perfect but works for me.
L #756 Just finished a rebuild on VMT457 and discovered a trap with recycling head gaskets. It
can be done - just anneal the old one and put it back in. Up to the point where it has become too thin,
that is. After tracing a misleadingly metallic chirping noise to puffing around the head joint, we lifted the
head and measured the thickness of the old gasket 0.025". We then rifled through the parts bin and
found a motley collection of new and used gaskets, some a good fit in the head, others loose and thus
prone to sit off centre and protrude into the combustion space (and in one case I heard of, protruded so
far as to actually catch on the edge of the inlet valve!). Chose a reasonable one and measured it
0.045". Annealed it, bolted the plot back together and problem solved.
L #771 What is the size of the standard Viper inlet valve head diameter?
#772 My information says, Inlet 1.69 inches, exhaust 1.56 inches - but I haven't checked Viper valves
physically
#775 So the exhaust valve is the same in all venoms and vipers but the vipers inlet valve is smaller
(and of course thruxton has 2" inlet valve I believe...). Is there a significant loss of power if I use a
Viper head with 30mm intake port and small intake valve in Venom (combustion chamber is shaped to
match Venom)?
#776 Now - Viper exhaust is smaller. check in the engine section here
www.croesus-consultants.co.uk/v-tec/ I have an engine simulation program, which I have just checked
for a Venom with Viper valves. While I cannot claim it's accuracy (vendors claim less than 5%) it shows
approximately a one BHP reduction in peak output, and a similar amount of torque reduction (ft - lb).
L #976 I have a Viper head in my venom and I'm thinking of changing the valves to the bigger
ones of venom. Now I`m wondering if there is enough room for the bigger valves to operate. The
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combustion chamber is machined to same size as venom`s. So is there a danger of valves to clash or
is the valve geometry and location same in Viper and Venom?
#988 Yes, the Venom, Viper and MSS shares the same valve angles ( and bare casting) which I
understand to be 35 degrees. The Thruxton valve angles are 33 degrees. You will of course require
new valve seats.
L #1174 Dave Smith, a Velo agent here in the US, offers a squish head conversion with several
stages of tune. I chose a 'fast street' rather than full race job, and here's what was done: The intake and
exhaust ports were reshaped, resulting in a 1 1/4" choke. New valve seat angles, new lighter valves,
coil springs w/ alloy retainers. The combustion chamber was shaped for a squish effect, coupled with
the new piston which looks like a Manx or G50 item; i.e. flat on the top, deep valve cutaways, with the
piston protruding about ½" over the top of the barrel at TDC. The combustion chamber sides were
milled flat to match the piston. After measuring the height of my connecting rod over the crankcase, the
barrel was shortened slightly for correct clearances, the piston being a little shorter than standard. The
oil return line from the valve spring cavities had to be bent a little to fit, and Thruxton type pushrods of
the correct length are used. As the pushrod tube is the sliding type, it is unaltered. I haven't tried the
engine yet, as I'm waiting for my TT magneto to be rebuilt. I'm taking the time now to polish and lighten
the valve train, again to 'fast street' and not too radically lightened. As the intake is now ported to 1 1/4",
and the bike is a '61 Clubman, I would like to use a TT carbs, as this is original for the machine. The
bike in general is completely correct in appearance and really beautiful; Dunlop alloy rims, early
reverse-lever rearsets, Tickle 2ls brake, chrono tach, braided zinc fuel lines, etc. I have the original
head and barrel sitting in a box.
L #1220 I'm intending to fit a thruxton type inlet manifold to my squish head venom. Does anybody
know (or is able to determine) the length of the inlet port, let's say from the valve to the middle of the
mixing chamber?
#1222 The required length for the inlet depends on the power characteristics of the engine. Say for a
VM with max. power at 5900 the length from valve seat to inlet is around 15.25" with max power at
6200 rpm (clearly non standard) the length would be nearer 14.5". If you have a GP carbs with a
longish tapering inlet bell mouth this will affect these lengths to some extent. I don't know how the VMT
manifold fits with the above figures but there is likely to be compromise due to the available room to fit it
all in. In practical use any extension can be beneficial and the calculated lengths apply only to that rev
range.
#1259 There are many formulas to work out ideal induction lengths. Gordon Blair from Queens
University Belfast, who has more expertise than most in this area gives the following empirical formulas
for induction lengths (see: “Design and Simulation of Four-stroke Engines”). He maintains that it is
accurate to about 3%. The induction wave is reflected up to five times, and the equation for the length
is: L = aC -- N Where L = Induction length from valve head to end of bellmouth in mm. a = reference
speed of sound at 340 at 15 degrees C, 346 at 25 degrees C C = Dimensionless intake ramming factor
for first ramming peak = 8900, second = 6600, third = 5150, fourth = 4150. If your playing around with
lengths I suggest you tune the length so you get the best peak at 6000 RPM, which automatically
determines the next ramming peak. This I work out to be secondary ramming peak with a length of
377mm, at 20 degrees C. This gives the third peak at 4685 RPM The theory is that then you get the
exhaust to resonate between these two peaks.
#1261 Does the shape of the inlet port affect the "intake ramming factor" and did Blair also determine
the corresponding outlet factor? If he did it would interesting to know the temperature of the exhaust
gas, as this seems to affect the sonic speed and is therefore important for the calculations.
#1264 The answer is yes and yes, to get an exact answer you need to create a computer simulation -
he tells you how to do it in his book. It really is a very complex subject, that's why I gave his empirical
equations! In particular the bell mouth taper has a major effect on the resonant frequency. Exhausts are
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even more difficult due to the "wave interference during superposition" (his words not mine) the
empirical exhaust formulas are not as universal as the intake empirical formulas. Next to Phil Irving's
"Tuning for Speed" this is the best book I have come across, but a word of warning. It's expensive, I did
thermodynamics at University, but a lot of the derivations of equations I found challenging (i.e. beyond
me). If you can get it on inter library loan it's worth a read, you will learn more about how a four stroke
engine works than you could ever imagine - but it also frightens you with what you don't know.
#1265 The Thruxton head to carbs manifold is (total length) 3 and 7/16 inches, note of course that the
carbs slips over this manifold by approx 3/4 inch. From valve stem (where it leaves the guide) to
manifold = 3 inches. From manifold to carbs bellmouth (measured using rubber mounted 38mm
Concentric Mk2 - (which is too big but gives a good guide)) = 7+3/4 inches, gives a total of 10.75
inches.
L #1269 I am considering to install coil springs on a Venom engine that is going to be used for
classic racing. Does anyone know if there is some kind of mathematical formula to be used to
determine what kind of spring to use with regards to weight of valve mechanism and desired rev limit.
#1272 I suggest you call Nick Peyton, who supplies racing coils springs and alloy retainers, cost about
GBP38. Nick's number is +44 (0)208 540 2118. Also Seymour's sell similar items. You will need to
machine a grove in your head to accept their length. I will mail you a picture of the springs and caps.
#1278 Is the modification worth doing. What I understand there is a certain risk on a nonThruxton head
that valves meet if revved over 6200. If this is correct will coil springs cure the problem.
#1304 Most of the serious racers in the UK fit them so I expect there is a good reason for doing it.
Slightly different bike, but I am about to fit them on my pre war MSS, for one thing the alloy caps are
less than half the weight of the original MSS ones. Obviously only fit them if you are going to seriously
rev the engine. If you are going to do that you should also lighten the cam followers, pushrods, rockers,
adjuster (drill and / or use a Triumph adjuster) and use a ally lock nut. If you are going to do this you will
need a bench grinder, Black & Decker Powerfile and polishing mops.
L #1339 I have a 49 mac 350 that is oil fouling the plugs, probably due to oil seeping past the
rings etc, it is slow to foul but it dose make it hard starting when it happens. have any of you had a
good experience with oil additives like slick 50 to tighten things up a bit? or should I just bite the bullet
and start saving / searching for rings etc.
#1343 If your oiling problem occurs after you have left the bike standing for a couple of days. Odds on
it's not getting past the rings, it's seeping past the valve stems and guides. If you think about it oil is
pumped to the rockers where it then flows into the valve spring cups. They then fill with oil, until it
reaches the level of the hollow rocker spindle, then it can flow back to the timing chest for recirculation.
So the valve cup acts as an oil reservoir. You may be able to fit valve stem seals as per MKII KSS, or
you can fit drains to the valves spring cups. I will include details of how to do this when I post the valve
lightening mods.
L #1356 Can anyone advise me? I have a Venom Clubman that I have done about 200 mile since
a complete rebuild, which someone else did. Yesterday when pulling away (quite gently) it suddenly
stopped and ground to a halt. When I tried to start it had no compression and was blowing back
through the carbs. I have removed the head to find that the valves have "kissed" each other with the
result that there is a small mark on the inlet valve and its slightly off its seat. I cant remove it yet as I
need to get a spring compressor. Anyone any ideas what caused this and what to check?
#1357 I have had this happen years ago after a rather heavy use of throttle which led to highish revs;
the valves touched! There is little clearance between the valves at certain times and valve float can
lead to an argument between them. Check also for foreign bodies keeping the valves off their seats,
incorrect tappet clearances or other 'sticking'.
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#1362 I had a new inlet valve stick in my Venom's guide after about 500 miles. It was a SS valve,
allegedly set at 2.5 thou, but still picked up the bronze in the guide. It ran fine the day before, but on
(push) starting after a cold night, it rattled. Had to pull down the head and sand the bronze off while my
fellow VOCNAers partied and made sympathetic noises. We made it home 400 miles the next day,
though. The slightly bent valve seemed to seal well enough. I replaced the valve, reamed the guide out
just a bit, and it ran fine for several thousand miles after that.
#1365 I have removed the head and inspected the valves. The exhaust seems to be OK but the inlet
valve has picked up badly in the guide and has some streaks of bronze guide material in several areas.
I have measured the valve in several places including the unworn sections and it seems to be two and
a half thou under 5/16 of an inch. However, when I checked the guide I am unable to get a 5/16 piece
of silver steel through it. I guess this means that the valve is running without the correct clearance. I will
be fitting a new inlet valve tomorrow and reaming the guide to 5/16 in an effort to achieve a few thou
clearance.
L #1396 If there are those of you who like me have been looking for OHC gland nut tool (part
KA55 ) here's a tip . At your local Halfords store you can get Draper tool stock number 59277 in the
cycling section , 'Locking ring adjuster ' for £5.99 ( $10 ) it needs a little grinding off so that it will go
behind the drive tube , but seems to do the job.
#1397 Another useful tool for removing cams from a cammy, is a ball joint extractor. It works as if it was
specifically designed for the job. You can buy them for about £6 /$10 from many car accessory shops.
L #1755 Here's a question for the cammy gurus out there, or those hot on performance cams .
I've spent the day checking and re-checking valve timing on the Mk IV KTT racer that I bought recently .
(fitted with a KSS Mk II head ) I'm sure I have it right with rocker adjusters set so that the rockers are
centralized on their eccentrics ( clockwise to decrease setting of exhaust and increase setting of inlet )
and 25 thou gaps as per KSS II checks. What I am getting is ; Inlet opens 70 deg BTDC Inlet closes 60
deg ABDC Ex opens 75 deg BBDC Ex closes 30 deg ATDC . I've compared this to the profiles on the
database , KSS 1,11, KTT IV and V settings and the M17/8 (KTT VIII )settings and see nothing like it .
In my case the inlet seems to open up to 20 deg earlier and close up to 10 deg later than most of the
Velo 'performance' cams , exhaust also opens earlier . Does anyone recognized these settings or have
any comment on them or experience with anything similar ? The bike hasn't run for years and that's
why I'm stripping it for a check . The cams and rockers show no wear . It has a 1 1/8 10TT9 carbs set
up to the same as Viper Clubman spec. and was pulling 20,44.22.55 teeth on the sprockets ( higher
than a Viper ) , it has TT ratio's in the box , so it was obviously going well . Combustion volume is about
42-43cc which makes it about 9.3 CR same as the Viper C/M My 39 KSS racer I used some years ago
had K17/8's in and went well .
#1757 Before considering the valve timing, have you set the rockers correctly? In the end of the rocker
there is a V. This points 'inwards' towards the plug on inlet and exhaust. Check the end pad is central
on the valve stem too. Next have you checked the degrees with the correct checking clearance? It
seems so but try 12 thou or 20 thou which is right for the K17/5. You may have a K17/8 which needs 20
thou checking clearance and your figures could be close for one of those.
#1758 That's one big lumpy cam, maybe e a custom grind. You might try retarding it some to bring the
lobe centers closer to Velo spec. I think you are at about 85/115 now. The intake valve must get close
to the piston on opening unless you have a big valve relief. Also with all that overlap the valves must be
getting close to each other. 60 degrees seems a bit early to close the intake with so much duration.
Have you run it this way?
#1761 I have checked the timing again with various gaps from 12 up to 30 thou and at 30 thou gap I get
69,57,73,27 . I am measuring from an accurate TDC and with an accurate gauge with the vales set
correctly judging the closure when it nips the smallest feeler I have ( 2 thou ). Things do indeed open
up early . I have not had the cam box stripped to see if there is any number on the cam as I was
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wanting to measure everything up before I pull the motor down for an inspection and clean ( Ignition
timing , valve timing , the clearances etc ) . How would I go about 'retarding ' the valve timing Paul , is it
a simple matter of putting the top drive one tooth out of current alignment ? It could be possible that the
timing is out as there is no scribe mark on the top bevel to align with that on the cam drive gear
,alignment is marked with paint dots . Having said that what marks there are and scribe lines are all in
the correct position at TDC. When I had my KSS racer I simply stripped it put it back as the Velo KSS
tuning sheets , put a new K17/8 cam on and ran it ( untouched and without fault ) till I sold it . So
playing about with the valve timing is something I am not familiar with . Maybe I will have to wait and
measure the valve to piston gaps then if it looks OK, wait again and see how it runs ? I'd like to find out
who built it and may be able to get some info via 'Fishtail', It does look to my eye as though the bike
was built by someone who knew what he was doing .
L #2164 I am fitting a thicker spacer / insulator between the head and the carbs on my Venom. I
will need to replace the studs with longer studs or bolts. Question: What size and pitch thread is in the
head ?
#2176 5/16 BSF, 22tpi.
L #2298 I have a 1951 rigid MAC and as there was a slight oil-leak from the head gasket I
changed it, but there's still a slight leak. I find oil between the cylinder fins and on the magneto just
behind the cylinder. The gasket was a copper ring. Should I have heated it up or anything before fitting
it?
#2299 Is it an iron head? If so there shouldn't be a gasket. If it's an alloy head then you should have
annealed the gasket by heating it to cherry red and then quenching it in cold water to make it soft
before fitting it.
#2300 There are no oilways running through the head gasket face on a Velo so the oil leak cannot be
attributable to a leaky gasket. More likely that you have the usual leak down the cylinder studs. To cure
this, countersink the stud holes in the top face of the head and fit a suitable "O" ring under the washer.
For additional oiltightness use a new Nyloc nut on each head stud.
#2301 I have a '35 MAC which has a copper gasket too - to anneal a copper gasket, heat it red hot and
then quench it in cold water. This should enable it to be reused nicely.
#2302 thanks for your advice too. There is oil running down the cylinder bolts, as you say. I noticed
when I last had the head off that one of these bolts is not quite straight, not by much, but it's almost
certainly making a difference.
#2305 I have been annealing copper all my working life by heating to 'cherry red' & quenching, & of
course it works if the heating is done correctly. But a few years ago, I was informed by an 'expert' that it
is only the careful heating that is necessary , the only thing that the quenching does, is remove all the
oxides etc. & make it nice & clean ! I have tried this, & it certainly appears to be true, - but I still quench
anyway as I can't resist that cleaning action.
L #2544 My MAC is running like a top at the moment and running in is going really well, I only
have one problem(for the time being) and I don’t know whether it is typically MAC or not. There is a
fairly light tapping noise on startup from the top end which seems to go after a run but it is either always
there and I sometimes don’t notice it (tappets are spot on and running a 17/7 cam and followers), a
regular Velo rider informs me this is because its an all alloy motor, any ideas?
#2545 What condition are the rocker bushes in? On an alloy MAC these are split alloy housing with an
oil feed. Hence they may well quiet down when oil is pumped to the head. The tappet clearances can
still be set even in this state. Its common and a sod to mend as one half of the bearing is in the head.
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#2546 I’ve seen better but I’ve also seen worse there was some minor scoring on the outer edge of the
uppermost part of the bearing surfaces which polished off easily I’ve had them apart since (200 miles)
and there is no repeat of the scoring which I put down to an old injury, my other macs bearings are u/s
and I have an engineer friend who has offered to syph bronze some sleeves with new oil ways, I don’t
know if this has been tried before but should be an alternative to the criterion conversion, anyway I am
still left with this noise. I seem to remember reading an article that suggested that a mac should sound
something like a bean escaping from a tin .but as this reads it doesn’t help at all
#2562 I had an MAC once that made similar noises though it had thick rubber grommets stuffed
between the alloy cylinder fins. Eventually, it was discovered that the oil pump's performance had been
seriously impaired by an air leak on the pipework 'twixt pump and tank and more bubbles than oil were
reaching the rockers. Without wishing to cause too much concern: I am slowly rebuilding the "Viper in
Clubmans trim" that was sold by the VOC when they were raising funds to buy The Chapel at Huncote.
Each element of this project was donated by a club member and so it was no surprise to find that some
components required attention. The valve gear had obviously been run for too long with zero oil
pressure and the alloy bearings were badly scored to the extent that aluminum had become "plated"
onto the rocker shafts. New rockers would not have retrieved the situation so I elected to have the old
ones metal-sprayed oversize. This is labor intensive as the shafts have to be ground concentric, metalsprayed,
hardened and then ground to the required oversize. It cost me £90 and that was three years
ago but any engineering firm that met-sprays crankshafts could do this work. The tricky bit is getting the
rocker housings and caps bored oversize (+0.020" in my case) as a fair degree of precision is required
and. of course, the oil feed groove must be maintained.
L #3250 My MAC has an annoying loud clacking coming from the top somewhere. I thought it
might be a noisy tappet, but now I'm not so sure. When I had the rocker cover off I was turning the
engine over with the plug out and noticed that the exhaust valve closed with a definite "click." Please
help a beginner - should the valve be making this noise? And does the whole description sound familiar
at all? Any ideas on how to stop the noise - it's interfering with the delicious thump-thump-thump from
the other end.
#3255 Make sure the valve lifter isn’t touching the bottom of the cam follower.
#3260 I had a similar problem with my MAC I tried the valve lifter and all seemed well, the rocker
carriage had picked up some swarf and was causing a tight spot on the rocker arm I took the whole
thing to bits polished the alloy surfaces and put it back together, be careful with reassembly making
sure the surfaces are well oiled I even prime the top of the carriage where the indentations are for the
feed, funnily enough both of my MACs have the same noise on start up a bit tinny but as soon as the oil
circulates they quiet down, that’s why I think its important to run them for a few minutes every week if
not in use to keep oil circulated
#3284 The rocker carriage is held down onto the head by 3 bolts. Make sure that none are stripped, as
if one of the end ones in particular is stripped the carriage will flex up under the load of opening the
valve, and 'clack' back onto the head when the load is released.
L #3430 I had resigned myself to the fact that I would have to take off the head and stripdown the
head and fit new valve guides to stop my 1957 Venom from smoking during running. This would mean
missing some outings in the spring sunshine. Following advice from a friend I checked the drain tubes
linking the rocker box to the push rod tube. First I found the exhaust rocker box full of oil and then I
found some very small pieces of debris (possible gasket sealer) in the pipe work. Five minutes later the
pipes were certified clean and after re-assembly - no smoke at all from the exhaust.
#3435 I found a similar problem with my 55 MAC it had oil residue around the barrel in the head gasket
vicinity I had noticed this when I bought it and thought it to be a possible leaky head gasket,I decided
when buying it a good check over off all adjustments would be a good idea my friend lent me a manual
and some advice ,we noticed that when we were checking the tappets the rocker block had no gaskets
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and the wells underneath were full of oil I got gaskets from Nick Payton and since they have been fitted
and the engine cleaned to oil deposit around the cylinder head has not returned.
L #3535 Hi, Which sealant is best with the VSL rocker box gasket ? Light compound I use so far
is efficient, but this greyish stuff of the gasket takes hours to be rubbed off from the box and head. I
wonder if polymer compounds like loctite or 3 bonds used for timing chest are suitable.
#3536 Try a tube of Yamabond. It's made for just this sort of application.
#3538 I use the sticky grey stuff (Permatex Ultra Grey in the US) on the bottom side of the gasket and
peelable silicone seal Permatex High Temperature orange stuff) on the top. This allows me to reuse the
gasket since it stays stuck to the head while the rocker box will easily lift off. Clean it off with acetone or
methyl ethyl ketone (MEK), reapply the silicone seal, let it set overnight, and Bob's your uncle. I easily
clean off the sticky grey stuff with the acetone or MEK.
#3541 I have raced an MOV (alloy MAC head) for 7 years and KTT Mkviii for 4 and used no paper
gaskets anywhere. I used mainly Permatex Ultra blue 77B . Tappet covers were regularly removed and
replaced with no subsequent leakage. Good idea to smear on one side only, remove after 24 hours and
carefully remove any inside overflow. Threebond 1211 is a good Japanese product too but 2 ½ times
the price of the "blue". (retired from racing in 2002 but restoring Mk1 KTT NO 96). noted previous
discussions re oil, Castrol R SYNTHETIC was best, stopped cam and follower trouble on high revving
MOV. Plus advantage of several meetings use against regular disposal of "R" (vegetable.)
#3546 I use a smear of copperease high temp grease on both sides of the re-inforced rocker gasket on
my Viper. It doesn't leak despite being removed 4 or 5 times recently (thats another story)
#3553 Dodkin and Seymour recommended Green Hermatite on the rocker box - horrible stuff, but it
works. By the way research and personal experience leads me to recommend Blue Hylomar on ali to ali
surfaces, Welseal on most gasketed surfaces. Grease on the gearbox chain case gasket, Silicone
ONLY on exhaust flange to pipe and with care on rigid pushrod cups rocker box joints.
#3557 The service manual says, for the rocker box gasket, "Fit a new gasket; sticking this to the rocket
box with a light smear of grease, or Gasket Goo jointing compound."
L #3663Does anyone have dimensions of original MK1 valves. In particular the stem length. My
Mk1 valve seats have been cut down so low into the head over the years that we are uncertain how to
set the inserts close to original. If the present valves were fitted with new inserts we would have no
hope of achieving correct tappet clearance even with valve stem caps fitted. The head is in Melbourne
and I have not had a report yet if there is enough "meat" left to retain inserts. The seats may have to be
restored by welding which I believe is a very tricky technical job. There is an old timer in Melbourne who
no longer works. He used to build a coke fire and set the cast iron heads in the fire , heat the head, and
then gas weld the seats while still sitting in the coke fire. Unfortunately these old craftsmen are a dying
race. ( I refer to Melbourne as I live in Shepparton 112 miles North of Melbourne). Any advice of
previous experience with this problem would be appreciated..
#3666 I have just had a rummage in the attic and found 3 old valves, 1 inlet and 2 exhaust. They all
measure around 3.64 inches (3 41/64") I hope this helps.
L #3672 There is a 1 1/2" long steel exhaust pipe pressed into the head. Mine does not quite
bottom against the head, it leaves about a 3/32" gap with almost an inch protruding. I heated the head
up in the oven at 300F for an hour and whacked the pipe but it didn't budge. Should I do something
about it or let it be? The head is stripped except for valve guides, seats, and carburetor studs. I don't
know if the pipe has moved during use.
#3674 My Venom exhaust stub is similar to yours Mark, except the gap is more than 1/8". When fitting
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new guides I thought to use the oven opportunity to shift the stub further in - no chance! I reckon that
it's been like that for most of its life and it hasn't moved in the 12,000 miles I have ridden so I just forgot
about it (until I read your e-mail). A regular Velo jumbler, don't know his name, once told me that
running a bead of MIG weld around the outside of the stub heats the alloy around it sufficiently for the
stub to almost "drop out". Only worth a try if your stub is so corroded that you really have to fit a new
one.
#3675 And when you fit your new one, do the "Thruxton mod" of drilling and tapping a hole up through
the bottom of the head and Loctiting a cap head screw in place to ensure it doesn't loosen again, as
sure as eggs is eggs, it will!
#3677 I appreciate the responses. The stub is in good condition so seems like I should put a holding
screw in now.
#3680 I recently replaced the exhaust outlet stub on a Viper head, because it had corroded to the point
where it was impossible to tighten the pipe onto it. It had moved out about 1/8" when I first noticed it
about 30 years ago, and had moved no further in probably 100,000 miles of severe thrashing. I had one
hell of a job removing it, and ended up cutting 2 grooves about 1/8" apart almost through to the ally,
chiseled this strip out the squeezed the remainder to remove it. If you are not going to replace it, I
would not bother with the locating screw, as it won't move on its own. I am certain any movement only
occurs when the metal is new, bright and shiny!
#3681 I removed a stub a while back by arc welding a spiral on the inside. I intended welding a thick
washer inside to get something to hit but this was not necessary as it "let go" while cooling. The
principal is that while the weld cools, the outside diameter of the stub shrinks. The same principal works
for bearing outer tracks. Remember the words of wisdom from Jean-Michel:- "You know it is going to
finish with the hammer, so hit it before you lose your temper."
#3682 I replaced mine for the very same reason, and using the same method. Mine too had moved out
by about 3/16", but was as solid as a rock. The replacement however continually came loose until I
coated it with a liberal amount of Loctite and fitted the retaining screw. It has never come loose since! It
does make me wonder though, If so many stubs are in the same position, with a gap behind but solid in
the head, if this was in fact how they left the factory?
L #3683 I recently tried to have an exhaust guide replaced. The machinist told me the new
replacement guide would be too loose in the head. It was decided to replace the guide with a steel one
made with a bronze sleeve put in by the machinist (machining a guide from another application was
abandoned after the parts supplier could not provide a similar guide to machine). Is this fix acceptable.
Should this have been tackled in another way. Would the steel pressed into the head rather than
bronze be a problem?
#3684 Your local friendly Velo parts dealer should have guides in oversizes.
#3685 You may have a problem with different rates of expansion, as the alloy head will open up the
hole at about twice the rate that the steel will expand, while bronze guides have about the same rate of
expansion as the head. Increasing the problem, the Velo head is not very thick at that point, resulting in
poorer support for the guide than some others. The Norton Commando 750 used cast iron guides in
some engines and they were well known for not staying tight. Norton solved that problem in the 850 by
increasing the OD of the guide quite substantially. If it were mine, I would see if a good Velo shop like
Dave Smith (in the USA), or Grove Classics (in the UK) could supply an oversized guide, and if not, I
would have one made up in bronze. A relatively new hard bronze material known as ColSiBro is
reputed to last well in that use. Those heads are too expensive to fool around with.
L #3759 I have decided that after some 20 years of neglect to attend to the total lack of
compression and performance of my Venom. Rebore now done, but valves, seats and guides in bad
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way. The seats I can get recut, and I have got new valves (bought new over 20 years ago) that are
marked V111 (inlet) and V112 (exhaust). Obviously lead-free was not an issue then, can anyone tell me
if these are OK to use or should I bite the bullet and buy some more? If so which? Also the VOC have
various guides on offer. Should I go for the Colsibro ones? The old exhaust valve is marked N80, but by
the look of it is where most of the compression was lost.
#3760 The inlet valve will probably be ok. the exhaust valve- N80 - was a nimonic one, Velo original
spec. Modern valve will be 21/4NS, maybe two part. The valve guides in Colisbro are excellent.
L #3782 I rebuilt my Venom engine in 1995 last time, and only had small jobs done since. It works
fine. So I decided to lift the head for a check and decoke, what I did last night. At first sight, everything
was nice. But when I cleaned the valves, the inlet one showed heavy hammering on the circumference,
on about 300/. The impacts seems to be radial on the valve head. The piston cleaning is not completed
yet, but it doesn't show any particular marks so far. There are three possibilities I can consider: The
valve was hit by the piston, a foreign matter, or the exhaust valve. The head shows some pits under the
plughole (not close to the valve) which where there for years if I remember well. Assuming the piston
will not show heavy marks when bright clean, I do not think the valve hit the piston nor a foreign matter,
which would have damaged the much softer alloy. So could it be a valve interference ? Camshaft is a
M17/8. Could weak valve springs have caused valve bounce (they are original '57)? I usually drive to
5000-5500 rpm, and rarely to 6000+, but it sometimes go. May be last time was too much.
#3783 I've seen valves that were hit by the piston or by the other valve, and the cause was obvious in
each case, the piston showing clear markings or the other valve showing markings or bent stems. In
either case, the inlet valve would not show markings around it's circumference as it does not rotate.
Foreign matter damage would show up across the combustion chamber, not just the valve edges. The
thing that makes the most sense to me is leakage around the valve, so I would turn the head over and
fill the chamber with petrol to check for leakage. Hairpin valve springs do not have a long life and
cannot be successfully adjusted for their weakening condition. They are difficult to test for strength and
will allow valve bounce when weak. The clearance measurement recommended in the manual is for
new springs and entirely avoids any consideration of weakness. I ALWAYS convert to coil springs
which can be easily assessed for strength or weakness. Do NOT use aluminium collars, as the
standard collets will pull through. I use collars machined from titanium bar or steel. I've usually used
springs for the BSA B50 (same as late Gold Star) which will give a seat pressure of about 100# and a
fully open pressure of about 220-230# when correctly shimmed. These numbers seem to work well with
a M17/8 cam. The last coil spring conversion that I made used a set of springs made by Kibblewhite
www.blackdiamondvalves.com/ to fit Triumph T140 which allowed slightly higher seat pressure, but I
really didn't see any advantage over the B50 springs. When packing up the springs you'll want to leave
.060"-.100" clearance to coilbind in order to prevent rapid spring weakening in use. Check the new
springs for pressure using a pillar drill (drill press) and a bathroom scale in order to find out the
pressures at various compression measurements up to coilbind. After checking new springs to coilbind,
they will take an initial set slightly shorter and weaker than initially and will remain in that condition until
abused by heat or over revving. If using the B50 springs (BSA P/N 65-2494 & 65-2495), you can avoid
a lot of work by simply packing them up to the above recommended clearance to coilbind, tested by
levering the springs to coilbind, using the rockers as levers after a trial assembly of the engine. Be sure
to include a heat insulating washer under the exhaust spring seat to prevent early weakening of the
spring
#3785 The valve timing is correct, although not perfectly on the spot, few degrees out. I really think
there were some impacts, as ridges can be seen on the valve edge. But no marks on the ex valve or
elsewhere. Still puzzled ! Suspecting weak springs, I will consider renewing them. As they are a nice
original Velo feature, I would prefer to stick to hairpin ones (they usually work, don't they ?), but will
consider coil ones if there is a real benefit.
#3786 I have 'dinged' an inlet valve like this in a VM. It leaves no mark on the exhaust valve.
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#3793 Closer exam (with a magnifying glass) shows tiny but undoubtful marking on the ex valve. What
surprises me is how small it is, versus inlet valve badly damaged. Inlet is marked M2/7, ex. M2/17N80.
Could Nimonic valve be so much harder than inlet material? So, or the springs are too weak, or the
chronometric tacho pessimistic and I over revved, or both.
#3801 All you ever want to know about valves can be found here
www.gsvalves.co.uk/technical_information.htm (download the pdf). G&S have manufactured valves
since the 40's, they manufacture valves for the VOC, Grove et al. The guys there are really helpful, and
rather than telling me to "go away" when I stretched and tuliped a valve that may not even be of their
manufacture, they were really interested and wanted to help. Regarding Aluminium valve caps, most of
the UK Velo racers use Nick Payton valve caps and springs and as yet I know of no one who has had a
failure. PS Nick springs are of Porsche origin. You need to set the installed lengths to 1.310 exhaust,
1.340 inlet. On a Venom or Viper this will probably require machining a counter bore in the head and
lining it with a shim to set the length and avoid hammering the Ali.
#3784 Just a small point re rotating valves. Veloce designed the collar arrangement to allow the valves
to rotate and thus even out wear etc. It is possible that the inlet valve can be struck by the exhaust
valve with some enthusiastic over-revving. If the springs are tired this happens more easily. Also, is the
valve timing correct?
#3787 Well, Velocette may have said that the design would allow the valves to rotate, but that doesn't
mean that the valves actually did. A careful examination of the striking points on the ends of my
extensive collection of used valves shows line contact from the rocker on most of them. And the ones
that do show wear all around on the striking point would do so after removal (to reseat) and
reinstallation. While it's true that the valve and collar assembly is not prevented from rotating, the only
way that they could rotate is if the spring pressure was released during operation, like during valve
float, eh? Even then, they would have to have something to cause them to start twirling in the guide,
wouldn't they? And what would that be? No, it looks like a propitious sales gimmick to me. " By golly,
the way those collars are designed would allow rotation, no? Well let's advertise it as a benefit, then"
#3794 Do you have / can you share any more details on HOW to make a coil spring conversion or point
me / us towards a source.
#3795 The easiest way is to contact Nick Payton on 0208 540 2118 and ask him.
#3884 I copied a Webco (US) alu alloy coil spring conversion in titanium, using B50 BSA (Goldstar)
springs. The Webco conversion of top and bottom spring seats retained by the Velo split collets were
known to fail due to the shallow wedge angle of the Velo collets pulling through the soft alloy collars.
Absent a Webco kit to copy in titanium, you'll have to get a set of the springs that you want to use and
define the configuration of the necessary collars, turn them up and install. Or buy a set that I'm told that
Nick Payton offers in England. The critical points are that the springs are compressed to within
.060"-.100" of coilbind at full lift (max. Tighter will lead to failure) and the seat pressure should be in the
area of 80-100#, with 220-240# at full lift. You can check these numbers on a bathroom scale under a
pillar drill. After making the titanium spring seats (collars), shim under the bottom one to get the
installed height correct and use a phenolic insulating washer under the exhaust spring seat in order to
prevent heat damage to the spring.
L #3897 Members may know from previous requests for help that I am putting a MKII KSS engine
in a Viper spring frame. I have to make a new head steady for the KSS in the spring frame as the frame
lug is further back. The old steady of tube with flattened ends has one hole elongated. Was that to
allow for variability in manufacture or for the engine to move?
#3899 Make your head steady to fit with round holes. The idea is to hold the top end still, not let it
shake about. I have a KSS / RS hybrid and I love it.
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L #3922 I have recently purchased my first Cammy(1938 KSS) and everything seems ok except
the bevels are whining. Any helpful hints on how to or where to get advise or technical information on
setting them up correctly? Any help much appreciated!!
#3933 One can pretty much assume that the bevels have done a lot of hours in their life, possibly,
(probably ?) in a state of incorrect mesh adjustment, so the whining may be no more that the anguished
cry of badly worn or incorrectly meshed bevels, or possibly they are in fact meshed too tightly. Back in
the old days when everything was new it was possible to reduce the noise, (by correct adjustment) to
an almost unnoticeable 'purr', but as the years rolled on, - a bit of 'whine' became the norm, despite
care taken in setting everything up correctly. Basic set up is still just that ! the bevels should mesh
completely with each other, that is, the outside & inside ends of the teeth should be flush with each
other when fully assembled. This normally accomplished by shimming the main bearing bodies
correctly, & at the same time ensuring that the bevels have only the minimum amount of clearance, &
are certainly not 'binding' Fanatical attention to the meshing, (too close) can result in damage to the
bevels, but over the years it is more likely that the teeth have suffered from being just plain out of
adjustment, & the resultant incorrect wearing pattern on the teeth ensuring that even though correctly
set up, there will still be noise. However, I have found that with care in setting up, the noise (whine ?)
can be kept at quite acceptable levels. The fact is that your noise could easily be from worn bevels, but
first, mesh & backlash can be checked by a visual inspection, - removing the plug (early cammies), or
cover from the top bevel case, & also remove the magneto drive. With the motor on TDC firing stroke &
no pressure on the cam train a rough idea of the meshing can be seen or felt with a bit of fiddling, it will
certainly be pretty obvious if the meshing is too wide, & with a bit of close observation, possibly see if
the teeth of the bevels are out of whack with each other. Apart from this, only correct adjustment can be
carried out, & hope that the bevels are not too badly worn from long term mal-adjustment. I have to say,
that unless you are completely conversant with the requirements of meshing bevels correctly, you will
have to turn to someone who IS !. You have to also consider that the motor may have been assembled
with the crankshaft incorrectly positioned endwise, or maybe the cam shaft has the same problem. The
vertical shaft 'end' float has to be checked, there is always the chance that fiddling with compression
plates etc. has caused pressure to be placed on the bevels - really - everything has to be fully checked
to ensure that all is as it should be ! At this point I have to point out that long ago I did away with
gaskets, (paper & otherwise) for the bevel housings. Oil tightness is taken care of by 'O' rings placed in
the 'corner' of the joint, & the adjustment is done simply by using appropriate metal shimming, without
the problem of sealing the housing joints, the faces of which in a lot of cases has been butchered &
scarred over the years by ham fisted mechanics. If this damage is bad, I machine the contact faces by
a small amount just to give a true surface, & also the thrust face of the vertical bushes, to bring the
vertical dimensions back to standard. This may seem rough justice, but carried out properly, is a simple
cure for years of bad maintenance. Surprisingly, the original methods of manufacturing the bevels must
have been of the highest standards, & most bevels despite rough handed maintenance are usually still
performing well. - I for one have never had a bevel disaster, but there have been times when I
assembled a motor & took it out for a test ride, & returned home & decided that I had set the bevels just
that tiny bit too tight, & so dismantled & re-adjusted, it's all part of the OHC mystique ! A simple test to
decide where the noise is actually coming from, is to run the motor just above idling, & with a
screwdriver handle pressed into your ear, place the business end of the screwdriver on the bevel
housings in turn. You will probably be horrified at what you hear, but it can give you some idea of what
is going on. This is of course an old engineer's trick used on all sorts of engine noises.
#3935 I've recently meshed the bottom bevels on my 39 KSS project. Goodness knows when this
motor last ran but it must have been some "tens" of years ago and was inherited in an incomplete state.
Anyway, on meshing the gears I have made sure that the tops and bottoms of the teeth are in line using
a combination of shims at both crankshaft and bevel housing. I have found that there's a "slack" point in
the gears as I rotate the assembly despite the majority being seemingly nicely meshed and no
backlash. Checking the throw on the crankshaft end whilst assembled in the casings tells me that it is a
quarter thou out from perfect which should be fine. The problem seems to come from the crankshaft
bevel possibly worn and is reasonably slight. I've decided to continue, assemble and try the motor as It
is but it crossed my mind to make up a simple rig to "run in" worn bevels using an mildly abrasive
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substance. I know that it goes totally against engineering ethics to carry out such a practice and has the
possibility of wrecking the tooth form but has anyone tried such a thing to "reclaim" worn bevels?
L #4336 Hello folks. Kim's new 1930 KSS ran well on it's first outing this week, until things started
to break. After 140 miles, the exhaust rocker sheared off at the valve adjuster. Opening up the cam
box lid, I saw the ex. and intake cam followers had worn about .125" Removing the rockers, I checked
the camshaft, and each lobe had worn about .125" also. For those of you using metric measurements,
this translates to "way too much!" I haven't had time yet to tear apart the motor to clean out the metal
slivers, or to properly diagnose the problem. My guess so far is that the valve springs may be too stiff.
Possibly there wasn't enough oil to the cam, but it was wet with oil when the cam box was opened up,
and the parts had not turned blue due to overheating. I'm checking with the previous owner/rebuilder to
see if he has any thoughts on this. But I wanted to check with all of you too. So I'm searching for the
following: 1. data on valve springs - spring force at installed height, etc. 2. a replacement camshaft
(possibly the KTT version) 3. a replacement exhaust rocker 4. exactly how much oil should flow to the
cam?
#4337 I too suffered from bad cam and follower wear on my KTP. I am no expert, but offer my four
pennorth for what it is worth. Any expert is welcome to correct me if I am wrong. With worn followers
the adjusters would be screwed through much further than normal, the valve moving in a straight line,
and the end of the adjuster moving in a curve, means that there is a skidding movement at the point of
contact, which is the force (with added leverage) that broke off the end of the rocker. Also I have seen
rockers that have been badly ground away to lighten them, In 1930 the camshaft was of a larger base
circle diameter than later models. This was reduced to reduce the surface speed of the cam past the
follower, and to reduce the wear you are now suffering. The cam follower skid inserts were
correspondingly longer. The oil gets into the cambox, via a groove cut ½ way through the bronze bush,
which lines up once a turn with a groove cut in the shaft to a point half way into the bush from the other
end. Disconnecting the drain pipe from the crankcase and running the engine will show the rate of
oilflow through the cambox. My KTP was producing about 1 drop a minute, despite winding the oil
pressure up to 16 PSI. ( recommended is 8 - 12 PSI ) My other Velos are not this oiltight anywhere! I
don't know what flow is recommended, but it must be a lot more than this. My Mk 2 KSS squirted oil on
the garage wall when I removed the drains from the head to check! I arranged 2 jets to feed oil under
pressure to the point where the cams and followers meet. I rode it to Stanford Hall, a round trip of close
to 300 miles, and for the first time, the valve clearance was unaltered when I got back. The oil now
leaking over the cylinder head is another matter, but I would rather that!
#4340 When replacing the bits in your cambox check: 1) There should be a groove in the large bronze
bush with a gap in it, this gap is opened by the flat on the camshaft once every revolution. I add another
half groove to admit a little more oil. 2) Check valve spring length & poundage. The MkI springs are a
little savage, I use a MkI outer and MkII inner to give everything an easier time. 3) Use castor oil. Any
mineral oil will result in knackered cams/skids. 4) Use a sensible cam a K17/5 will give performance as
good as any MkI type KTT. 5) If there is oil inside the cambox it will also show outside! Hence no oil
leaks = no oil. Pressure should be 10-12psi but this is at over 3000rpm and with clean warm oil. If all is
well inside pressure as low as 4psi can be OK. 6) Follow the above and you should be able to ignore
tappet clearances, my MkI goes for hundreds of miles without adjustment or wear. 7) Another thought,
carefully stone the skids to the cams to ensure full width bearing, use marking blue to show the high
spots; these will cause early wear.
#4338 I rode & raced only early cammy's for many years, & as I recall, even the heaps of wreckage that
I bought cheap because of oil starvation to the cam box never matched what you have described ? .125
inch is as you mentioned quite excessive. One thing that you don't mention, & that is that Kim's jeans
had not received a generous quantity of oil spots in 140 miles of riding ?, & this indicates that maybe
despite what you wrote, that there was little oil getting to the cam box internals ? My experience with
these machines is that if you have set the oil pressure to what the book says, & you have actually
checked with the engine running, that the top cam drive housing is in fact filled with oil under pressure,
there is a good chance that when you take your first ride, oil will in fact escape past the oil sealing
72

arrangements around the rocker pivot openings. & from here on it is a fine balancing act to make sure
that there is plenty of oil arriving at the cam/ follower sliding area, and the first line of defense oil
troughs inboard of the rocker pivots have a free flow path all the way down through the drain tubes, -
even then under normal running conditions, you could expect oil to get out of the cam box, especially
under extreme riding conditions, ( this assuming that the pressure was set as per the book) . There is
one point to make here, & that is that ' IF' the R/H side 'big bronze bush' has in fact been replaced
during the engine rebuild, & has been machined correctly, (?) is it in fact letting oil pass through into the
cam box ? . I have seen cases where a new bush has been fitted & holds the oil pressure in the bevel
chamber beautifully , but doesn't allow a metering of oil into the works department, due in fact to some
unthinking alterations in clearances (?) This situation is a virtual impossibility as I remember, as the
camshaft ( certainly on some models) has 2 precision ground diameters the outer one being the
greater, & this has to pass through the bush, for the bush to arrive at it's correct position with the
predetermined camshaft/bush clearance. Veloce played about with this system a bit, with odd oilway
metering tricks in the bush, but seizures at this spot were not unknown if the owner/rider/ home
mechanic, had reduced the oil pressure by fiddling with the regulating screw at the rear of the bottom
bevel housing, to the point where he no longer had the problem of oil leakage from around the cam
box, ( the worst case scenario starving the big end of oil also !). The point that I am making is that such
wear over such a short mileage would have to indicate oil starvation on a grand scale at the cam
followers. This despite the lack of blueing of the worn surfaces, - which had already gone to the place in
the sky anyway ! ? It doesn't take much oil to leave a 'film' over the working parts. There is also the fact
that the rocker arm lost it's business end, - I have heard of this happening but never experienced it. I
bought one 'bargain' with a split cam box housing due to complete seizure of the camshaft to the
bushing due to a complete lack of oil. It would seem that the rocker arm failure may have been the
result of a long fractured part, rather than too high valve spring pressures. One would have expected
this to happen shortly after start up, certainly not after the valve clearances had opened up due to the
wear. ( .125 plus .125 equals .250 that is a quarter of an inch !!!!) That would have reduced spring &
valve movement to Zero ! Sure check up on your valve spring pressure, but have along searching look
at quite a few other things. If of course the rocker had failed at start up, take note that there is a slim
chance that the valve springs may be so far from the correct spec. that something 'bottomed out' at
start up, & bent the rocker, & started the fracture. One thing puzzles me, If the rocker sheared at the
adjuster, why didn't it just fly off into the bushes, it would appear that the breakage must have been
further in, & even then I still cannot figure out how the cambox cover plate would have been destroyed
? One last thought, - have the cams been replaced with something with 'higher lift' without checking for
possible complications ? I would certainly check everything closely, I cannot logically explain the rocker
failure at 140 miles but lack of oil has to be the reason for the rapid wear.
L #4378 I was hoping someone out there had an excellent solution for sealing the bottom of inlet
and exhaust Valve cups on iron pushrod Velo Engines. Specifically my problem is a '38 MSS but
they're the same for all. Got to stem the flow for the Velo Rally at end of month. Any tips, materials,
recommended goo's appreciated.
#4379 I noticed in the "little red book of Velocette repair" (I apologize for not remembering the author's
name off the top) specific mention of this point. He offers several comments in this regard. I don't have
it by my side at this instant, but if memory serves, he states the following: 1) the cups themselves can
become distorted, and I believe his recommendation is to replace them. 2) he also addresses the
washers that are located between the cups and the valve guides that effectively pin them in place. It is
noted that these washers were redesigned at some stage, in such a fashion that they establish a more
effective seal. Again, he recommends replacing them when refurbishing the cylinder head assembly.
#4397 As Burgess's book explains the valve spring cup was modified to improve sealing. One type has
an indent the shape of the gasket washer, the other type has a simple chamfer, unfortunately I do not
know which one of the two is the improved type. To seal the cup I use the standard fibre washer/gasket
smeared with silicone - similar with the joint on the top where the two halves of the rocker box grip the
valve spring cup, but only use silicone on the part of the joint that grips the cup ( the actual rocker box
cover to rocker box joint I use hylomar) This seams to work quite well.
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#4380 On my mac I get almost no leakage ( or it burns off before I notice ). I use the two fiber washers
listed ( m224/2 4 of them ) and blue hollimer ( sp ). seems to do the trick.
L #4572 I have a problem(again!)with my 36 rigid mac, this time it’s the head gasket I cannot
seem to get a good seal between head and barrel, when I first got it leaked and it had no gasket at all,
according to the spare parts list this particular replacement barrel should have one so I fitted one, still
leaked! tightened the head bolts up a bit more very gradually and you can guess the rest snap!
managed to break a bolt, the questions I am asking are can I get the barrel and head reground
flat?,could the problem be that it’s a replacement barrel but not head? are the any torque settings for
the head bolts? or have 68year old bolts just weakened with age and should I replace them all?
#4573 You don’t mention annealing the new ( or old ) head gaskets. Have you done that ? Makes a big
difference to sealing the joint.
#4574 Iid heat up the gasket before refitting it, not sure how hot I should have got it though.
#4575 I am a bit worried where you mention regrinding head and barrel flat. The head at least would
need to be turned, if anything. The barrel spigots into the head by approx 3/16", and the head gasket is
a copper ring about 3/16 wide that fits snugly into the head, on top of the barrel spigot. There should be
a small gap between the bottom face of the head and the top of the barrel, round the spigot. If not you
will need to turn back the top of the barrel a little to make the spigot longer. This will raise the
compression ratio a little, but will not be a problem as the MAC was made to run on 68 octane and can
be raised quite a bit with advantage ( I took 1/4" off the barrel (at the bottom) and it goes like heck!). I
am not certain what torque to tighten bolts to, I would guess around 20 ft/lb. If you sheared a bolt that
was too tight and you were lucky not to have pulled a base stud from the crankcase. Good luck. I think
the MAC one of the most under-estimated Velos. By the way, anneal copper by quenching in water
when red hot. This is opposite to what happens with steel!
#4576 f you are concerned about having a pit or something that is causing a compression leak or if the
two faces do not mate correctly ( even with the gasket ) you can lap the two together with valve grinding
paste, my old ariel has a head that is spec to run with no gasket and that is how they tell you to do it in
the service sheet, it sealed very well but next time I had it ( the barrel) in for some work I had the
machinist let in a copper o ring into the top of the barrel, that did the trick but you still have to make
sure that the surfaces are pretty close. BTW it is also will raise the compression a little which is good,
unless you already have heat problems.... then it is bad, if you are worried you can fit a shim at the
bottom of the barrel.
#4618 On further investigation of the head joint leak on my mac I found that the sealing surfaces that
the head gasket seals against do not meet so by tightening down the head the outer flanges between
barrel and head meet first so there is no proper seal for the combustion chamber ( hope this makes
sense!) can I try a thicker gasket or two thin ones?
#4620 I would probably try two head gaskets for a fix until I had the cylinder off for some work, then I
would turn it down for clearance. If someone asked my advice on the matter I would tell them to see
someone about turning the cylinder to insure clearance. If your bike would be happy with two head
gaskets and you get no leak then bobs your uncle ( at least until you can make a proper fix).
#4582 Hi all, well known to some Velo owners, but not common knowledge, the fact that the early
cammies had a foolproof arrangement similar to Ariel system mentioned. The early cammies have 2
joint faces, the actual head to barrel mechanical surface, (outer & lower) & the separate inner sealing
surface. The procedure is to lap the mechanical surface with coarse grinding paste, then the upper
sealing surface with very fine paste. You check your progress until you have a perfect sealing surface,
checked with bearing 'blue' or fine chalk marks, then once again a final grind on the mechanical surface
with the coarse paste. (thoroughly clean then of course !) This system was pure Veloce design, &
properly carried out was perfect, having a full mechanical surface, & when this was pulled down hard,
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you had the minute difference between the 2 different grinding pastes giving a perfect pressure on the
seal area with the head pulled hard down. Never ever had a problem if it was done properly, but usually
the first job that you had to do when you bought a second hand bike ! The crankshaft drive was also by
a lapped taper, & worked well, but there were cases when a backfire may just 'crack' the joint. ( or it
wasn't fully tightened) & that old shock absorber would wind off in a flash, & apparently go through the
early cast ally cases, later it could sometimes damage the sheet steel primary case. I never had this
happen, but I did have the taper just let go a couple of times when I first bought a KSS (second or third
? hand ). Lapping with very fine abrasive powder & oil, & checking with 'blue', & it never happened
again. I am not sure about this, but I think Veloce may have modified the taper angle a little to stop this
occurring, possibly before full production began, but it could still let go, usually at the worst possible
time!
#4594 That other old Oz chap used the same head grinding system on his Vincent design. It does do a
good job but it does mean the barrel has to be off the bike and you have to be fastidious in removing
the grinding paste as it gets everywhere.
L #4676 I am a new member, returning to the fold after a break of 15 years, having bought a '60
Venom back in March which is in very nice condition.(I previously had a viper clubman which I used
day-in day- out for nearly 15 years and rebuilt twice having covered in excess of 100,000 miles.) After 7
months of relatively problem free, enjoyable riding and winter being upon us, I have decided to sort out
a few niggles, mainly oil leakage. The oil loss must be about 1 pint per 200 miles which mostly ends up
on the rear tyre. There is no evidence of loss from one particular gasket or seal the oil appears to be
seeping from various places mainly from the timing case cover (seepage all around the gasket.) and
running down the barrel/head retaining studs. Also the oil in the tank became black very quickly after
topping up the level. The seepage also was more evident when running the bike at high speeds for long
periods, therefore I assumed that the timing chest and rocker box was getting over-pressurized and
thought about fitting a crankcase breather. I have now stripped the top end and have found that the
exhaust valve guide is badly worn and I suspect the wear is due to the valve guide not being fitted
correctly i.e. the guide not being concentric with the valve seat, as the wear is only on one side.
Obviously the guide needs replacing and possibly the seat cut to suit. As I have not done this before
could anybody tell me if it is an easy operation? and are any special tools required? (The Red Book
simply says "Heat the head to 100 DegC and press the guide out"!) and if not, can anybody
recommend a specialist, preferably in the north west (UK) who could do this.
#4677 I use Martin Adams who is located in Brighouse between Wakefield and Halifax just off the M62
Get the parts from the club take them to Martin who will do an excellent job. He always has for me. If it
needs seats which after considerable mileage it most likely will he will fit these as well. His phone is
01484 715288
#4685 Try Nick Payton, one of the best Velo men around and fair prices too. I would be worried going
to an unknown cylinder head shop, first would they be able to source the valve guides and second they
have to be installed to a set length, I'd be happier with a Velo man set up and used to working on our
precious metal.
#4686 The Cylinder Head Shop NE Lincolnshire is probably the best known and most famous one in
the world. Heads are sent to him from all over the world and it is surprising how many Veloettes he
does particularly for the USA. He will also do your Tiger Moth engine or your racing engine. We paid
about £140.00 some four years ago for: - Inlet valve re-cut. New exhaust valve. Seats re-cut with
multi-angles. Valve guides resleeved with a corrugated liner (to retain the oil) allowing the inlet valve to
run at 0.001” and the exhaust at 0.0015” The man is a genius in his field.
#4698 I have recently replaced valve guides on a venom and viper head. It was a straightforward job
and successful. Follow the instructions in the book and you won't go far wrong. However before you
start have made up a pair of mild steel drifts for the purpose. The drifts need to be about 12 inches long
with an outside diameter of one sixtenth of an inch less than the outside diameter of the guide and
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turned down at one end for a length of about one inch to the inside diameter of the guide less about 10
thou of inch for a light easy sliding fit. I placed the head in the kitchen oven at 150 degrees for half an
hour ( make sure it is absolutely clean with no oily traces - wash with Gunk or similar and rinse with lots
of fresh water or your significant other will never forgive you). Take immediately to the bench and have
a pal hold the head steady and you'll find a few sharp blows on the drifts with a good size hammer will
take the guides out easily (don't pussy foot around at this stage as the head will be rapidly cooling). To
fit guides follow same procedure but also place guides in freezer first for an hour and I also rubbed a
smear of light oil on them. As to how far to have the guides protruding into the rocker cover area, I have
had conflicting advice as to what is advised in the workshop manual. However both heads had the old
valve guides protruding about three eights of an inch into this area and I set the new ones to the same
height as there seemed to be plenty protruding into the combustion chamber for support at this setting.
#4703 There has been some good advice posted concerning guide replacement, but I did want to
address your question of doing it yourself. The procedure itself is not terribly difficult. To me the issue is
that when the guide is badly worn, then the valve and seat mating surfaces will be in need of work as
well. The old workbooks recommended lapping the valve with a light grinding paste after guide
replacement, which might be ok if the guide was not badly worn...., but. With modern(ish) tools, this is
best accomplished by recutting the seat and valve using the new valve guide, using tools not usually
available in a home shop. The issue is getting a good mating surface to form both a good seal and also
allow transfer of heat away from the valve head to the valve seat. So while the guide replacement is
something you could do, recutting the seat and grinding the valve face to correct angles is not. That is
the reason I think most Veloists have the valve, seat and guide repaired by a machine shop.
#4693 I have changed valve guides in my 54 MAC with no problems. I have a shouldered punch which
knocked them out with no trouble. Valve seats I haven't recut before as I don't have the tools. If you
need new seats then you might as well have the whole job done in one go.
#4694 Replacing a valve guide is easy-peasy! You will need a suitable drift and also a gauge to know
when the new guide is in far enough. Heat the head - to 'spitting' heat i.e. when a ball of water will
bounce around on the head and no hotter. With the head on a solid location - I use a wooden board on
concrete floor - drift the guide down into the port (not the other way round as there will be some carbon
etc that will not be removed.) The new guide goes into the freezer for a while. The drift to fit the
replacement needs to go over the outside of the guide and preferably have a spigot inside to locate
nicely. Heat the head and again fit the guide from above- i.e. from the valve spring side. Tap it in to the
correct point 0.343" above the lower face. After this the valve seat needs to be re-cut using the new
guide as a reference. It's not too difficult and was a task that just about every owner would have done
up to a few years ago. Read the workshop manual first. And get a decent sized lump hammer - makes
the 'drifting' in & out so much easier!
#4720 Valve guide removal should always be done from the combustion chamber side. Ed G. has an
assortment of Venom cylinder heads that have been broken by attempting to drive a guide out
downward. The top of the guide is often deformed during installation and may not go through the bore
easily. I prefer to tap the top and install an old bolt; then after heating the head a long punch can be
used to push the guide out. This avoids damaging the guide bore in the head. Installation is helped if
you have the correct stepped drift, this is easily turned from a piece of brass. Drive the new guide in
from the top. The head must be hot (275 - 300 F.), the guide cold. MAC guides and VM/VR intakes can
be turned from Harley ones, they are readily available in many ODs, in .001" steps. I've used bronze
Ampco 45 guides for '84 - '99 Evo twins with success. They only need to be shortened a bit. Having the
correct OD can be important, a mate's Clubman once had its exhaust guide exit via the fishtail - in
pieces and in public.
#4704 The 'accepted' way to do the job these days is to have the seat re-cut. This can be done at
home. Use the right tooling & its easy. However, before we were all educated, the way it was done is to
fit the new guide & grind the valve in as normal. If the valve & seat make good contact you need go no
further. As the Velo guides are a simple and normally accurate concentric turning there is a very good
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chance that the lapping in will be sufficient. That's the way it always has been done and I've never had
a bad experience. Why make work & expense?
#4708 Can any member recommend a source of 45deg Valve Seat Refacing Cutters (preferably
carbide tipped)? I have that many seats to cut (not all of them Velo) it would be worth the investment. I
can make my own mandrels and am willing to part with good money for the right tool but the
Sykes-Pickavant prices are simply frightening. It's especially galling to find out that S-P do not make the
kit but import it from the USA - marked up by about 100%.
.
#4709 Buy a set of Neway cutters. They are well made, using indexable carbide cutters and make sets
and individual cutters for almost every possible situation. They are really nice to deal with. A set for
your head will include at least a 30 degree, 60 degree and a 45 degree cutter. The 30 and 60 degree
cutters are required to get the seat width correct and in the correct location for your valve. Cost is
approx. $400.00 USD.
#4710 Replacing valve guides is straightforward - providing you feel confident! If you are a little timid,
you won't hit the drift hard enough and it will heat up and bind in the head - I know from experience. If
you have access to Fishtail 113, I would recommend you make yourself special drifts that automatically
set the correct length from the head. Seymour's used to put the head in the oven until the temperature
reached the point when you smeared hand soap on it went black (the soap that is). Does anyone know
what temperature that occurs at?
#4722 I tried it once on a Venom and the valves picked up in the new guides so I sent the head to
Geoff Dodkin. Worth checking diameters if you also are fitting new valves. re reseating Many years ago
I saw a rig consisting of a drill with a grinding wheel with pilot The wheel was dressed with a diamond
on the same rig to the correct angel before each head.
#4761 As far as I remember, temp of soap blackening is about 400/C, which is about the annealing
temp of usual aluminum-copper based alloys. It seems quite hot for guides replacement.
#4714 A more scientific approach to determine the temperature of the aluminum would be to use a
product called "Tempilaq" which is a crayon that is rubbed onto the surface and which melts at a very
precise temperature, and is readily visible through a glass oven door without having to keep opening
the door to spit on the head. The product is available in a variety of temperature ranges so the melting
point can be precisely tailored to the application.
#4737 Thanks for the information about Tempilaq. For people in the UK I've found this site, but haven't
contacted them yet. www.waltersandwalters.co.uk/index.html [editor’s note: www.tempil.com]
L # 4832 I am currently looking at replacing the valves and guides in my KSS engine number
7360. It appears that there was an increased head diameter for the inlet valve after engine number KSS
8972. My existing inlet valve measures 1 1/2" across the head. Is this the early or later dia? The
exhaust is also 1 1/2" dia. Should I use valves and guides to suit the KTT, as I have been
recommended to, without valve seals? Has anyone experience here? The oil feed to the rockers is to
the later standard without the feed pipe and with the feed groves in the camshaft bushing, so some
work has been done at some time in the past. If I go to, or already have the later valve dia. what should
the carb. size be. The head now measures 1" bore. I have been advised to have the cams reprofiled to
17/8 form to gain a bit of extra power as the engine is going into a spring frame with the attendent extra
weight.
# 4930 In March 63 Veloce issued a document titled ""Engine modifications and settings for a MKII
KSS when used for racing" Essentially they recommended cr 7.8:1 for 75 Octane petrol, 9:1 for petrol
benzol valve sizes as per later KSS which are the same size as KTT For the road a K17/8 (confirmed
by Peter Miles) Inlet port 1 3/32" (as KTT) Ignition 30 degrees with contact breaker 0.015" Tappet
clearance 12 though inlet, 25 thou exhaust Hope that helps - there's some other information on piston
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diameters, ring clearance that probably is of little importance for a road bike.
# 4913 I think the Big inlet was introduced in 1939 along with the suction filter crank cases , you can
tell if you have a big valve head because the inlet is visibly bigger than the exhaust ( 1.68 " vs 1.5625" (
1 9/16 " ) ) the small valve head has valves about the same size in and ex . Part number for the big inlet
valve is K2/16 and the earler valve K2/14 . exhaust valve is K2/15 Inlet and exhaust valves and guides
are available from the VOC spares Co.
L # 5397 Apparently on MACs there are two covers on the rocker box held in place with four
screws on each? A question that arose at the club tonight is what is the thread size for the screws?
# 5398 Just looked, but my MAC has only one cover held on with a lot of 2BA bolts. Have I been
short-changed? Why have I only one cover? Now I really won't sleep tonight worrying.
# 5399 www.velocetteowners.com/photogallery/machinesmotion/ramaceng1.jpg
# 5400 The older iron MAC cylinder head has 2 covers on a vertical joint, which clamp round the valve
spring covers. Off the top of my head, I think these are held on with 4 1/4" whitworth bolts. Later ally
MACs the cover is held down with lots of 2BA screws.
# 5402 Must be talking about the earlier iron models. My 54 swingarm MAC had a one piece rocker
box held down with 8? BA screws.
# 5405 Thanks for the notes. The MAC in question is a '46 Iron head. There were two opinions the
other night (i) the screws were 1/4" whit and the other (ii) 2BA. I will add your comments next week
when the article appears at club night.
L # 5875 As part of the cylinder head holdown stud upgrade from 5/16" to 3/8" I was given four
skinny o-rings for cylinder stud to head seal and told I should chamfer the head before installing them.
Any particular angle or depth for the chamfer? Are these seals effective? Anyone need a set of 5/16"
crankcase & cylinder head studs?
# 5878 You can use a standard 90% countersink tool,(do not use a large Drill instead) to get an even
depth I found it best buy one fitted with a handle. It is easier to use a hand held one rather than one in a
hand drill. A drill press however would also be OK as you can adjust the depth accurately. I accept
what the previous answer said but I preferred my chamfers to be a small amount bigger than the O
rings. How skinny is skinny? the O rings I use are 68 thou thick, best not to use ones much thinner.
They should also be a tight fit on the studs. Use nylock nuts as they also help to prevent oil migration
down the studs..
# 5880 Your O rings should be fine.
# 5881 The proper tool is available from Mike at Grove classics. It makes the job easy!
L # 5982 The guy who is willing to refurbish my 1936 MSS 500 head by reusing the old
valves/guides and adding a sleeve to the guides,is concerned because he says both valves ARE
magnetic. I am assuming his concern is that someone used an inferior/improper valve in the past or
perhaps fitted an intake valve in the exhaust side sometime in the past. (He does a lot of porting/head
work but I doubt if he is familiar with the old Velos...) I am only looking to keep the top of the engine
somewhat oil tight as the guides are going to leak (air/oil) in their present state. Bear in mind this is a
1936 machine that will be putting down local roads and I am not terribly concerned about a small
reduction in performance by NOT replacing valves, seats, guides, etc. So the question is this...is it
normal for this exhaust valve to be non magnetic? And is it ok to keep using it? I always use high
quality fuel in all my old bikes.
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# 5973 Originally it would have had a magnetic exhaust valve. However if you are going to the expense
of rebuilding the engine I would recommend new valves, even if it is just due to the fact that a ground
exhaust valve will sit even deeper in the no doubt pocked seat. Not such a performance issue on the
exhaust side, but certainly will be on the inlet.
# 5984 The original valve material is magnetic for both IN & EX. If you get new valves from the VOC the
EX will be higher spec than original. The material Veloce used was EN52 for both - and that is quite OK
for road use - the exhaust will suffer on unleaded fuel though but probably not enough to worry you. If
you intend to thrash it, get a better one. I would not sleeve cast iron valve guides though - get new.
Does your head man know what he's doing?
# 5930 I would be more concerned about the guy doing your head rather than the valve itself!
Providing the exhaust valve is not bi metallic, i.e. different materials for head and stem (check with a
magnet) it should be OK. It's probably 21/4N rather than Nimonic (although it could be a Venom valve
that is fitted as - while their head size is identical the length is not). Your inlet is probably EN52. If you
want to learn more visit the G & S Valves web site. Odds on your valve originated in their factory, as the
VOC, Grove, Dodkins, Uncle Tom Cobly and all source their valves from G & S.
http://www.gsvalves.co.uk/technical_information.htm The reason for the difference between the inlet
and exhaust valve and guide is that the stem diameters differ 3/8" for the exhaust 5/16" for the inlet,
plus there's also some minor detail differences in the guides. Everyone at some time should experience
the pure pleasure of replacing valve guides in iron heads. Just a big hammer and suitable drift -
guaranteed results each time with none of the stress of: Is the head the right temperature? Will it pick
up? Have I put it in too far / not far enough? By the way if your valve seats are pocketed in an iron
head, you can replace them with inserts. While the recess has to be machined accurately, its another
big hammer and drift job. Regards Dai Hello all, I have a question about valves for my 1937 MSS 500.
The guy who is redoing the valves on my cylider head said he is concerned because the exhast valve is
non magnetic. He says both valves are the same size... I notice my parts book says the intake is a
M2/4 and Exhaust is a M2/5 also I noticed the guides both have different part numbers... If they are the
same why the different numbers?
L # 6023 Hi guys. I thought that I would send a quick note to let you know how things are
progressing on my mkI KSS. Remember, the cam and skids wore out very quickly on it's first ride. I've
borrowed and bought some spares, and loosly assembled the bits on the workbench last night. When I
placed the cambox onto the head, I realized that the inlet tappet is not centered on the inlet valve. The
tappet is only hitting it halfway. I looked closer at the valve to see if it was bent, but it seems straight. It
appears that the tappet must have been putting a sideload onto the valve. That rocker broke at the
tappet, so the stresses must have been severe. The end of the valve has mushroomed quite a bit, and
now I cannot remove the valve from the guide without cutting the valve end off. So.... I'll try to fit my
cambox onto another head if possible, to see if they cambox or head is at fault. Does anybody have
any other ideas of what could have lead to this? Maybe the valve guide is in the head crooked, and
now the valve end is too far away from the tappets?
# 6025 The early Mk1s had a camshaft that had a much larger base circle diameter than later models,
the rocker skid inserts were correspondingly shorter than later models. If the cams and skids don't
match, the rocker will strike the valve at the wrong angle, and is possibly what your problem is. I am no
expert, and cannot tell you when the change occurred, or what the skid lengths or base diameters are,
perhaps someone else out there can oblige! I ended up adding oil jets aimed at the cams to cure the
rapid wear on my KTP, the head now is no longer in danger of going rusty!
# 6027 Has the inlet valve been pocketed into the head through too much seat grinding? It’s a common
problem with old K bits. If not is the valve the right length? A miss-match of bits eg followers, rockers,
cam will give problems with contact areas and angles on the rocker movement. Have you got the skids
& tappets sorted out? I now have some to measure if required.
L # 6182 I have just bought a 1967 Venom and have taken the head off to check there was no
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damage to valves as one of the tappets was tight. At first sight the valves look OK but I am wondering
whether to replace the valves anyway to use unleaded petrol. I have receipts that show new valves
were last fitted by Geoff Dodkin in 1987 but it has not done many miles since these were fitted. Is it fair
to assume that these valves would not run on unleaded? Do you have to do any other adjustments for
unleaded? I would welcome any comments and suggestions.
# 6183 I've run extended miles (100K on a commando, over 50K on a Royal Enfield, etc) and about
5000 miles on a Velo, all with standard valves with no problems or excessive wear. Don't worry, be
happy.
# 6184 No need to change anything. Just set your clearances and check every 3000 miles or so. If
they gradually close up then you are getting valve seat recession and will have to consider having the
seats replaced with a more suitable material. But in fact the original bronze seats are normally quite
suitable for running unleaded and I doubt if you will experience problems. Do use Super Unleaded
(97/98 RON) though, or the audible knock will be horrendous!
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B.4. Timing Gear and Pushrods -
L #79 One way is to run the engine at tick over, and slowly screw out the adjuster until you just
feel the cam follower and valve lift lever (on the engine) make contact. Keep your hand on the lever,
you will feel when it makes contact. Back it off two to two and a half turns and tighten the lock nut. That
should give you 80 to 100 thou clearance. Check that the valve lifter works OK
L #81 My 1960 Velocette Venom is fitted with both the 0.010" and the 0.031" compression plates
on the cylinder base. Prior to my recent engine overhaul the tappet adjustment has always been at the
end of the useful travel with the adjusters screwed right through the rockers so that there is only just
enough tappet left for the nut to be tightened on. I have just renewed the valves, guides and springs
and had the seats recut. Very little recutting was required and the seats are in good condition, i.e. not
recessed into the head. When I torque the barrel and head using the info on Dai's database I now find
there is no adjustment left on the rockers at all. Did Velocette just have one size of pushrod for engines
fitted with or without compression plates or was this considered unnecessary. I could not find any data
on the length of the pushrods to allow me to check that mine are standard. Is this data available or
does anyone have a solution. The rocker arms are not significantly worn. I can always get longer
pushrods made up but I would prefer to understand first of all why the problem exists.
#82 I had a similar problem on the exhaust side of my Venom. On investigation I discovered that the
replacement Nimonic 80 valve was shorter than the original. This reduction in length was from the collet
groove the top of the valve. Apparently these were manufactured in this way to improve the valve
striking angle. The effect of recutting the valve seats, and settlement of the compression plates will be
positive regarding your adjustment problem. Remanufacturing push rods is not difficult. Use 0.325 inch
16 s.w.g. tube (I have the spec somewhere if you need it)for the pushrods, you may need to ream the
bore 0.250 to get the spigots to fit in the bore. I used high strength retainer as well as a precaution. By
the way there is a simple lever tool you can make to help you lift out and in pushrods without removing
the rocker box. Get a steel bar about 18 inches long and on one end drill to fix a bolt about 3 to 4
inches long that will fit into the hollow rocker spindle. Then drill the bar and fix a shorter bolt that will go
under the rocker. You can then lever the rocker up and lift the pushrod up to get the lower end out of
the cam follower cup, so that you can slide it out of the push rod tube
#96 I actually managed to track some pushrods down that were 3mm longer than mine that were just
the right size. I am now able to adjust the tappets easily, with plenty of adjustment to spare. Incidentally
I tried two different Velocette parts suppliers and their push rods varied by 2mm
L #272 Help/advice required from any LE cognizants I have twice had teeth broken from the
camshaft gear of my 1956 Mk 2 LE. I could find no reason for the first breakage, except that the gear
appeared to have had a broken tooth repaired on some previous occasion and perhaps the repaired
tooth let go and the bits took out a few of its neighbours. I then replaced the gear with another which
appeared in very good condition, but which had come from an LE which had burnt. Within 50 miles, two
more teeth broke on this gear, one of which was in the same relative location as one of the first. There
is no evidence of any seizure of the camshaft or tappets or valves, the pinion looked in worn but
reasonable condition, valve springs not spring-bound, valve heads did not hit the heads. In the second
case, the two broken teeth were on opposite sides, i.e., 180/ apart, leading to my thinking that the first
broken tooth had jammed in the pinion and done one rev to hit the opposite tooth, just a surmise. The
teeth are broken at the point of the camshaft rotation where the exhaust valve is in the fully open
position. I am looking for a replacement set.
L #674 I've just had a magneto overhaul and refitted it and done all the business with TDC
finders and degree discs. My problem is with refitting the auto advance mechanism. It came off fine,
the bolt loosening and tightening as it drew off the taper just like it says in the manual. Putting it back
on, the fibre gear meshes perfectly and the bolt screws on but goes solid about 3/8" before the bolt
head buts against the mechanism leaving the horseshoe washer and the round plate that locates on
the 2 little pins totally loose. I took the mag off about 3 months ago and I've never messed with an auto
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advance before so it may be that there is something else under the bolt head I've forgotten. I also
wonder if the auto extraction (can't get my head around how that works) in reverse means the bolt
goes tight early and then loosens but I'm reluctant to apply too much force without asking first. I can't
see how I could have put the mag on wrong. Any thoughts welcome!
#675 Forget about the Mag. With the ATD in your hand / on the bench, screw the bolt in until it slops
about. Your then past the self extract thread and can get on with the fitting.
#678 your advice was sound and the ATD is on and the timing done. A couple of lessons I've learnt
which may be of use to other ATD virgins: on manual advance mags I've tended to hold the gear or
sprocket on the taper by finger pressure whilst tightening - if you try that with an ATD you push the
ATD body too far in ahead of the bolt so the mag thread and the extractor thread can both engage
locking everything up. Basically refitting the ATD and setting the timing are 2 distinct operations, my
main mistake was trying to do both together, best to get the ATD on first and then set the timing.
L #687 Has anybody gained experience aftermarket or self made camshafts for the ohv velos? I
know that the original cams were quite good (50 years ago) but I think knowledge has improved a lot
since then and I wonder if can increase the performance of my venom with a cam of a more "modern"
shape.
#688 Wholeheartedly Agree. Dave Lindsley converted mine thus and, I think, even used the original
cam ring with a bit of deft grinding. Never gave a moments trouble since. I used to find that the fibre
gear would strip if you cogged down for a steep hill or to overtake. Sadly the bike is no longer in one
piece. Starting was vastly improved too.
#689 There is a gent in the midlands who will take your ATD unit, remove the fibre pinion and cast it
into the bin for you, then replace said item with a beautifully machined and lightened steel pinion which
will solve all the tooth shedding problems and still retain the advantages of an automatic timing device.
Drop me a mail and I'll put you on to him.
#692 That man is John Hales, who can be contacted on +44 (1509) 813507. His price now is around
£60.
#1619 I'd like to add a few words regarding the replacement of the timing gear with a steel item. Yes
John Hales is the man to deal with but has been noted he does it in his spare time so hence the delay.
Also he has the means to replace Vincent, BSA etc with a steel item as I believe Velocette were not the
only other manufacturer to use Tufnol items. However John has never seen any other than Velocette
stripped of teeth perhaps due to the fineness of the teeth. Also the weight of the steel can be made the
same as the Tufnol item. Could the use of Tufnol perhaps have been used for conductivity reasons?
L #1213 has anyone done any work on valve timing on a venom? If the cams won't match the
book timings, how far out can one be before the performance is impaired? Is it best for the inlet to be
correct and the exhaust out or vice-versa, or somewhere in between?
#1215 Regarding Velocette cam timings as the inlet and exhaust cam are one "blob" you can only
really set one cam event. Even then this is not strictly true as the cam is pressed into the camwheel,
each tooth representing 7.5 degrees of crankshaft movement you can get it to within 3 or 4 degrees.
The most important valve event is inlet valve closing (IVC), followed by EVO. So I suggest you set the
cam as close as possible to the book IVC mark. You can also of course advance or retard the cam 7.5
degrees. Advancing the cam you should get slightly better acceleration, by retarding the cam you
should get slightly better top speed. However as I am playing around with cams and cam followers on
my sprint bike, I have mapped ex-factory M17/2, M17/7 and two M17/8 cams, lining the cams up using
the etched timing marks. Guess what, they are all over the place! I will load up the excel spreadsheet a
little later.
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#1217 Basically the intake valve closing event far surpasses any of the other three events. It
determines at what point in the cylinder compression begins. Early intake valve closing creates higher
compression at lower engine speed and increases mid range power. Later closing allows more air in at
high revs and increases top end, provided the rest of your engine is up to it. Intake valve closing comes
in second in importance. Exhaust events are a tradeoff between extra time to push on the piston or
increased scavenging, but again with one two lobe cam the intake closing is the one you want right. So
what is right? On my Venom engines with /8 cam I run the timing as advanced as possible (more than
stock). It can only be advances so far as the intake valve will hit the piston on overlap. Gives great
mid-range with no noticeable loss on top but a bit of pinking at low revs if compression is too high or
timing too advanced. On well breathing motors such as Thruxton I run the cam about standard spec
(get the intake closing at spec and forget the rest). Also and engine that continues to pink at low and
mid range regardless of timing, fuel , etc., can be compensated by retarding the cam. With the Velo's
fine pitched teeth the cam can generally be advanced or retarded one tooth (8 degrees) without
interference but ALWAYS check piston to valve clearance. This can easily be done by screwing in the
rocker adjusters until the valve hits the piston and calculating how many turns from zero lash (one turn
equals .040) . Don't run with less than .060.
L #1400 With the Velo starting technique the valve lifter enables the exhaust valve to be opened
to get the engine turned over its compression stroke ready for the big swing (also good for stopping the
engine and other maintenance tasks). As I remember there is a flat at the end of the lifter that sits just
below the valve lifter thingy (exhaust bottom rocker). When you pull the decompression lever, the flat
rotates to come into contact with the rocker and lifts the valve. On my machine the valve lifter has to
travel a little before it comes into contact with the lifter thingy so I would imagine that it wouldn't take
much wear before it has difficulty in lifting the exhaust rocker. I perhaps wouldn't look too much further
and I'm sure that you've tried adjusting the cable.
#1401 On my 1960 Venom the cable did not lift the cam follower and hence exhaust valve enough; not
sufficient adjustment on the cable. I fitted an adjuster, from a bicycle I think Halfords, and that enabled
me to adjust so that it lifted the valve. The adjuster has a slot to pass over the cable so I put a turn of
fine wire round it. Make the adjustment with the timing cover off to see the effect. The alternative is to
move the nipple on the cable by using a soldering iron to melt the solder and pull the cable further
through the nipple. Mike
#1405 The valve lifter is supposed to just lift the valve off its seat enough to let the compressed air out
of the cylinder and allow you to set up a good swing during the start ritual. If you set it up to lift the valve
too much it could interfere with the valve getting back onto the seat during normal running. That would
make noise before you smelled it.
#1406 The valve lifter is also used to stop the engine.
L #2628 First is it normal to be able to hand pull all the timing gears out of the case without any
pullers including the cam gear except of course for the mag gear? Is it possible to do valve timing any
other way than it says in the manual?
#2630 Yes the timing gears (except for the pinion on the crankpin!) are retained only by the steady
plate. And I will repeat the cam timing tip I got from an old Fishtail, thank you "Rastus":
At TDC on the "off" (non-compression) stroke the valves will have equal lift. Worked for Rastus, worked
for me. This seems obvious when you think about it. A /8 may have asymmetrical opening and closing
but the valves still must not hit the piston at TDC. Remember that each tooth on the camgear equals 8
degrees of crankshaft rotation. Cam timing is not an exact science. Ignition timing is!
L #1631 One of my 'foot' of followers have a 1 1/8 inch radius another 1 inch but I suspect
someone grind one in order to copy thruxton? Because there are no mark of intake or exhaust( quite
looks professionally done) but surely someone used before ( I can see the mark where they rubbed on
cam) so may be I will wait and see how timing and lift change when I put the crank in. but it was taken
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from engine means it dose more harm than benefit? By the way , does large radius mean less lift?
#1635 More radius gives exactly the same amount of lift. While the valve timing remains the same, the
amount of valve opening is increased and acceleration loads on the valve gear are reduced. The best
way to see this is by looking at the valve lift diagrams I posted in the files section of the site a few
months ago.
#1641 Thank you for cam data sheet very nice stuff. while I was watching the graph, I felt bit scared.
because if cam follower have more the radius, just before closing exhaust valve and opening inlet valve
have more the chance of hit together , piston might be there as well! valve angle change of Thruxton
should be come from this? Or because of it 2" inlet valve? some one experienced the Thruxton
followers in standard venom head with high compression? I would not think that changing valve angle
of my alloy head MAC is non starter as well as changing the kissing valve each time I did over rev. If I
made the lift and timing graph, do you think there are any way to assess the chance of kissing valve or
piston on the paper? not in reality. If I have time I could make the animation of what happing in cylinder
head. but I do not think it is less important as I can not consider the floating valve by higher rev, etc.
#1649 Don't worry changing followers in itself will not make your valves tangle. Regarding, hitting the
piston if you use a HC piston always check clearance with Bluetac. Dave Child's who successfully hill
climbs and sprints a Viper, has been experimenting with Thruxton followers. On the track he can't see
or feel any difference, it may of course show up on the dyno. If you fit a M17/8 into a iron Velo, make
sure that the top rocker does not make contact with the rocker box, this can happen on both sides of
the rocker. You will need to carve some ally off the drive side to gain clearance and make up pushrods
of a calculated length to avoid contacting the timing side.
L #1656 After reassembling my venom engine, the exhaust valve tappet adjustment, at correct
clearance, is screwed to the absolute limit of its travel, leaving barely enough thread for the locknut. It's
as if the valve stem has been shortened, causing the rocker to lift away from the pushrod in the valve
closed position. I suspect this extreme adjustment may compromise the valve opening. I don't
remember it being like this when stripping it down. I've thought through some possible causes, like a
thicker rocker box gasket, but none seems to make the kind of difference I'm seeing. Any suggestions -
glaring mistakes are not unknown in my workshop.
#1658 Just a few thoughts/things to try/check: Did you renew anything other than gaskets ? Did you
forget top of pushrod ? - too obvious ? Did you use new pushrods ? new valves ? if so - check lengths
etc. Is ex valve seating properly ? - i.e. is valve really closed ? Is pushrod properly seating on cam
follower ? Is inlet ok ? Is r/box tightened down ok and evenly ? ditto head. Did you pick up the wrong
tappet from another engine !?! (I did this once........) have you got a washer stuck under the r/box
between it and the head so its not tightened down properly (I did this once too.....a long time ago I must
add ! ) Does engine turn over ok by hand ? - take the t/cover off and watch what happens if you have
not already done so. If nothing seems amiss I'd be inclined to take the r/box and head off and check
carefully again. Make sure valves/springs/collets/shims etc all correctly installed esp that valve is
seating correctly. If re-using pushrods - did you maybe swap pushrods so in is now ex and vice versa ?
Did you dismantle the r/box at all or install new or 2nd hand r/arms ? Hope this helps a little - there isn’t
that much to go wrong in this respect so you should find it quickly enough with systematic checking.
#1662 I had a similar problem when I rebuilt my engine last year (see group message 96). In the end I
just got slightly bigger pushrods (try Nick Paynton or Grove).
#1666 Andrews just about covered all the variables, I've had a similar problem caused by an exhaust
valve where the distance above the grove was shorter than on a standard valve. A slightly longer
pushrod cured the problem. The only thing I would add is there is no need to strip the rocker box off to
get the pushrods out ( it takes ages to clean the Green Hermatite of the head and rocker box). Just
make up a F shaped lever out of 18 inches or so of flat bar with the top of the F a bolt about 4 inches
long that fits into the hollow of the rocker, and another shorter bolt that will just go under the tapered
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end of the rocker. You can then lever the rocker up through the inspection cover and slip the pushrods
out of the cups. However taking the rocker box off may be easier!
#1667 Alternatively - to remove pushrods without removing rocker box - take t/cover off, then steady
plate, then loosen off tappets and fiddle the pushrods out at the bottom - bit of a nuisance if you have to
remove exhaust first though if you have the swept back type. Also a tiny bit more fiddly with one piece
Thruxton pushrods this way. Where do you get the green stuff? - I cant find a supply up here in the
frozen North (where everything is blue)
#1678 You can also get Green Hermatite by mail order direct from Hammerite
www.hammerite-automotive.com in the frozen North!
L #1669 Anyone care to guess torque setting for installation of a fiber ATD?
#1674 Snug, yes - about 10 - 12ftlb should be enough, but please, no Loctite. Make sure the tapers are
in good condition and clean before you assemble the plot and it should stay tight until the next time you
need to do a rebuild. Loctite can find its way into all sort of places you don't want it, and if you don't use
the correct grade you may never get it apart again!
L #2050 I have approximately .008" end float on the idler pinion in the timing case of my Viper.
This should be .001". Has anyone had experience of shimming out this end float? If so which end of the
bush is the shim placed ?
#2053 Shimming is not the answer. The official Velocette line was to replace the PB bush and line bore
it, as a eight thou shim will probably wear and break up. Also due to the helical cut gears, the thrust
face on the idler wheel is on the inside. The thrust face on the cam is on the outside plate; his is why
the crank case aluminum does not wear, and when you time the cams with the steady plate off the cam
constantly tries to jump out of mesh. If you do shim it I would periodically keep an eye on the state of
the shim.
L #2399 There are a couple of ways to deal with the end thrust created by the angled teeth of the
timing gears. Either use a lipped roller arranged so that the end load comes up against the lip, or a ball
bearing on one side with the same arrangement. The pre '53 long stoke engines did not use tapered
bearings.
#2401 As Frank suggests, I have used lipped roller bearings and they are set up with .005 end float
which increases to .010 when running. Side thrust caused by the helical gears appears to cancel itself
out especially with using the lipped rollers.
L #2491 I would be grateful for some help too. My 1967 Venom just stripped its second fiber gear
this year. I had the magneto rebuilt by Warren Wheeler last fall and it appears to be working well. The
fiber gear drives the magneto and has a centrifugal advance mechanism integral with is (i.e.. riveted on
the outside). At the end of a 1000 mile tour in June, the very fine teeth on the fiber gear stripped,
leaving me stranded. I obtained a reconditioned unit (the advance mechanism on a used gear) from
Dave Smith in July and bike ran fine until a couple of weeks ago when I was stranded again. Some
folks advise replacing the fiber gear with a metal one and some folks advise converting to a manual
advance as well. I would be grateful for some advice.
#2493 I had similar woes when I bought my Velo MAC a good few years ago. I went through a few
fibre wheels as you describe. In the end I had a new fibre wheel fitted by Roy Price (he advertises in
Old Bike Mart) and have had no problems since. I do, however, always carry a spare. Others have had
a metal wheel fitted in place of the fibre wheel. As a long term solution, this has to be the best (other
than going to manual ignition ). Can't remember who does this conversion off hand but someone on the
list will remember.
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#2495 The guy's name is John Hales +44 (0)1509 813507
#2498 But be warned that John Hales can take a long time to get the job done. 6 to 8 weeks was the
quoted time for me, but it was over 6 months before I got the ATD back.
#2500 Dave Lindsley does magneto work and has 30 years experience. 4401706365838. He did an
auto to manual conversion for me in the 70s and a complete overhaul last year. I had the hot mag
problem but now a good spark and starting. He advertises in Old Bike Mart. Another name I have been
given is Ross Davies in Wellingboro 4401933279134. Mike Daly may do Al gears 44 01785822568. He
makes a range of new parts, some in stainless, for Velos.
L #2524 I replaced the fibre wheel this year on my Viper after it stripped and have done 3 or 4
hundred miles since. The wheel was supplied by Mike at Grove Classics but the steel rivets supplied
were too short to peen over, I used brass rod of the same diameter instead. Over the years I have had
2 or 3 fibre wheels strip on other bikes and I would like to understand the real purpose of these, and if
replacement with a steel/aluminum version would be harmful. Also why are non fibre wheels fitted to
manual advance magnetos?
#2525 the only reason I have come across is steel wheels tend to be for manual advance retard
therefore need to be stronger as mistakes are more likely but easier rectified whereas fibre wheels are
reliant on automation and less able to make quick adjustments in the event of advance retard failure
which would result in major serious engine damage, by the way how much did it cost I need anew
/spare as well ,I usually depend on auto jumbles but!!!
#2526 The cost was approximately £27 for the fibre wheel including rivets (but check these are long
enough). replacement wasn't difficult.
#2527 The right way to do a mag is for it to be manual advance/retard. However in the interests of
making machines easier to handle, auto advance was provided. However, the timing wheels are then
changed to a fibre (and there are differing types) to reduce noise. Fibre being what it is any play or
out-of-true shafts will begin to break it up and the rest you know! Personally I would not use a fibre gear
and hence every one of my Velos has had manual ignition. The debris spread around in the motor, oil
tank & oil pipes when one lets go is a blasted nuisance (I know from a mates machine which firmly
made my mind up many decades ago)
#2528 Fitting a steel wheel increase the weight of an ATD from 500gm to 680gm. As ATDs have a
habit of slipping / unscrewing themselves under severe engine braking / kickback (particularly on high
comp engines), the extra inertia may increase this tendency.
#2529 An advantage of the automatic advance not mentioned so far is a better spark for starting. The
manual advance retards and advances the contact breaker relative to the armature. The magnetic flux
when the points open and the resulting spark are strongest at full advance. At full retard, which is
otherwise a good idea for starting, the spark is weaker. The automatic advance retards and advances
the contact breaker AND the armature relative to the crankshaft. Magnetic flux and spark are always at
maximum and starting is easier.
L #2537 Is it actually OK to use (or is it possible to fit) a steel wheel on a Velo auto advance
mechanism and use as per normal. I agree with what has been said that any BSAs' I owned in the past
did not strip the teeth but were known to occasionally slip. Has anyone a sure fire method of ensuring
the ATD does not slip in service ?
#2538 Make sure the tapers are clean, dry and undamaged and tighten the centre bolt properly - mine
has NEVER come loose or slipped and I have ALWAYS been able to remove it when required. I use a
John Hales steel wheel on my ATD and don't believe there is any significant difference in weight
between this and a fibre wheel although I will admit to not having weighed it!
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L #2596 Im rebuilding my '58 Venom and have a few questions. Is the cam spindle hardened? Or
is it just some piece of nickel or silver steel. The cam spindle is worn oval and I wondering if I can put it
on a lathe, take 0.1 mm of and turn a new bronze bushing
#2597 The cam spindle is made from EN32A, case hardened to a depth of 20 - 25 thou. If it's that bad,
I would buy a new one - Mike Fotherby and others sell them for GBP11.
L #2770 I was just wondering if anyone has had any experience with a two piece magneto gear?
#2771 Are you referring to the Criterion two-piece set up? If so, I have them fitted to two of my engines
and they are extremely useful in setting the ignition timing. You can even leave the centre part
attached, when removing the mag from the case and therefore never have to worry about it moving on
the taper. Criterion (Engineers) Ltd. Greenoak, Bishopstone, Swindon, Wiltshire, SN6 8QA (01793)
790219
#2776 I have been running a Criterion 2-piece kit for a while now when running with manual magneto
and find it excellent - helps save a lot of fiddling when it comes to mag timing etc. and has no apparent
tendency to slip/wear etc.
L #3418 Does anyone know where I might get a pair of cam followers for a Thruxton that I'm
rebuilding?
#3420 If you’re in the usa dave smith will regrind them. He`s doing a set for me right now not very
costly. His phone num. is 815-254-3998
#3466 Thanks for the contact. I phoned Dave Smith, Dave grinds the profiles on the inlet and exhaust
followers based on the same location of the centre (but a different radius, of course) and swears it's
OK. I spoke to Nick Payton today and he said that he's traced these out in the past and inlet and
exhaust profiles were machined on different centres. Maybe it's not too sensitive to that variable. The
other comment that Dave Smith made was that Venom followers in a Thruxton do not perform well.
#3469 I had venom cam followers in my endurance engine. I changed the top end to thruxton parts, the
timing for cam to valves didn’t seem right when I set it up and when I ran the engine you could tell they
were not right.
#3450 I've recently been in contact with a Velo specialist who has given his opinion that the lower
rocker skids were ground to the same distances from the pivot shaft and that the difference between
Thruxton and Venom rockers was only that the Thruxtons were ground to a larger radius for quicker lift.
This prompted me to prepare a profile comparison of the three types of lifters MAS 118 (MSS/VM),
MAS 118/2 (Thrx Exh) and MAS 118/3 (Thrx In) from lifters in my possession. An outline tracing with a
sharp pencil of these three types does show the differences among them with the difference between
Thruxton inlet and exhaust obvious to the eye. Inasmuch as the above evidence failed to persuade him,
I did a little research in the factory manual and spare parts catalogue and other published items. In my
reading of Velo information over the last 20 years, I've seen numerous references to the unique
Thruxton timing. Bertie Goodman was credited in a contemporary published article on the Thruxton
(which I remember, but cannot find) with the clever devising of the modified lifters so that they would
not have to create a new cam, but could continue to use the VM cam (lifted from the KTT MK VIII) with
the special lifters. If you'll take a look at page 13 in the blue parts book, pub. F.482/7R, dated 1 M JULY
1981, you'll see that ref #42 shows P/N MAS 118 used on all models but Thruxton for both inlet and
exhaust, while P/N MAS 118/2 is used as the Thruxton exhaust and MAS 118/3 is used as the Thruxton
inlet. The assignment of different modification numbers indicates the difference in the parts. Page 105
of the 'Red Book' factory service manual states under "Re-adjustment of Tappet Clearances" that the
lifters "are not interchangeable" and must be "replaced correctly" So if you are buying new lifters for
your Thruxton or especially if getting the old ones reground, you might want to verify that they are
ground on different centers. This is easily done by mounting them side by side on a drill bit and
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comparing with the MK I eyeball. If they are the same, your Thruxton will be giving away some
horsepower. The inlet rocker is set nearer to the pivot shaft.
#3452 There is no doubt in my mind the VMT followers differ from each other, seen enough of them
and read the material you mentioned, but have you come across timing spec unique for VMT? If I
remember correctly the exhaust has a longer distance resulting in later events and more overlap. Could
be the end result is only a few degree and not worth publishing spec for. Be nice to know.
#3455 First off, there are the early follower configuration with the 3/8" radius to the skid (think of the
skid as the circumference of a roller that is 3/4" in diameter, but just doesn't roll), and the later
configuration used on the 1954-1971 engines ground to a 1 1/4" diameter (I think, without looking it up),
both styles using the same part number for inlet and exhaust. These should have no markings etched
on them. The later, larger radius followers (MAS 118) were designed to create more rapid valve lift in
order to increase the time that the valve is open, also unmarked. Then arrived the VMT lifters, ground
to 1 3/8" radius (again, I think that's the spec) to further increase the open time of the valve (duration)
with the center of the inlet 'roller' moved toward the pivot shaft (retarded) in the order of 5-10 degrees
(again, no one seems to know how much) and the Exhaust 'roller' moved away from the pivot shaft
(advanced) to a similar(?) measurement. These VMT followers are (should be) marked 'IN' (MAS
118/3) and 'EX' (MAS 118/2) with an etching pencil. The purpose of the changes is to increase the
open time (duration) for the valves in order to develop more performance (generally at higher engine
speed) with a given camshaft. The two different followers for VMT are designed to also increase the
'overlap' period when both valves are off of their seats. This allows a higher specific horsepower to be
developed by exhaust tuning, although within a narrower power band. The increased overlap and
duration created by the VMT followers causes the M17/8 cam to give the engine a different valve timing
spec. than is given the VM engine, but the 'Red Book' fails to address this timing spec and I've not seen
a VMT spec published anywhere else. Perhaps a VMT owner who has checked the timing of his engine
could contribute his findings to the list. Should you want to try the VMT followers, a good starting point
would be to set up the engine with MAS 118 VM followers and a degree wheel to the factory spec and
them substitute the VMT followers and recheck the valve timing. Perhaps I'll do that with an engine that
I'm now assembling and report it to the list. Bear in mind that engine performance for specific purposes
may be enhanced by using other than standard valve timing, but that's what custom cam grinds are all
about. If you're working on a street engine, mixing and matching with different cams such as M17/ 5,
M17/6, M17/7 and M17/8 and the various styles of followers could produce some interesting results, but
check carefully to prevent valve to valve or valve to piston contact when doing so.
#3456 Sorry. error in the posting above. VMT followers are: Inlet advanced and exhaust retarded from
VM, opposite from the below stated info.
#3480 If you look at the Cam file I loaded in the files section of the site you can see the implications of
using various cams and various followers: http://autos.groups.yahoo.com/group/velocette/files/
#3503 Anent the recent thread about Thruxton followers, and being blessed with possession of VMT
816RC, one of ten special Thruxton racing engines hand built for dealers by the factory, I decided to
assemble enough of it to check the valve timing. This engine was acquired by me in a disassembled
but unworn and otherwise unmolested condition. It was originally shipped to the shop of E A Lavington,
a racing dealer and Technical Secretary of the UK club in the late 60s. The engine had apparently been
placed in a racer for a short period of time, as the clutch and gearbox have never been used and there
is no burned oil anywhere, the forged squish piston showing no heat under the crown. I mounted the
timing gear and valve train complete on a VM bottom end and used a 7" degree wheel mounted on the
LH end of the crankshaft, reading from a sharp sheet metal pointer affixed between two cylinder fins
and a dial gauge on top of a pushrod. I established TDC by use of the dial gauge reading both sides of
TDC equally and placing a pencil mark central between the two aforementioned points on the degree
wheel. The large wheel gives about .080" of circumference per degree, so it's easy to be accurate. I
double checked each valve event for accuracy, and here's what I found: Inlet opens 45 ½ degrees BTC
@ .053" clearance Inlet closes 60 degrees ABC @ .053" clearance Exhaust opens 60 degrees BBC @
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.052" clearance Exhaust closes 41 ½ degrees ATC @ .052" clearance. I read this as 87 degrees of
valve overlap. It's actually a lot more due to the excessive clearance for checking. Additionally, the Inlet
Open event is advanced 4 ½ degrees and the Exhaust Open event is advanced 2 ½ degrees from
Venom timing. I then substituted a pair of standard VM followers on the same setup for the following
numbers: Inlet opens 41 degrees BTC @ .053" clearance Inlet closes 60 degrees ABC @ .053"
clearance Exhaust opens 57 ½ degrees BBC @ .052" clearance Exhaust closes 40 ½ degrees ATC @
.052" clearance These numbers give 81 ½ degrees of overlap. My conclusions are that the VMT
followers do have the skids ground with the centers of the radii at different distances from the pivot in
order to increase the overlap as well as to advance the valve opening events.
#3515 Thanks for clarifying the matter of VMT cam followers...it needed recording. Message #3503,in
conjunction with the information in message #3480 will be of great help in upgrading run-of-the-mill
VMT towards "toolroom specials" provided to the selected few by the factory. My own experience with
VMT followers is as follows (1) I purchased a pair from Reg Orpin at Stevens before VMT went on sale.
These were faintly etched "in" and"ex" respectively, unfortunately they were probably incorrectly
marked. They were ground to a greater radius than VM followers, the hole pierced in the web was
smaller than the corresponding hole in my VM followers. Before fitting the Stevens followers to my
machine I ground and polished redundant metal from the parts only preserving the portion that ran on
the cam, it is difficult to estimate the radius of these followers in their present used condition. I don^
think their presence made much difference to my sprint times. (2)Shortly after Goodman took over
Dodkins business I paid a visit and had a pair of Vm followers reground to "VMT spec". Theses were
reground to a greater radius but with no offset, swapping them over and measuring valve events
convinced me that although marked "in" and"ex" they were identical. Reverting to case(1),these were
sold with the warning NOT FOR USE WITH VM HEAD. The included valve angle on a VM is 70
degrees. The included valve angle on a VMT is 67.5 degrees, the change was made to accommodate
the 2"inlet valve, the exhaust guide and seat being tipped sideways to prevent valves kissing.
Elsewhere Dai has mentioned slight variations in VMT valve stem dimensions to"improve the striking
angle".Further information on this topic would be useful. Goodman sold his remaining "special squish
engine",when I saw it stripped it had some special features... overhead rockers solid spindles
,presumably for better torsional rigidity...cam follower and idler spindles reduced in diameter to accept
needle rollers, the thin spindles struck me as looking weak.
#3528 Quite a few late VM Club seem to have Thruxton followers fitted- retrofitted? I'm not convinced
that, in a Venom, this would be a good idea, not with a change in centres. Does anybody positively
know if the quick-lift type were ever fitted by Veloce, and if so, did they have the centres modified?
#3608 While I had VMT 816RC set up to check the cam timing, I decided to check a number of
additional points for future reference. I have an early 'Red Book' marked for VM 1248 that stipulated
that the timing figures be checked at .030" clearance, so I did that and then checked the valve timing at
.006" INT and .008" EXH. Then I wondered what the timing would look like with the early 3/8" radius
followers, so checked that setup at all three clearances as below: M17/8 cam with VM followers: Inlet
opens 41* BTC @ .053", 56* BTC @ .030", 53* ABC @ .006" Intake close 60* ABC @ 053", 71.5* ABC
@.030", 33* BTC @ .006" Exh opens 57.5* BBC @ .052", 70* BBC @ .030", 46* ATC @ .008" Exh
close 40.5* ATC @ .052", 53* ATC @ .030", 55.5* BBC @ .008" M17/8 cam with M 9/3 3/8" radius
followers: Inlet opens 44* BTC @ .053", 62* BTC @ .030", 45* ABC @ .006" Inlet close 47.5* ABC @
.053, 64.5* ABC @ .030", 40* BTC @ .006" Exh open 61* BBC @ .052", 77* BBC @ .030", 34* ATC @
.008" Exh close 28* ATC @ .052", 44.5* ATC @ .030", 65* BBC @ .008" The above notes offer more
questions than answers. The first that comes to mind is the different clearances for timing between
early and late workshop manuals. My guess is that the long ramps varied from cam to cam due to
inaccurate grinding, so the solution was to check at a point of greater lift in order to achieve more
uniform results. The second thing that struck me is that the valves don't spend much time on their seats
at running clearances, and therefore could be expected to run hot. Prolly the reason for the change to
Nimonic 80 material for the exhaust valve as well as the heavy 3/8" stem. I have the idea that it might
be interesting to do some mix and match with the followers, eg: A VM follower on the inlet for long
duration and a M 9/3 3/8" follower to shorten up the exhaust duration for better torque curve. Other
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possibilities may occur to some of the heavy thinkers on the list.
L #3665 Somehow the notion of retarding the valve timing by one tooth can improve high speed
power output seems illogical ? As far as the inlet cam action is concerned it would seemingly give the
engine less opportunity to "breathe in" ? Flex in the valve train as mentioned by P.I. would only
compound this, wouldn't it ? Interestingly, I know someone who (intentionally) advanced his (Venom)
cam one tooth, and has been grinning from ear to ear ever since ! Anyone else tried this ? Can anyone
supply timing figures for the M17/6 cam by the way ?
#3667 Retarding the cam, thereby closing the intake valve later, allows more time for cylinder filling at
high rpm. Of the four valve events the closing of the intake valve is by far the most important. That said,
I generally run my Velo /8 cams advanced a tooth if I can get away with it. This closes the intake valve
sooner and allows for more compression at mid range rpms (the piston is traveling up on the
compression stroke when the intake valve closes) and a noticeable increase in mid range power. I have
never been able to detect any decrease in high speed power though theoretically it should be there.
Maybe I don't wind that high. If you are having that familiar 'it's just starting to come on the cam when I
hit red line' Velo phenomena though, you may want to try it. Two caveats: Advancing the cam will
decrease piston to valve clearance on the intake opening. You should have .060, I have run .040
without trouble. Stick some .060 solder in the spark plug hole (cold) towards the intake valve and turn
the engine over gently to squish it and see what you have. Second, the extra compression may cause
pinking in the mid range if you are close to it now.
L #3806 My Venom is down investigating engine noises. A new big end assembly is to be fitted as
there is a little clearance. On stripping I found that the axial clearance on the cam shaft gear assy to be
8 thou and the idler shaft axial clearance to be 4 thou. This is well above the 1 1/2 thou recommended
in the book. This can contribute to noise they say. Looking at the cam assembly the bushing fitted is
exactly the same length as the cam/gear itself. Is there a fix to get the clearance back to what is more
acceptable. This also applies to the idler gear assembly. The radial running clearances appear OK Any
comments from the experts out there would be welcome.
#3807 On my Velo and other bikes I own the excessive play was eliminated by punching shims out of
brass or steel shim stock. Make the shims the same OD as the shoulder on the cam wheel.
#3810 If the engine is out of the bike heat the cases up to about 130 degrees C. Place two pieces of
0.0015" feeler blade under the cam and with a counter bored drift that clears the threads on the spindle
(but makes contact with the cam) give the drift a healthy thump. However, due to the helical gears
creating outward thrust, the camplate also wears a thou or two. So either get the plate surface ground
or live with it! If the crankcases are in the bike use a Black and Decker paint stripper to locally heat the
cases. Regarding the idler gear, the only solution is to rebush the gear or precision grind a smidging of
the end of the spindle.
L #4616 It seems when I push on the steel magneto timing gear, and gently tap it into place finger
tightening the nut, the magneto shaft still just spins inside the gear. Is there a washer under the
magneto timing gear nut? How can I tighten this nut up properly without revolving the shaft of the
magneto and keep the timing in place? Why did it take 500 tons of force to get it off and wont tighten on
the taper even enough to stop spinning? And finally does it tighten by pulling the shaft out as there is
no more movement for the gear to tighten against the shaft because it is fully seated against the
housing?
#4617 First make certain that the nut will spin onto the shaft with no resistance, then use a socket to
drive the gear onto the taper. Then bring the nut and washer up to the gear rather gently to exert some
pressure on the gear. Tap the socket (that is large enough to fit over the nut) to further drive the gear
onto the taper, repeat, repeat, repeat. Or... make a puller for the shaft consisting of a substantial cross
bar drilled and tapped in it's center to accept the shaft thread, with two more holes drilled at 180
degrees and tapped to accept bolts that will press the gear onto the taper. If you're pulling the gear up
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to the housing, either the magneto flange gasket is too thick or the drive end bearing is incorrectly
assembled in the magneto. The fully assembled gear must be free from the engine housing.
#4625 I had a similar problem assembling my 66 VMT. The steel gear was rubbing on the engine case
just so slightly, and the magneto shaft did not want to lock in the taper. I took a skim cut on the back
side of the gear removing ten or twenty thou to provide the clearance and reassembled the bits. The
gear has more than e'nuff face to turn the magneto after taking the light cut. That was about 8,000
miles ago. I suspect either a thicker gasket or a slight altering of the location of the armature inside the
magneto housing occurred after it was rebuilt.
#4628 Re mag tapers - it is amazing how much further onto the taper the mag gear will go if it has been
re-ground a few times. I have a couple of mag sprockets here that are scrap as a result because the
chains are out of line. Same happens on M series gear pinions.
#4621 There is an alternative to the magneto gear 'tap tap' ritual mentioned by Frank (which has
always worked for me as well). I'm fairly sure Criterion sells a vernier magneto gear, which eliminates
the problem altogether, and makes accurate ignition timing a snap. If the magneto gear slips when the
nut is tightened, its possible the threads on the mag shaft or the nut are damaged. Another nut is
usually a good test, and that's what a decent spares kit is all about. This is best tried before the mag is
installed, to make sure that the nut will turn freely all the way down the mag shaft thread; otherwise
you're screwed!
#4623 If, after trying what has been advised, you still cannot get the gear to "grip" the taper, it's
possible that it may have slipped in the past and a previous owner has used Loctite or similar (this
could explain your difficulty in extracting the gear). Concentric grooves or ridges on either the shaft or
gear tapers are an indication of earlier slippage. The usual remedy is to lap these away using fine
grinding paste but, if carried out to excess, could explain why your gear fouls the crankcase. Beg or
borrow another gear and see if that is a better fit. The magneto drive gear should line up fairly well with
the cam gear that drives it; if it doesn't - it's time to worry. If/when you get that sorted out, the centuries
old method of ensuring that shaft and gear stayput was to pee on the taper prior to assembly. I'm not
kidding! Huge wheels in cotton mills and mine winding gear received this "attention" if they showed a
tendency to come loose but note that the necessary delivery was the prerogative of the Works
Foreman.
L # 5306 Can anyone tell me how I can take the atd unit apart? It’s a lucas type and Ill like to
change the fibre gear, but I don’t understand how the weights and other revolving bits are fitted to the
central shaft.
# 5308 Get John Hales to fit a steel gear in place of the fibre gear - fit and forget! John Hales +44
(0)1509 813 507
# 5313 John Hales is your man. Excellent job, good value for the workmanship, a nice bloke to speak
to, and lighter than the original fibre - but be prepared to wait months.
# 5315 Well yes, thank you.. But I like to do me own repairs! It's a hobby after all. I did renew my velos
big-end, surely this cant be more difficult than a crankshaft overhaul?? Its only an atd unit!
# 5317 To get to the gear take a look at the back side and you will see a steel ring about 3/16" thick.
This is a press fit on the center shaft and holds the whole thing together. Press it off carefully and you
will be able to get to the gear. Then it is just a matter of removing the four rivets going through the gear.
# 5319 I'd still recommend you get hold of one of John Hales' gears, even if you're going to fit it
yourself. They really are nicely made and as someone else pointed out, lighter than the fibre one as
well as being a damn sight more robust.
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# 5321 Actually I have got a steel gear from Grove Classics. I thought Ill give that a try. The fibre gear
has lost 4 teeth.
# 5324 I don't believe the Grove gear is the correct one - I went down that route before I got JH to do
mine. John's gear is a beautifully made really well lightened piece of work. As I remember, Mike
Fotherby's one is actually either a plain steel gear or a manual ignition one, definitely not a replacement
for the fibre gear. As it happens my engine is dismantled at the moment. I'll take a couple of pics and
post them on the site for all to see. I'm sure the difference will be immediately apparent.
L # 6216 Has anyone on this list experience the failure of a cam spindle in a VM or VMT. If so,
were you able to determine the failure mechanism, what went wrong?
# 6229 I had a problem 2 years ago with a MAC when I was doing my runs out to all the VOC centres
in UK. ( Cam spindle setup is the same) Presumably I had failed to properly tighten the nut on the end
of the spindle on the outrigger plate. By the time I reached Scotland, there was a lot of valve gear
clatter, and on checking, found that this nut had come loose. the now unsupported spindle had worked
loose in the crankcase and had migrated inwards, allowing the nut to drop into the timing chest to play
with the cogs where 2 adjacent teeth on the camshaft were knocked off. The timing was still OK, as the
angled teeth had not come away from mesh before the tooth after the gap came into mesh. The now
wobbly fit spindle was pulled back through the outrigger plate with long pointy pliers, and the nut
locktighted on. The bike ran fine on the trip to see the some racing at East Fortune, and the run home.
Once home, I locktighted the spindle into the crankcase as well, replaced the cam, and have had no
further trouble (touch wood). Use 'em and abuse 'em !!
L # 6337 I am putting the cylinder head back onto my 1967 Venom (engine no 6420). It has the
one piece push rod cover tube ie no gland nut in the middle). My manuals and spare parts lists only
show the type with the gland so I need some help please! When I dismantled the head, there we no
gaskets fitted on either the top or bottom of the push rod tubes- only the two O rings. Is this correct?
Does the seal just rely on the O rings? If it does, do you assemble the o rings with oil/ grease or does it
need any gasket cement?
# 6346 No gaskets required, the O-rings will do the job of sealing the joints on their own far better than
the gaskets ever did! A little smear of grease to aid assembly is all that's needed, no gasket cement
required, although you could use a very thin smear of silicon sealant in place of the grease for a belt
and braces approach but this will mean a bit more difficulty when it comes to dismantling things again
in the future..
# 6359 My venom has a shim over the O-ring before putting on the rocker box or the lower plate cover
on. I believe this was how Veloce assembled them.
# 6366 The spares list makes no mention of any shims, could it be possible this was an early version
of the one piece pushrod conversion, or something someone has added in order to utilise an undersize
O-ring? I cannot see any necessity for any shim in this position, if the recess is machined to the correct
depth the ring should seal without any additional help.
# 6371 Yes could be someone has changed it, my Venom is a 1970, one of the last made (in the last
batch of 20). In theory it should be better without the shims but I use them because they were there and
I don't suffer leaks.
L # VOCNA 163 I have found a source for new and rebuilt Velocette camshafts. Gary Robinson,
on the Isle of Wight, can supply these parts. He has been rebuilding Vincent and Velo cams for 30-40
years. He can build new cams from scratch, using EN19 steel, or build up the lobes on a worn cam with
stellite and then grind it to the correct profile. He can supply cams with the following part numbers: K17
K17/2 K17/5 K17/8 K17/10 K17/11 M17/3 M17/7 M17/8 Here is his contact information: Gary Robinson
(calling from USA): 01144 1983 760 765 Cranmoore Ave Cranmoore Isle of Wight UK PO41OXS .
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Paul Zell recommended Gary Robinson to me, as did Ivan Rhodes. cheers pete
# VOCNA 165 Does anyone out there have any experience with the built up lobes? Particularly those
built up with stellite? Any chipping or cracking?
# VOCNA 168 My racer had a stellite built up core with a polydyne grind and wore extremely well
even with the elevated revs of 7500 to 8000 I was running at. I detected no visible wear after 5 years of
racing. I have worked with satellite in years past and the key is not to overbuild. The layer thickness is
somewhat dependant on the grade of satellite but a general rule of thumb is not to exceed a .020 -
.030 build up. Too bad he doesn’t list a polydyne grind for a Velo as I am interested in getting a couple
done.
# VOCNA 176 I'm delighted to learn that stellite faced cams may be available. I have had a scuffing
problem with the piston skirts and cam lobes in my race and customer high performance engines. The
skirt problem was resolved with liberal assembly oil and 50 weight high contact pressure oil. The cams,
though improved, still have a problem. Stellite cams may be the answer. Thank you for your insights
from you experience. Years ago in my tool room engineering days we used stellite in forming dies in
high wear areas. In those cases the thicker the stellite the better to resist cracking and chipping. Of
course we used inserts as compared to a welded on surface. Apparently the coated cam lobe is rigid
enough to prevent cracking. The question of the polydyne cam came up several months back. I tried to
research it with varying degrees of success. The best answer I got was from Dave Holder, the receiver
of Velocette when they folded. He said that the Thruxton cam followers with the M17/8 cam gave the
equivalent valve events. This was accomplished by changing the cam follower pad radius and its center
distance from the pivot. He gave me the dimensions and I can forward them to you if you like.
# VOCNA 178 Gary does custom cam profiles too. He may also have other Velo profiles listed other
than those that I quickly wrote down during our phone conversation. Call him and ask, he may have a
polydyne master profile. If not, you could loan him one of yours to make a new master from.... He told
me how he has done all the cams for the "Hogslayer" Vincent 500 sprinter (drag racer). He would
modify an old cam profile with grinding, then build it up with fiberglass. Then put it into the motor to
check the timing specs. If it seemed good, he would use that master to grind a new cam profile. Test it
at the track, then modify it again. He did this over and over for years, the bike now runs very fast, I think
he said an 11 second quarter mile. Pretty damn quick for a 500cc motor!
# VOCNA 166 Any estimate on costs?
# VOCNA 179 My rebuilt k17/5 cam cost 70 pounds, plus I'm sending him the k17/2 worn out lobes to
use for a future customer.... It sounds like a bargain to me. Megacycle said to call them back in a month
or two. They were too busy to take on any work, it was tough to get them to stay on the phone long
enough to talk about the cam. Their cost was about $250, plus $500 to make a new master.
# VOCNA 181 I contacted my friend John Watson in England who prepares Velos for short track and
MGP racing. He is well acquainted with Gary and says he does a fine job. Only problem is Gary is very
busy and we should plan on at least a 6 month wait. It appears Gary is a good source. I want to get a
couple special cams made more lift. I tried Megacycle last year and they too costly, too long of delivery,
and not really interested. Gary may be able to provide just what I need at a reasonable price. Mirek,
can you wait 6 months?
# VOCNA 167 Got Robinson cams and followers in my KTT and Egli Vincent. Both stellited cores and
all doing well. Gary has a superb reputation in the Vincent world for hard wearing cams and followers.
Prices are cheaper than you will find anywhere else.
# VOCNA 170 I have many original KTT cams from mk1 - 8, and none are stellited. Repro cams seem
to be. The used stellited cams in general are in much better shape than the used originals.
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# VOCNA 171 Yes they are. Stellite #1 (the hardest available) built up, no brazed on pads. He
switched (when I don't know) from softer and different grades for cam and followers to straight #1 on
both by recommendation from Stellite corp. He has done Vincent cams/followers for years. Vincents
are notoriously hard on them, poor oiling, small base circle, etc.. I've never heard anything bad from
the Vincent guys (also notoriously hard), only good. Gary talks quite candidly and mentioned the
failures he has seen have attributable to some peculiarity or problem with the specific engine. My Egli is
new so I'll be keeping an eye on them but can't comment personally. My original KTT cam went flat
toute suite after I got it. Rob Drury recommended Gary as he had done some KTT cams for him with
no trouble and already knowing his rep I went for it. I checked mine religiously after every ride for
about six good rides and they looked just perfect every time. BTW I have not had any trouble with
stock M series Velo cams or followers, they seem to last very well. All that oil flying around the timing
chest must be good for something!
# VOCNA 172 A comment on the m-cams. I had mine go flat by virtue of neglecting to measure the
distance of the protruding valve guide from the head, as you know there is no shoulder, thus the cam
was trying to push the guide into the head with the spring collar of course this constitutes operator error
and has nothing what ever to do with hard face quality but I thought a reminder of stem hieght might be
an apropriate note
# VOCNA 175 Good point! I rebuild 6 to 8 cylinder heads a year and it is not un common to find the
guides have moved into the head in the direction of the valve head. But, one head had the exhaust
guide moving in the direction of the spring retainer. Why? Go figure! Anyway as you say good idea to
check the valve guide height.
L # VOCNA 267 Why on earth would one trade a fiber gear mag drive for an alloy item anyway?
What's wrong with steel? I know its heavier, but I have a heavily drilled item on my clubman which can't
be much more than the alloy. I was under the impression that it was a Good Thing not to lighten the
timing gears too much, as their mass dampened some of the shock from the power pulses.
# VOCNA 262 Aluminum alloy gears should be ok, if they are sized for the job, and made from a good
alloy. Berg sells thousands of part numbers, from 2024 aluminum with T4 heat treatment. If you want
damping, cast iron is a good material. But gears made from cast iron ~may~ shed teeth easily. Same
for gears made of plastics or composite materials. I don't know if Veloce sized the gears properly for
materials other than steel, and for the loads from various cam proiles and strong magnets in the
magnetos. Paul, you may find that reducing the mass of the timing gears is much the same as reducing
the mass of the crank, or the rockers, pushrods etc. Reducing mass of any of these will allow the
engine to rev easier. The reciprocating parts (rockers, tappets, etc) give you the best performance
results, as they changing direction, and thus acceleration, very often. Of course, these parts are under
high stress too, due to these accelerations, so we must be careful. I would think that changing the
weight of the timing gears would affect the balance factor of the engine, just as changing the weight of
the flywheels does. (to a smaller degree though, with their light mass compared to the flywheels). Me?
I'll stick with a steel magneto gear, undrilled
# VOCNA 264 I've never bothered reducing the mass of the timing gears. First of all they are only
spinning at half crank speed. Their weight and diameter in comparison to the flywheels is small and
they are round and symmetrical so should not have an effect on balance. They don't have any real
influence on valve springs like the reciprocating mass. I know some guys do it for every last potential
gain, more power to 'em. I only bought the alloy gears because at the time (5 years ago) I was told that
was all that was available for fiber gear replacement. There are definitely steel replacements out there.
Don't know what it takes to drive a mag power wise. Wouldn't the magnetic field be something like
valve springs, whereby they take power to open but add power on closing? Or perhaps the spark
reduces the magnetic influence.
# VOCNA 266 I don't know either, but as a magneto is a generator, converting mechanical power to
electrical power at something rather less than 100% efficiency, the power transmitted through the drive
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gear must be more than the wattage produced - a few thousand volts times a few milliamps! I think it
will absorb rather less power than a regular dynamo producing the same wattage, and considerably
less than a dynamo or alternator powering daytime lights. The two main causes of premature fibre gear
failure are 1. slack in the magneto bearings and 2. the fact the the same teeth gets the load
on every revolution, both from the magnetic flux, and from the operation of the contact breaker. Both
these causes are preventable by diligent maintenance: 1. by reshiming the bearings as necessary and
2. by periodically repositioning the atd on the magneto spindle. OK, we know neither task is easy. In
fact it's rather less trouble to wait till it fails and replace the whole thing. But if that routine is followed
one will get trouble free service for tens of thousands of miles.
# VOCNA 308 Other then striping the teeth off caused by loads in excess of the shear strength of the
material the gear tooth is made of there are generally just two types of gear tooth failure. One is when
the load, or torque, on the gear is uniform and not high enough to shear the teeth off but the contact
pressure on the tooth surface exceeds the fatigue strength of the material. In this case "spalling" occurs
caused by sub-surface fatigue of the tooth resulting in small chunks of metal coming off the surface.
(This is very common with Velocette transmission gears.) Eventually the tooth surface erodes to the
point not enough thickness remains to take the load and the tooth sheers off. The other is when cyclic
overloads, or hammering, occur that are large enough to bend the tooth. Depending on the amount of
overload the tooth bends back and forth 100s or 1,000s or 1,000,000s of times until the tooth fatigues
at it's root, or base, and breaks off. Spalling can occur in cyclic load failures too. However, the failed
tooth of a cyclic load failure is usually near full thickness where as the uniform load failure tooth is
usually eroded thinner. When we think of vibration in or Velos we usually think only of reciprocating
balance factor. However, there is another vibration caused by the power pulses of the engine called
"torsional vibration". Simply put torsional vibration is caused by the flywheel speeding up every time the
engine fires and then slows down until the next fire when it speeds up again, all in the same direction of
rotation. All piston engine exhibit torsional vibration. The more pistons the smoother, or more constant
the velocity of the flywheel rotation. Single cylinder engines are the worst. This is one of the reasons
why our Velos have round flywheels in addition reciprocating balance correction and cushion drives on
the crank shaft. For four stroke engine the torsional "impulse" occurs in the second order, or every
other revolution. At 4,000 rpm the flywheels accelerate and decelerate 2,000 times a minute. In
automotive work an un-flywheeled V-8 engine crank shaft commonly instantaneously accelerates 6 to 8
degrees ahead of it's continuos rpm at each cylinder firing then slows back to it's continuos rpm before
the next firing. I have no idea how many degrees the crank shaft accelerates in our velos. But, given
the large bore, high compression, and low mass of the flywheels I'm sure it is a lot. Where is all this
breeze going? Here goes: Our engines exhibit torsional vibration, the gears have mass, and the device
on the end of the gear train has mass and in some cases a load or resistance to turning. Since all the
gears in the timing chest are positively locked to the crank shaft by their teeth they are accelerated and
decelerated at the same rate as the crankshaft torsion vibration. Since the gears have mass and
maybe a rotating weight at the end of the gear train the load on the gear teeth is a function of the mass
times acceleration. In rotating machinery kinetic theory the toque to accelerate, or decelerate, a
flywheel possessing polar moment of inertia approaches infinity as the time for velocity change
approaches zero. So the gear teeth can "feel" high cyclic loads due to engine torsional vibration simply
because of their own mass, weight, even though there is a low load at the end of the gear train. In the
case of our aluminum gear a way to tell if tooth fatigue occurred is the look at the broken surface of the
tooth under a magnifying glass. If the failed surface looks grainy or crystalline it is likely a fatigue failure
from tooth bending has occurred. Never use aluminum or fiber gears in a motorcycle!
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B.5. Oiling System -
L #143 I had a Venom Club, and from time to time, possibly connected with bore wear and engine
speed, it spat out considerable quantities of oil via the engine/oil tank breather. A friend, more thorough
than I, believed on his similar Club it was the oil frothing too much and thought he'd pinned it down to a
certain make of oil- we're talking of 25 years ago. The only result was I checked engine oil, as a reflex,
every time I stopped.
#145 I'm wondering if the MAC puts out less oil mist then the higher powered units, if the pump is a
lower volume pump then the venoms. If not it means I have plenty enough oil flow. Interesting thing;
when I run up the rpms, on the center stand with the oil tank cap off, the oil is seen to be flowing back
into the tank but not under much pressure, and in sort of a pulsing flow. Is this normal for the Velo? So
many details, so little time.
#146 This pulsing flow is very normal on Velo returns. According to the manuals it's due to the fact that
the return side of the oil pump has a greater capacity than the supply side-this is designed to avoid the
possibility of crankcase flooding. On matters like this I'm in agreement with Bruce's recent comments-
Velocette were not theorizing when they built their bikes ! How many TTs did they win ?
L #179 The modification to the 1960 V models uses two pipes and the length of both is important,
but probably not critical. The lengths prevent the Pressure/Vacuum from syphoning the oil. Steve of R
F Seymour, The Velocette specialist, will inform as my information has gone "walkabout". Tel +44 (0)1
844 212 277
#190 Listed in the parts book the respective lengths are FA138 Engine to oil tank 21.375 inches,
FA141 oil tank to wheel(!) 27.5 inches.
#195 You are spot on, but I have never found whether this includes the coupling at the engine end.
The inlet to the tank is at the back and I will find the dimensions and inform. The vent from the tank to
atmosphere is from the rear and at the top of the froth chamber
#626 If your breather arrangement on the crankcase is correct and you are using the late spec oil tank
(or one modified to Keith's spec), the pipes should be as follows: 1.. Breather hose - engine to oil tank
(21.375" long x ½" bore) 2.. Breather hose - oil tank to rear of machine (27.5" long x 3/8" bore)
L #350 History- Top end rebuild about 6 years ago but to my knowledge the bottom has never
been touched. Symptom- The bike has been unused for about 2 years, so the sump had filled with
about 1 cup of oil in that time. After draining this and starting the bike the engine smokes for about 2
minutes then stops smoking and runs cleanly for appro another 15 minutes then resumes smoking
quite heavily. After re inspecting the sump I find about 2 cups of oil unscavenged back to the oil tank. I
have been told the Velo pump is fairly reliable a gives little trouble, I have investigated all the simpler
possibilities but to no avail. Checked and washed filters in the circulating system. Plenty of oil is getting
to the top of the motor etc Checked and cleaned return lines to tank, no blockage found. Checked that
the oil tank is not pressurizing (and ran it with the cap off there is a constant flow) Checked if overflow
was blocked or kinked. OK Has the pump had it ?,and were do I find a replacement in Australia. or and
I hope, could it be that the gear/shaft of the pump has warn a groove into case endplate and on
heating up the gap increases far beyond spec (which I don't know) an the pump fails on the return. If
this last point is a common problem could somebody let me know, and would refacing the casing on
glass with lapping paste solve my problem.
#351 I also have a smoking MAC, a 1952 Alloy engine. My Mac started smoking after winter storage
several years ago. It also accumulates oil in the sump, but after draining that oil it will continue to
smoke and oil will ooze from the exhaust port. It has been sitting in storage in my shop office trailer
ever since. Several people have told me, that my engine probably has a broken oil scraper ring. That it
probably rusted to the cylinder during the winter. I did neglect to pour a small amount of oil into the
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sparkplug hole before storage. I just bought a blue shop manual reproduction on eBay, that covers a
lot of motorcycles other than the MAC. Better than trying to go in blind I would think.
#352 Have you cleaned the filter PLUG at the bottom of the crankcase 7/16" BSW Spanner
#353 Don't know your full case but I would strongly recommend that you investigate the oil return,,,, it
sounds like the oil accumulating in the crankcases cannot be transferred back to the oil tank quick
enough !!!.
L #375 I'm rebuilding a 1957 MAC and have a couple of problems that I would appreciate some
advice on. It has suffered a fair amount of neglect, and the oil pump (which I have removed)feels a
little 'rough' turning it by hand. Is it a very specialized job to rebuild these or would a secondhand one
be more advisable? If the latter is the case, anyone out there got one for sale? The other problem is
that, at some time in the engine's life, the main bearings have been turning in their housings, causing
some slight damage to the faces. The current bearings are in good condition, and the outer races feel
tight in their housings. I have heard that one can use Loctite in cases like this, or have the housings
machined and fitted with inserts.
#377 The pumps themselves aren't that difficult to overhaul. The trick is getting the components lined
up so that the pump turns freely and then goes back into the case without wrecking the bore. If you're
unsure, take it to someone who is. I think I would take the pump apart before I bought a new one and
assess the damage. You may find that it's only minor damage. As far as the cases go, again take your
cases to someone with experience in that area. I'm sure the problem isn't that bad, but you don't want
to put the engine back together until you've verified it. I am not a big fan of Loctite on main bearings.
There's too many things that can affect adhesion. The better way would be to bore and sleeve the
mains back to standard.
#378 Please read the manual. There is a special "clamp" tool to line up the oil pump casings. The
removal and replacement of the pump assembly required the heating (carefully) of the crank case to
allow the differential expansion of the two dissimilar metals to release the pump. Always bolt the two
halves of the crank cases together to prevent distortion. Brute force and ignorance will result in
damage to the oil pump drive spindle and the crank case housing bore.
L #410 I'm having problems locating 40 grade oil for my Venom in Ireland. Does anybody know
the location of a supplier? I am reluctant just to top up with Multigrade as I don't know the history of the
engine vis a vis rebuilds etc.
#412 I wouldn't use a multigrade after a straight 40. Try www.castrolclassicoils.co.uk/ They deliver
free for orders over £30 in UK mainland. or you could try Silkolene who also do a straight 40
www.a-pp.com/ There may be other suppliers of Silkolene oils.
#482 We cured most of our oil leaks by changing from a modern multi-grade to Castrol GP50. Last
Sunday at the Tyne Valley Classic Motorcycle Club show we were informed by an IQ0 that Velocettes
were never designed to run on straight oils. He had so many modern reworked parts on his bike the
only thing missing were the Honda badges..
#733 I won't be able to resist having a go on it before taking it apart but feel I should at least change the
engine oil before I run it. I have Silkolene 30's and various modern multigrades. Any thoughts?
#736 Strait 40 at this time of year, in the engine, gearbox and chaincase. Drain and refill the gearbox as
water may have entered. Silkolene is a good choice.
L #542 I have a 1950 MAC that recently underwent a complete nut-and-bolt restoration by a very
reputable builder. Although I have not asked him directly, I assume this included a new or rebuilt oil
pump as well. On occasion, the crankcase floods with oil, presumably involving some sort of problem
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with the return pump. This only occurs after I have ridden very close to 22 miles (but again, does not
occur in every such case), which would seem to indicate a possible mechanical distortion arising from
thermal effects. The problem appears to rectify itself when the machine is shut off and allowed to rest
for approximately 5 minutes. I have checked for obvious causes, such as air leaks in the feed and
return lines, or any obstructions in the suction plug. There are no identifiable oil leaks from the suction
plug, the oil pump base, any of the feed or return lines, or any of the fittings associated with the oil tank
itself. A knowledgeable individual opined that the pump is probably not as pristine as I would like to
believe. In such a case, it would not develop adequate suction to reestablish prime should it be lost
(this is plausible, since the last occurrence followed a long downhill stretch at high RPM, which would
presumably empty all of the oil from the crankcase and the return side of the pump). Allowing the bike
to sit would cause enough oil to drain into the crankcase and reestablish prime, which is also
consistent with my observations.
#543 Do you mean the crankcase floods whilst the engine is running ? If it does this you've certainly got
a problem with the oil pump (which should be able to scavenge a greater volume of oil than it can
supply). I think I'd take it back immediately to your highly-reputed restorer ! Presumably it didn't have
this problem before it was rebuilt ?
L #544 I have recently built a Venom engine out of parts obtained from various jumbles and other
sources. the oil pump has been checked and is in excellent condition and there are no obvious air
leaks. The problem is when I fit the ball valve no oil will feed to the rockers. Remove the ball valve and
instant feed is there. Anyone had this problem before??
#545 Probably too obvious, but have you put the ball and spring in the right way - ball on top of spring.
Also the seat for the ball needs to be almost a knife-edge for it to work efficiently. If you can see a clear
chamfer where the ball sits on the seat it is probably too worn. Also obvious check again for air leaks,
even a pin hole will upset it.
#546 Make sure you prime all the air out of the delivery oil pipe so that the negative pressure exerted
by the oil pump will suck oil past the feed valve. You can, initially, pressurized the oil tank to do the
same job. The elasticity of any column of air in the pipe will forestall this. We note the comments about
ensuring the ball is the correct way round in the valve assembly. We have never had any "sumping"
problems with any of our Velo's.
L #601 All this talk of oil levels / oil breathers reminds me of a story the late, great Phil Irving used
to tell. During his first stint at Veloce, he took it upon himself to point out to Mr Percy that the oil tank
transfers were misleading and impossible to abide by. When queried he explained that the wording
"Keep Oil Above this Level" literally meant that the oil tank had to have oil in the top and only air below
the line on the transfer. He was told to mind his own business. Later models had a subtle change to the
wording - something simple like "Minimum Oil Level". So one can presume that Mr Percy took note of
this comment, having slept on it. On the subject of oil level and its effect on engine breathing, early
experience with VMT 457 and many other late model Velos shows that if you overfill the tank it will
pump oil out the breather system until the level stabilizes at about 50 to 60 mm below the top of the
filler. So one soon gets an eye for the level which avoids excessive waste, with the extra oil simply
blown all over the machine, whilst keeping enough in circulation to cool and lubricate. By the way, I've
never been one to be too concerned about what oil goes in - sometimes special (expensive) 4 stroke
oils, and sometimes cheap generic brand multigrade (as long as its API spec was SE or higher) and
they all seem to work - never a seizure and now completing the first major overhaul in 20 years with
nothing more than a hone, new rings and fitting a better second hand Nimonic exhaust valve (the
original was pitted because it was only a KE965 to start with and obviously didn't survive the
degradation of fuel quality these past 4 years or so). Oh and I did do a bottom end overhaul as well,
not because it needed it, but because I didn't want to be having to pull the engine out again within the
next 10 years. And the engine was only sitting on the bench in the first place because I needed to
remove the gearbox - give me an iron MOV or MAC any day! And those who have toured with VMT457
will vouch that its longevity has little to do with a gentle hand on the throttle.
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#604 My good, and lamentably late friend John Anderson used to reckon you should just be able to
touch the oil with the tip of your finger. Saves looking for a depth gauge every time.
#605 I also had a '47 KSS ( why did I ever sell it??) that had a breather pipe extending to the rear
mudguard and never had the slightest problem with oil levels or usage - in fact I never had any
problems of any kind over the 8 years of using the KSS. My "new" '61 Venom has an unvented oil tank
cap but has the half inch breather pipe referred to by Pete C. In this case it is directed to the chain just
by the footrest/brake pedal ( Clubman rearset). I have tried overfilling the oil tank - to see what
happens! - and it simply blows oil out onto the chain , which ends up on the tyre, rim etc, until the level
in the tank is back to more or less half way between the max and min level, the level seems to stay
there then irrespective of whether I'm in ride to work mode or having a long thresh down the M4.
L #607 Interested in the comment, "if no froth tower is fitted to your tank you are very likely to
have a big problem with excessive external lubrication, since the function of the tower is to separate oil
from breathed vapour." Specifically, what is a frothing tower? Perhaps a failure in my British to English
translations skills is at play here? The return pipe in my oil tank does stick up about an inch above the
oil itself (setting aside the rather active dialog about where to properly set the oil level). Is this the
tube/tower that is being referred to? I was also fascinated by Pete's remark about the, "lead the pipe
(whose length is specified in the parts book and is important for correct operation)." With due respect,
the pressure drop in a 1/4" line at the flow rates in question is relatively minimal, and I fail to see how
the exact length would matter whatsoever. We're not exactly talking about the reflected back pressure
wave in a tuned exhaust system here.
#620 the froth tower is the name given by someone in Velocette history to the inch and a half diameter
tube that rises from the top of the oil tank by about two inches inboard of the right hand frame tube.
Inside the tank there is a tube running from the top of this tower down to the back side of the tank with
about an inch sticking out, to which a flexible pipe should be attached and led to the rear of the
machine. This is the tank breather outlet. I believe that the purpose of the froth tower is to keep the end
of the tube inside the tank well above the level of the oil or any froth (air/oil mixture) and to prevent oil
from being discharged via the breather. I cannot tell you whether there is any additional baffle
incorporated in the tower, perhaps someone else might be able to enlighten us? When the later type
engine breather system is fitted, the pulsations in the crankcase are transmitted into the oil tank via the
½" bore pipe, and yes, there is a tuned length to the system. The factory worked out the lengths of the
pipes and if correct, the system is quite effective. If not, the system has been known to pump oil out
and lubricate the rear tyre. The return feed to the oil tank from the engine enters the bottom of the filter
chamber which is about 2 inches diameter, and runs up the inside of the Aluminum tube that surrounds
the through stud retaining the top and bottom caps on the chamber and prevents unfiltered oil from
returning to the crankcase through the scavenge side of the pump. Oil flows then through the filter and
returns to the main body of the tank through the short tube to which you refer, just below the filler cap.
#623 having read your detailed description of the frothing tower, crankcase breather, vent lines, etc., I
can only observe that my '50 MAC as I received it does not have any of these features. It has a sealed
oil tank with two tubes entering at the bottom. One is the feed union, the other the return pipe which is
an integral part of the tank itself. That's it. I spoke with fellow who restored this machine, and he says
the tank, crankcase, etc. are as he received them (i.e. no vents anywhere). I did not think to ask him if
the unvented cap is a replacement. It's essentially perfect appearance indicates that it is most likely not
original, and may be incorrect in that it is unvented. I only began thinking about any of this when I
encountered a scenario wherein the crankcase floods with oil, but only after several minutes of
sustained, high RPM operation. Otherwise, everything appears to function properly. I noticed that there
are no vent lines whatsoever on the oil tank itself (or anywhere else for that matter), and that the oil
tank cap is unvented as well. In looking further, I noticed that a vented cap is available, which
reinforced my notion of the possibility that the tank is probably pressurizing. Unfortunately, my scheme
[notice the overt use of English phraseology] to explore this theory by temporarily replacing the cap by
a stopper with a reasonably large (1/4" or so) hole in it has been thwarted by the loss of top gear. I
have disassembled and carefully measured every part in the transmission, and everything looks just as
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it should. Figured I would think a bit more about the situation before posting this problem for others to
offer their useful comments. [At present, I am leaning towards the possibility that there is enough play
in the camplate that it tips sufficiently to allow the actuating pin in the upper fork to slip from its slot,
jamming the camplate into the actuating pawl and binding up the shift lever]
L #614 Oil filter tube , If the fibre gear strips it will certainly block up the oil return , I've had it
happen in the past and a friend had it happen only a few weeks ago on a club outing , the pump
pressure split the return line . I do NOT recommend removing the tube from the Filter , When the
engine stops all the muck in the filter will drain down with about a half pint of oil back into your crank
cases , a) it makes it difficult to start with all the oil drag ( especially cold), over-oils the engine till it all
clears , c ) think of all the grit ,swarf and silicine that is in there ! Nots /bolts for the MOV . I don't know
of anyone who does Kits , but the VOC have many bolts sized according to listed part number/length
/thread .
L #638 While on the subject of oil tanks, I strongly recommend the fitting of the VOC oil filter kit in
place of the original. The cartridge filters are so much more efficient at straining out contaminants. On
early oil tanks it fits without any modification, on later tanks you need to file away about 1-2 mm of
protruding tube. If you do this put the tank cap on and block the tube off from the inside with a small
piece of rag to avoid iron filings in the oil tank. Details of the kit can be found here
www.velocetteowners.com/sparesco/specials.htm
#639 Problems to translate, what do you mean "to file away 1 - 2 mm of the protruding tube" ?
#641 On later Velos, the plain hole from which the oil flowed from the filter chamber back to the oil tank
was replaced by a very short piece of tube. The tube enters the filter chamber and stops the oil filter
cartridge from fitting easily, so it needs to be filed away to allow the filter to fit into the chamber.
L #640 A more general question about oil filtering. In disassembling the oil feed tube on my '50
MAC, I noticed that it did not have the "gauze filter" described in the owner's manual (it did have a ball
check valve which seems redundant, since there is already one in the crank case). It occurred to me
that some sort of filter would be in order. In discussing this with some more knowledgeable people, they
essentially told me not to bother, as long as I was vigilant in changing my oil regularly. There rationale
was twofold: I) the tolerances in the pump are rather large by today's standards, so small particulates
will essentially pass through the pump anyway, and ii) any filter with even a small pressure drop across
it will prevent the oil pump from doing its job properly, since it is a volume (not pressure) based system,
and will not tolerate significant pressure drops. They further opined that the gauze filters were suitably
porous that they didn't do an effective job of filtering the fine particulates anyway. Apparently, the filters
under discussion here are meant for later [and different?] machines. Regardless, should I be pursuing
the installation of some sort of filter on the input line?
L #659 What's the best low-tech method of sealing the poly tubing to the copper tails of the
banjo(etc) connections in the oil system?
#660 Take them to a hydraulic hose or lorry parts company and get them crimped.
L #761 I've got a couple of questions which I hope someone can answer. The oil filter in the tank
has been taken out and an external (RGM) filter fitted on the return line. Is this a real advantage or not?
I'd really rather not have the external one on, simply because I don't like the look of it. If it were a real
advantage I could (just) live with it. I would have thought that the original filter is adequate providing oil
is changed regularly. Any views welcome.
#762 A few years ago while changing the filter in a BMW twin I found it fit the Velo oil tank quite well,
so that's what I use. It's a paper cartridge filter. All that's needed to fit a Velo is a couple big o-rings or
washers to center it in the bore. Some tanks will need to have the small tube trimmed back to let the
filter slide by. Framm and Purolater market this filter if you don't feel like frequenting the local Beemer
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shop
#770 On the oil filters, I wouldn't worry too much about a bypass valve. Since it's on the return side the
worst that can happen if the filter plugs is too much oil in the sump. Never seen it happen.
L #774 I plan to modify my "old fashion" oil tank to the more recent standard. The crankcase
having been modified by the previous owner, I would like to "recycle" the oil coming out from the
crankcase breather. My first series oil tank being already fitted with its own breather outlet, coming from
the froth tower down to the outlet tubing coming off the inside face of the tank, if possible, I would like to
know the exact location and dimensional information of the additional tubing to be fitted to receive the
21.375 in. crankcase breather pipe.
#785 Weld in a piece of half inch od tube about 1.5 inches long at the top of the rear of the oil tank.
Make sure it clears the down tube when fitted. For a better pipe run, you can weld the tube in angled
towards the front.
L #783 has anybody converted an engine to the later oil drain from the timing chest to the bottom
of the motor. I think this mod came in about 1964. it looks like an external rib. I believe you can do this
but you have to plug the crankcase in the bottom of the timing chest to stop oil draining into the motor
internally. I was going to this some years ago but hit a problem with clearance between the motor and
the frame, to put a union on the bottom of the motor was going to foul and I decided not to bother, but
having thought about it I could come in at an angle and tap the hole and then screw in a tube much
like the later breather tube under the mag. has anybody tried this ?. it would then be straight forward to
connect to the tube, and then to the bottom of the timing chest. velocette did some tests and
discovered that when the engines were running, oil was backed up to as much as three quarters of the
timing chest as it was unable to drain into the bottom of the motor fast enough due to the flywheels
stopping the oil going down the internal drain hole. this was one of the reasons why they did a revision
of the crankcase. you should end up with a better crankcase than the later ones with this mod because
the earlier cases have the restrictor in the oil passage way to stop debris going into the pump and the
later cases do not have it. any feedback is welcome. Regarding the later breathing arrangement, I read
that people are doing this and breathing into the oil tank, I hope that when they are putting the tube
under the mag into the timing chest that they are also putting a hole from the timing chest into the
crankcase otherwise it is a complete waste of time, because with out the hole from the timing chest to
the crankcase the air cannot be expelled. just my two cents worth. thanks for taking the time to read
this. cheers.
#784 I have added the oil drain line to the timing case. I used two 90 degree 1/8" US pipe fittings, one
tapped in at the bottom of the timing chest and the other at the bottom front of the side of the case
(thinking the oil level would be lowest at that point while running). This is a tight fit in the frame as the
frame curves near the case at that point (swing arm frame). To do over again I would put it further back
where the frame rails are straight as I can't remove the fitting with cases in the bike. A side benefit with
this mod is that with clear tubing I can always see how much oil is in the sump when sitting. I did not
plug the old drain hole figuring it would now function as a breather between the crank case and timing
chest along with several others holes I added. Wet sumping while running has not been a problem
even with pump spinning 50% faster than stock 2 start (1/4 vs. 1/6 crank speed). I'm getting ready to
test pumping additional oil to the exhaust rocker box for cooling which may create a drainback
problem, we'll see.
#899 Having done that, throw the tube away! I did that over 40 years ago, and have never missed it!
Then you have permanent peace of mind, at least as far as a blocked return goes.
#941 Do it that way and you won't be able to take it apart easily to clean it when you do a filter change.
The Velo factory guys weren't stupid, their way is still fairly well thought out most of the time, personally
I would leave it the way they intended or replace with the cartridge filter conversion.
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#900 If you dispense with the tube inside the filter, the entire contents of the filter chamber will drain
back through the oil pump into the crankcase when the engine is stopped. NOT a good idea to remove
it.
#902 Entire contents? The whole half cup-full? As I said, I have never noticed any deleterious effects
whatsoever! Maybe you would if you are one of the traditionalists who insist on using SAE50 oil, but not
with the recommended 20W /50.
#907 And all the crap that has been pumped up into the chamber on the dirty side of the filter? I think
I'd rather leave that in the filter and not draining back through the oil pump whatever oil I use!
#918 I'd suggest that most debris from the oil is already well embedded in the filter felt, and any oil
which does drain back will do so slowly that any metallic pieces large enough to cause damage will
settle to the bottom of the filter chamber. The 'drain' hole (the cross drilling) is not at the extreme
bottom. The oil returning to the sump has to dribble through the .001" clearances in the oil pump, so it
will hardly gush! Having experienced a blocked return due to the existence of this tube, and losing all
the oil as the result of the return pipe subsequently blowing off, I MUCH prefer to dispense with the
tube and risk a little debris returning from whence it came, rather than a complete engine seizure! By
the way, if all the blocked return does is to cause a build up of oil in the crankcase, there is a serious
weakness in the oil pump. The pump cannot revolve at running speed and not pass more oil than could
possibly squeeze through the pump clearances. You will therefore get a very high pressure in the
return pipe and excessive wear on the pump drive gear and worm (creating damaging debris in the
sump!!!).
#911 Both my bikes came without this mystery oil filter tube. Can someone please spec one out so I
cam make one?
#915 Part number A293/2 is what you want - sorry I can't give you dimensions without taking my oil
tank to bits! As I remember, it is a piece of alloy tube which is a push fit over the LE547 filter cap
adapter shoulder below the cross drilling. The OD is just about the same size as the hole in the bottom
filter cap and it is long enough to come to about an inch short of the top cap when fitted. The ¼" stud
runs up inside the tube. It's not unusual for the tube to come off the adapter, perhaps when changing
the filter and either thrown away or simply dropped back on to the stud without being properly located
whence of course it will not do the job it was meant to!
#925 The tube is 0.500 od, 6.850 in length made of aluminum. The wall thickness is approx 37 thou.
The tube is a heavy push fit, light press fit over the fitting at the bottom of the studding; you can clearly
see the step it fits over on the fitting. Bore a piece of ali tube or bar out so that it fits. For what it's worth
I would fit the tube for the following reasons. 1) the filter holds quite a quantity of oil, and this together
with the oil left normally in the bottom of the crankcase may make starting more difficult 2) If you fit the
club filter kit which I recommend www.velocetteowners.com/sparesco/specials.htm you will need it. 3)
if it serves no purpose, Veloce would have saved the pennies by not fitting it I agree that it is unlikely
any debris above a thou will find its way past the oil pump, I just don't like the thought of all that debris
dropping back down.
L #936 When my piston "holed" it also bent things in the oil pump making me rebuild that as well
as needing now to take the engine apart to clean everything out. Would this new filter have saved me?
#938 Unlikely, as the filter is after the pump not before it. What it does is strain out the very fine
contaminants that cause wear in the engine.
L #1055Here I am spannering my Venom racer, trying to reduce all the leaky areas ... I've fitted
a much larger bore to the engine breather - ok. I've drilled the timing case to crankcase hole - ok. But - I
undid the pokey leaky external (1/8 bore !) pipe and fittings to see that the fitting in the crankcase
shows me the side of the flywheel ... now this type of mod is a 'good idea' isn’t it ?! Well, surely if it lets
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all the oil out straight onto the flywheel it's going to cause drag ?
#1058 I assume you are talking about a drain mod from the timing chest to crankcase? - There is no
technical article that I am aware of. If you think it through the oil supply to the timing chest is constant,
so you are going to get the same amount of oil through to the sump, it just takes a quicker route to get
there. The scavenge rate is greater than the feed, so when running most of the oil is scavenged from
the crankcase. The cupful or so that you get when you drain the chain case, is the oil that makes its
way from the rest of the engine when the pump has stopped.
L #1275 I'm seeking info on the oil pump as fitted to the mid 60s Venoms. Can someone shed
some light on the pump rate or volume for supply side pump?
#1285 I'm not sure why you want this information or it's accuracy, but using SAE20 at room
temperature to replicate normal engine oil at operating temperature, a pattern pump delivered 1.07
pints per minute at 1080 rpm with a pressure of 18 psi. This information came from Fishtail.
L #1282 While looking at options, before I stuffed a brand new oil filter comprised of wire mesh
and felt into my newly restored oil tank, I slipped a BMW airhead oil filter into the tank's recess. Wow, I
suspect many folks figured this option out years ago but it was new to me. With the addition of a simple
adapter turned up from aluminum bar stock in about 2 minutes, the BMW 11 42 1 337 572 filter is a
perfect fit. Together with new gaskets cut from a sheet of 1/8" nitrile replacing the fiber gaskets, I'm
expecting a neat oil tight oil tank.
#1283 There is also a smart oil filter kit available from the Velo Owners Club in the UK, fits inside the
tank and its leak free! Doesn’t stop oil leaking from everywhere else though.
L #1367 It might be not important to my velo. But I can not stop wondering, how Mrk8 oil tank
inside like. Because it seems to be just box with cut out for down tube and cab. But it should have
something inside as I can see the cylinder shape marks appearing to the side of tank. What is it? I
would be glad if someone supply the sectional drawing of tank. It might be secondary tank mentioned in
Velo saga book for warming up oil quicker for racing?
Thank you
#1368 There is nothing special inside the Mk VIII oil tank. The pressed pieces are just to make the
sides stiffer. There is a mesh oil filter and a return pipe, that's all!
L #1391 Got the bike running over the winter and did about 50 miles with no problem. Then last
weekend I set off on the first club run of the year and when I started the bike I had an oil leak from
under the disc at the top of the filter on the top of the oil tank. The leak was not a drip but a continuous
flow. I tightened the nut (and the locknut) which sorted out the problem. I put it down to a new gasket
bedding in. The run was about 200 miles and I had no problem so I thought I had sorted it out.
Yesterday I started the bike again and had the same leak though a bit slower than before. I removed
the nut, washer and disc and found that the gasket had been cut through by the rim on the oil tank.
Maybe me overtightening the nut? Didn't have a spare gasket so bodged it by using silicone sealant.
Started the bike this morning and there is no leak from the disc/tank joint (probably because of the
silicone) but oil is leaking up the stud and out under the nut. To me this indicates a very high back
pressure from the filter. I'm running on Silkolene 40, the filter is new, there is a good flow back into the
tank. Any ideas?
#1392 When you put the new filter in, did you take off the alloy tube that goes over the stud that bolts
the whole assembly together. there is a cross drilled hole in there and it can block up with debris
coming back from the motor. If the motor has stripped the fibre teeth off the magneto wheel in the past,
the oil pump will pass it back to the oil tank but they are to large to get out of the cross drilled hole, or
even gasket sealants or bits of metal will do the same thing. I have heard of bikes blowing their oil line
off on the return side due to this problem. If it cant blow the oil line off the next thing would be a
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pressure build up in the tank. I might be wrong but it is worth checking out. cheers.
#1408 If the alloy return tube or the cross-drilled hole were blocked the oil line might blow off but there
is now way this could result in a pressure build up in the tank, since no oil can find its way into the tank,
or even into the filter chamber. However, if the return stub from the filter chamber into the main body of
the tank were blocked then there would be a distinct possibility of the contents of the filter chamber
trying to exhaust themselves from the filter chamber cap gaskets or stud seals. The things to check,
apart from making sure the holes and tube are clear, are that the filter itself is not clogged solid, the cap
gaskets are either new or in very good condition (these are quite a thick and solid material and if the
chamber flange has cut through them it might hint that the wrong material had been used) and the
adapter at the bottom and the nut and steel washer at the top have fibre washers fitted under them
(Dowty seals can be used if you can find the correct size). The alloy tube MUST be fitted and should be
a good push fit on the return adapter to prevent the contents of the filter chamber from returning to the
sump when the engine is stopped. When the machine is reassembled make sure that there is a good
flow from the filter chamber back into the main body of the tank - with the engine warmed up for a few
minutes this will contain a fair amount of air since the scavenge side of the pump has a greater capacity
than the feed side and attempts to keep the sump "dry".
L #1694 Wet Sumping: Ever since I bought the bike about 9 months ago, oil has disappeared
from the tank into the crankcase. I tried the "recommended" application of a copper hammer to the ball
to form a new seat but with no success. A few days ago I decided enough was enough and bought a
new ball, spring and seat. Fitted them and the problem, if anything, is worse. This morning I found an
oil puddle under the bike because the oil had filled the cases so much that it leaked out through the
main bearing. Despite this it started well (thanks partly to the new carbs). I really can't accept this as
OK so am looking for some advice. Should I call the supplier of my new bits and complain? Should I
accept that it's going to wet sump (surely not), or is there something I can do? Lap the ball/seat with
fine valve grinding paste? Any other suggestions?
#1695 As you guess, you shouldn’t have to tolerate this. Your course of action sounds ok to me - its
one of the things I'd do - making sure I'd cleaned everything off before reinstalling of course ! But first -
check the spring is the right one/length etc - this should be a 'truncated conical' shaped spring approx
1.25 inches long. The thin end of the cone presses against the ball (obviously). Check the spring is
holding the ball on its seat ok - best done off the bike. Sorry if this is obvious, but in my experience
springs (of all applications) are the things pattern parts manufacturers most often get wrong
#1696 I always put the ball valve seat in the lathe and using an end mill or slot cutter in the tailstock
chuck, just skim off the existing seat. A very, very light tap with a soft hammer recreates the seat. Using
this method I have found that no oil passes the ball valve.
L #1713 I have been told that non-detergent oil is preferred for the older machines which do not
have oil filters. Does anyone have any experience with Aeroshell aviation oil? Their "100" is the
equivalent of non-detergent 50W.
#1717 The non-detergent aviation oils are only for break-in. Even aircraft reciprocating engines have
gone to detergent oils once the rings are seated. The detergents in aviation oils are formulated to
absorb the products of combustion of aviation fuel, not the lamp oil we're being sold as gasoline. I think
you may have your viscosity indexes backwards, the way I recall it is that a 50wt aviation oil is the
equivalent of a 100wt automotive oil. Check this out from a couple of sources to be sure. You can't go
wrong with just about any good quality 50wt motor oil (40 or 30wt in cold weather).
#1723 I am a pilot. Aeroshell 100W is a 50 weight non detergent oil. Works fine in a motorcycle but why
would you want to pay such a high price for oil? Most modern 50 weight oils will work equally well. I
have used Aeroshell in my Sq4 with no adverse affects. I used the Aeroshell because after I sold one of
my planes I had an extra case gathering dust so why not use that expensive oil in one of the
motorbikes? Aviation "break-in" oils are mineral oils that are specific for aviation break-in purposes.
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It's a long story but aircraft engines are slightly different from automobile/motorcycle engines and
require a different break-in procedure and oil.
L #2015 I wonder if any of you velofellows out there could help me with a problem I have had with
my 56` MSS. At any speed over 50 mph oil is coming out of the vented oil cap breather hole and
around the cap itself. I have checked the breather hole and it`s fine. Any thought`s???
#2017 Over-full or if the oil cap is like the gas cap the two holes are offset, to prevent this. it is possible
that someone drilled a non vented cap straight through. Probably over-full.
L #2054 When starting my cast iron MAC, it smokes significantly from the tailpipe for about fifteen
seconds, then stops. This occurs if the bike has sat for several days or more. It runs wonderfully, and
does not consume any measurable amount of oil from the perspective of the level in the oil tank. I let
the bike sit for a week, then pulled the crankcase drain plug. Approximately two ounces of oil drained
out. It is not clear to me whether such an amount would typically accumulate by settling, or whether the
ball check valve leaks. I am inclined to think it is the former, since the amount of oil that drains out does
not increase with time (specifically, if I let the bike sit for a month, the same two ounces of oil drains
out). Could the observed smoking at start-up instead be attributable to oil that has accumulated in the
rocker boxes, and then drains down into the cylinder? If so, would this imply that I have sloppy valve
stem clearance?
#2056 Your diagnosis is correct. If you remove a rocker cover you will find the spring cup full of oil.
Reduced valve to guide clearance will reduce smoking, but not stop it. There are two solutions - fit
auxiliary oil drains or wait 16 seconds before you look backwards.
L #2136 In previous messages regarding oil tanks/frothing towers I don't seem to see an answer
to this one:- In the collection of parts which I acquired to build my MAC were two oil tanks, both with
frothing towers. Naturally I fitted one of these. The only visible result was a serious oil leak where the
polythene pipe fitted on to the outlet spigot, despite being a good tight push fit. No oil ever issued from
the poly pipe. I have since swapped one frothing tower type for a plain tank, and am considering fitting
this. The question is, which models were originally fitted with which type of tank?
#2150 Froth towers were introduced in 1959 the MAC was discontinued in 1960. Therefore the very last
models may or may not have froth tower oil tanks, depending on how Veloce used up existing stocks.
Velocette Springer oil tanks had quite an evolution during their life. Original had a long filler neck Later
the neck was shortened Mounting brackets strengthened (but not strong enough) Froth tower
introduced Pipe fitted to accept breather from engine Rubber mounted Thruxton variant Brackets
strengthened again by using one piece of steel to run from top to bottom mountings. Veloce also
produced a small number of drive side mounted oil tanks for special applications.
#2155 Thanks for the chronology of the oil tanks. Using this info I'll fit the plain oil tank. I've since
discovered that the oil leak from the froth tower tank was not from the outlet breather but from a hairline
fracture at the bottom bracket weld.
#2140 Mention of Velo frothtowers brings to mind a common (?) problem with oil tanks on RIGID
models fitted with the towers. If you own a KSS or a MSS that has a tower, & appears to have a small,
but persistent oil cap leak that cannot be cured, investigate the area on the top of the oil tank between
the vertical top mounting strap & the tower to tank joint, which is also the point where the 2 pressed
halves of the tank are originally gas welded. If you have the 'incurable' leak, you will find a minute
hairline crack in the enamel, which indicates a welding stress crack underneath. This occurred in the
original welding process & may, or may not have been completely cracked originally, but vibration may
(?) have eventually caused the leak. I am not sure that it's a good idea to attempt to repair by welding,
as excessive heat may restress the area. In the several cases that I have found, I just grind out the
small crack, & repair with a small spot of 'bronze', keeping the temperature as low as possible, & as far
as I know, it has remained an effective repair. I would be interested to know if anyone finds this fault ? -
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check any unused tanks that you have !
L #2472 Is it necessary for me to remove my Thruxton type oil tank from the bike in order to fit
renewable paper filter system which I got from VOC? (The frame loop gets in the way upwards and the
swing arm pivot downwards)
#2475Yes you will need to move the oil tank.
#2473 I am converting to paper element system and am at a loss as to how I get clearance to remove
wire and "army blanket" style filter The frame interferes upwards and the swing arm pivot downwards.
Any tips out there?
#2474 If you replace the oil filter, you will need to drop the tank off first. This also allows you to wash it
out to remove any debris inside.
#2479 On later tanks you also need to carefully file the short piece of tube inside the filter chamber,
otherwise you cannot get the filter in. Stuff the tube with a tiny piece of rag from the inside before you
file and push the rag through into the filter chamber, so that you don't get iron filings in the oil tank.
L #2482 Hi I spoke to Castrol's technical group, regarding corrosion and gumming when using
Castrol R. As part of the conversation they forwarded me the attached:
TECHNICAL BULLETIN - WHAT IS ENGINE OIL 02/12/2002
What does it do? Engine oil does more than simply lubricate, in fact there are five basic functions:-
Lubrication: Prevents metal to metal contact between moving surfaces and reduces friction Protection:
Protects against corrosion and wear caused by the results of fuel and lubricant decomposition. Sealing:
Acts as a seal by filling the gaps between the piston assembly and the cylinder wall. Cooling: Transfers
heat away from pistons and bearings to areas such as the sump where the heat can be lost. Cleaning:
Maintains by-products of combustion finely separated until they are removed by filtration (dispersive
action). Resists black sludge formation (detergent action). What does 15W-40 mean? The numbers,
such as 15W-40, are the viscosity rating of the oil. The viscosity of an oil is a measure of its thickness
or resistance to flow. Thin oils are good for cold starting, especially in winter but are too thin for high
speed driving in summer. Thick oils are good in summer, but too thick for starting in winter. The Society
of Automotive Engineers (SAE) defined a classification system for viscosity (see table above)
Obviously, for all year round use, an oil which combines the cold temperature viscosity of a winter
grade with the high temperature viscosity of a summer grade is required. This is achieved by adding
viscosity index improvers (VI) to the base oil to create multigrade oils such as 10W-40, 15W-40 or
15W-50. What does API SL/CF, ACEA A3/B3 mean? As engine technology develops there is a
corresponding increase in the demands placed upon the engine oil. New performance standards are
introduced which supersede the previous standards. Therefore, even the latest ones e.g. API SL, will
be superseded at some point in the future. There are two major bodies setting standards: the American
Petroleum Institute (API) and the Association des Constructeurs Européens d’Automobiles (ACEA).
There are different standards for petrol and diesel engines. The most recent standards are listed below,
NB these are not equivalent eg SG does not equal A1! These standards are based on a series of
engine tests, often referred to as sequence tests. Each test measures a different aspect of the engine
oil's performance, such as camshaft wear. Only when an engine oil passes all the tests can it be
labeled with the standard e.g. API SJ. What's in it? About 80% of an engine oil is the base oil which
may be mineral, synthetic or a mixture. The remaining 20% consists of additives which give the engine
oil its performance. What's the difference between mineral and synthetic oil? The mineral oil used in
engine oils, although highly refined, still contains undesirable compounds that limit the performance of
the engine oil. Synthetic oils are very pure, only containing compounds required for lubrication. This
enables the production of very high performance engine oils that offer significant benefits over mineral
based engine oils. Although synthetic engine oils were originally developed for high performance racing
engines, their benefits are just as important for standard engines fitted to passenger cars. These
include very low wear levels, increasing the engine life, increased engine efficiency for more power or
fuel economy and easier cold starting. Will they mix? All Castrol engine oils will mix with each other,
106

even fully synthetic Formula RS and standard Castrol GTX. Obviously, to obtain the maximum benefit
from fully synthetic engine oils they should not be diluted with mineral engine oils. Castrol engine oils
will also mix with any other manufacturer's engine oils. The only exceptions are specialist competition
oils containing castor, such as Castrol R, that should not be mixed with any other type of engine oil.
Interpreting manufacturers' recommendations Interpreting the vehicle handbook can be difficult
because the information is often out of date. In general, later standards can replace earlier ones, so SJ
can replace SG, SH etc. It is important to keep the recommended service intervals to maintain the
engine in the best possible condition. It is also important to do this to maintain the vehicle warranty,
whether this is the manufacturer's or a third party insurance policy. What's different about Castrol?
Castrol has always seen the API and ACEA standards as the minimum requirements for an engine oil.
These standards are often based on tests in old engines that have little in common with today's
engines. To overcome this problem and to ensure that Castrol engine oils protect today's technology
engines, Castrol has developed a number of special tests. ALOFT measures the actual oil film
thickness between the camshaft lobes and camshaft followers, the most heavily loaded engine
components, whilst the engine is running. BOFT measures the actual oil film thickness between the
crankshaft and bearing shells while the engine is running. Castrol 500 mirrors a standard engine test
but uses a modern technology engine to ensure that Castrol engine oils lubricate today's engines
effectively. As well as these specific tests, an extensive fleet of test vehicles is constantly on the road
ensuring that Castrol engine oils protect your engine throughout the life of your vehicle. Any questions?
If you need any further information then consult the Castrol Technical Help Desk on 01793 452222.
Health and Safety information sheets are available for all Castrol products from the address below.
Castrol International, Pipers Way, Swindon, Wiltshire SN3 1RE, England, Telephone: Orders/Enquiries
(08459) 123011, Technical Enquiries (01793)452222, Fax (01793)453750 .\
L #2552 I am trying to fit the VOC filter kit into my Thruxton style oil tank . I would like to know why
the filter assembly seems too long for the tank. I am having difficulty putting the upper cap on (the lower
cap seems to be fixed in place). Does the alloy tube that fits over the central long stud extend so as to
cover up the two lateral apertures at the bottom of the stud assembly ;or does it just sit loosely on the
ridge above?
#2553 On closer examination the alloy tube appears to sit on a machined ridge right below the oil feed.
I am led to believe that the alloy tube should be a tight fit over this machined ridge, the instructions
stress this and even suggest lactate. It seems to me that considerable force or reaming is going to be
necessary as the alloy tube has a smaller bore.
#2558 A light tap with the hammer is all that is normally required to locate the tube on the bottom union
- often they are slack. Perhaps your tube has been distorted. Before you fix the tube make sure the
stud does not screw too far into the bottom union and obstruct the oil holes.
L #2784 I recently received a replacement tube from Grove. It is steel whereas the tube at present
is aluminum alloy. The steel tube sent by Grove(U.K.)is 4 and5/8ths long but the alloy one is 6 and
7/8ths.This component is referred to in the parts list as A293/2 and is described as "Oil tank filter centre
tube".Being keen to do this right I am asking if any Velo person can assist. I am considering shortening
the longer tube to the 4 and 5/8 length.
#2789 The alloy tube in my oil tank is 6 and 3/4 inches long. This brings it to about 5/8 inch from the top
of the felt filter. When I've assembled this in the past I've thought that since the tube is a fairly tight fit
within the filter, the vast majority of the oil must be passing through the top inch or so of the filter. I have
sometimes had a small weep of oil from under the top nut which seemed to me to indicate a high back
pressure (which you would have if only part of the height of the filter were in the flow). Previous posts
on this site indicate that the 6 and 5/8 length is correct. Personally I think the filter's performance would
be improved if the tube were shorter but others with far more experience may well disagree (and be
right!). As part of my current rebuild I've bought a paper filter kit from VOC spares. Not used it yet but
the filter is well clear of the tube and the whole thing looks very well engineered.
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L #2785 I am getting towards the end of a 1964 Venom rebuild, and one of the things left is to
position the oil tank level, and the chain guard transfers. I thought it would be a novel idea to position
the oil tank transfer at the level at which the oil should. Since the oil drains to the crankcase with time
(I'm guessing this will happen even with the new ball valve), let's define oil tank level to be "the level
seen, immediately after stopping the engine". So with this definition where should the transfer be
placed? If there is another definition of oil level - let me know. Looking at period pictures, placement of
the transfer at best, looks to be pretty random. Some bikes appear to have the transfer placed below
the center line of the tank. There must be an explanation here .. Anybody know? On the subject of
transfers, the chain guard transfer also seems to have been also placed at random angles. There is no
obviously logic here either. The angles used do not seem to line up with anything.
#2786 One of my friends in the North American Velo club gave me the best advice on oil levels. This
was after several episodes of over-filling the tank on my '66 Thruxton. This is exciting as the oil comes
blasting out of the breather onto the pavement as the most embarrassing time. On that model, the
transfer is essentially under the carbs and not visible while looking into the tank. His comment was you
should just be able to touch the oil level with a finger with the bike warm and on the centre stand. This
assumes you have the standard hand, with standard dimension fingers, traceable to NIST (formerly the
Bureau of Standards). This has actually worked well for me as I usually have a number of fingers with
me while I'm out riding and wish to check the level. One additional note, 1/4 liter of oil seems to change
the level in my tank about 5/8 of an inch.
#2788 My understanding is that the oil tank transfer height depended on whether the tank had a froth
tower. The froth tower allowing a larger volume of oil to stay in the tank rather than on the back wheel! I
don't know about exact heights, but I put mine on so that my British Standard finger just touches the oil
when it's near enough half way between the max and min lines.
L #2787 The only job I'm not looking forward to is fitting the oil pump. I've read the red book and
previous posts about the amount of heat needed, it sounds a bit daunting. I was wondering about
getting the whole lot up to say 150C before I start then if I have to use more heat, the rest won't be as
much of a heat sink - any views?
#2790 When I recently built up a bottom end I did as advised but used a freezer to cool the pump for 24
hours, I wouldn’t say it dropped in but it was a damn site easier than the removal, plus I had a nice mix
of third degree burns and frostbite to amuse the locals.
#2792 Assembly is always easier than disassembly due to the fact that the oil pump hasn't been
heated as it is during the disassembly process. Further cooling of the pump may make things easier
still, but personally I have never found this necessary. If the cases are heated generally with a suitable
heat source - I use a good hot air gun, NOT an oxy-acetylene torch! - up to "spit and sizzle" point, the
pump will slide in easily and still allow enough time to line up the screw holes. This method ensures the
cases are heated sufficiently, but not to the point at which the material properties change. I would think
150/C is far too high a temperature, spit will sizzle at not much over 100/C.
#2793 I always bolt both halves of the crankcases together when heating to prevent any distortion.
#2794 I had assumed that this went as read. On assembly it is necessary to have the crank assembled
into the cases and the joints sealed and bolted up fully. The timing side crank pinion, oil pump worm
drive, locking washer and nut should also be assembled, but that's all - any more and you will
unnecessarily be wicking heat away from the cases.
#2799 Good news - the oil pump's back in. Thanks for the various bits of advice. Assembled
crankcases in oven at 120C, oilpump in freezer at -18C. Went in with a few very light taps of a hide
hammer. I'd cut the heads off a couple of old screws to make studs and fitted them to the crankcase
before fitting the pump. This made lining up the holes simple. I'd cut screwdriver slots in the end of the
studs to get them out after fitting the pump but they came out by fingers to let me fit the correct bolts.
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L #3034 A mate of mine has the following problem: He primes the oil lines, starts the Viper, which
quickly drops about two inches of oil level in the oil tank. Once the return starts feeding back into the oil
tank, it flows fairly heavily and continuously from then on. Upon inspection, the crankcase is then full
with way too much oil, almost to the crankshaft bearing height, which floods the piston, flywheel etc.
flinging oil all over the internals. He has replaced the oil pump with a new one previously as he though
this may have been the problem, but this has had no effect. He has removed the oil filter in the oil tank,
the tank is well vented, and oil lines seem to be in good condition. Any thoughts
#3037 Are the feed and return pipes connected correctly? That is the feed to the feed side of the pump
and visa-versa.
#3067 The tube is in place, so there goes another option. My last thought at this stage is that he has a
double speed drive on the pump which in my experience causes major flooding to the point where the
exhaust port is full of oil, along with the top end etc! Both John Jennings and I had the same problem
and reverted back to the single worm drive - no more problems! I had suggested this to my mate last
year when the symptoms first appeared after his engine rebuild and thought he had already done this,
but apparently he had not. As he's just about torn all his hair out trying to find a solution whilst retaining
the double speed screw, I reckon he may well change it this time!
#3041 Feed and return lines crossed over?
L #3256 I have a problem getting oil to circulate after a rebuild. I have just finished re-building the
bike, although I didn't touch the bottom end of the motor except to blow and clean out all oil feeds. I
seems as though the oil pump doesn't have the strength to pull the ball valve off its seat. Remove the
ball and oil circulates - replace it and it does not. I have primed the pipe as per the handbook (4 times).
I carefully sealed the pipe unions as per BMS service manual. When it last ran (admittedly 27 year ago)
it was ok. Anybody got any ideas. I am using Castrol 20-50. How do I figure if the ball spring is the
correct strength? Return feed (scavenge) seems really strong.
#3257 It has been known for the ball and spring to be replaced upside down. However to pinpoint if the
ball and/or spring is the, problem take both out and see if the oil circulates. By the way general
consensus is that SAE 40 oil is better in a Velo engine (although this will not stop the oil circulation.)
#3258 You are probably sucking air. Did you make sure the oil feed line was primed i.e. filled with oil,
from a can and with no air pockets. One method of "force feed" is to seal the top of the oil tank (Flat of
hand) and blow down the breather pipe. It worked on an A7 BSA but we have never needed to do it to
the Veloplonk. Once the pump "takes up" all should be OK.
#3261 Check the ball valve & see its assembled correctly. Then - whilst its clean - suck on the bottom
to see if you can lift the ball of its seat (thats about 3psi) if you can , the motor will lift it OK but if not it
probably won't.
#3262 The oil valve spring is pretty feeble, if tried by hand. The ball should be nearest the oil tank,
with the spring below it. The sucking test is best, taking care not to get oil in your mouth. But assuming
the valve isn't gummed shut, and the ball isn't the wrong way round, and the spring is really a Velo
spring, the damned thing has to work. Problem of air in the line is physics: air can be compressed but
oil can't. If you blow a little compressed air into the oil tank, engine running, don't overdo it. If all the
above seems OK but it still doesn't work, could be the feed side of the pump. But if it works well with
the ball out, then it isn't the pump, it is the ball valve. I presume that you have the alloy tube in the
centre of the oil filter, as otherwise, filling the filter chamber before you see the return will tale even
longer. Sometimes, due to that, it takes time before you see the oil ejaculating into the tank, and your
nerve may crack before the oil starts returning, causing you to stop the engine. Another way is to take
the little screw out the big end quill, and run the engine (but not too long). Engine oil should squirt out
there if the feed side of the pump is OK and there is no problem with your ball, or air in your plumbing.
But this starves the big end of oil, so should be done for only a few seconds. I presume the feed pipe
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hasn't gone hard with age. Lot of riders use clear braided plastic, which doesn't last long, and isn't
really made for the job, but does allow you to see if there are any air bubbles. You sometimes have to
insist, but not too long.
#3264 We always "crack" the Rocker oil feed pipe bottom union nut to verify flow.
#3263 John I doubt many of us feel confident running a 'new' motor waiting for evidence of oil returning
to the tank. A few seconds seems like hours. Try the Nick Payton method of spark plug removal and
walking the bike in gear.
#3268 I would like to thank you all for your fast responses. This group is great. The oil pipes are new
and are made up of clear plastic, so its pretty easy to see when the return feed is working. Every thing
looks good here. The feed to the engine is filled with nice clean engine oil and its difficult to determine
visually if the oil is flowing. I am relying on the cracked rocker feed pipe to determine if the oil is being
sucked in and been circulated. Without the ball everything looks OK. With the ball oil doesn't circulate.
The spring in my old union was a bit mangled and since I couldn't buy a new spring separately, I bought
complete unit - ball, spring and housing. I actually tried both units, and oil did not flow in either case.
Anyway you have given me a few things to try. I will let you know what happens
#3270 When I reassembled it I pored oil down through the rockers to check the return feed (I did this
after following the "smoking Velo problem" discussed a couple of weeks back) so when it was started it
for the first time there was oil in the crankcase
#3271 I don't like to disturb the oil pump unnecessarily, and would recommend that the crankshaft is
removed through the timing gear and worm drive rather than removing the pump, but I had a Venom
that was reluctant to take its oil. I decided to remove the pump to check it, and it virtually fell out when
the 4 screws were removed, either the hole in the crankcase was too big or the pump was too small. I
cured this one by replacing the ball valve with a tap, which has its own dangers!. Also a MAC I still have
would circulate its oil when cold, only to seize up after about 20 miles, when the oil had stopped
circulating. On examining the pump I discovered that the body of the pump had a countersink machined
where the 2 gears meshed. I checked every other pump I could find and no other had this feature. I
replaced with a pump without this countersink and have had no more trouble.
#3272 With clear oil lines. already primed, it should be simple to detach the line at the outlet of the oil
tank, remove e'nuff oil to create a void of about 1 or 2 inches at the top of the line and re-attach. Start
the engine and observe the level of the oil in the clear line. As the pump pulls 1 cc out of the pipe, 1 cc
of oil should come through the ball valve. As long as you do not allow all of the oil to be pulled from the
line, the pump will not be starved and the engine will not be harmed. In a moment or two of running,
you should be able to see if the ball is being pulled from its seat and oil flowing as designed. In essence
the oil line will become a drip feed sight glass. After the test, refill the pipe.
#3276 As you'll realize I've thought a lot about oil circulation recently (Smoky Venom). I've also learnt
(again) that often the problem is basic and not at all complicated (K-Tec). It seems to me that if you
have a good oil return when the ball valve isn't fitted this must mean that you have a good oil feed when
the ball valve isn't fitted which must mean the pump is OK. If the return stops when you fit the ball valve
it must mean there is a problem associated with the ball valve.
L #3288 I know you gentlefolk have discussed this before but that’s what you get for not keeping
all e mails ,I have 2 Macs and one I s being restored and I have just had a look in the oil tank and
cannot for the life of me find any info on the length of the alloy scavenger pipe, and what length it needs
to be from either the top or the bottom, can you help
#3291 You mean the pipe up the middle of the oil filter? The oil filter is sealed top and bottom. The tube
is a force fit over the central union, at the bottom, so that the oil rises into the filter chamber. The tube
cannot go to the top, or the oil could not pass into the centre of the oil filter. So the tube stops short- by
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how much? Not critical, maybe 0.5" to 0.75". Thought of the week- below the filter, there is a closed-off
part of the filter chamber. It fills with oil. I see no way how that oil circulates.
#3294 Something which I think happens at times with new owners is that when they first change the
filter, they throw away the alloy pipe with the filter. I've wondered why it wasn't made to fit from top to
bottom, with some holes to let the oil into the filter. But normally, Velocette knew what they were doing.
But that "slug" of dead oil under the filter?
#3298 I have an alloy pipe on my VM approx 6.5 inches long ,it was loose so I contacted Grove(uk)
who sent me a replacement steel tube approx 4.75 inches. So then I was really confused so
counterbored the ally tube and used loctite to attach it to the return oil flow spigot -seems to work but I
wonder why the oil only flows into the filter in the top inch or so --this would seem to be inefficient use
of the filter. Something about the arrangement does not seem right. That said using common sense is
often a mistake when applied to machinery. Do have to second guess what Veloce had in mind or does
someone actually have the lowdown on this one?
#3300 . I met a guy with a Thruxton who in one breath was telling me about how he had modified this
tube to make it more efficient, in the next breath was complaining it was as smoky as hell when he
started it. The penny dropped when I pointed out the two are connected, drilling the tube causes all the
oil in the filter (and gunge) to drain back into the crankcase when the engine is shut off!
L #3951 On the KSS /Viper I fitted the non return valve to the feed at the oil tank. I now have a
doubt as to whether the pump can pull oil past the ball on its spring. The valve has the advantage that
you don't have to remember to close it at the end of a ride and, more important, open it before you start
the engine. The KSS has a spring valve on the supply side and I am told the KSS pump is smaller than
the Viper pump. As always any advice welcome.
#3953 The pump is the same size as the MAC uses, which on the later ones manages to draw oil
through the ball valve,(earlier ones had a ball valve in timing case one the pump outlet), also the KSS
pump turns at ½ engine speed which is much faster than the MAC or Viper turns it. If in doubt, check
the circulation when good and hot, if you have used the bike much, I guess you would have found out
by now if the oil stops circulating. My KSS/RS hybrid has a tap and a reminder (dymo) stuck on the
steering damper knob, and I live in fear of forgetting one day! -
#3959 You can use a waterproof micro switch attached to an oil on/off valve to insure safety. Just
install the micro switch to your oil valve so as it will ground out your magneto unless the oil valve is in
the "ON" position. If you forget to turn on your oil valve all that will happen is that your leg will eventually
get tired.
L #4055 Rode my Velo about 100 miles in light rain yesterday -- gutsy move for a 6v Lucas bike,
but all faired well. Each time I go out I lose a couple of fasteners. I suppose this will happen until I
eventually get everything locktighted. Yesterday I lost one of the screws that holds the oil pump into the
case. Does anyone have a thread specification for this screw? I took another one out and it doesn't
match any of my thread gauges for SAE or Metric, so I'm guessing it's a British Whitworth or other?
#4058 They are 3/16" British Standard Whitworth, as are the ones around the timing cover. The original
ones have a plain screwdriver slot, if they are replaced with allen key headed ones, don't do them any
tighter than you would turn a screwdriver, they are easily stripped!
#4068 The reason you are losing bolts will be one of two - either they are not tight enough so that the
required preload is not there to keep the bolts in tension, allowing the nuts to run off the thread, or the
fasteners have been overtightened causing the assembly to go into the preferred failure mode which is
that the bolt breaks at the first engaged thread, just under the nut. I'm not a great lover of Loctite,
except in a few particular applications, but believe that properly tightened and occasionally checked
fasteners, fitted with the appropriate shakeproof or locking washer, Nyloc or other appropriate locking
111

nut, will normally stay put. Overtightening can also cause premature thread failure (stripping) in some
cases - Helicoils are the best cure for stripped threads in alloy in my opinion, but must be correctly
installed. The alternative solid inserts sold by some places are not worth a light.
L #4160 Hello all, after fiddling with the oil lines, and reading the stern warning on the oil tank
about ensuring that the oil pump is primed before running my 1954 MAC, I thought I should know how
to carry out this procedure. What is the best way to make sure the oil pump is primed and all will be
well?
#4163 I use the old fashion thumb operated oil can, undo the feed line(oil wont come out of the tank
due to the sprung valve) pump oil into the oil line, if you hold the spout hard on to the oil line you will
actually be able to force oil into the engine oilways once the pipe is full. You will see when the oil lines
are full or if you don’t have translucent pipe you will feel the pressure build up on your thumb pumping
the oil. Just replace the oil pipe and your ready to start the engine. With the engine started keep the
revs low whilst watching the oil level in the tank, it should start go down, if it does not stop the engine
and find out why. After a while you will see the return oil spurting into the tank, you can now breathe
again, all is well. It always takes just that bit longer than you think before the oil returns to the tank, it
has to go round the engine collect in the sump before being pumped back where it then has to fill the
filter chamber first so don’t worry as long as the oil is going down, your engine is being supplied with oil.
All in all not an onerous task.
L #4290 In am ready to refit the oil pump into the crankcase on my KSS. It came out using the 1/4
BSF tapped holes into two of the retaining holes, fitting two screws and tapping out from inside the
case. The case was heated pretty hot but it was still reasonably tight and I get the impression that it
isn`t going to slide back in easily. I am concerned about the gears coming out of the pump body during
reassembly and can see that the job ought to be done upside down which is a little impractical. Any
ideas out there from people with experience.
#4291 Fit four lengths of 3/36 BSW studding for the pump to run along - back into the recess. Heat the
case up, possibly cool the pump in the fridge/ freezer. Holding the cases vertically, the pump will slide
down the studs and into the housing with no bother. The gears do not fall out - a little oil to hold them in
if you are worried. Once the pump is in the case check to ensure its seated right home - don't forget the
brass seating shim - tap the pump home if needed and fit the screws ASAP.
#4295 I've done this a couple of times on my Thruxton. Put the pump in the freezer overnight with the
sliding surfaces covered in grease. Heat cases well as suggested fit some guide studding. The
difference comes now - I didn't find that it just slid in easily..... line up and THUMP IT. If it tries to seize
THUMP HARDER! it WILL go!
#4299 Always bolt the two halves of the crank case together and heat as a unit. To prevent differential
distortion.
#4303 It should NEVER be necessary to deliver more than a light tap on the inner end of the pump
body to REMOVE the pump, and refitting should involve no more effort required than SLIDING the
pump back into place. If the cases are heated sufficiently (and cooling the pump might help but is not
really necessary) then the pump will slide into place very easily with no effort. Thumping it into place
could cause the faces to score or pick up in the bore causing irreparable damage probably to the softer
material of the crankcases. I've said this before in previous postings - the proper method is to heat the
cases, ideally in an oven, but careful general heating with a blowtorch or a good hot air blower will do
equally well, just don't concentrate the heat in one spot. Heat until spit just starts to sizzle off on
contact, no more, and the pump will slide in or out perfectly. No damage will occur to the cases by
overheating when using this method, I can assure you.
L #4316 As I appear to be spending a bloody fortune on my MAC I think I would like to fit
Stainless, braided oil pipes. Anyone know where I can get these please. I just had the front brake
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skimmed and oversize linings fitted to the front. Lovely job by SRM Engineering but really expensive as
well £105 !!
#4317 This may help - www.goodridge.net They make braided brake pipes and I think they make oil
lines as well, but you will have to check for correct thread.
#4319 Hello all, I have not had any experience with Goodrich, but I have used a company called Baker
Precision in Signal Hill California. I redid all of the brake lines for a vintage Ducati. I gave them the
desired lengths, and about two weeks later I had very beautiful crafted lines, with all the correct banjo
fittings etc. They indicated to me they had most all of the strange British threads and sizes; and yes I
can really relate to spending a small fortune on a MAC.
#4320 Can anyone tell me the correct lengths for these pipes please? I have the fittings but no pipes. I
can send them the old ones as a pattern but will need to make up the correct lengths.
#4351 The return hose is 19" long. However I would make up the oil pipes on the bike with cheap and
nasty clear 5/16" or 3/8" tubing and just wire the hose on. You can then send these as complete
patterns to whoever makes your hoses, as even being a quarter of an inch out spoils the line of the
pipe. You will then be assured that they will fit when you get them back. You can try Autohose in the UK
on 01782 542486 as they are old bike specialists.
#4353 That's exactly what I did - made up pipes with some bits of piping I found and marked them with
the internal bore that was needed. I sent them to Goodrich but if there are any problems I'll give
Autohose a call.
L # 5014 I hope someone can help me with a problem with the oil pump housing on my late model
iron head MSS. The bike came to me in large lumps and very oily. On cleaning up and closer
inspection a number of problems have become apparent the fist of which is the oil pump housing.
Someone has been ham fisted and damaged (and I think also cracked) the oil pump housing on the
timing side crankcase and I need to find an engineer who can repair this for me.Anyone got any
suggestions of a competent person in the UK?
# 5015 This sounds like the sort of problem which can only be solved by replacement of the cases.
You can be sure that if the oil pump housing is cracked it will need to be welded, which will involve
notching out the crack, thorough cleaning and very careful welding to make sure of proper penetration.
There WILL be distortion and a certain amount of porosity no matter how well the job is done, and the
pump bore will have to be machined out which will result in an oversize bore, requiring an oversize
pump to be sourced. All with no guarantee of success I fear.
# 5017 As luck would have it I do have an over size pump marked OS .4 So maybe I have a chance.
Know any one who could do the machining? I know an ace welder to do that side of it.
# 5016 Nick Payton, the Velo Guru in South London, can remachine and sleeve the timing side
crankcase. Let me know if you need his phone number/address. He has just done it for my Thruxton.
# 5018 Well, I would agree that if anyone can do it, Nick Payton can - 0208 540 2118 will find him.
# 5019 I agree as well. Nick did this excellent job on my Venom some years ago. This is now one of
the driest area of the engine : ) But the case was not cracked, only scored.
L # 5343 Does anyone know what oil filter is used on the club conversion, I can't believe it is not
used on other applications. It would be helpful so as not to have to rely on them being in stock when
needed.
# 5344 I believe it to have been fitted to a Duccati if this is any help.
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# 5449 I finally managed to get into the garage and have a look at the spare cartridge I bought when I
did the oil filter conversion . Unfortunately there are no makers marks on the cartridge of any kind (
dimensions 1 5/8 dia x2 5/8 long across the plastic end caps with a 7/8 hole . ) Single layer paper
element construction on punched stainless steel mesh support . Construction looks very simple and
straight forward . Somewhere in the recesses of my mind I seem to think I once read in Fishtail that
Citroen did a cartridge the same size.
L # 5775 When I disassembled my broken KSS (worn cam/skids) I saw that the lower end of the
oil drain from the cambox, into the crankcase, was broken. The soldered joint had failed, either during
my 100 mile ride, or previously. How much trouble could this have caused? There was plenty of oil in
the tank... That oil line should allow the cambox oil to drain, a broken line couldn't drain too fast, could
it? The cambox should still be filled with oil up to the height of the camshaft ball bearing? --for iron KSS
engines-- Jeff Clew's book "KSS" recommends joining the cam box drain oil lines, the front two.
Eliminating the feed to the engine shock absorber, and instead feeding that oil into the crankcase. This
is claimed to help stop oil leaks. But I do not see how that can be true. Any ideas? Ivan Rhode's book
suggests taking the feed to the shock absorber and feeding it instead to the exhaust valve guide... But
then we must oil the shock absorber with an oil can from time to time. I'm inclined to leave the oil lines
as Velocette built them. Does anybody have other suggestions?
# 5776 Pete, The broken oil drain could not have affected the cam box & rockers. The joining of the
two pipes and connection to the flap valve helps to drain the cam box and prevent (some of) the oil
leaks. The copper pipe should be hard soldered (silver solder) into the copper union, not soft solder. If
you are using castor oil in the engine without a chaincase, there is no need to worry where the oil goes.
However, R with a chaincase means you should drain the cambox into the crankcase; veg. oil on a
clutch is a real pain!
L # 5919 Hi Group I have just acquired a 1935 GTP in reasonable condition but it requires the
oiling pump arrangement set up from scratch. Any advise on how to do this please. Also the gear lever
does not return to centre between changes. Before I go ripping the box apart any thing else to look for?
# 5922 When adjusting the oil supply do it gradually and put some miles on the bike before making the
next adjustment as it gives time to burn off the effects of over oiling in the silencers. Otherwise you may
end up thinking that you need to reduce the oil supply even more and end up starving the engine of oil.
PS good luck with the Miller dynamo and coil ignition!
L # 5985 I am attempting to sleeve the oil pump housing on a '66 Venom. Can any one tell me
what the correct interference fit is between the oil pump and the crankcase?
# 5988 Have just measured a crankcase bore at 1.687" dia. and an oil pump at 1.689" dia. They have
not been together before but soon will be. This 0.002" interference is in line with a maximum BS 'keying
fit' for this size (A 1954 standard gives Hole +0 to +1.4 thou and Shaft -0.4 to +0.6 thou.). Should think
that an interference of between 0.001" and 0.002" would be satisfactory but this is not from direct
experience of this particular issue. Other group members will have specific experience and will surely
point out if this is not right.
# 5990 I have not done this myself but would agree that 2thou should be about right in theory. One
thing I would be concerned about is what do you intend to sleeve it with? If you fit a steel sleeve I feel
you should consider sleeving the pump rather than the crankcase. If you don’t you may find it difficult to
get the expansion you need when warming the cases to fit the pump. You may well need to bore the
cases first of course if they are damaged. Maybe someone else will be able to add their first hand
experience to this thread.
# 5989 Richard My recent practical experience suggest that you are spot on with your advice. Last
year, Norm Trigg and I measured a range of Velo cases and pumps in our possession and concluded
that there was a tolerance on sizing as summarized below by Norm. " I have measured 20 pumps and
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the bores in 20 crankcases. Measuring the bores is not easy. On some old engines the bores are
tapered a bit (I guess due to being pushed in and out) and even on new cases the bores are not
perfectly round ( I guess due to the uneven thickness of material around the bore). So I took the
maximum in each case. I found the following: Average diameter of bore in new cases 1.686" (maximum
variation + and -.0005"). Average diameter of the later pumps with the larger feed gears 1.689"
(maximum variation + and -.005") Therefore interference is .003". Average diameter of early pumps
with the smaller feed gears 1.688" (maximum variation + and -.0005" having excluded one pump at
1.686"). Interference of these pumps in new cases would be .002". However things become interesting
when we look at the measurements for used crankcases. The average diameter of bores in used MSS
cases was 1.688" (variation was +and -.002") So late pumps could have an interference ranging from
.003" to a clearance of .001" and early pumps would range from an interference .002" to a clearance of
.002" The average diameter of bores in used MAC cases was also 1.688"(variation was +.002", -.0025",
excluding one case at 1.6892"). So some late pumps would have an interference of .0035" while others
would be loose by .001" , early pumps would be .0025 interference and .002"clearance. It appears that
over the years the bores will be enlarged or scored and I have pump bodies that have been copper
coated or chrome plated to increase their diameter to try and overcome the problem." Back to my own
experience, I chose a pump with a 0.0015" interference fit to replace a damaged one in my MAC racer,
and fitted it with engine in situ after about 10 minutes gentle heating. A few weeks later I had to refit a
pump in another case on the bench (a much better way to do it compared to in situ) which was 0.0035"
interference fit and that was a real challenge, requiring several rounds of cooling the pump and heating
the cases to get it in. Therefore from our experience we'd conclude that 0.0015" to 0.002" interference
fit is the best practical target for Velo oil pumps.
L # 6185 I am just stripping down an iron head mac engine for spares and have noticed an oil
feed from the base of the rocker box oil feed pipe to behind the barrel where it is screwed in to the
crankcase never seen one like this, just curious to know its purpose. should anyone be remotely
interested I can send a photo thanks.
# 6254 It was introduced in 1938 to reduce piston slap only to be deleted late in the 40's. It doesn't
appear make any difference either way if you have it or don't.
# 6255 Do you have any documentation on the subject? Vincents squirt oil to the back (thrust) side of
the piston as did some Manx and some other Velos (iron MSS for one) do it via internal passages. I
have added it to a couple alloy Velo engines in the hopes of increasing lubrication and cooling the
piston, not for piston slap. Hard to deduce any benefit. Outdated, perhaps questionable. Many Vincent
owners plug off the cylinder feed with no problems.
# 6263 It was common in the early days to fit the front cylinder of V twin engines with an oil line. The
rear cylinder was sprayed with oil as the big end swung around through the oil in the bottom of the
sump. But the front pot always went dry. I've seen the oil lines on several different engines, at the rear
of the front cylinder.
# 6272 Information is limited, but what there originates from Bob Burgess and can be found in "Always
in the Picture" (pg79) and the Pearson Velocette book (pg17). The engine numbers of the start of the
modifications can be found in some versions of the spare parts list, and modification ceased sometime
in 1951.
# 6273 Just to add to the subject my 39 and 48 ironhead MSS engines has these also.
# 6264 As far as years they used it ( Velocette) my Iron head MAC has one and it is a 49, maybe it
went out in the 50's.
L # 6190 The problem is that my friend has almost stripped the thread on the banjo joint on the
oil pump return. At present we have managed to bolt up very gently with the ally washers and note that
the recommended torque is only 10lbsft which seems low. I presume there is very little pressure on this
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joint. He is still rebuilding the gearbox so we have not yet recommissioned the engine and oiling
system. If we have to repair the joint is there any recommended way to do this. Is the thread 3/8ths
BSCycle i.e. 26tpi ? He has obtained a 7/16ths Banjo Bolt but of course this would need a larger banjo,
are these available or would he have to make one or mod the existing unit?
# 6197 Helicoil the damaged thread, but carefully! The thread is 1/8" BSP. Helicoil kits or the cheaper
but equally as good Recoil kits are available from such suppliers as www.uni-thread.com - just make
sure that you use an insert that is not so long that it obscures the oil passage, and all swarf and the
tang off the insert is cleaned out before running the banjo bolt into the hole.
L # 6228 I have a friend who runs his BSA A10 on Valvolene 5-50W fully synthetic oil. Having
read articles on the superior protection of fully synthetic oils and of course witnessing it in modern cars
which travel round the clock without major wear to their engines on extended oil change intervals often
of 12 to 15000 miles, I'm keen to introduce it to my Venom. Can there be any reason that such a
viscosity of fully sythetic oil could not be used? The Velo oil pump is well designed and pumps copious
quantities, the major bearings are all roller and the amount of oil that appears to circulate around all the
other components provides high levels of saturation. There is a very interesting article in
realclassic.co.uk under the tech section entitled "The oil truth" that gives a very strong argument for
using synthetic oil that's worth reading. My own car, a Mondeo, runs on 5-30W semi synthetic with
12,500 miles oil change intervals. Whilst in Canada last year I hired a Ford Taunus (very like a
European Mondeo) and noted on the engine filler cap that the recommended oil was 0-30W ! Are we
missing out on this new technology by sticking to the oils specified when our bikes were sold 40 to 70
years ago. Surely Velocette, along with all other makers, specified the best oils available at the time,
but I cannot believe they are the best anymore.
# 6230 I am no Tribologist but all mentioned have plain bearings with the loads fairly evenly spread.
Roller and Ball bearings have Line or Point contact and therefore more extreme pressures. This can
break through the oil film on the modern oils. The older “straight” oils do not suffer from this affect. We
use a SAE 50 in the Venom and we have the extra effect of the sidecar.
# 6231 It may be sheer coincidence, but at the beginning of last years Summer Rally, I changed my
VMT to synthetic 20-50w oil. After 1k miles, the big end went in a big way; the rollers look as though
mice have been at them. And I was actually riding at a pretty sedate pace, for me, over those miles.
BUT, I know several other VOCNA members who swear by their synthetic, so what's a fellow to think?
# 6232 Paul, As I understand it, air cooled engines should use straight grade oil - not multigrade.
Going to synthetic oil doesn't really help as it's still too thin! I found problems with Castrol multi grade
oils many years ago and changing to straight 40 or 50 solved it.
# 6234 I use "Morrisons Best" 20W50 multigrade oil at £4 or £5 per gallon in my MAC with no
problems. I do change the oil every 1000 miles though.
# 6237 I understand that it is o.k. to use these modern oils i.e. full/semi synthetic/ multigrades etc. with
their detergents or whatever if your engine is clean inside, so if you've recently done a rebuild and use
these oils straightaway you're o.k. but if your engine has only had the old straight 40/50 etc. engine oil
in it is most likely coated with "gunge" the modern oils will shift thus causing damage when pumped
around the system.
# 6242 Tom and others If interested in Penrite's take on oil issues then follow this link.
www.penrite.com.au/nextpage.php?navlink=techbulletin&PHPSESSID=b1c952d9eb73c4a18b223a081
6ae425e Bulletin V3 deals with castor oil versus modern oils in old engines while Bulletin V6 talks
about the pros and cons of using full synthetic oils in old engines. Bottom line is Penrite would
recommend a high quality mineral oil rather than synthetic in old engines. There's even a very short
bulletin on Harley transmissions.
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# 6249 There was an interesting article some years back in Fishtail, where an owner replicated the M
series oil system (MAC/MOV). He used 20W at room temperature oil to replicate 40 W at operating
temperature. At 1080 pump RPM, which represents some 6000 RPM the delivery was 1.07 pints per
minute at 18 psi. Using paraffin at the same engine speed to replicate low viscosity the delivery was 1.0
pints per minute at zero psi. The Velo oil delivery system needs to be looked at as a system, in which
oil is an integral component of the system. Each "jet" in the system must have been carefully calibrated
based on a specific oil viscosity. Stick with it (as pointed out in an earlier post) how many of us are
going to ride enough miles, fast enough to wear out an engine! The VOC sell magnetic drain plugs that
I have used in all my bikes in both the oil tank and sump for a number of years. The sump picks up
more detritus than the oil tank. Most of which appears to be fine cast iron with a few silvery bits.
# 6293 Thanks for all your comments and feedback guys, but I'm none the wiser as comments have
ranged from encouraging to dire warnings. But hey- that's what chat rooms are about ! I was puzzled,
about the comment on a thin viscosity oil breaking down due to point loadings within roller bearings
whilst 50 weight oil was able to withstand these loadings. Doesn't a modern vehicle running 5W/30W
synthetic oil with overhead camshaft have higher point loadings between the camshaft and the
buckets/followers/valve stems and operates at far higher revolutions than the big caged roller bearings
of a slow reving old Velo ? I was not able to follow the logic from a contributor about the comparison
test done on an oil pump operating with 20 weight oil and then paraffin. I don't know the viscosity of
paraffin but I do know that it pours like water and that the 5W/30W synthetic oil used in my car for the
last 70,000 miles is thin when cold, but it certainly does not pour anything like water, or paraffin - not
very scientific I know, but you get my drift. The contributor who ran his big end within 1,000 miles of
switching to synthetic worried me. Can I ask what was the state of the main bearings and camshaft and
followers upon strip down ? and was the engine well worn already or were major components still within
normal wear tolerances prior to the big end failure ? I feel there must be someone out there in this
world wide Velo Web who can give a definitive answer to this oily question.
# 6294 Responding to the query; after the 'thousand mile synthetic oil big-end test', the mains and
cams/followers were fine. Just the big end rollers were damaged, although with all that steel running
around the oilways I imagine some other wear was accomplished, and I replaced the lot with parts
which looked better. Mind you, the 'rapid' wear after changing to synthetic may have been coincidence,
as in the course of the 15 years since the big end was last replaced, about 40k miles had gone under
its wheels. Plus, there was a stretch of a few years where it seemed important to duplicate the
Velocette 24-hour record whenever possible, albeit for shorter periods. In that regard, the bike and its
owner have held up remarkably well.
L # 6243 After looking at the sorry filtration system I have on my 1937 Velo MSS, I have decided
to place a very thin and very strong magnet on the bottom outside of my oil tank. The magnets I have
are from computer hard drives. My reasoning is the metal debris will collect on the inside of the tank
near the magnet area and prior to changing oil, one can remove the magnet and let the shavings (few I
hope) mix with the dirty escaping hot oil.
# 6244 Sounds like a good idear, but would not the tank and particles become magnetized and tend to
"stick" inside the tank? How about fixing a magnet to a probe mounted on the tank filler cap where it
can be remove to wipe off the debris?
# 6246 I use 3/16 diameter high strength magnets from Radio Shack in the brass drain plugs for oil
tank and sump. Just drill a hole in the plug and press them in. Always some swarf on removal.
www.radioshack.com
L # VOCNA 205 I am getting near the point where I will have to check/set up the oil pressure in
the KSS. I know this is done through the access on the top bevel drive cover, which is tapped 1/8"
BSP. I understand the oil pressure should be 8-10 psi. To do that anywhere near accurately the oil
pressure gauge should be scaled around 1-30 psi. Most car pressure gauges are 0-80 or 0-100 psi,
and are not accurate enough to measure 8-10 psi. So any suggestions? Where do I find an oil
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pressure gauge that reads in 1 lb increments to 20 or 30 psi? I have some extra bolts threaded 1/8"
BSP, so I should be able to make up an adaptor ok.
# VOCNA 206 I have a fuel pressure gauge on mine (a cool old Moon Equip. one), 0-15 lb. seems to
work fine.
# VOCNA 207 I wonder what the application is (was) with a 0-15 scale, I doubt it is an automotive
gauge. That is the sort of thing I am looking for, but I googled Moon Equip. and the only have 0-80 and
0-100 gauges now and there is nothing on eBay.
# VOCNA 208 Back in the good ole days, when cars had carburetors and you could tell what was
what once you opened the hood, 6-8 pounds was normal fuel pressure as I recall.
# VOCNA 209 I do not know much about these gauges and was focusing on oil pressure gauges - I
assume adapting a fuel pressure gauge is not hard - I guess I will find out. Do they have a capillary
tube like a "good ole" oil pressure gauge? I am not sure I want to go the route of a sender unit that
converts pressure into an electrical signal.
# VOCNA 210 Mine has the same compression fitting affair as a mechanical oil pressure gauge.
While we're on the subject, I also have a gauge on a push rod Velo but it's next to useless. The
peculiar thing is that on start up it will have upwards of 10 psi, then within 4-5 minutes (way before the
oil gets hot) it will drop to 1-2. Not that they need a bunch of pressure, I just have never understood the
reason for the big drop. The things it feeds, crank, cam, followers and rockers all have fixed size
orifices. Tried it on a couple engines with same result.
# VOCNA 221 What you describe is very common. It is one of the reasons why a cold automatic
transmission has such a harsh shift for the first few accelerations but diminishes before the engine and
trans warms up. It is caused by three things: pump leakage, viscosity of the oil, and a little to the
amount (mass) of the oil to be pumped. Mostly it is the viscosity of the oil. Our Velos are old engines
with rather large clearances compared to modern engines so we have to use high viscosity oil. Oil
viscosity is not linear to temperature. Most viscosities are given at 100 degrees C. Viscosity increases
rapidly below 50 degrees C and usually triples around 20 degrees C (room temperature). Hopefully it is
apparent that the oil viscosity is high when the engine is started which causes the high pressure. As the
oil warms it reaches a much lower viscosity long before the engine reaches operating temperature. The
Velo oiling system is a flood system not a pressure system. Even so 1-2 psi is too low. With o-rings
between the timing cover gear oil jets a new pump will deliver 5 - 6 psi a pump with normal wear will
deliver 3-4 psi. Pump wear occurs mostly on the gear and body faces. A new pump has .001" to .0015"
gear end play. If more than .003" clearance is present the pump should be rebuilt or replaced. You can
check the pressure side of the pump gear end play be pulling on the worm gear shaft in the timing
cover.
# VOCNA 213 You're right in your understanding that the 0-15 or 0-30 PSI gauge is likely to be more
accurate than those with bigger numbers on the dial. A Bourden Gauge is operated by a flat tube coiled
up in the casing, with the central, closed end of the tube connected to the spindle through a gear
reduction. As fluid (or gas) is admitted into the open (threaded) end of the gauge, the tube is
pressurized, causing it to uncoil, or attempt to straighten, thereby rotating the spindle with it's attached
needle.
# VOCNA 216 Lots of cheap gauges are available. McMaster Carr has them on their website:
www.mcmaster.com/ Do a quick search for pressure gauges. The catalog page 512 has a tutorial on
gauge types. Page 513 has several gauges with 0-15 psi ranges for $8-$9US each. They have 1/8NPT
fittings. Page 515 has some 0-15psi gauges with metal frames for $7.24 and $13. Grainger has similiar
items. www.grainger.com Page 1198 has liquid filled 15 psi gauges for $16. part # 4ZG16 is 15 psi for
$8.55 You can also try MSC. You may need to open an account with some of these guys to order from
them, but it will be worth the hassle.
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# VOCNA 217 I'm curious if you're going to fit one of these guages to your KSS! I think it would show
quickly if your cam wear issue is oil or hardness related.
# VOCNA 218 That is assuming that the oil actually moves in adequate quantity from the bevel housing
where the guage is reading the pressure, to the cam chest where the oil is doing it's thing. As I recall,
the RH cam bushing is the restriction that causes the pressure to build and it must allow the oil to pass
into the cam chamber. Perhaps a flow test from the drainback lines would give indication of oil
presence.
# VOCNA 219 These are identical to the gauge that is in the Ariel. Cheap and effective. The only
problem is that the bike vibrates the needle so much that I can't get a good reading, much like an
ammeter. Frank is correct of course, knowing the oil pressure inside the top bevel chamber will not tell
me if the cam is being lubricated, only that there is back pressure behind the cam bushing.
Coincidentally, Paul and I were speaking about this after our ride on Saturday. I'll be checking for oil
flow from the cambox drains.... I'll use the oil pressure gauge to verify that sufficient pressure is built up
in the cambox, as dictated by Veloce. But again, this is only telling half the story. I don't plan to leave
the gauge in place, only use it for testing. Who knows, maybe I'll come up with a good location for the
gauge, and leave it there for a few test rides. One chap in the UK recommended using clear plastic
tubing for the cambox drain lines, then I can SEE the oil flow.
# VOCNA 220 Thanks for the dope on the oil gauges - I have several options now and things are
sorting out. Is it possible to fit an oil line up to spray directly on the cam like the early Mk 2s? I really
don't know why Velo discontinued this oil line (in '37 I think), which runs from the top bevel box to a
small nozzle somewhere on top of the head, and sprays oil directly onto the cam face. Dave Poole
sent me some nice drawings and accompanying text showing how to retrofit this to late Mk 2s, but I
have no idea how much work it would be to fit on a Mk 1. I have the drawing digitally, and providing
Dave is OK with it (I can ask him), I could forward them on to anyone who is interested. My latest
roadblock appeared last week when I went to re-fit the oil tank and found someone had lined it with
some kind of sealer and it was cracking and flaking off. I figured this might not be good for lubrication
(that restrictive RH cam bearing being a case in point). So I proceeded to track down a good stripper
(something Gwen did not understand at first), and went to work on it on the weekend. Inevitably, the
reason for the stripper presented itself - pinholes in the top of the froth tower (weird how that could
happen on an oil tank). So tonight I pulled out the torch and solder and had a go cleaning it up and
soldering the pin holes. It seems to have worked and was holding liquid well, and I even got a lick of
paint back on it before coming up to check email. I am almost back to where I was 10 days ago - a
typical rebuild!!
# VOCNA 222 After all the technical stuff is bandied about I thought I might throw in my 2 cents worth.
Just remember that 2 cents doesn t buy much these days but here goes. How many KSS owners do
you think bothered to buy a gauge to measure the oil pressure at the upper bevel drive? Not many me
thinks and I am one of them. I m surprised that Veloce would actually give a specific value to something
like the oil pressure when in general they never bother to spec something so elemental as the cylinder
stud nut torques. Statements like tighten until a gas tight seal is achieved do tend to be a bit vague at
times. In keeping with the Veloce spirit of ambiguous specification I have measured my upper bevel box
oil pressure by loosening the plug about 2 turns while the engine is running. By the time I get to 2 turns
copious amounts of oil are oozing out the plug threads such that the whole timing side is covered in oil.
This necessitates at rapid shutting down of the engine because the process of tightening the bolt while
running will result in an oil slick of Exxon Valdez proportions. My theory is that the pressure sufficient to
push the oil up at least 6 threads in that quantity is more than adequate to push through to the cam.
With 8,000 miles on the engine and no detectable cam wear this theory seems to have a bit of validity.
If I were to only see a small weep I would be very concerned as I would estimate the pressure to be in
the 1-2 psi range. This sophisticated pressure measuring tool is to be found at any store offering a
selection of adjustable wrenches, vice grips and cold chisels.
# VOCNA 230 I must admit that after removing the rockers and looking at the head, it seems that the
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cams rotate through a generous cavity below the camshaft that would be full of oil, and this must fling
around the inside pretty well. Dave Poole noted that when he put a 17/11 cam in (from a Mk 8), he had
to mill out the inside of the head a bit, suggesting tolerances are close, and adding to the likelihood that
oil would get picked up by the cam lobe through every rotation of the shaft. Given this, I am surprised
at the suggestions that the oil feed is insufficient and contributes to early cam failure on the KSS. I am
going to do the oil feed conversion on mine next year just because it's cool and I want to mess about
with it. My curiosity is too great not to hook up gauge and see what is happening up there.
# VOCNA 233 I had my KTT cam go flat soon after I got it. Not quite sure why. Surely the more
aggressive cam profiles and spring pressures contribute. I had Gary Robinson stellite the cam and
followers back to /11 profile with 5/8 radius followers. Noticeable change, a bit soggier in the mid range
but a good wallop on top. Most of the long time cammy racers I queried still swear by bean oil. Not
wanting to deal with the hassle, I'm using Redline synthetic and so far no wear issues. I check the cam
feed jet (a bit different set up than KSS) for blockage on occasion and have kept the pressure gauge
installed, doesn't hurt anything and at least tells me I have pressure to the jet. Bevel drive set up is not
something I want to do on a regular basis.
# VOCNA 234 Bean oil is good! While at the Manx Grand Prix last summer I met an ex-Ralph
Seymore mechanic now retired and living on the Isle of Man. He took pity on me and took me under his
wing. One of my problems was cam, cam follower, and piston skirt scuffing. I was given a gallon of 50
weight Castro (not Castrol) oil. Castro is an organic oil heavy with caster bean oil. Anyway my scuffing
went away. Two problems though; One is being organic it separates and spoils if not run on a regular
basis. I left it in my engine until February and it smelled terrible when I flushed it out. Other problem is it
absolutely incompatible with Mineral oil and will form globs if mixed together. This year I've also been
using Red Line 50 weight synthetic racing oil with no wear problems so far. I was also told for push rod
engines, in addition to o-ringing the pump body and timing cover to oil jet interface, to open up the cam
feed jet oil holes with a .010" larger diameter drill and extend the rocker oil groove the full length of the
rocker.
# VOCNA 235 Were these considered racing mods? How does one put an o-ring around the oil pump -
that's a new one for me. I have rings on my timing jets, that's easy enough. The only reason I don't use
bean oil on my mkIV KTT is convenience, really. I use the thing quite a bit, and it pumps out copious oil
from the top end... and bean oil can't be found at the local gas station. On the summer rally, I'd have to
carry a case of bean oil, and although it smells great, its expensive. These are all now sounding like
really lame excuses... who's supplying it in the US, anyway? Also, when I switched the KTT OFF bean
oil, I used Redline Conversion liquid to flush the engine; I understand that Castrol won't glob up if there
is a little mineral oil, but your Castro has me worried.
# VOCNA 243 I didn't think of it until you asked, but, I believe the enlarged cam oil jet holes and
elongated rocker bearing oil groove are intended for racing. The O-ring mods simply improve the
efficiency of the oiling system. The oil pump O-ring mod is actually a rather old dodge. It is intended to
reduce or eliminate the cross port or external body leakage of the pump in its' bore. Experiences and
opinions vary, but, basically, many think there is a short circuit between the pressure and scavenge
ports of the pump. I am of the opinion that there are losses between the ports. Particularly if the pump
has been removed from the crankcase a few times resulting in the bore being out of round and/or
scored. The most common modification is to put a 1/16" dia. O-ring between the pressure and
scavenge ports. Some add two more O-rings on the outside of the pump ports. I have added the O-ring
between the ports on a few engines that had low oil pressure and observed an increased pressure by
about 2 PSI. I don't know who supplies Castro in the U.S. I tend to think the Red Line 50W is a more
practical alternative. Read Line states in their catalog "Even though Red Line Race Oils are straight
grades, their low temperature properties make them exceptional multigrades". The catalog goes on to
list the oil as "SAE 50 (15W50)". What all that means I don't know.
# VOCNA 239 Someone else may elaborate but the oil pump o-ring mod is very common, done it
myself a couple of times (I'm sure you'll find it in Tom Ross's compilation). Just turn grooves around
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the pump circumference, I put one between the pressure and scavenge side and another at the other
end of the pressure side to seal potential leakage and sucking air into the pressure side. My KTT had
bean oil when I got it. I flushed it with conversion oil to avoid teardown (mine was Blendzall, didn't
know Redline made it). Problem was the stuff cleans so well it dislodged years of swarf which ended
up plugging the oil system. I ended up tearing it down anyway. Alan Goldwater (writes Alan's Wrench
for NOC) sold me on the Redline oil. He did a heap of testing with heat sensors, lab analysis, etc. and
found it to be the best, Mobil 1 also very good but Redline comes in straight 50w. Before you say it, I
know some of you performs his yearly oil change outside the McDonald's on day one of the rally using
oil from the French fry vat and seem to get away with it.
L # VOCNA 318 On the standard Velo anti sump system, the column of oil under the ball valve
must remain in place because if it were to 'leak down', it would have to be replaced by air. Since there
is no way to supply air, it cannot leak down. That column of oil must be in place before running the
engine, as the oil pump cannot pump air efficiently enough to open the ball valve against it's supporting
spring. Using a weaker spring is not required, as if the supply line is properly filled with oil, the pump
will open the valve due to efficient 'suction'. In reality, there is no such thing as 'suction', but simply
pressure differential (above and below the ball). Above the ball you have atmospheric pressure plus the
weight of the vertical column of oil described as the area of the cross section of the supply line
muliplied by the height of the oil measured from the surface in the tank to the supply orafice to the
pump gears (assuming no air bubbles). When the pump begins to move that column of oil, the entire
weight of the column is moved by the pump, aided by the atmospheric pressure. The ball absolutely
cannot remain on it's seat, as there is no way for any air to enter the vertical oil column and the oil
cannot be either compressed or expanded as it behaves as a 'fluid solid'
# VOCNA 380 The check valve is a great idea, but I'd put it down by the oil pump, not on the underside
of the oil tank. With the check valve up at the tank, the oil pump may be forced to suck 6 inches of pipe
air to pull the valve open. Mirek says his will do that, so that's good. But some say you must fill the
pipe with oil. Which is it? Putting the check valve down on the motor, right next to the pump,
decreases the amount of air that the pump may have to suck to open the valve. Also if the bike wet
sumps without any valve, and you then install a check valve at the oil tank, wouldn't the oil in the pipe
(between the check valve and the motor) just wet sump too? Or does surface tension keep the oil in
the pipe? It must, otherwise the pipe would be full of air after a few days.
# VOCNA 385 I hadn't thought about the need for air to get in to allow the oil to leak down.
# VOCNA 382 It is right that the pipe must be filled with oil - I always prime the pipe with oil before start
up. I did my test by sucking on the end of the pipe which, for reasons of personal taste, was devoid of
oil at the time. The oil that is in the pipe between the valve an the oil pump should not leak through to
the cases as there is no way air can get in to allow the oil to flow (this is, for some reason hard to
explain). It is the same principal as a pipette - fill a tube or pipe with a liquid an put you finger over the
top - the oil will not drain out unless you lift your finger off and let air in to displace the oil. As I
mentioned in an earlier note on this - it is really important not to have any air leaks in the oil supply line,
regardless of whether you have a check valve or not. If you have an oil leak the oil pump will be
sucking some air in as the engine runs (probably sucking more air at higher RPM as the pump will be
turning faster). The check valve may work as well at the engine end of the supply pipe, but would be
harder to fit given the way the pipe winds up into the tight space between the gearbox and the engine
cases. The VM check valve was originally fitted near vertical on the bottom of the oil tank and so was
designed by Britain's finest engineers to work this way - how could you doubt them? Seriously, I have
no idea if anything but a more or less vertical mounting affects the operation of the valve - would the
ball still seat OK if the valve is on its side?
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B.6. Crankcase Breathing-
L #143 I've seen some weird systems with standard chaincases. One, probably practical but not
too pretty, was to weld a "blister" down the bottom of the chaincase, to increase the capacity. Another
guy put his engine breather into the chaincase, not the oil tank. Some schools of thought say to take
the engine breather, the one under the mag, straight out the back of the bike. This, they claim, avoids
re- cycling sulphur-laden oil back to the engine. This breather can be retro fitted. Stay around long
enough, you'll hear everything from the brilliant to the dangerous in mods.
#170 I'm in the process of adding crankcase and timing case breathers to my race viper and venom.
The viper had a small bore breather (1/8 in) on the timing case and the rocker inspection cover which
were obviously far too small to do anything useful. I've now added a 3/8in hole from the timing case
into the crankcase and a 3/8in bore breather fitting under the mag. I think these should be enough to
stop the piston pumping oil out the main bearing on a 350. The venom only had a 1/4in 8in bore
breather fitting under the mag, which I judge as woefully inadequate. This is being uprated to 3/8in
bore too, and I will put a 1/2in breather hole from timing case to crankcase. These are essential mods
for race bikes - or road bikes used in anger ! If you don’t screw the throttle, you wont pump much out
of the main bearing ! The side benefit that noone seems to discuss is that these breathers should also
allow the timing case oil drain work, as the piston will not be pumping oil back up it all the time ! Tony
Finley has a specially made garter seal on his main cos he races hard ! BTW - there is another belt
manufacturer - Ray Thurston's son - who fits a seal as standard on his kit..
#178 Regarding engine breathing: updating the engine to the latest Velo spec is about as good as you
will get. This involves drilling through the back of the timing chest into the main crankcase and fitting a
breather outlet adapter in the back of the timing case underneath the magneto. A pipe should lead
from here to the oil tank which doubles as a separator, the oily stuff stays in the system and the acidic
gases then escape to atmosphere via the tank breather pipe which should lead out to the back of the
bike. This should NOT be returned to the chaincase or led in a misguided attempt to lubricate the drive
chain. Either of these options will result in premature failure of either chain due to the corrosive effects
of the breathed gas. This system is very similar to those used on many modern machines and in
racing, the only real difference that nowadays the gasses are led back into the air box to be taken
through the induction system and burnt as part of the emission control system. If everything in the
engine department is in good condition you should find that the machine remains pretty well clean and
dry, and there should be little or no fluid around the end of the tank breather pipe. If the breather
under the mag is led simply out to the rear of the machine you will find it very quickly covered in oil!
#181 I used with great success on my Thruxton a Moto Guzzi Le Mans Mk1 breather collector box fitted
under the seat at a greater height than the oil tank. The crankcase breather pipe ran into the tank via a
one way valve in the box, another pipe ran into the oil tank and a third pipe breathed to atmosphere.
The box needs a bit of modifying, but is well worth the effort. Royce Creasey described the box in an
article on engine breathing several years ago in Motorcycle Mechanics.
L #422 An article in a Fishtail some years ago mentions a Crankcase breather alteration. It
described how to do it, but had no technical info with it. It says, Drill a half inch hole behind the
camwheel from the timing chest into the crankcases. Drill a 1/4 BSP hole below the magneto and
insert the adaptor M275. I would quite like to do this, but would like perhaps a few more accurate
measurements before I attack my valuable cases with the pillar drill. Has anybody done it? or can
provide some measurements. The article was written by James Plant.
L #584 As told previously, I got some noticeable quantity of oil coming off the crankcase breather
line. As seen in Parts List, would that help to drill a vent hole in the oil tank filler cap even though there
is already a breather line fitted to the oil tank ?
#596 The hole in the filler cap is about 1mm in diameter so it has a marginal effect on breathing,
however if it's like my Venom the hole will ensure that your leather trousers will require little in the way
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of preservative. A fellow VOC member who has researched the topic of oil levels has recommended the
level to be 55mm below the top of a short necked filler cap.
#597Having previously posted a question relating to occasional crankcase oil flooding in my '50 MAC
(only occurs at sustained high RPMs), I now suspect that it is attributable to pressurization of the oil
tank. When I obtained this bike, it had no vent lines of any sort, and an unvented cap. Unfortunately, I
am currently prevented from verifying this theory, since having lost top gear two weekends ago, the
internals of the transmission are adorning my workbench. Hopefully, I will fix the latter problem, and
have a more definitive answer shortly. Ironically, while looking at a '47 KSS that a friend recently
obtained, I noted a tube that emerged in the vicinity of the rear mudguard and remarked, "What's that. I
don't have one of those." So it does appear that properly venting the tank/return leg of the oil system is
critical. My question relates to how much venting is required. Apparently, most [all?] bikes equipped
with a vented cap had a vent line as well. Is a one millimeter hole in the cap really adequate, or should I
add a vent line to the oil tank? I believe the originals were on the order of 1/4" I.D.
#598 Having similar problems with a 54 MAC- flooding the crankcase after a reasonably hard run, I
have no additional breather other than the 1mm hole in the oil tank cap either. However my main
intermittent problem which may be related has been -getting far to much oil into the combustion camber
at start-up. Obviously splashing up from the crankcase literally heaps of white smoke for about-10-15
minutes far to much and long for just a guide wear draining back issue and yes my valve guides and
rings are tired). I have fitted a new ball/spring/seat in the one-way valve to no avail and have checked
for air leaks the pump is also returning a good flow, which is basically constant. Being a novice looking
for advice, and not knowing the correct oil level for the tank-I have been experimenting and found that
lowering the oil level in the tank to just below half and changing to a straight 30 grade oil seems to
reduced the problem considerably. Is there a correct ration re oil- tank volume and engine/oil line
capacity that determines the correct oil tank level or have I been basically overfilling the tank ? What is
the approximate volume of oil that should be left in the crankcase after standing overnight? Like to
know more about additional breather set-ups.
#599 The breathing system on older Velos is a bit marginal to say the least, and if no other breather is
fitted to the oil tank other than the 1mm hole in the cap it's no wonder that at times the cases will flood.
My Venom always had a breather on the back of the oil tank which internally went up to the top of the
froth tower and externally was led via a 3/8" bore pipe out to the back of the machine to atmosphere.
This always provided adequate breathing even when the machine was modified to the later engine
breathing system where an adapter is fitted to the back of the timing case below the magneto and the
½" bore pipe leading from this breathes into the oil tank. I don't have a vented cap and have no
problems with excessive amounts of oil smothering the machine or my leathers either! The engine does
still breathe into the chaincase through the hole in the drive side mainshaft as well and although this
has recently been a bit excessive and necessitated regular draining of the case, I've recently had the oil
pump overhauled properly for the first time in its life and hope that this will cure that particular problem.
I think that a 1/4" bore pipe would be a bit too small to do the job right, and you should remember that if
no froth tower is fitted to your tank you are very likely to have a big problem with excessive external
lubrication, since the function of the tower is to separate oil from breathed vapour.
#606 One point I perhaps ought to point out re breather vent pipes is that they should NEVER be
routed to discharge on to the chain. Whilst it may seem to be a good idea to lubricate the chain with
any vented oil, the breathed vapour is in fact acidic and will shorten the life of the chain and sprockets if
allowed to exit in this way. The best place I have found is to lead the pipe (whose length is specified in
the parts book and is important for correct operation) out of the rear of the machine by ty-rapping it
along the underside of the nearside rear mudguard stay
#608 Do you mean that a pipe shall be routed from the crankcase oil breather the small tube at the
bottom inboard side of the oil tank ? I expected this small pipe being a breather outlet ?
#609 The small tube at the bottom of the oil tank must be blocked and takes no part in the breather
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system. A hole is drilled and tapped into the crankcase just under the magneto. A screwed hose
adaptor is positioned and a 12mm plastic pipe attached. A hole is drilled into the back of the oil tank
and a 12mm tube brazed or silver soldered to place. The dimensions and angles are fairly critical. (I
have them somewhere) A second hole and tube at attached to the top, rear, of the froth/foam tower.
The tube from this is lead to atmosphere. The dimension of the lengths of the two tubes are critical if
the pulsations created by the positive and negative pressured in the crankcase or not to cause a
pumping effect and evacuate the oil. Also the vent hole in the oil tank cap should be blocked.
#619 You are right to say that this is the breather outlet. For the original
Venom/Viper/Endurance/Scrambler/MSS/Clubman tank this is, if I remember correctly, a spigot for a
5/16" bore pipe, 11" long which is clipped to the rear mudguard in front of the rear wheel - a positively
diabolical place to locate it if you are prone to overfilling the tank! I do know that you have had some
details from Keith about the later crankcase breather mods so I won't elaborate on these other than to
say that the position of the outlet on the back of the timing chest is quite critical and there is only a very
small space to fit it! There is a cast wall which surrounds the bottom circumference of the magneto
pinion inside the timing chest, below which is a small almost triangular area which is the target to aim
for when you drill through from the back of the case. If you drill above this the hole will be shielded by
the pinion which will then proceed to pump oil out at an alarming rate. In addition a ½" hole should be
drilled through the back of the timing chest into the crankcase. I'm not sure of the exact location for this
and since my engine is currently in one piece I do not intend to take it apart to find out! I do believe
however that it is documented in back issues of Fishtail.
#624 looking to my Venom, (because I've read that someone has nearly the same problem for a MAC
and may be this would make some difference) I already have a breather adaptor on the crankcase with
a tube fitted to it going no-where, but no other tubing on the oil tank than : the tank breather itself (only
5 or 6 in. long) and the engine feed and return pipes. If this is a standard arrangement, how long shall
be the oil tank breather tube, and the engine breather tube ? or how can I have the tank modified so the
engine breathes into the oil tank ?
#625 Since your oil tank has no other form of breather I think you would be correct in thinking that you
should have a vented cap, and the flooding scenario suggests that the build-up of heat during
sustained high speed operation is causing the tank to pressurized and prevent the return of oil to the
tank from the engine. The simple solution would be the vented cap of course, but I don't think that a
hole as big as 1/4" would be necessary and may result in a well lubricated right leg! Your engine will
breathe through the 1/8" diameter hole that runs through the drive side mainshaft into the primary
chaincase via the channels cut in the inner diameter of the engine sprocket. This system was found to
be inadequate for higher performance engines and was eventually developed into the alternative
system as I described, and incorporated in all late models, I think from about 1967, but I stand to be
corrected on this. My own Venom is a 1962 model which originally had only the mainshaft type breather
and the oil tank was fitted with a filter chamber as I described earlier, and only the 1/4" bore tank
breather tube from the rear. I have since fitted a Thruxton spec tank which sits a little further rearward
than the original to give room for the longer inlet tract (or a decent length of velocity stack), and have
modified the crankcases to bring them up to the latest spec. So far I've retained the original system of
breathing into the chaincase as well, since this must help to lubricate the shock absorber cam, sprocket
and primary chain, but it still suffered from what I considered to be excessive breathing into the
chaincase. Following advice from the good people at Seymours, I've just had the oil pump overhauled
for the first time in the machine's sometimes hard life and hope that all will now be perfect enough to
report soon that the chaincase remains reasonably dry. We shall see! Shall be interested to hear what
you find on the gearbox front. We happen to be on common ground here since mine too is dismantled
at present for renewal of the sleeve gear bush in an effort to restore efficient clutch operation. I
sometimes think that we old bike fans would be lost if we weren't tinkering with bits of machinery!
L #761There is a breather from the inside of the timing casing to a stub (3/8 bore) at the top inside
of the oil tank. I can't remember this from my last Venom, though it is a long time ago and it seems a
reasonable thing to do. The oil tank also has a stub pipe (1/4 bore) on the inside at the bottom. This
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has no pipe leading from it. It seems to be a breather with an internal pipe leading to the top of the tank.
Is it? If it is, why does it come out of the tank near the bottom? Should it have a pipe on it and if so
should it just exit somewhere convenient or should it be piped to somewhere in particular?
#765 Regarding the additional engine breather. Apparently at certain rpm it was found that crankcase
pressure prevented adequate draining of oil from the rockers / cylinder head. An additional breather
was added from the timing chest, underneath the magneto, to the top of the oil tank. This then vented
via a tube from the froth tower to the rear of the bike. This was introduced in the mid sixties, but it is an
often found modification - my machine included. I believe prior to this normal crankcase venting was
through the chaincase. A previous owner of my machine even vented the chaincase via a snazzy little
breather tube arranged from the chaincase inspection cover. I think the small 1/4 bore pipe at the
bottom of the tank was a breather which was also used to lubricate the chain (this being blanked off on
my machine). A cartridge conversion is available via the Velo owners club which replaces the felt filter
with a paper cartridge type. This fits in the original filter tube and is spring mounted which allows oil to
bypass the filter if it becomes blocked.
#766 Reference to previous postings will yield a lot of info on the breather subject and in general what
Brian says here is correct. However, I can see no advantage to the breather tube from the chaincase
since this is already very free to breathe due to the huge hole through which the shock absorber spring
protrudes, and secondly, the 1/4" bore pipe at the bottom of the tank really should not be led to the
chain in an attempt to lubricate it. This is the tank breather which should vent to atmosphere well away
from the chain since the acidic gasses that exude from this pipe will help to cause premature corrosion
of the drive train. Mine is led along the rear subframe and simply vents to the rear of the machine
where it can do no damage.
L #828 My apologies for taking so long to get back to you on this one. My oil tank is one which
began life as a standard Venom tank and has been modified to Thruxton spec including relocating the
mounting position rearwards to provide clearance for a long velocity stack or inlet manifold, and is now
also chamfered on the inner rear corner to clear the rear mudguard, so the actual position of the
breather pipe connections may not be quite where you would want them on your machine. However,
the 21.375" crankcase to oil tank breather hose is 10mm bore reinforced PVC, pushed on to a 1½" long
stub of fairly thin walled tube which I think is 3/8" ID. Off hand I can't remember the dimensions of the
crankcase connection but the hose is a good fit there too. The tank connection is welded about ½" from
the top of the tank, just behind the filter chamber in a position which will clear the frame down tube. The
tank breather is also relocated about 2" below and 1" to the rear of the engine breather connection in a
position to clear the rear mudguard. This is ¼" tube and extends up inside the tank to the top of the
froth tower, and has a length of ¼" ID reinforced PVC hose 27½" long venting to atmosphere at the rear
of the machine.
L #1223 Many modern engines employ a one-way check valve in the crankcase breather system.
Wouldn't a 500cc Venom engine benefit from a check valve in the breather system? Can anyone here
supply any info on past efforts to use such a valve?
#1224 I have fitted to my Thruxton a Moto Guzzi Mk11 Le Mans breather as advocated by Royce
Greasy in Classic Mechanics and it has being very successful. The box and pipe outlets needed
alteration plus a couple of outlet pipes blanking off, the box contains a one way valve and I found it
"cleaned up" my Thruxton brilliantly. It must be fitted so it is above the oil tank so excess oil drains back
into the tank but with a little thought this is easily achieved.
#1235 I have not seen the breather article either but I have been using a reed valve in my Thruxton
breather for some time. I might add this works most effectively if you have fitted a seal to the end of the
drive side mainshaft. Otherwise air is just going to be pulled right back in at that point. Interesting that
the KTT engine is fitted with a timed breath (same effect) but Velocette did not see fit to add it to later
models.
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#1237 Good point about the shaft seal. I'd not realized the size of the opening. I've intended to use a
reed valve from a airhead BMW. The valve is an aluminum disc approx. 25 mm in diameter with a reed
and stopped in the middle. The disc will be inserted in a aluminum cylinder turned up from some bar
stock and finished with a couple of barbed nipples for the breather hose. It will cost me about an hour of
time to build it and 7 bucks for the reed valve. The whole affair will be about 1 inch in diameter and 1
1/2 inches long. What did you use for your valve? I may be able to beat the size and buy one off the
shelf.
#1248 A few aftermarket companies make one way breathers, especially for Harleys. Try Spyke.com
for one. I've also run, with varying degrees of success, automotive PCV valves, smog (gulp) valves and
power brake booster valves. Bring your girlfriend to the auto parts store and have her find one that
blows a lot of air in one direction with least effort to open and nothing the other way. Sealing the
mainshaft is tougher. Only way I've found is to put the case in the lathe and open the hole out to 1.875
for a .188 wide lip seal. One could easily make a tool to do it in situ. I've heard of lubing the shaft and
squirting silicone seal in there to make a seal of sorts. Might work, might make a mess.
#1249 I have been using a breather intended for a certain American motorcycle for two years now. Its
available from www.dohertymachine.com. I don’t know if it’s worth installing, had quite a lot of work to
get it operating properly. One problem which is not finally solved yet is to plug the mainshaft breather
hole, haven’t found a reliable way to make a plug stick and it seems to work better when that hole is
plugged. Another problem is that there comes quite a lot of oil from the below mag breather outlet and
that must be taken care of somehow so now I have a hose from below the mag to the oil tank and the
breather valve is installed on the oil tank breather outlet. This tends to pressurize the oil tank so my
only engine leak is now from the oil filler cap. I still have problems with oil leaking from the gearbox into
the primary chain cover and eventually out from there in the usual places. Third problem is the sound,
the description oink oink is quite accurate. Have tried several ways of insulating the breather valve but
its still audible if You listen for it. It did cure the problem though of very small oil leaks from several
places on the engine especially after a hard ride but the system still needs further development.
#1255 Surely if a valve of this type is fitted it should be in the breather line from below the mag to the oil
tank? This would prevent tank pressurization due to the positive pressure required to open the valve
and consequently prevent leakage from the tank cap. The tank will still act as a separator/catch tank to
catch any oil returned through the engine breather and the tank breather will still work as intended and
vent only dry(ish) gasses.
#1257 I just happened to fit a drive side oil seal, because I use a Watson belt drive and oil always was
pumped into the primary drive up to the point when it exits through the felt ring after 200 miles. Now we
in Europe are strangled finding the correct diameter size seal. And the seal must be of tiny proportions
anyway that it can be fitted. The nearest solution was a metric seal with 35 mm inner diameter, and this
is not a proper shaft seal with an inner wire spring, just a lipped seal like for fork stanchions. For fitting
the crankcase has to me machined with a recess, in my case the top hat bush was the victim, and the
boss and recess of the primary sprocket as well to get it down to 35mm. I plugged the breather whole in
the crank and used silkone gasket on the slots in the sprocket facing the flywheel. To lubricate for the
rocking motion when the shock absorber is acting, I filled the inner recess in the sprocket with grease. If
the whole system works I can not say yet.
#1262 Thanks for info. I will try that this summer. I thought there would be a risk that the hose would be
filled with oil after the breather valve.
#1266 A little oil may collect in the pipe but it should be of no consequence. If there were no valve in
the pipe then any oil there would either lie in the lowest point of the pipe or drain back into the
crankcase when the engine is stopped, but if the breather adapter under the magneto is in the right
place then the amount of oil finding its way into the pipe is quite small, the main purpose is after all to
breathe gasses, not liquid. There is of course some liquid content but this is separated out in the tank.
The majority of this liquid is carried into the tank while the engine is running, and only a minuscule
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amount which drops out onto the walls of the pipe actually remains there when the engine stops.
L #4066 At long last my '55 MAC is getting a long overdue rebuild (to my usual standards!) I have
flattened all joint surfaces in a bid to slow the leaks, and have drilled and fitted a breather under the
magneto. The question is what do I do with the pipe? Can it be just run to the back of the bike or must it
go via the oil tank? The MAC tank would need some pipework welded in to do it properly, but it has no
froth tower, just a raised filler cap. Any suggestions would be most welcome.
#4069 The crankcase breather must breathe into the oil tank since it will carry a lot of oil out with the
breathed vapour. This is normally separated out in the tank, and the froth tower system keeps the oil in
the tank and only dry (ish) vapour out of the rear breather pipe. If you don't have a froth tower you can
only hope that not too much oil finds it's way out of the breather hole in the tank cap, but this hole really
isn't big enough to allow the engine to breathe correctly and I would recommend that you invest in
having the tank modified to incorporate the full late breather system plumbing.
#4072 There are two critical lengths for the pipes to balance the natural frequency of the engine.
Without them it is said that the oil will be evacuated. Someone will tell you the correct lengths, or if not
we will find the information in the Veloplonk draw and respond.
#4086 The adaptor to oil tank pipe should be 3/8 bore 21.375". Oil tank to wheel 27.5"
#4088 Please advise where exactly do you take these measurements from? They seem very tight
tolerance!
#4092 You don't take the measurements from any point to any point, they are just the length of the
pipes.
#4070 Agreed, I have tried several times to vent the timing chest breather directly out to the rear of the
bike, even going as far as putting a baffle inside the timing chest in front of the outlet hole. All in vein,
there is just too much oil flying around in the timing chest. In desperation, during the summer rally, I
routed the hose into the side of a plastic bottle, the air free to flow out the top. This worked fine except I
had to empty the can back into the oil tank at every stop! You mentioned you drilled the breather tube
hole under the mag. Make sure you also have the required holes leading from the crank case to the
timing chest.
#4111 My first attempt to correct excessive oil breathing on my VM (aka "The Torrey Canyon") involved
fitting the standard BSP hose connection under the magneto and piping it to a small cast alloy box
mounted on a bracket under the dualseat. The other end of the box was piped to the general area of
the rear number plate. I ran a flexible quarter inch pipe from the bottom of this box through a hole
drilled in the top of a scruffy old oil tank cap and stuffed the box with pot scourers. There were BSP
stud couplings everywhere but the installation was fairly tidy and it just about worked. Until, after about
3000 miles I looked inside the alloy box to find a disgusting mixture of mayonaise and rust - no sign of
the pot scourers. That's what happens if you get the breather pipe lengths wrong. Since then I have
done the proper job as outlined in Rod Burris' book but I've only piped to the oil tank; no external pipe
to the rear. The timing chest / rocker box behaves as a plenum chamber and, to a limited extent, so
does the oil tank; hence the reduced oil loss to the rear wheel when the tank is half full.
#4105 I reproduce here exactly Les's article. It appears that I am mistaken in that over the years Les & I
discussed, (mostly by mail ) various ideas on breathers & other things, & while I am sure that at one
point he was playing with some sort of timed 'valving' ideas, this article & the only drawing that I have
which is listed numerically, has no corresponding 'valve' drawing as I mentioned in my last mail, & I
have to draw the conclusion that this 'valve' is nothing more than an oil trap & drain idea that he
discusses in the article. The idea behind it's success being no more than the use of a large diameter
vent which he states should be routed well up above the unit, & the fact that any oil picked up remains
in a chamber & large capacity outlet tube of relatively static, though pulsating air, from which it drains
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ack to the bottom of the casing, & eventually back to the crankcase. Any 'timing' is no more than
striking a situation where pulsating air flow is reduced to minimum movement, - or even made static, at
which point oil has the chance to settle on the surrounding surfaces of the breather chamber, as well as
the inside surface of the large diameter vent tube & drain downwards. Further to this one would deduce
that as RPM rises, the oil would tend to settle out closer to the timing case, while if the engine was
running at low RPM, the fluctuations in the air direction would move towards the outlet vent tube,
whatever, theoretically if the point of comparatively static air can be kept within the confines of the
'valve chamber' 100 % of the oil held in suspension, should drop out & drain.!
ENGINE BREATHERS 'M' SERIES VELOCETTES - By Les Diener.
Over the years much has been written, & many designs of crankcase breathers used on various
machines, & without doubt the single cylinder engine presents the greatest challenge, due to the
amount of 'suck & blow' on each revolution. The greatest problem is to provide sufficient means for the
c/case to pass air only during the breathing cycle, & not a mixture of air & oil which, unless suppressed,
finishes up on the rear tire with possible disastrous consequences, & generally leaving a mess in the
process. The problem becomes rapidly worse with increasing engine speeds, & also when flywheel
assys. are more snugly fitted into c/cases, both situations demanding almost complete evacuation &
refill of the c/case voids during each revolution, whereas with slower revving engines, & those having
oodles of space around the flywheel assy. there is a form of 'cushion' on which to act. Reflecting back
over the years it would appear that in most cases c/case breathers were too small, but a notable
exception will be detected on most Italian machines. Moto Guzzi, Benelli, Morini, & others always had
huge c/case breathers which were mounted in a vertical position at some convenient spot on top of the
c/case, & with some form of 'trap-& -oil-drain' provided to separate oil & air. In later years one Japanese
example of this design was featured on the little CR 93 Honda, & whilst this was only a 125 cc racer, a
huge breather tube of some 20 mm I.D. hose went out along the upper frame member to the rear of the
machine, preceded by a large 'trap' housing, which no doubt would have contained some form of baffle
which would have allowed the oil to drain back into the sump. Timed breathers which have been used
on all KTT engines & others, have been reasonably successful but are not altogether foolproof as the
engine RPM goes beyond 6000, firstly because the orifices through which the air must pass is so
small,& also that very positive seals are required to allow the breather valve function to operate
efficiently. Disc or 'clacker' valves are much the same. So, in summarizing, the Italian concept would
appear to be the best compromise, in that BREATHERS must be 'BIG'. The design shown is what I
have on the 'ELDEE' classic racer, & whether by luck or coincidence, has turned out to be the most
efficient breather that I have ever used, for even with the engine running to 9000 RPM, not one drop of
oil leaves the trap housing, & this is evidenced in the 3/4 inch I.D. transparent plastic vent tube. The
'trap' can be fitted to all the earlier M series without problems, but on the later 'domed' timing chest
covers, a small 'platform' must be built up by tig welding. First it is desirable to drill 2 additional ½ inch
holes between c/case & the timing chest. Then drill a 7/32" hole, on an angle, underneath the timing
side main bearing, into the c/case, this is to always keep the timing chest free of oil build up. This is
only possible on later model c/cases, which have a large radius cast below the T/S main bearing. Next
drill a 5/8 " hole through the timing case cover in line with the magneto spindle, a 5/16" hole is then
drilled 11/16" below the centre of the 5/8" hole. (it may be necessary to skim the surface of the timing
cover at this point to provide a flat surface ) The housing is then mounted to the timing cover with the
5/16" hole directly in line with the annular groove in the housing & immediately below the 3/8" wide
drain slot. Drill & tap the 4 mounting holes, & fit the housing with jointing compound. ( At this point I
have checked photos of the ELDEE & noted that Les actually used 6 screws instead of the 4 shown in
his drawing ) Take the 3/4 inch clear PVC hose straight up as far as possible & route to the rear under
the seat to the rear of the machine, & if my experience is evidence, you have a breather that works !
Signed Les Diener.
#5417 It seems that there is room for comment here ? Re. Les Diener's experiments. As I remember it,
he started with the idea of a 'timed' device, & with this in mind, he machined a flat spot on the outside of
the timing case centred on the magneto spindle. The idea was to have a light circular body that was
ported internally, & vented back to the 'catch tin' via a hose in the usual manner. A light rotary valve
arrangement to be supported on the magneto spindle, but with ample running clearance to the body of
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the valve, no contact whatsoever ! The idea being that despite air leakage via the clearances in the
device, the ports closing off at a critical point in the engine's rotation, the pulses moving out through the
outlet pipe, would be reduced to a minor steady flow, where with the centrifugal force of the spinning
valve & the construction of the body would induce most of any oil laden air to drop the oil in suspension
on to the inside of the body, where it would simply drain back internally into the timing case. I believe
he opened up the hole from c/case to timing cover to reduce the pulses in the c/case somewhat also.
Some of this may be in his writings somewhere ? He kept me informed of his ongoing progress, at one
point stating that the timing of the porting was extremely critical both in the timing & the size of the
ports. I must have missed the end of the story, as I was surprised to find that the end result of all the
experimentation was just the original simple chamber, with no valve whatsoever, but working simply
because he had come to realize that the device equipped with a VERY LARGE BORE outlet hose,
running up as high as possible, - & eventually to the catch can, was in fact working in a harmonic
fashion after the style of a 'tuned' exhaust pipe. The action of the original timing device body having
been re-worked to act as an efficient oil trap in a convenient & efficient point in the system. All this is
apparent in his detailed drawing, & according to him, it worked perfectly, one would assume , best at
racing RPM ! Les has been gone for more than 10 (11?) years now, & I still haven’t located his original
ELDEE engine drawings, or his casting patterns, someone out there is sitting on them I guess ? -- on
the other hand, - maybe they were just burned by someone who never considered them valuable .
L # 5619 The breather system on my Thruxton is linked up by two pieces of 0.5" bore plastic
tubing of as I understand it "critical" lengths. At a recent local VMCC meet I was asked what these
"critical" lengths were. I have measured mine which have been on the bike since before my ownership
and they seem to work OK with the dimensions of timing chest rear(below mag) to oil tank = 22" and oil
tank to atmosphere (and/or rear tyre!!) = 28" but is this correct? Does anyone know the "Correct"
lengths for these pipes please. I would not like to pass on duff information.
# 5620 The hose lengths are given in the parts book. P/No FA138 - Engine to oil tank - 21.375", P/No
FA141 - Oil tank to wheel - 27.5". Pete C.
# 5621 I have seen these lengths quoted before but how do you measure plastic pipe to .005 and
where exactly do you measure from? The "inside" ends of the stubs to which the pipe is attached or the
"outside" ends?
# 5622 ! 0.375" = 3/8", 0.500" = 1/2". Measurement to the nearest 1/8" is probably close enough. The
pipe is measured end to end of the plastic pipe.
L # 6063 Does the air breather hose from the crank housing connect to lower or upper
connection on the oil tank? (or does it not matter)?
# 6064 It connects to the top and there are many on the site that will quote that it has to be exactly
21.375" long.
# 6065 On the Venom it connects to the connection at the top of the oil-tank with the vent pipe
connected to the froth tower. Remember the correct lengths.
L # 6265 Adding a check valve, one way valve, or PCV valve has a big advantage. The venom
engine displaces 500cc within the cylinder. Put the engine on top dead center (TDC) rotate the crank
180 degrees and 500cc of air/fuel mixture will fill the cylinder. At the same time 500cc have been
displaced below the piston and have been compressed into the internal spaces inside the engine
cases. The higher air pressure, from the piston dropping, raise the crankcase pressure above
atmospheric pressure, assuming 14.7 PSI (1 BAR) at sea level, and this air pressure escapes the
engine thru the crank case breather. Rotate the crank an additional 180 degrees and the rising piston
displaces 500cc of air inside the crank case and creates a partial vacuum. If the crank case breather is
working properly, it prohibits the ingress of air and the crank case remains below atmospheric pressure
until the piston again drops to bottom dead center (BDC). If there is little to no blow-by around the
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piston or up the valve guides, AND there are no air leaks, the engine will remain below atmospheric
pressure for all but a few degrees of the crank shaft near BDC. The vast majority of the crank angle will
create a partial vacuum, helping to reduce oil leaks, air pumping, and the loss of power from the added
work load. Obviously, the engine will need to rotate rapidly a few complete cycles to pump out the air in
the rank case via the small copper tube on the crank case breather. However, in only a few seconds
this will occur and the engine will essentially remain below atmospheric pressure inside the crank case.
Having a crank case breather keep the air out, the engine will show far fewer oil leaks, and the best
part, there will be no loss of energy by having to pump air in and out of the crank case. Less air
churning around, less oil being blown out into the primary chain case or the breather. There are
numerous one way valves available at any decent auto parts house. Ask to look thru their assortment of
PCV valves, or use a check valve like used on most autos in the brake servo hose. These are generally
about 1/2 inch spiggoted check valves and fit very nicely in the vent line going up to the tank. Cost is
under ten bucks US. Almost all modern engine employ a breather. Ride oil weep free.
# 6267 Wasn't Percy Goodman clever to devise a timed breather on the early K engines? This allows
the down going piston to breath out and restricts it's inhaling. Same device is still there on the Mk VIII -
and no other breather is required. Not bad for a 1925 design is it? For those poor souls who are
ignorant of the ways of a 'K', this timed breather is a cast on section that overlaps the drilling in the
drive side mainshaft and effectively blanks off the hole as the piston rises. No additional pipes, valves,
reed valves or other wot-nots.
# 6271 You have made some interesting points, however a lot depends on the design of the engine
&/or modifications, & the placement of the NRV, there is a case for claiming that in some cases, the
addition of an NRV can make the underside of the piston an excellent device for pumping oil out of the
internals & on to the road unless some sort of baffle chamber is fitted to separate & drain surplus oil
back into the system. However, -- my old mate Les Diener had a terse saying for this sort of thing, & he
had designed & tried timed breathers as well as various NRV's. And you are dead right about the
simple KSS design, --- maybe that is why I never worried about engine breathing in all my years of
riding Velocettes daily, -- they were all KSS's ! - apart from Les Diener's MOV which I rode at odd times
during the WW2 years, - mainly for petrol economy, ( my cammy had a sidecar attached & was
registered, -- but only for the petrol ration that it was entitled to ! ) it wasn't until the late 70's that I finally
got around to riding a MSS & it never seemed to need a breather!
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B.7. Racing and High Performance -
L #35 The easiest way to get your Viper to go faster, is to fit a Venom barrel and head. Better yet,
a Thruxton barrel and head! I have a Viper clubman, and it won't do over about 90, with a fairly fresh
motor. But, I remember at Montlhery several Vipers, and in discussion with their owners, they all
claimed to get over 100mph out of them, with no great trickery. Any thoughts on this, fellows? P d'O
#54 Try shedding some pounds. This is easier to do to the bike than the rider. A 50 pound reduction in
stock bike weight should be close to trying to gain 5 hp on a Viper. I have a Venom based racer that is
down to 240 lbs with fuel and oil (non-stock frame). It makes a big difference A box of clean spark plugs
and a selection of sprockets will do wonders. Spend the time dialing in your carbs and ignition. Make
lots of high-speed runs and immediately take those plug readings. A crisp running engine can add an
easy 5 mph to the top end
L #36 I am taking up sprinting using a 1937 MSS running on methanol with an 1 3/16 inch 10TT9,
running on a standard M18/2 with standard followers. The clutch is to Thruxton spec. In my first year
my key objective is to be able to slow the beast down, as currently it has a rigid MAC 6 inch hub (frame
and forks are MSS/KSS). I seem to have been spending the last month converting a cast MAC/MSS 7
inch front hub to fit the webs. Turned up lots of 5/8 inch to ½ inch spacers (in titanium), and converting
a 5/8 inch diameter spindle to having ½ inch BS Cycle ends. Titanium is a funny metal; do you know
you can get it to ignite when you turn it? I have been researching the subject of speed. First thing is to
speak to all the fast Velo boys at the meetings; they are only too pleased to be of help. Secondly there
have been some excellent articles on tuning Velos in Fishtail and Fishtail West by Nick Vann, Dennis
Quinlan, Bill Melville, Marin Violette, Robert Gussman, peter Witman and Laurie Nunn. These appeared
in a reprint of the technical articles in Fishtail, by our American cousins.
#59 While you are busy tossing the weight off your frame, think about getting some serious weight off
your valve train. That will help you raise the rev limit. Velos breathe fairly well with the 17/8 cam.
Problem was they tangle valves just over 6200 rpm (Venom). Actually they seem to be pulling hard until
then which indicates that power is still being made. Lightening the valve train will allow the revs to
increase. There is a problem with this though, as the revs increase the stresses on the crankcases built
substantially. As such, at the same time you lighten the valve train think about using parallel roller main
bearings or machine a steel top hat reinforcement piece for the drive side main bearing if you stay with
the taper rollers. The drive side case is definitely a weak point. I run a 9.75 to 1 compression ratio,
Sommerton polydyne cam, and my rev limit is 7,500 rpm (self imposed). I have run it out to over 8,000
rpm (undergeared and I wasn’t going to let that Manx get past me on the long straight) and the bike is
still pulling hard. I wouldn’t try go to this level without extensive engine work. I have lots of mods,
titanium bits and extensively reinforced engine cases (and even they have cracked). Many bikes tend to
run out of breath as the revs increase. The Mac, for example, with its mild cam just tends to let you
know that there is no gain in wringing the throttle any more, time to shift.
L #64 I am a member of the local WA Historic racing Club and have a '38 Mac. I'm having trouble
with second gear, it broke and I am advised by those that know that this is a common problem and the
best way out is to replace it with a pre-war MSS box, or it will just continue to happen. Any thoughts? I
am having great difficulty in finding a replacement 2nd gear in Oz. The Mac has close ratio gearset
and close ratio sleeve gear, SW springs, triumph front wheel, and runs on Methanol. The barrel has
had the cast iron fins removed and replaced with shrunk-fit alloy roundies for better heat dispersion. I
was using Castrol "R" but due to the difficulty in obtaining it and the high cost, am flushing out the
system and replacing it with a 50w oil, any suggestions on what to use given that it does not get very
cold over here and we do a maximum of about 6 laps per race, three races a day plus 2 practice
sessions. 4 others from our local Velo club are also racing this year having built up pre-war 350's to
come and play! We are trying to encourage other pre-war machines as this class is just me at present,
so I'm looking forward to solving a few minor niggles before the season starts.
#65 I have checked the spares lists of the major suppliers in the UK and no one has this gear available
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as new old stock. Probably because they break!
#66 Hello MT, yes, if the power goes up on your MAC, the second gear will continually be a source of
trouble. I don't know whether it's cheaper to have a batch of gears made or replace your 'box with one
from a K or MSS, as you'll have to make frame mod's as well. Probably the cheapest way is to source
used MAC clusters and expect a gearbox teardown frequently. If your average race is only 6 laps and
you're running on methanol, I would think synthetic 20/50w oil should be plenty for your bike; you might
even get away with straight 20 or 30w synthetic, and I know several vintage racers who use this. NSU
used pre-heated 15w in their GP racers, and that was 1950's oil. I doubt your engine will get hot
enough to really thin the straight 50, so you'll be losing hp to drag. People use straight 50 to keep film
strength in a really hot engine, but I think in your case it's just a hindrance.
#78 Strangely enough while a close ratio gear cluster was never listed for a MAC, it was for a GTP!
(Owning a GTP, I can’t think why). The alternative that some of the serious racing carry out is to grind
Venom gears to suit.
L #75 Can anyone help me with this one? My Mac racer (pre-war) has Iron head and barrel, with
fins machined off and aluminum fins shrunk fit, running methanol. Should I run a copper head gasket as
per later models, or just lap it in as per earlier ones? At the moment the exhaust valve is just marking
the piston and rather than reset it, I'm thinking that the extra clearance gained by using the copper
gasket might be a better option. Any thoughts?
#76 I think the copper gasket is essential in this case unless you want to start machining things like
piston crowns. If fact, you could pretty accurately measure your piston/valve clearance by varying the
head gasket thickness (it will compress slightly when you torque the head bolts). Especially as it
seems about at Zero at the moment; a good starting point! Just out of curiosity, what sort of CR are you
running with that piston?
L #283 Over the last ten years or so I have been planning to build a MAC sprinter. During that
time I have been researching what I need to do to tune the engine by reading about and speaking to
everyone that races iron Velos. In the end I opted for a 1937 MSS, which is very similar to a MOV.
Some of what I have described, I have carried out – some I will carry in the near future. Crankcases.
The MOV/MAC crankcase is as thick and strong as a Venom, it also has less cylinder overhang. David
Holmes and Nigel Lines who have produced the fastest iron pushrod Velos have not reinforced the
crankcases, so I doubt if you will need to. One of our fellow club members has converted his main
bearings to roller mains, but I am not sure what best solution is in this area. My MSS has been
converted to post war specification that is taper rollers similar to a Venom. Polish both the inside of the
crankcase and the crank to reduce drag. Also polish the con rod to reduce the likelihood of the rod
fracturing. I am not sure what the balance factor is best so I would leave it as it is. - Cams – The ideal
cam for a MOV is a M17/6 similar timing to a Venom but slightly less lift. Unfortunately they are very
difficult to find. Use a M17/8, but you will need to remove about 3mm. from the valve spring cup and the
bottom of the rocker box where the rocker touches when on full lift. Finally if you can’t get hold of any of
the above, you can use an iron MSS cam M17/2. - Valve Gear. Lighten the rockers, cam followers and
pushrods as shown in the attachments. There is also an oiling mod to supply additional oil to the
guides, but it is difficult to describe in print. - Carbs – for a MAC a 1 3/32 inch TT carbs is the most
appropriate and as big as you should go. However a 1 1/16 inch Amal 276 will do a similar job.
Increase the induction tract length by fitting a one inch spacer between the carbs and head. You can
use a larger inlet valve up to 1.5 inch. Ideally use a Nimonic 80 exhaust valve from a Viper and turn it
down to fit. The exhaust valve needs to be a loose fit in the guide to avoid seizure. Ideally you should
remake the guides out of aluminum bronze. - Valve springs. Use light alloy collars and springs
available from Nick Peyton. Approx cost £ 38. You could also consider fitting rocker return springs
available from R. F Seymour, although the jury is out on the benefits of this. - Pistons – methanol
pistons although rare do exist. However the most common solution is a high compression Triumph
piston. It will need some fettling to make it fit and to obtain the correct compression ratio. - Oil system.
Replace the single worm oil pump drive with a double drive worm from a 86mm Velo. While you are at
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it, fit a 86mm cam steady plate with the cam oiling jet. This will involve silver soldering a boss onto the
existing timing cover feed pipe and drilling into the pipe, not the easiest of jobs. If originality isn’t
important use a Venom / Viper timing cover and save yourself all the extra work. If you have a
crankcase with the rear cylinder oiling jet you can blank this off by using an ordinary bolt, rather than
the oil feed bolt. Then drill two small holes the same size as those found in the cam oiling jet in the feed
to the back to the cylinder – this is tricky to get them at exactly the correct angle to spray oil onto the
cams. Finally silver solder two one eighth inch bore pipes near to the bottom of each of the valve spring
cups to help drain the oil away. Use of flexible tube to connect this to a Venom type pushrod tube.
Finally buy a copy of Phil Irving’s book “Tuning for Speed”, it’s packed with practical and useful
information. Perhaps some of the MAC racers in the group can comment or add to my note May be
vibrations or force makes to flax the crank shaft? What I think is, primarily chain sprocket have to be
run as close as crank centre to reduce effective distance of shaft. This mean sprocket as close as
crankcase? The end of shaft there is a shock absorber. I think they have to go as they are hanging a
lot! This mean have to use rear hub like Triumph (with absorber inside) or convert to the primarily belt
drive?
L #257 1961 Venom with fairing and 3.9:1 top gear = 110-112 mph Standard Venom top gear
ratio 4.9:1 = 96 mph.
L #560 I got a 58 Venom since two years now and try to get it to its 100 MPH told capacity. By
now, the Lucas Racing magneto has been overhauled and the carburettor is a new Amal Monobloc
(checked and re-checked by my workshop), fitted with a 330 main jet. Test after test, the engine is very
smooth, but the power "flattens" when reaching 75/80 MPH with only 3/4 throttle with some impressive
vibration. Looking for any possible reason, I would like to know if this 100 MPH performance can be
reach with the standard 18 teeth sprocket, or if I need to fit a 19 or 20 teeth sprocket in order to be able
(may be) to get the bike to 160 km/h ? Regarding the vibration, may be the wheel chain tension is too
high, and I will correct that as soon as I got time. Another question is that it seems that the engine oil is
"jettisoned" through the oil breather tube. I got a recovery bottle (half a litter), fitted with its own breather
tube facing the road to limit the spillage. What is interesting is that the bottle is full after 300 or 400 km,
but when oil drops comes out of the forward outlet tube, the oil consumption is then ridiculous. I had in
the past a Ducati Darmah. In the oil breather line, there was a restrictor dedicated to prevent the oil
breather to act as a jet pump (or a jettison as we call in my job). Does the oil breather adaptor
mentioned in the Velocette Parts List contain a restriction or shall I fabricate one in order to be sure that
only oil "smoke" only goes through the breather line ? The fact that oil consumption comes back to
normal figures when the bottle is full tends me to think I shall.
#566 You will need minimum 19 tooth sprocket, or an enormous rear tyre with an 18 tooth sprocket to
pull the ton on your Venom, assuming 6200 rpm rev limit. For an Avon 100/90x19" rear tyre gearing
charts show these speeds per 1000 rpm and maximum speeds in top gear for the commonly used
gearbox sprockets. All speeds quoted are mph: 18 T 15.389 95.412 At 6200 rpm 19 T 16.244 100.713
At 6200 rpm 20 T 17.099 106.014 At 6200 rpm 21 T 17.954 111.315 At 6200 rpm
#567 Earlier posts discussed top speed of a standard Venom and in my opinion a well set up Venom
with the rider sitting upright will do about 85 mph + - 5 mph. The 100 mph in past road tests, were when
riders were flat on the tank. Why? Due to the petrol now available, most Venoms have to run with
compression ratios of 8;1 rather than the 8.75: 1, which reduces the power by approximately 2 BHP.
Amals tell me that a TT carbs only flows 3% better than a Monobloc so it’s not that. Finally I think as
riders we are all presenting greater wind and frictional resistance as a result of maturing! How can you
make it go faster? Apart from setting the engine und the rest of the bike up well, short of fitting a
Thruxton head, probably you could get your Venom head gas flowed. Has anyone noticed that some
Venom heads are stamped G or OK on the cylinder face, anyone know what this means? You could
also fit a spacer between the carbs and head to get the induction pipe length to resonate at somewhere
between 5-6000 RPM (if you have room between engine and oil tank). Lightening the valve gear will
only really allow you to rev quicker and safer. The M17/8 is the best readily available cam around. Even
at 85 mph a Venom does not normally vibrate to any noticeable degree. Check the following Head
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steady fitted and tightened Engine bolts tight and holes not worn. Check your petrol and oil tanks are
tight (I spent days worrying about excessive vibration, only to find I had not tightened the petrol and oil
tank bolt) Check ignition and cam timing. Check the carbs is set up OK
#571 Don't forget the most important part needed for a ton-up Velo, as used on the 24 hour record bike
- a good racing fairing! Worth at least 10 mph, given proper gearing.
#572 regarding vfr 232 a 1960 venom clubman which was a very fast bike. it was fitted with a 12r box. I
was reading one of the posts regarding max rpm and top speed with a 19 tooth sprocket,
which was about 100 mph. I know for a fact that vfr 232 was cable of a bit more than that. it used to
show 105 on the straight with me lying prone. the question I have is, was there three top gears. one
for mss one for venom and one for tt close gears. 26 teeth seems to ring a bell. if a bike was fitted with
a higher top gear, it surely must give it more top end. my bike was always good for 90 in third. I still
have the bike, although it hasn't run for some time, but if someone wanted a go on it to prove its
output, I wouldn’t be against it. did a tt close box have a higher top gear than a standard 12 box ?
#573 Top gear ratio is all in the sprockets, not the internal ratios of the gearbox, as I've never heard of
an internal top gear ratio other than 1:1 in a Velo. The options on sleeve gear and (I think) first gear
are what differentiates the suffix R from the standard series 12 box. A close ratio sleeve gear in any
box will leave top gear at the ratio determined by the final drive sprocket (or custom combinations of
any of the other sprockets for that matter) but it will bring all of the intermediate gears closer to top - for
instance a 17 tooth sleeve gear (in place of the standard 16 tooth) in my MAC racer left me with 1:1 top
but overall drive ratios of all the other gears were higher by the equivalent of almost two gearbox
sprocket teeth, when compared with the overall ratios available with the standard sleeve gear. So if
you'd like to run a 19 tooth sprocket for your ton and a bit Venom, but have first, second and third the
same as if you had a 21 tooth sprocket, then go close ratio sleeve gear, which for series 12 gearboxes
means an 18 tooth sleeve gear as the standard sleeve gear in the series 12's is a 17 toother to start
with. For sidecar use go 16 tooth sleeve gear - it will have the opposite effect, and was used in the wide
ratio series 14 boxes. And of course whenever you change sleevegear the layshaft pinion needs to be
changed accordingly (from 16/28 to 17/27 to 18/26 and so on). Read the chapter on gearboxes in
Burris - it’s a good explanation for those wondering how the hell to calculate these things called gear
ratios.
#575 thanks for the info regarding sleeve gears, mine has a 18 tooth fitted, it is a genuine 12r box.
these boxes make a world of difference for performance on a venom, but are a pig to use in traffic. they
are definitely for the open road. regarding fitting a thruxton cyl head to venom, if you don’t shorten the
barrel by 90 thou it will be as flat as a pancake. I considered trying to buy the venom cyl head patterns
and having my own head made. thruxton valve angles are at 39 degrees whereas venoms are at 45
degrees. if I had some venom head blanks I could have the valves at 39 degrees and keep the stock
venom valve sizes. a thruxton inlet valve at 2 inches is a bit on the heavy side, and a venom inlet
valve at 1 inch and three quarters is a better bet for higher rpms. any feedback on this is welcomed.
when fitting a thruxton barrel to venom head and tightening up the valve to piston clearances, these
bikes transform into a fast bike. dialing in the cam is a must for performance as is accurate ignition
timing, it needs to be set at 38 degrees, and on the money. I seem to remember that Taylor Gue of
Stroud in the sixties made a venom very fast and that when they were doing a road test of a thruxton in
motorcycle sport in 1966, they also tested his bike to compare it with the thruxton and found it to be a
faster bike. dig out your old copies and have a look.
L #945 The Velo tech website (thanks again Dai) has the formula for C.R. vs. compression plate
thickness. Plates normally come in 0.030" and 0.010" thickness, I'm running 0.050" under my Venom's
similar barrel (it came with these plates from the factory). It never pinks now, even on our watery U/L
premium, as long as the fuel mixture is adequately rich. Plates are available from the Usual Suspects -
oops I mean Sources, check the List archives. As a Velo rider, you will soon be on a first name basis
with them. And I strongly recommend that you join the VOC and VOCNA; the VOC's Spares Service is
excellent. See the VOC website for links. I assume you have an Omega piston, I have had some
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trouble with them seizing but never had one fail structurally. There are few alternatives in any case,
unless our Aussie mates have made some more? Pretty please? But before I detuned my VMT I'd
double check the ignition timing, make sure you haven't fitted an extended tip sparkplug (such as NGK
BP7ES instead of B7ES) and that the fuel mixture is adequate. There must be no blocked jets or air
leaks.
#959 I might make another suggestion since most of the logical things have been mentioned, if you
want to take advantage of your compression and use the highest available octane, install a cam with
more overlap and a even little more lift (commonly referred to as "hotter")if you feel cheeky. This will
effectively lower compression by opening the valves longer during the cycle and give you the power
that the compression is there for and should stop the pinging if everything else is standard settings.
The shim plates are poopy in comparison.
#961 Increasing overlap gives more time for the fresh fuel/air mixture to cool the combustion chamber.
It will also reduce low rpm power and fuel economy; there is no free lunch here. I have two modern, 4valve
per cylinder motorbikes that suffered intake valve damage from inadequate cam overlap for their
higher-than-original compression ratio. The symptom is that the intake valve clearances close up over
time. Interestingly, the seats are harder than the valves these days. The cure in one case was to
change the cams, in the other a reduction in compression ratio is needed - it already has a hot cam.
The easiest way to increase overlap on a Velo is to increase the radius of the cam followers - oops
Veloce already thought of that! The difference in power characteristics between MAC and Viper
illustrate the difference perfectly.
#962 I meant to mention that this cam change should include a duration and timing change as well
(this goes with high performance cams as a matter of course), which will require a regrind. It is
definitely true that changes like this are detrimental to low end performance, you will get a lumpy idle
and less grunt off the line, but in the mid range and up, it will be sparkling! I like regrinding because
you can get a higher lift without a taller cam profile from centerline (the backside of the cam is ground
down to give the higher lift), thus avoiding clearance problems.
#1020 I have my race venom in bits just now, so I will measure the pipe for you. It is more than
thruxton spec, so I think it classifies as 'tuned' ! I run end-cans on the venom and viper for racing that
seem to do enough silencing, and will measure those for you too. In general terms, if you are going to
sprint, you will obviously get a bit more power if you run an tuned straight pipe, but you always lose
out if you think in absolutes ! The answer is usually a compromise, and reverse-cone megas are exactly
that.
L #1030 I have now spent the season experimenting with a variable exhaust pipe extension and
settled on 45 inches along CL. This seams to resonate with the induction length at about 5500 RPM. I
knew I got it right as for the first time the bike wanted to over rev, the valve hit the piston and the rest I
am sure you can imagine.
L #1959 Hi Does anyone have a table of drill sizes to drill out main jets. I have a table up to 500,
but need information above that size. Even better if anyone has any surplus main jets above 1000, that
they would be happy to swap with me for smaller sizes to save me butchering them by drilling them out.
#1960 What bike needs a jet size of 1000? You running methanol?
#1962 Yes in my race bike - in my experience a much nicer fuel than petrol. Only problems are: - you
use 2.25 times as much as petrol - when it's cold it can be very difficult to start - virtually impossible to
take a plug reading - contaminates and washes the bore of oil - can rust the inside of the engine But it
runs cooler, will give you between 10 - 15% increase in power, and allows you to raise the CR to give
you the same increase again.
#1975 My MAC runs happily on a 800 main, it starts very easily and revs right through to 6000 without
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a problem. To improve the starting add 1% Acetone to your methanol, it improves cold starting.
L #2486 As I am building an engine now that will not run for at least six months, My query was
what lube to use when assembling engines to run on R. I spoke to both Castrol and Morris, they said
the same - only use R to oil components on assembly and not to use any other lubricants as they will
not mix. Basically their advice was to try to keep the engine in a warm dry atmosphere to avoid
condensation. They reckon corrosion is no more a problem with R than mineral oil, the problem is the
amount of methanol swilling around the engine. Oxidation is only a problem when the engine has run.
There is a company that sells an additive to add to engine run on dope and R that inhibits corrosion,
but I have not tried it as it appears very expensive (during the season I change oil every couple of
weeks.)
#2487 I think Morris sells a special oil for grasstrack and speedway engines, this oil is supposed to be
for use in methanol engines.
#2488 Oil of castor type for use with methanol is Castrol M. This should not be mixed with R or you will
get a very pretty purple sludge!
#2489 I use Morris MLR40, which as it says on the can, is designed to be used with methanol. Even
has a picture of a speedway bike on the front! Still drains out purple with a nice bronze sheen to it
though.
#2490 I'm curious, did either company say much more about the advantages or disadvantages of using
'R' compared to a good modern monograde? I spoke to both asking advice on what oil to run an OHC
Velo with and couldn't get a clear opinion either way from both companies.
#2497 No I didn't ask that question as I run on methanol. Regarding lubricating dope burning engines
on mineral oil, one grass tracker I know uses mineral oil but extends the feed pipe some 4cm into the
oil tank. Between races he undoes the oil tank drain plug and drains off the separated methanol that
settles below the oil.
#2494 I don't think there is any particular advantage to using vegetable based oils in petrol engines -
the advances in lubrication technology over the last 60 years or so mean that modern oils have far
superior properties than before - but if you are running methanol then it's a different matter. Dope will
degrade mineral oils severely due partly to the diluting properties of the fuel but mainly to the fact that a
considerable quantity of the fuel finds its way past the rings and into the sump. Vegetable oils are not
degraded by methanol to the same extent so are preferable in engines running this fuel. I think you will
find that the majority of speedway and grasstrack and some vintage competition engines run on "R" for
this very reason.
#2499 I firmly believe that castor oil still has the edge in extreme air cooled situations. In particular
consider a MkI cam box with iffy lubrication and high point loads. Castor has still the highest film
strength. Other oils work very well under higher flow rates and in the case of synthetic for longer
periods. The drawbacks are non-detergent, hygroscopic tendencies and the goo! If you want the motor
to last though, frequent oil changes and acceptance of the goo factor is a price well worth paying. As an
aside, multi grade oils do not suit air cooled engines. As synthetics are generally thinner I presume they
would be even worse?
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C. The Electrics
C.1. Ignition and Timing -
L #129 Have just finished restoring a 1956 Mk II LE, and heard today that the correct timing was
with the timing marking holes coincident (TDC), and the points just opening with the auto timing device
weights fully extended. Surely this is incorrect? When I set mine, I set it with the weights closed
(retracted) and it starts and runs OK. Thanks for any advice.
#177 (LE Model) The timing settings for all engines I know of are quoted as "full advance" i.e. with the
ATD springs fully extended. This will give a setting which when using the design intent fuel will produce
an approximation to maximum available torque at all engine speeds, while keeping clear of damaging
detonation limits. If you set your ignition timing on full retard i.e. with springs in closed condition, the
effect will be for the engine to run with excessive spark advance which may improve torque, but only if
the optimal spark timing has not already been reached. The trouble is that the increased advance may
also cause the motor to run past the detonation limit at some speeds. Modern pump gasoline (even
unleaded) is generally much improved on the equivalent available in 1956, so it is possible that the LE
might stand a little more advance, but the only way to tell for sure is by running spark sweeps on a
dyno. Remember too that ignition systems of this era were very primitive by modern standards and are
only capable of a small amount of automatic advance which will retard spark at low engine speeds and
reach full advance at around 2500 - 3000rpm. With modern engine management systems it is possible
to calibrate the system to run the ideal amount of spark advance for all running conditions e.g. speed,
load, throttle opening, engine temperature, air temperature, even making adjustments automatically
for whichever gear you happen to be using! With our old things spark timing can only ever be a
compromise, and was specified to provide the best performance while keeping within a safe running
condition. In light of this, unless you have the facility to find out otherwise, stick with the factory
recommendation and set up with the ATD wedged in the full advanced position. Happy riding, Pete C.
L #182 Looking at page 3 of "Tips" on www.le-velocette.co.uk/info.htm I read the following:
(Quote) "1. When setting the timing on Miller systems, bring the flywheel into alignment of TDC by
setting the hole in the flywheel central to the hole in the mounting back plate. Adjust the cam unit to just
opening the points, in a clockwise direction, with the bob weights in a FULLY OPEN POSITION. i.e.
fully advanced. This is not clearly stated in the workshop manual." (End of quote) Surely this will give a
large amount of retard at starting, and will only advance the spark to TDC at full revs? I have
assiduously studied all the manuals and documentation I can find, and nowhere do they give a degree
figure for the fully advanced setting for the LE Miller set. They all tell me to set TDC with the holes
referred to in alignment (TDC) and fit the ATD with the points just opening. This would be fully retarded
at TDC, and presumably the degree of advance is set by the operation of the bob weights, of an
amount not specified. I will do a little experimenting/measuring to find just how much the ATD does
effect an advance, but nowhere have I been able to find a figure
#187 your interpretation of the instruction appears to be correct in that you are told to set full advance
at TDC. I can only assume that the engine is extremely det limited if this is the correct method. If on
the other hand the method should be to set to full retard at TDC, i.e. with bob weights closed, then the
only control on the critical full advance setting is the amount of advance provided by the ATD, again a
fairly primitive device which was likely to have had a tolerance of a few degrees of range even when
new, never mind after half a century's use
L #313 Has anyone got to hand the Valve timing figures for a MK8 D.O.H.C. works engine?
#444 My 1967 edition of the Red Book lists 30 thousandths checking clearance in the Data section
(p.7), but the Sports/Clubman Preparation section (p. 102) states that "Greater accuracy of reading is
obtained..." using 53/52 thousandths, with identical cam timings. Anyone care to comment? There is a
shortcut, though - courtesy of a "Molegrips and Hammers" article in an old FT: For fairly obvious
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easons, both valves should be equally open at TDC (of course, one is actually closing). That is, at
TDC the rocker arms are lifted equally, which is easily verified. The actual limit on accuracy is finding
TDC in any case. This has worked acceptably with the /8 in my Venom, not needing adjustment in
25,000 miles.
#446 Quite obviously something wrong here. Greater accuracy may well be obtained by using a wider
clearance when checking because you will be on a steeper part of the cam, but the timing will of course
be different - with wider clearances the opening time will be later and the closing time earlier. It is for
this reason that I prefer to check the peak lift point when checking cam timing. If you assume the cam
to be symmetrical, which they normally are, then this is easily worked out. As regards finding TDC
accurately this can be done easily to less than half a degree if you use a positive stop for the piston
when setting up the degree disk. An old plug can be easily modified to do this by carefully cutting round
the steel body just above the hexagon and removing the insulator assembly. remove the outer
electrode and tap 10mm x 1.25 through the body. Fit a 10mm bolt around 60mm long into the body and
file or grind its end to a nice rounded profile to prevent damage to the piston and you have the tool.
Remove your spark plug and rotate the engine so the piston is in the lower half of the stroke and fit
your new tool in the plug hole, tightening gently. fit your degree disk and pointer and rotate the crank
slowly until the piston is hard against the stop and take a reading on the disk. Turn the crank back until
you are hard against the stop in the other direction and take another reading. Using the two readings
set the pointer to read equally either side of TDC when the piston is against the stop and you have a
very accurate setting which accounts automatically for any.
#448 It seems obvious that increased clearances change timings, but as we all know, the Red Book is
never wrong! M17/5 and /7 cams are fairly symmetrical, but the /4 and /8 are far from it, with a much
gentler opening ramp. The beauty of the "Rastus" trick is that it requires no degree wheel. I have a tool
that measures piston position, it is a sliding scale in a holder that is threaded for the spark plug hole. It
makes finding TDC to within a couple of degrees quite simple. One tooth on the cam gear is four
degrees; no better accuracy is available unless you are willing to disassemble the cam from its gear.
This may make your racer a tiny bit quicker but is not needed on a street machine.
#449 My Red Book (for the swingarm models) shows a 10 degree difference between /8 cam timing at
.030 and .052 lift. One tooth changes the valve timing 8 degrees at the crank, where timing is
measured, and it is certainly noticeable. Careful with piston clearance, particularly the intake valve
when advancing. The lever action followers create much more action on the opening side, so although
the ramps on the cam are different, actual valve rates are probably much closer to symmetrical than it
appears, I've never graphed it though. If timing for split overlap gives correct timing when measured at
.030-.052, then the valve action can't be symmetrical. On a /8 cam, assuming the timing was
symmetrical, lobe centers based on the book would not be the same, more like 95 and 105 degrees..
L #850 At 38 degrees btdc what is the exact imperial measurement that a Venom piston is from
the top of it's stroke. I will use this to time the engine with a dial-gauge.
#851 A word of advice: use a degree disk, this will be considerably more accurate than using a dial
gauge and does not necessitate the removal of the head to do the job. If you use a positive stop
method to find TDC this is the most accurate method of timing. My positive stop is a spark plug body
with the insulator carefully removed - just run a fine hacksaw cut around the shoulder above the hex
and the insulator will drop out - run a 10mm tap through after removing the earth electrode and fit a
10mm allen bolt or similar with the end suitably rounded to prevent damage to the piston and long
enough to stop the piston before it reaches the top of its stroke. By rotating the crank back and forth to
the stop (slowly and carefully), TDC can be found by splitting the difference between the readings. The
result is an exact TDC setting which needs no compensation for backlash.
#852 From 36 to 38 degrees the piston drops 20 thou per degree, so this is a more consistently
accurate method of setting timing than messing about with degree wheels. And certainly more
convenient, you can even do it by the roadside. But the measurement is taken along the bore
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centerline, so a dial indicator that screws into the spark plug hole will not yield accurate
measurements, due to its angle and the probability that the point will move on the piston as it drops.
Use a small steel rule, this will give more than adequate accuracy. So here are the numbers - 36
degrees is 0.3957" BTDC and 38 is 0.4384". Keep the rule vertical as you measure. I use 0.040" and
0.4375" (7/16"). I marked an old spoke with a file and keep it in the toolkit.
#855 Back of an envelope and IE6 calculator stuff (scratch scratch) Venom stroke is 86 mm, right? (not
sure - I am an LE man) I reckon piston rise = (86/2)-(cos 38 x (86/2)) = 43 - (0.788 * 43) = 43 - 33.884
= 9.116 mm = 0.359" or 23/64" in Imperial. You did ask for "exact" and my IE6 calculator works to 33
decimal places,
#856 I have an alternator on the end of the crank and have it degreed so I use a strobe light. And I
always find no matter how carefully I set the timing statically, it's always a few degrees off when
running, presumably due to gear lash, bearing float etc. That said, a few degrees off, unless over
advanced to detonation, is hard for me to notice in the seat of the pants. Could make for a hot piston
though, and we all know what happens next
#861 After a recent engine rebuild I established TDC with the positive stop through the plug
hole/degree plate system, then tried two others, purely out of interest. A sensitive dial gauge, anchored
on a rocker cover bolt, through the plug hole, got me within one degree every time (read off the degree
plate, still in place). Slightly more accurate (here comes the heresy) was a fine pointed scriber inserted
through the plug hole and held against the piston top with the fingers pressed tightly against the plug
cavity. Rocking the piston back and forth either side of TDC, then judging the moment of no movement
consistently found TDC +/- less than one degree.
#866 I think the equation is d = S/2 + L -S/2 cosX - L sin {cos (power -1)(S/2L sin X)} where; d = equals
distance before TDC S = Stroke L = length of connecting rod X = angle before TDC in degrees You can
still ask your granddaughter to work it out though, as I haven't used log tables since I was forced to give
up engineering 24 years ago! By the way, for those of you that don't want to drill / chisel out the centre
of a spark plug, Seymour's sell the correct graduated tool for the job at about £5
#868 if you're stuck on the road re-time the mag to open the points at TDC on full retard. Its good
enough to get home.
#869 38/ BTDC is the correct timing for the old leaded fuel. 36/ is more likely to work with standard
leaded fuel without preignition.
#871 I have tried a few different methods and I have heard about the positive stop method, but for me,
I find that I need to go through my own method. firstly remove the gas tank. then remove the dynamo
outer cover and pull out the split pin out of the crankshaft. then unscrew the dynamo pulley off the
crank. then slacken the dynamo strap and undo bottom mounting for inner dynamo cover. pull the
inner cover forward and turn clockwise to about 20 to the hour. then push it back and tighten the
dynamo strap. this now puts the inner cover out of the way and gives access to the crank. next, get a
thin piece of wire and slacken one of the primary screws and make the letter u at the end and put it
under the screw and refit it and tighten it up. bend the wire so that when the degree plate is on you will
have a pointer. you will need a timing disc, a plastic one is fine. make sure that the hole of the disc is
comparable to the crank. now, you will need two big penny washers, they need to be not too thick and
have a hole comparable with the crank. now, take the castellated nut off the two dynamo discs and
sandwich the disc between the penny washers and put on the crank. then put on the castellated nut
and tighten up. this serves two purposes. one. it makes the degree disc strong and flat, and two, you
can now kick the bike over. next remove the spark plug and now you will need a dial gauge. a draper
one works well. now you will need to find the compression stroke. put your finger over the hole and turn
the motor over until it starts to hiss. you are now on the compression stroke. bring the piston up to the
top of its stroke and then slacken the castellated nut and set the degree disc to twelve o’clock. i.e. zero
at twelve. now the trick is to find an accurate tdc. with the piston at the top of its stroke, screw in the
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adaptor for the dial gauge and then insert the dial gauge. you may need to screw an extension on it.
let the dial gauge down until it just kisses the piston. this is important. now what I do next is to get a
trolley jack and put it under the frame on the l/h side where the mainstand would be, as I don’t have a
mainstand. I then lift the bike so the back wheel is off the ground. put the bike into first gear and now
you can operate the crank via the back wheel. if you have a mainstand fitted that should work good as
well. turn the rear wheel clockwise to turn the motor backwards to take it off tdc. now bring up the
piston up to tdc again and watch the dial gauge needle and slow down as the piston contacts it. set the gauge to zero by turning the
outer on the gauge, as the needle starts to lift, keep zeroing the needle. this has to be done very
slowly as it blips the needle quickly. when the needle starts to drop, stop and bend the pointer back to
zero on the degree plate. Look straight at the degree plate as looking at it to on side will give a slightly
different reading. now, your dial gauge is showing the piston starting to drop away after the rock on the
crank at tdc. turn the rear wheel anti clockwise very slowly and watch for the needle stating to move
again, when it does stop, and look at the degree plate. check the amount of degrees of movement and
split this in two and that is tdc set very accurately. turn the motor back off tdc by turning the rear wheel
backwards to past 40 degrees. then bring it to 40 degrees and set the points to just breaking, a
cigarette paper is spot on for this. make sure that you have pre set your points gap. get your paper
between the points until it will just pull out but there is still a little resistance. I find the next step is to
have two people to do the job, as with one it is just about impossible. have one person hold the points
in the mag with his hand as it is breaking at the points and have the other person put the magwheel
on the other side and tap it smartly with a deep socket and a hammer to put it on to the taper. I
guarantee that if you set the degree plate to 38, you will end up with 36. been there, done that. when
set at 40 you will get 38 when it is rechecked don’t ask me why, but I always get 2 degrees of
movement. the motor is now set at an accurate 38 degrees. super unleaded is a highish octane and
with silkolene pro-boost added with it you wont get detonation provided that the motor is not running
too lean of course. I hope somebody can use this info. regarding setting the timing at the roadside, I
have never had to do it as I make sure that nothing will slip when doing assembly. if the magwheel is
foreign to the magneto shaft, lap it on to the shaft and when it is pulled up it will never slip. remember
that when assembling, that doing it wrong ends up in failure sooner rather than later. if the mag fails
when you are on the road get the yellow taxi home.
#874 I use a stiff metal degree wheel, drilled out to just slip over the threaded part of the drive side
mainshaft. Then I replace the nut which holds the generator pulley (after removing the shock-absorber
spring and pulley), tightening it onto the disc, which abuts the slotted part of the mainshaft. I then turn
the crank with a wrench on my timing side mainshaft (Thruxton - I check the valve clearances at the
same time), using the positive stop method to find TDC, and remembering to move the crank 30
degrees or so when trying (again!) to get it all right, in order to accommodate any backlash in the
timing gears. By the way, I time at 38 degrees, and have had no problems with pinking or melted
pistons.
#891 I have formed a golf ball sized piece of Bluetac (plasticine) around a thin nail, then
pressed/screwed it into the plug hole far enough to achieve a gas tight seal. With the nail withdrawn, a
depression formed around the top of the resulting hole and a drop of washing up liquid in the
depression, bringing the piston towards TDC results in a growing bubble. As TDC is passed the size of
the bubble diminishes. The bubble is very sensitive to small movements.
#896 A very novel idea! this cannot fully account for the backlash caused by running clearances at the
big and small ends and piston rock due to both the taper of the piston and the piston to bore clearance.
The ONLY method that will accurately find TDC irrespective of these factors is the positive stop
method. It will however, still be necessary to account for backlash when setting the ignition timing by
only ever turning the engine FORWARDS to the timing point so the backlash in the timing gears is
taken up.
#897 I still reckon that by using a dial gauge and a degree plate you will get as near as you can get to
get an accurate tdc. to allow for slack in the small and big ends, I can see where you are coming from,
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ut when you use the dti like I do, you can work to a minuscule fraction which has to be more accurate
than the positive stop method. as for timing back lash, velos have fine helical cut gears and any
backlash can only be minimal compared to a triumph or BSA which have corse cut straight gears. I
was always told to take the timing past 38 degrees and then bring it back to take up any lash. without
question you have to time at 40 degrees to get 38. I have tried forever at 38 and when rechecked it is
36. beats me why but it is.
#898 At the end of the day, if you have found a method of timing which gives good repeatable results
then stick with it. The Velo will never be as critical as regards ignition timing as a modern racing twostroke,
so this argument is largely academic!
#901 what is the positive stop method?
#905 The positive stop is a method of setting up the degree disk accurately prior to setting or checking
ignition or valve timing. First obtain a suitable degree disk, these are available from most good tuning
part suppliers or classic bike part dealers. You will also require a piston stopper tool, these are
available commercially although may be harder to find - I have made mine by modifying old spark plug
bodies, since I regularly work on a variety of engines I've made a set of three to suit engines with 10, 12
and 14mm plugs. These are made quite simply by running a hacksaw cut around the steel body where
it is crimped over just above the hex and withdrawing the porcelain insulator complete. Cut off the outer
electrode and run a suitable sized tap down through the hole. I found that 6, 8 and 10mm threads
respectively worked well. Take an Allen cap head bolt of a length which will run through the plug body
and protrude about 25 - 30mm through into the combustion chamber and round off the end so as not to
cause damage to the piston. You could also file a flat on one side of the bolt to allow air to escape as
you turn the engine over. Screw the bolt into the plug body and Loctite in place. Remove the dynamo
pulley and shock absorber spring and fit the degree disk on to the end of the crankshaft using the
pulley nut finger tight for the moment to retain the disk. Fashion a pointer from either a piece of sheet
metal or stiff wire - I use 16G welding wire bent in such a way that it can be mounted on the sprocket
cover mounting studs and triangulates up to the edge of the disk and doesn't move unless I want it to
but any suitably solid mounting point will do. Remove the timing cover and with the spark plug removed,
turn the engine over with a ring spanner or socket on the timing side crankshaft nut until the piston is
roughly at the top of the stroke - at this point you will be able to feel for the piston with a small
screwdriver inserted in the plug hole. It doesn't matter which stroke you are on at this time, the stopper
will not foul the valves. Loosen the pulley nut and turn the disk on the shaft until the zero mark lines up
approximately with the pointer and tighten the nut finger tight once again. Turn the crank back or
forward, it doesn't matter which way, by about 90/ and fit the piston stopper tool to about 10 ft-lb torque.
With your spanner, turn the engine over either way slowly until the piston stops against the tool and
hold it tight in this position while noting the reading on the disk. Turn the engine over the opposite
direction until the piston once again stops against the tool and take another reading. You will now have
two readings which should be fairly close to each other, e.g. 35/ on one side and 45/ on the other. By
splitting the difference you should now reset the disk or pointer to read in this example 40/. If you now
recheck by turning the engine back to the other stop, you should have the same reading, i.e. 40/ on the
other side of zero. Now remove the stopper tool and by turning the crank until the pointer is on zero you
will have true TDC. Now you are ready to start your timing checks. Ignition should be set at 38/ BTDC
fully advanced for 98 RON or better fuel. I would say that if you can only get 89 - 92 RON then this
could well be the cause of holed pistons and audible detonation (pinking) would be horrendous with 38/
timing. If this is the only fuel you can get I would strongly advise to retard the timing by a significant
amount. You could try 34/ and see how it goes - retarded ignition timing will cause the exhaust
temperature to rise and consequent blueing of the exhaust downpipe is probable together with a loss of
performance but this may be inevitable if you want to prevent engine damage. Ideally you should try to
find higher octane fuel, in the UK our premium unleaded is 95 RON which I consider too low for the
Velo. Super is rated 97 RON, but pump average is in the region of 98 - 99 depending on supplier. I
don't believe that unleaded fuel will do the engine any harm.
#906 on an old banger such as the Velo - no disrespect intended - accuracy to this degree is
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unnecessary. Having said that, I prefer to use a good old fashioned Rizla Blue cigarette paper between
the points
#910 One more question pops to mind. How many degrees of change does the manual\retard advance
lever make? Can it solely be used to retard the engine from say 38 to 36 degrees with any kind of
practicality?
#914 Sorry I can't answer this - perhaps someone with a manual mag might comment? But while it is
possible to back off the ignition slightly with the lever, most of the time you would want to run fully
advanced simply for ease of riding - at normal engine running speeds even an ATD will be at full
advance - the ATD and the manual lever are only an aid to starting really. To trust that you did not over
advance the lever I would suggest to be a bit risky. However, you could use the lever as a test,
gradually increasing the amount of advance until you identify the point at which excessive pinking
occurs, leave the lever at this point and check the timing to establish the exact figure. Ideally this would
be done on a dyno by running spark sweeps over a range of throttle openings to establish the MBT
(Minimum spark for Best Torque) and BDL (Borderline Detonation Limit) curves, to give the technical
terms, but more practically for the average enthusiast, a good degree of patience and feel coupled with
a lot of trial and error will get there in the end!
#917 The magneto, if set up correctly, will produce its best spark only at full advance, but I doubt if 2/
will affect it significantly. The problem would b e to move the lever only enough to give you 2/
retardation.
#923 I checked this a few months ago on my MSS sprinter and from memory the manual mag control
allowed a variation of between 4 to 38 degrees. Originally I marked every degree as I wanted to try to
check what advance gave the most power. I gave up on that idea as the greatest variable was the
consistency with which I coordinated the clutch and the throttle.
L #2123 Hello all, Can anyone tell me if ATD units are interchangeable? If I have a 1951 MAC and
see a spare one for sale from another model, will it fit? Or do I have to look out for particular
models/years?
#2130 With the exception that the control spring has a different rating I believe, but can't fully confirm
that they are identical, . This is certainly true for VM and VR as the Lucas part numbers are different
47576A and 47545B respectively, differing only in the spring part number.
L #2315 Folks, My Thruxton is a late, 1970 model, and fitted with coil ignition. I've read good and
bad about the coil ignition, but have a problem I could use some advice or help with. The velo started
making a mechanical clatter, which was traced to the distributor gear, with the help of a long time velo
man. It seems the distributor bushing or bearing, (not sure yet) has given up. This seems strange, as
the bike has less than 6,000 miles on it from new. Anyone have experience repairing the distributor? I
haven't removed it yet, but wanted to get some ideas on how to dissect the thing.
#2330 If I remember correctly, my distributor (69 MSS) probably got crappy with not many more miles
than that on it. At that point, I got a Bosch conversion done by a Canadian.
#2347 The Lucas distributor was a great idea but the wrong execution. The needle bearing and shaft
were prone to rapid wear. It is almost impossible to set the timing on a worn unit as the points return
spring causes the shaft to deflect which results in a point gap that varies but not in any sort of
controlled or predictable manner. When this happens you will find the bike hard to start, near
impossible to idle smoothly, and generally a poor performer all around. I built a Bosch points and coil
conversion about 20 years ago to get rid of the magneto problems on my Thruxton and sold a few to
friends. Nowadays it is much easier with the availability of electronic ignitions to cure these distributors.
The short term and cheapest fix is to throw the Lucas advance unit in the trashbin, install an electronic
ignition such as the Boyer Bransden, and the engine will start and run a treat, without fixing the bearing
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and shaft problem. The pointless magnetic pickup is not affected materially by the wobbling shaft so the
timing will be as set. Ideally though, a proper fix will require you to remove the distributor and have it
bored to accept 2 deep groove ball bearings and the shaft altered to suit. While you are at it have a
small lip seal added on the timing gear side to minimize oil blow by. You will find that there is a huge
improvement in performance. The built in electronic advance curve will help with starting and give you a
nice boost in mid-range power. You will find that ‘pinking’ will also decrease. The Boyer unit has a
rather rudimentary advance curve similar to the stock Lucas advance unit but it works. If you really want
to maximize performance get a unit that allows you to program your own curve. I have a modified Lucas
unit with a Boyer unit on a ’54 MSS that works fine. My 20 year old homemade Bosch points and coil
unit has my own advance curve of 32 degrees total advance (twice that of the Lucas or Boyer). I have
had one kick starting and a Thruxton that will tolerate city traffic and pull hard from 3,000 rpm. The best
part is that I can burn mid grade gas (89 octane) if I have to and still get virtually no pinking on 9.2:1
compression.
L #2664 I am not sure how to use the manual advance lever on my Viper, what is the most
efficient position to run it on, I know how far to retard it to start but what then?
#2665 Run it at full advance. If properly timed, full advance will give the most efficient operation. If your
engine is at idle speed, running very slowly, or on low octane fuel, it may run better with the very
slightest amount of retard. If the idle running is irregular at full advance, you can experiment with
various amounts of retard to create a smooth regular idle.
#2673 I also knock back the timing a little when pulling a long hill in top gear, or when the engine
seems like it would be laboring, as when two-up pulling a hill and the revs can't be brought up. Haven't
melted any pistons this way, yet.
L #2667 Talking about timing I run a Mac with an auto advance and for timing purposes the
manual (haynes) instructs to jam the auto adv unit into fully advanced position what does this mean?? I
am running my mac with a Daytona piston and wonder wether this affects the usual 38 degrees btdc?
#2668 It depending on the year of your MAC, Lucas specified one of two auto advance units: 47522A
or 47545A/B. These units provided 16 ½-18 ½ degrees or 11-13 degrees respectively. These auto
advance devices have two bob weights which swing outward when being driven by the gear train (I.E.
centrifugal force takes effect) and in doing so, advances the ignition timing in a smooth timing curve
under the influence of two coil springs on the bob weights. At rest or at low engine speeds, the timing is
automatically retarded and the auto advance unit will only achieve full advance when spun at engine
speeds approaching 3,000 RPM. This provides the rider with easier starting and a more tractable
engine. A good thing, no? Since engine timing is really only critical at higher speeds (I.E. generally >
3,000 RPM for most engines) the maker tells one to ensure the ignition timing is correct at FULL
ADVANCE and in this case, you are told 38 degrees before top dead center. This makes sense, since
this is the engine speed most of the time while riding the bike. Since the auto advance unit at rest is at
full RETARD, not full advance, you are instructed to manually move the bob weights to the full OUT
BOARD position (full advance) and hold them in that position with a wooden wedge or scrap of rubber.
Should you attempt to set the engine timing without manually forcing the auto advance unit to full
advance, upon running, the engine will move from 38 degrees to 51 degrees (assuming the later
47545A/B auto advance unit is used). The effect will be difficulty in starting, an engine with a reluctance
to achieve low idle speeds, and severe pinking under light loads. A holed piston may result! As to your
question about the "correct" advance for your bike with the Daytona piston, I can only comment that
you should start at 38 degrees and use the highest octane fuel commercially available. If the engine
easily pinks when under a load, retard the spark two degrees and try again. Depending on the
compression ratio with the Daytona piston, you may have to either retard to 36 degrees or add a few
compression plates. Caution: If this engine has been run with the Daytona piston a few thousand miles
and has created any ridge at the top of the barrel, you must not reduce the thickness of compression
plates without absolutely removing any ridge or sever ring/piston damage may occur.
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C.2. Sparking Plug -
L #217 I have a standard 1960 Venom which has had the piston rings and valve guides and
valves replaced. This was only about 100 miles ago. I am having problems with the spark plug oiling
which may be due to the guides and the slightly rich mixture. However it did that before I rebuilt the
engine. I have used Champion N3C and NGKB8ES plugs although the NGK ones seem better.
However, even that let me down coming away from a classic bike show, about 30 seconds after I had
started the bike. Very embarrassing as I was being critical of all the competitors who were loading
their bikes onto trailers. A fellow competitor lent me a plug which had a centre electrode that protruded
more than the plugs I normally use. It got me home and still had a big fat spark when I checked it out.
Does anyone have any suggestions as to whether I should use a hotter standard plug, go for an
equivalent plug with the protruding electrode or try to deal with the cause (if there is one) or the
symptoms.
#218 In my 67 Venom I have had excellent performance from NGK B7ES and BP7ES, the latter has
the projected electrode. Unlike some other brands, you can decipher NGKs as follows: B means 17mm
threads P means projected tip 7 is heat range, higher is colder E means long reach (iron head MAC
takes H) S means standard materials (not platinum, etc.) At high altitude (over 8,000 feet) I have also
used B6ES successfully.
L #553 Sparking plugs KLG FE70. Lodge HLN ChampionNA8 & Bosch W.175/T1 all seemed to
be unlisted nowadays all the above are probably unsuitable now days with unleaded fuel anyway, the
plug in it is a Bosch WW4DC that tends to carbon up a bit which suggests it's a bit on the soft side.
what do you guys recommend for a standard MAC
#554 NGK B6ES is the equivalent plug to the FE70
#669 My Venom was having the sulks and simply was showing no signs of life on the kick starter. So
we tried a NGK Iridium IX spark plug type BR8EIX. I interpret this to mean it is equivalent to a B8ES
except it has a resistor in the plug. It was like throwing a switch, an immediate response from the bike
and it started on the second kick. What is the experience with NGK Iridium IX spark plugs and Venom /
Vipers? On the basis of this experience they may well be worth the price.
#670 1. What other new plugs did you use as a comparison, before opting for the Iridium plug? 2. Are
you running a mag or electronic ignition? 3. If you are running a mag, I thought I read somewhere that
you shouldn't use resistor plugs. 4. How many miles have you done since fitting the plug and does it
still start perfectly? Either way I hope it keeps going for you.
#671 My Venom has a recently reconditioned "standard" Lucas magneto. I have been running NGK
B8ES and recently NGK B7ES plugs. I had been trying a softer Bosch W7CC that day, I've been using
this type of plug with some success in my Viper (it has a slappy piston, burns some oil and runs on
lead replacement petrol). In terms of the Venom's recent starting behavior, all plugs have been the
same. Yes, I'm also puzzled about that resistor. I'd appreciate feedback from others who may be
running this NGK Iridium IX BR8EIX type of plug.
#672 Sorry, but I just have to ask....what gap are you running? Perhaps the iridium plug had less gap?
Mags can use as little as 18 thou, which definitely helps starting. I've tried both platinum and iridium
plugs in Velos and moderns with no real advantage. They do seem to last a bit longer in the moderns.
Also, adding a bit of leaded racing fuel to my VMT's tank definitely improved starting.
#673 VMT 260 has been running the same factory-spec KLG FE 220 for about 2400 miles, with no
problems starting or running. I've always used these plugs for the VMT, and there seems to be no
problem with longevity or fouling, even when the bore was clattering and the valves tockling away in
loose guides. Perhaps some plug trouble is experienced with the 'aperturus restrictus' syndrome. Open
those throttles wide once in a while; Velos can take a spanking!
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#819 Accessory Mart has KLG FE 220 plugs, standard fitment on Thruxtons, on sale at $1.80 ea.
currently. They are at 513 871 6682, in Ohio. Part # 06-00384. I've had the same plug in my Thruxton
for three years, and it starts first kick.
#935 Is there an alternative to the NJK plug; what is the best plug for the totally standard Thruxton
running on the poorer octane unleaded gas.
#939 I run an NGK B8ES. The equivalent Champion is N3 but I found NGKs a lot more reliable. Either
should be OK or you could try a B9ES if you ride particularly hard.
#957 Interestingly three of us have been experimenting this summer with using softer plugs in our
Venoms. Two of us have moved down to B7ES, giving noticeably improved starting, and one has even
gone down to B6ES. Probably most of our rides are only 50 or 60 miles, albeit pushing close to the
legal maximum speeds (!), no holed pistons to report yet.
#958 There are as many spark plug preferences as there are plugs. I suggest reading the spark plug
article in Dai Gibbison's website (and just about everywhere else one looks) by the late Gordon
Jennings. This is widely recognized as the bible for engine tuning via the spark plug. After reading,
take his advice and get a projected nose plug for your Velo. I run NGK BP7ES. You will have the
benefit of a hotter plug for starting and idling, plus a cooler plug at speed when the incoming air charge
(especially with the Velos hemi head) will cool the plug. I noticed the improvement in low speed
operation immediately in my Thruxton. Additionally, timing may be able to be retarded a degree or two
with the faster burn having the spark occur further into the chamber. Don't worry about piston
clearance, I have run them at 10.5:1 compression.
L #975 Any experience with what a resistance plug will do to a BTH, or a Lucas mag? I
understand that a wider plug gap puts an increased load on any magneto, but I don't know of any
correlating information on air gaps vs internal resistance of a high tension system.
#989 For interest how/why do non resistive plug caps and leads help with a magneto?
#993 Resistor type plug caps, leads & plugs introduce a resistance into the ignition set up. Using any
magneto it is a distinct advantage to reduce the resistance as far as possible hence leaving more
power for a decent spark. This is the reason for the smaller plug gap which encourages a fatter spark
over the smaller gap.
#995 I should add that certain resistance plug caps may increase resistance over time and with wear. A
30 year old resistance plug cap that started at 1000 ohms could test at ten times that or more today.
L #3547 Should the spark plug cap on my '55 MSS be of the resistor, or non resistor type? The
current one is the black plastic KLG variety and it was acquired 30 years ago. It is marked 15K ohms
but measures 20K ohms.
#3548 If using a magneto, you require a non-resistor type plug cap.
#3562 Mags aren't that robust to gross overvoltage. Probably the best thing you can do is have a
smaller plug gap. The rotating-coil mag as built by BTH, Lucas etc was a stupid design for the
1950s'/60s. The reason it was done that way was that when mags were first made - early 1900's? the
magnetic materials available were very poor and needed a long magnetic path between poles. So
these early mags had big horseshoe magnets - you must have seen pictures of them. But by the late
30's much better stuff was available - alnico permanent magnets. Rather than fix the coil and spin the
magnet they saved money on redesign and just ced the big horseshoe magnet with a short cast-in one.
Lucas made a few spinning magnet mags for Matchless, and they were much better. Why is the
spinning-coil so bad? Because it means you need brushes and pick-up rings working at thousands of
volts. It means the coils are very limited in size - look at the size of a standard car coil and compare
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with the armature of a mag! and so can't be insulated nearly so well or have as many coils.
Abomination though they are mechanically, the mags on magdynos are a bit better as they have a
larger diameter armature.
#3574 Having parted with real money (£.s.d.) in 1965 to obtain a full drum of "RIST" carbon fibre cored
suppressed HT lead plus the special tool required to crimp the little spiky widgets on the end, I am not
about to dump it all in favour of copper cored lead. With suppressed cable you do not need the resistor
plug cap and you put an end to mean green copper corrosion misery. After 10,000 miles in all weathers
what caused my KF1 to fail? A botched solder connection to the capacitor by the last "restorer", that's
what.
#3576 A scientific answer: www.ultralightnews.com/enginetroublshooting/resistorcapsandplugs.htm
looks like no resistor (cap or plug) is the way to go....unless you have an electronic ignition system that
requires it, then the lower resistance the better.
L #4535 Hi, Having recently returned to 'Velo' ownership - a Viper - after a bit of a gap (nearly 40
years) I am having to relearn some old skills like getting it to start with the most economical use of a
right leg that is not getting any younger. Starting is not a major problem, am pretty confident about mag
condition and carburation so I'm now looking for refinement hence the interest in spark plugs.
Coincidently, whilst sorting some of my Dad's stuff, I have just come across an NGK V-Plug conversion
chart. Does anyone have experience of 'better starting performance' by using a B8EV rather than a
B8ES and also for better cold starting in winter is the hotter B7ES / B7EV an acceptable alternative i.e.
won't misfire too readily at higher loads.
#4536 All you want to know about different plug electrodes can be found here www.ngkspark.com.au
Running a B7ES/V will give you easier starting and no problems - well that's my experience anyway. If
you are doing mainly motorway mileage at 80+ then stick to B8ES/V
#4549 I've been using an NGK platinum plug in my Viper last 2500 miles runs ok and starts easily
even in cold weather last few days.
#4550 Plug grade I've been using is BP7 EVX
#4552 In the UK B7ES is fine all year round, unless you are doing long motorway runs. B7EV is even
better - well that's what I and others use anyway.
L #4609 Hi all, I'm having some running issues with my '38 MSS and would like to eliminate the
old (Lodge I think) spark plug as a possible cause. Can anyone recommend what the equivalent in a
modern plug might be, and if one brand is better then another?
#4610 I use NGK B6HS in my 1938 MSS. It was recommend in the Nicholson Brothers book. They
have a chart showing several plugs from several manufacturers, and their equivalents. Let me know if
you want a copy of the chart. I've been using them for 5 or 7 years. They seem to work fine, and are
easy to find at the automotive shops. Every so often on one will be bad, right out of the box though
(maybe 1 in 20). Luckily my bike doesn't foul plugs too often.
L # 5000 In the UK in the 1970's Champion did a promotion of a free plug spanner with each set
of four plugs. The spanner was small and almost undoubtedly useless in most car applications, but
could be used to take the plug out of a Thruxton with tank and fairing in place. Sadly all three spanners
that I had, have gone over the years. Anyone got a suitable alternative that works?
# 5001 Try here: www.tool-up.co.uk/shop/diy/MELPS14.html I keep one of these in my pocket with a
boxed spare plug taped into the handle. Pete C.
# 5003 www.123bikes.co.uk/acatalog/index.html?http%3A//www.123bikes.co.uk/acata
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log/TOOLS.html&CatalogBody Just scroll down, it’s an MT004 and I use an MT005. But I'm sure you
can buy them locally cheaper.
# 5004 Just shows how much mark-up some people put on when you mention motorcycles -
Tool-Up.co.uk list the MT004 and MT006 under their own part numbers of MELPS14 and MELPS21
and at £1.65 and £1.75 respectively compared to XS Parts (123bikes.co.uk) price of £4.41 each, which
they also charge for the fixed head MT005. Your choice - but is it worth looking further at that price?.
# 5005 Pete, Didn't pay anything like that for mine either, but it was the only place I could find that
showed the type of spanner I use. I've also got a similar one for a Cyclemaster from the 50's which
works a treat!
#5007 We use a single end of "thinned" 7/16" BSW Ring key cut to 6" (152mm) long.
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C.3. Dynamo, Magneto and Battery -
L #112 By the way, are there any sources for good used or rebuilt Lucas K1F mags, or is this a
cry in the dark. Even though I have electronic ignition and 12V sparks for the lights, I'd like to have a
standard mag in reserve.
#157 Would it be possible to get the names and contact info regarding the Lucas K1F mags we talked
about?
#159 Sorry for the delay in getting back to you. Below you are the telephone numbers of UK suppliers
of reconditioned mags, I have not used them so I can make no recommendations. Some may only
provide exchanges. Dave Lindsley +44 (0) 1706 365838 FTW +44 (0) 114233 6269 Independent
ignition supplies +44 (0) 1237 475986 Dynamos only P Dunn +44 (0) 1782 856839
#165 I am sure many people are familiar with Dave Lindsley. There was an article on him in FT 310
which describes his attention to detail. He has reconditioned both my mag and my dynamo and I am
very pleased with the results. Independent Ignition supplies have a website at www.magneto.co.uk
L #346 Don't know if people are generally aware of this, but a modern alternative self-generating
magneto ignition system is being developed by Rex Caunt Racing using the BT-H trade mark. The
results can be seen by following the links from www.rexcauntracing.com . Rex makes ignition systems
for classic racers which are considered to be one of the best. The magnetos are not cheap, estimated
price on his web site is £500, but it might be worth it for a reliable system and a weight saving of over
3/4lb over a Lucas K1F. Base mounted units already in production for AJS/Matchless etc are available
with a choice of 2 advance curves built in so I would guess that they can be run without an ATD -
another positive point for those who want to run a tacho drive from the timing cover but don't want the
hassle of manual advance.
L #592 Just "lost" the battery retaining strap on my '61 Venom this morning on the way to work
.Found the old-type black battery cover on my left foot at a set of traffic lights! Retraced my route with
special emphasis on the gutter - found the retaining strap but no sign at all of the bolt. Question - what
is the size and thread type of the bolt?
#593 The bolt is a 2BA thread, I think about an inch and a half long. There is a trick which might
prevent future losses - fit a nut to the bolt before running it through the threaded trunnion, as you
tighten the bolt it will trap the nut between the two strap ends and act as a lock nut, and if the bolt
should come loose after this the nut will usually help to retain the bolt and plain trunnion in the strap.
L #652 Spent part of the weekend investigating a low / zero charging rate on my '61 clubmanised
Venom. The Miller ammeter was showing a very intermittent or zero charge. Dynamo drive is a vee
belt and no sign of slipping. I discovered that although I have a Miller headlamp switch and ammeter I
have a Lucas dynamo - I thought that these did not come into use until '65? I couldn't make out any
model number on the casing - but I assume it must be an E3L? If this is correct can I get 12 volts from
it? I discovered a Lucas RB108 regulator fixed under the seat but the bonded rubber mountings had
parted and hence the regulator was held in place only by the wiring. Does anybody have any
experience / tips for repairing the bonded rubber mountings ? I have done a quick fix of taping the
regulator body to the mounting bracket but clearly this is not a long term solution! The various
tinkerings seem to have solved the charging problem - a nice steady 7 - 8 amps all the way to work this
morning.
#656 Rubber mounts normally go. Answer - Super glue
L #709 Anyway I now have an early Venom and am considering upgrading to electronic ignition.
My question - does anyone know where I can get a waisted 3/16 box spanner to remove the magneto
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#712 if you are such a heathen (like I am) as to fit electronic ignition, why not go all the way and just fit
an allen headed bolt, it makes life oh so simple. It's fine if you are not regularly taking it off, (then a stud
would obviously be better - so you don't wear the hole in the crankcase).
#713 Fit a BSA "long magneto nut" and solve the problems. Autocycle Engineering sell them at £4.99.
L #751 I was led a merry dance by a carbs spitting problem at kickstart/low revs. The culprit
turned out to be the ( peripheral ) slip ring in my manual BTH magneto; there was a section missing!
Presumably, at higher revs the points operating arm jumped the gap.
#788 it dawned on me that I had made a foolish mistake recently in claiming that I had traced
starting/spitting problems to the fact that a section was missing from the cam on my manual BTH
magneto. Of course the cam is steel and easily inspected. It was the brass HT pick-up ring that was
found to have a section missing.
L #768 A tip for other electrical know-nothings like myself. I've a very pretty, obviously reconditioned,
model of a Lucas 6V dynamo which I was considering setting up on the bench to see what
joy I could get from it. However, along with the stampings E3LM-LO 6v etc.,came an arrow pointing in
the exact opposite direction to what I needed. A quick phone call to Dave Lindsley(see prev msgs)set
my mind at rest. His first comment was that the whole caboodle was a re-con job ,and that the
laminated case was from another model, but it would be perfectly O.K. To check(on neg earth
bikes),join 'F' and 'D' contacts together, run a wire from here to the pos. terminal of 6v battery. Run a
wire from neg. term of batt. to the case of the dynamo and the dynamo should run as a motor in the
correct direction. If it doesn't, just reverse the brushes(with wires).
#806 I have added a copy of an excellent article explaining, how and why to uprate your dynamo to 12
volts to the files are on the group site.
#808 Here are three short answers to your electrical system questions. 1. The dynamo can operate in
either direction, this is determined by connections and polarization, as described in Dai's articles and
the literature that accompanies the electronic regulators. 2. Operation at 12V reduces losses in the
wires and connectors, giving brighter lighting. Sealed headlamp units are also commonly available in
12V. 3. The original Lucas regulators shatter at the mountings (takes about 10k miles). The various
electronic ones do not. Also, the contact points in the Lucas reg can stick, burn out, etc. etc. You
could adjust a Lucas reg to give 12V if you wanted to, but most owners take the easy path and fit an
electronic one.
L #797 As soon as I'd sent the e-mail earlier I had a thought and explored the insides of the
"RB108" regulator. All is not what it seemed! Mounted inside is a solid state 12v voltage regulator made
by TEB Technology. This still doesn't explain the dynamo marked Lucas E3LM-LO, 6v and running in
the opposite direction to that marked on it. The system is positive earth if that is relevant.
#818 The insides of an RB108 are essentially the same as an MRC2. Someone replaced the original
guts and replaced it with some solid state thing. Best solution, use a Podtronics from Kizer.
L #821 The lighting system I'm building up on my MAC is Lucas. The voltage regulator I have,
which looks in good nick, has a flat base with two bolt holes at 3 5/8" centres. It's not obvious to me
where it's meant to be fitted.
#823 that one is usually somewhere under the seat. Often bolted to the rear mudguard. Recommend
you throw away the 'innards' and install a new electronic regulator into the box. I'm told that the
Podtronic device is 'The Best'.
#834 The original position for the regulator was on top of the dynamo, it was moved in 1958 to the top
of the rear mudguard. You can just about see it in this photo.
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www.velocetteowners.com/photogallery/machinesworks/xvenomusts.htm
L #991 Does any body know the size of the front holding down bolt on the dynamo strap mine is
1/4 o.d but I don’t know what thread.
#992 This bolt at the bottom of the strap is part number SL8 15 which is 1/4inch BSF x 7/16inch bolt.
The bolt at the top of the strap is SL9 22 which is a 1/4inch Whitworth x 13/16inch.
L #1253 Where in the USA to get the proper size 6v battery for my 1948 MAC (I brought home
from England/Beaulieu last year) It has the hard rubber battery box now. I'm not sure if the battery
replaces that or is meant to just go inside.
#1256 I have been told the hot setup is to: I) purchase a dummy battery box, then ii) insert into it a
sealed six volt conventional motorcycle battery. Having previously purchased an original-type
replacement with vented caps, I now also have the unpleasant experience wherein the escaping and
subsequently condensed vapors have corroded my nice, chrome battery strap. The dummy boxes can
be purchased from Groves in the U.K., or here in the States from Ed Gilkison. Others may have them
as well. Sealed 6 volt cells are easily obtained from almost any motorcycle dealer or accessory
provider.
#1258 You can get 6V rubber batteries that cost about $60 in the UK, but I wouldn't waste your time. If
you are running 6v, buy a 5ah sealed battery from www.burlen.co.uk . It's a fit and forget, the lights still
work even after a winter lay up, no need to charge during this period. However, you do have to fit it
inside a dummy case.
#1260 Just one thing to be aware of on this - would also recommend the 6V Burlen - but I have found it
a very tight fit in some of the dummy battery cases on the market. (Needed to cut part of the bottom out
of mine) - externally this doesn’t notice if you are careful. And it may not apply to all dummy cases. The
battery is well worth it though.
L #1759 I have a Miller dynamo transformed to 12V with electronic voltage regulator (don`t know
the maker..). I have a very small 12V battery inside that rubber case what Grove sold. Now the dynamo
popped and is completely dead. It worked well about 100 miles. Question: how big the battery has to
be, how many amperes that it takes all the charge and won`t cause any damage to other parts? I think
mine was too small, I don`t know it`s amperes but I can't risk to use it after dynamo repair if it possibly
breaks it again. There are obviously lots of other reasons why the dynamo breaks but this is my main
problem.
#1762 Sorry to hear about your problem with your dynamo. The size of the battery is not critical, but
bigger is better. In most cases, finding a battery small enough to fit inside the black rubber case will
limit you small lead-acid battery in the range of 3 - 5 amp/hours. This small size is OK. Your dynamo is
probably rated at 60 watts. A watt is a volt amp. When the dynamo was used as a 6 volt generator it
would produce 60 watts or 10 amps @ 6 volts (10x6=60). Now that it is being used with an electronics
converter, it still will only produce about 60 watts but at 12 volts or 60/12 = 5 amps. Batteries are
storage devices, like water tanks. You can not have them too big. A 5 amp, 12 volt battery will become
completely charged with your existing dynamo in 1 hour, if you do not run with the head light on, or use
any electricity. A 5 amp battery will light your headlight and tail light for about 1 1/2 hours with the
engine stopped. Common small lead acid batteries are best for this application, although, there are
some other forms of batteries that may work such as nickel hydride or nickel cadmium. Too small a
battery can be a problem.
What size and type battery did you use?
#1765 I agree, having a small battery shouldn't cause the generator to fail. I'm running on 12v with a 6v
generator and a small battery in a Grove box and have had no problems. The only downside is that you
need more revs before charging starts so if you were to ride in traffic all the time, particularly with lights
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on, the battery might become discharged. There is an article on the group site under \files\electrics
which explains why it's OK to run a 6v generator into a 12v system, it is well worth reading. It seems the
most important thing is to control the rate of increase of charge rather than to limit the maximum
voltage. This is what the black box regulator does. The most interesting part of the article to me is that
a 6v 60Watt dynamo when run at 12v will produce around 100 Watts (theoretically 120W but losses
reduce this). This means that you can run higher wattage headlight bulbs etc. Obviously you don't get
something for nothing and the biggest one is that charging starts at higher revs than before. Other
people might be able to give you some ideas about why your dynamo has failed, but I'm sure it's not
been caused by having a small battery. You say it lasted 100 miles. Is this 100miles on a
new(reconditioned) dynamo or 100 miles since you went to 12v? If it's 100 miles on a new dynamo I'd
be speaking to whoever supplied it!
#1766 Here`s more info: Battery: small 12V and about 3-4amps. Dynamo: history unknown, but can
be more than 10 years since conversion to 12V,we did all the tests described in service manual and
nothing worked, it won`t spin with outside battery and meter shows nothing when running. So maybe
it`s hours are up... Regulator: metal box under seat in top of rear fender, painted grey "hammer
laquer",main fuse on the right side 15a and next to it green led which lights when charging, so what
make is that? It had broken diode which I replaced (kept burning that main fuse). Box has lid which is
detached with four small screws. My friend has left over Alton generator from Gold Star single and I`m
gonna try that one soon as I can get a pulley machined to suit Venom. Any experiences with Altons?
Does it rob much power because it feels so stiff compared to Miller?
#1767 For a number of years I have lived with unsatisfactory 3.5ah 12 v lead acid battery in a hollowed
out battery case. It never had the capacity to smooth out the fluctuations in current requirements to
provide steady lights. Also, every year I had to replace it, as even when trickle charging during the
winter it never fully survived. Two years ago I replaced my lead acid battery for two 6 v 5 ah Cyclone
batteries in series www.hepi.com/monobloc.htm They hold their charge really well, and work perfectly
even after laying idle over the winter. You will need a replica case and not a hollowed out case to fit two
batteries, as they are a tight fit. For six volts either wire them in parallel or use the 6v 8ah version.
While you are at it fit a Xenon headlight bulb and get 30% extra light for no extra load.
#1770 The UK distributor is DMS Technology Ltd, www.dmstech.co.uk located in Romsey, Hampshire
(just round the corner from me). Unfortunately they have a minimum order charge of 100 pounds. They
suggested that I go to RS components. A quick look at their web page rswww.com/uk shows that the
2v 5A/H (p/n 591-483) cell is 6.25 GBP each (plus VAT) or the 2v 8A/H cell (p/n 265-1947) is 9 GBP
(plus VAT). At those prices, a 12v 5 A/H battery would cost 44 GBP and a 12v 8A/H would cost 63.45
GBP. Another solution would be for a group of like minded people to get together and place an order
greater than 100 GBP direct from the distributors?
#1772 Hi I buy my Cyclons as Kempton Autojumble approx GBP 12 for the 5 ah and GBP 15 for the 8
ah. If you can wait, I will get his phone number when I go later this month. Alternatively call CMES who
sell them all be it a little more expensively. However they will give you excellent technical support as I
have heard they have an excellent reputation on rebuilding dynamos. Their number is 01454 323434
#1773 If you go back to Fishtail # 324 page 20 I gave some details of a Cyclone battery 'contact'. I
presume he still does it.
#1775 For those of you w/6 volt lighting and Mag ignition, I recommend using a sealed lead acid gel
battery. These are available for emergency lighting and a 4.2 amp/hr unit fits perfectly in a hollowed out
Exide black rubber case. You could use 2 to create a 12v source. I have a connector wired into my
loom so that one I am not using the bike the battery is on a charge. Because the battery is sealed there
is no worries about boil over. I've been utilizing this set up for about 15 years and it works great.
#1778 I've just finished making a slightly larger battery box from sheet steel, complete with a curved lid
and bolting it to the original battery platform. It will now house a conventional lead acid battery but also
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have the capacity to take a choice of others when the time comes. Once powder coated the whole job
will appear to be in the spirit of the machine. I've obviously kept the original straps etc so I can revert if I
wish.
L #1829 Having only recently finished the restoration of this Thruxton and completed about 800
miles over the last couple of weeks, I'm learning its personality. The dynamo belt seems to go slack in
rather short order. Say 200 - 300 miles. I can tell I've a problem when the amp meter shows a dramatic
jump from near full charge to near full discharge on a Lucas 8 amp gage. This seems to occur at
around 3,500 RPM. I'm running the Miller 60 watt device on a JG converter with a new wiring harness
and new 12 amp hour lead acid battery. After finding the dynamo has rotated under vibration of the
engine, I've re-tightened the clamp bolt to 12 - 14 Ft./Lbs., and drawn a pencil line on the dynamo to
observe any movement. I've fitted a new Gates brand 2210 v-belt and tensioned the belt to what seems
normal for a drive this size: perhaps 1/8 - 3/16" deflection mid belt under 5 - 10 lbs. force. I've checked
alignment on both pulleys and have both angular and groove alignment within about 1/16". Pulley
grooves are clean and bright and no evidence of the belt "bottoming" in the pulleys. After my most
recent setting, the belt was slack e'nuff to allow some slipping which was detectable by turning the
dynamo pulley by hand. Yet the dynamo had not rotated under the clamping screw pressure.
Something is causing the belt slip and belt wear. The engine is rather oil tight and there is no evidence
of engine oil being blown in huge clouds into the belt housing. So how does one keep these belts
working for their keep? Any thoughts would be appreciated.
#1830 Try the toothed belt conversion from the VOC. The complete kit is £55 and the belt does not
have to be too tight and is resistant to the slightly oily atmosphere it occasionally encounters.
L #1953 My magneto has suddenly lost its spark. I have checked the points, cleaned the earthing
brush, high tension pickup and contact breaker assembly but still no spark. Does anybody know how to
test the K1F magneto to determine what is wrong? What about temporarily converting to coil ignition?, I
would like to have the bike running before next weekend as I am due to attend a rally on the Yorkshire
Moors Railway. Finally, if all else fails, can anybody recommend a magneto repair company?
#1954 I have used FTW recently with good results, they are based in Sheffield - 0114 233 6269
#1956 Did you check the connection between the spark plug lead and the mag pickup and/or the spark
plug lead and the spark plug cap? Any foreign material between the points will also render a magneto
mute. Check the timing and see if it's slipped, too.
#1964 I would try Dave Lindsley if you are in the North West or are willing to use a courier. He once
offered to lend me a dynamo to get me to the TT when I was in a similar situation. As it happened he
rewound my own one in good time and Lucasised it too. Also check that the little key on the back of the
CB assembly hasn't flattened and slipped, likewise the cam ring in the end of the mag. both have
happened to me in the past!
#1966 I had mine rebuilt by Bell Engineering in Colesville, Maryland--great job.
L #3431 I'm trying to reinstall my recently rebuilt BTH magneto to my '46 MAC. I am setting the
crank to 4 deg. before TDC on the compression stroke and the points just beginning to open. The rub
is, when I torque down the ATD, the magneto rotates and the settings go out of whack. What is the trick
to keeping the mag from rotating? I hate the thought of just wedging something in there to stop the
rotation. With the Lucas Magdyno, a "U" shaped "keeper" kept the gears in sync when reinstalling but I
don't see a similar option with the BTH.
#3433 Most folks simply place a deep socket over the magneto shaft, up against the drive gear and
smack the gear onto the taper. Then tighten the nut. The "U" shaped "keeper" you mention is intended
to allow the rebuilder to set the slip friction to 4 - 10 Lbs./Ft. to keep the fibre gear from shedding its
teeth, under the greater resistance of the dynamo's mass. There is no need to synchronize the dynamo
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to the fibre drive gear as there is nothing to "time" between these two devices. Since the magdyno
needs to have the outer cover in place when installed, the holes for above mentioned "U" shaped
keeper could not possibly be used to restrict the magneto from turning once the magdyno is mounted 4
degrees BTDC sound a bit late to this reader. Is it possible you are setting ignition time with the ATU
bob weights in the "at rest" position? As most engines spend the bulk of their working time at full
advance, there is great advantage in always setting ignition at full advance, I.E. bob weights wedged in
the "out" position.
#3446 I too recently faced the problem of trying to stop the mag from rotating while setting the ignition
on a '46/47 MAC which I was bought for Christmas! (same age as me). I simply held the contact
breaker fixing bolt and tightened as much as I dared; it has covered a few miles since with no problem.
However, the timing was approximately 35 degrees too far advanced when I had checked it, so it may
well slip again. If only I had the sense to solicit advice from this forum at the time ( thanks "Doctor" ). I
can confirm that the 4 degrees before TDC fully retarded is correct according to the manual. The
advance-retard mechanism on these machines does not use conventional bob weights.
L #3470 --Re topping batteries. I use a gel battery off a modern bike, no acid to spoil paintwork
while breathing and no need to top up as its sealed after the initial filling.
#3472 I don't know the reason why but these modern gel batteries are not recommended for bikes with
magnetos/dynamos, read it recently in one of the monthly classic mags, would be interesting to know
why as I know many that do use them without problems..
#3493 The reason is that the old electrotechnical regulators were set too high in volts. With a normal
battery this just meant they gassed off a bit, so you had to top them up with water once in a while. Gel
batteries can't be topped up, so if you overcharge them they lose water and eventually don't work.
Electronic regulators can be set accurately below the voltage at which this happens, so no problems -
when did you last top up the battery in your car?
L #3476 I'm planning on using wheel bearing/high temp grease on the magneto bearings, any
suggestions of a better lubricant? Also, is the points cam follower oil wick effective or should I use light
grease there as well?
#3483 Almost any NLGI grade 2 grease specified for disk brake applications should be fine. The CB
end will definitely benefit from both oil and a dab of Bosch or comparable contact breaker grease,
especially of the ring cam still has both felts still in place. If the bike gets ridden in the rain, you might
want to use boat trailer (water resistant) grease on the control spring and plunger, and a fresh rubber
boot (Lucas #458731) to keep things dry.
#3484 Only one wick hole in my mag cam...it has the auto advance/destruct mechanism. I'll replace the
wick. Do you think it's advisable to put some kind of removable coating on the armature windings? I've
read where the shellac eventually turns to goo, deposits itself on the armature, and locks up the
magneto. I appreciate the help.
#3487 Look carefully, is there a round felt in the hole, or just a rectangular felt in the recess at the
bottom of the mag housing. Unless both are present, there is no way capillary action will "wick" (pun
intended) the oil thru the cam ring and lubricate the breaker. As to the armature, your question leads
me to believe this armature has not been rewound. If that is the case, I trust you have a plan for hauling
your bike back home when the magneto fails. They all do! The 50 year old windings will fail sooner or
later, and the ancient capacitor will fail to restart the bike when the magneto is hot. This always occurs
when you have just come out from a store after a brief ride, some fellow is admiring your bike, and tells
you he had one in back in 19XX, and wishes he still had it. He will tell you about his travels while you
get red in the face trying to start yours. Bite the bullet and get the mag rewound.
#3488 Anything you put on might do the same - specially if it's 'removable' - what did you have in mind?
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#3490 I was hoping a modern plastic coating had been found and used. By removable, I mean non
permanent that could be taken off without damage in case the windings needed to be redone. On more
thought.....I should do it the right way....rewound and a new capacitor. I'm planning on total loss battery
arrangement and will be relying on the mag completely.
L #4062 Hi, Does anyone know the procedure for testing Miller Dynamos in situ? Mine is on a
Rudge, but I'm sure Velo's use the same Miller parts.
#4063 From page 74 of the Red Book: "The dynamo can be checked quickly and with very little trouble
by removing the driving belt, and the commutator cover, and pressing the cut-out points together. If the
dynamo does not begin to run as a motor from the battery current there is a fault in it. "This is not a
100% check, as in some circumstances a dynamo with a faulty winding may 'motor,' but by testing in
this way a lot of time can be saved."
#4075 Doug is bang on.. but shorted turns in the field or armature can allow the dynamo to motor but
still not charge. Measure the field resistance - should be 2.5-3 ohms. The armature is best tested with a
'growler' - see an old fashioned motor rewinder in your area. Obviously check all wiring is sound and
that the brushes are in good condition and move freely. Might be worth cleaning up the commutator - if
badly worn trim up in a lathe taking as little off as necessary. My experience with miller setups is that
the dynamo is less likely to be faulty than the regulator.
L #4749 Hi Does anyone know where I can obtain dynamo brushes for my Miller dynamo, mine
are getting low and the spring pressure is becoming ineffective, I don't mind modifying substitute
replacements.
#4750 Dave Lindsley in the UK has them as his part number 404.
L # 4890 I am changing my K-tec regulator +v for a VW 6-v but I'm not sure quite how to go
about changing the dynamo polarity has anybody any idea's how this can be done, I have the
instruction from a N American fishtail from 1985, there is one part missing and that is on the polarity
change of the dynamo. Any advice gratefully accepted.
4892 Bob, You will need to swap the two field-coil wires one for the other. ie the one which is now
grounded goes to the 'live' 'F' lead and vice- versa. When you have done this a motoring test with
correct battery polarity (-ve earth now) should have the dynamo rotating the same way as when driven
by the engine = anti-clockwise at the pulley end.
# 4895 All the answers are contained in an article called "Uprating your dynamo" in the files section of
the group site http://autos.groups.yahoo.com/group/velocette/files/Electrics/Uprating%20you
r%20Dynamo/
# 4898 You are getting some bum info here! Do not reverse field winding connections unless you are
reversing the direction you want to rotate the dynamo. To reverse polarity all you need to do is connect
the required battery teminal to earth, and with a wire on the other terminal, dab it momentarily onto the
'F' (field) terminal of the dynamo. Make sure you have removed the old regulator as the reversed
polarity will destroy it!
# 4907 I know where your coming from re reversing the field connections as far as the old regulator
that was a k-tec that already passed on.
# 4901 In principle it's very easy - just motor the dynamo with the polarity you want. For a lucas-style
dynamo this means connect the F and D wires together, connect them to a charged battery of the
appropriate polarity , and the other end of the battery to the dynamo case. The dynamo should rotate it
the direction it goes on the bike. There's a small complication. Some regulators require the dynamo to
be connected like a Lucas - ie one end of the field coil is permanently earthed, and some require one
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end of the field connected to the D. I'm not sure about either the Ktec or the VW regulator's
requirements - perhaps you could inform me and I'll go on from here
# 4904 I have found that often if you just connect up the new regulator and run you engine after about
5 seconds you will automatically reverse the polarity of the dynamo field coil. I believe the solid state
regulator will put a current in the correct direction that changes the residual magnetism in the field.
Works for me.
# 4909 Hi this might well work with the old electromechanical regulators, but probably won't with an
electronic one! And may damage it.. ( I'd need to see circuit diagrams and ponder to be absolutely
sure) Repolarise the conventional way!.
# 4905 Anyone here made their own voltage regulators? I have been told it is a pretty simple circuit, it's
just the picking out of components for your exact needs and making a decent housing that's difficult. I
am working on a Non-velo with a 12 volt Bosch Dynastart and the 12v mechanical regulator is dead. I
have heard 12v mechanical car regulators can be adapted but I'd rather use the original housing with a
Solid State regulator in it- so if the regulator gives problems I can replace the components. If anyone
can point me to a book that would have the design criteria even that would be helpful. Would the testing
procedures etc be the same between the dynastart and a lucas dynamo? I guess the velo content here
is that the same principles could be used on a velo.
# 4908 Look in the archive for my FT article on building your own - but unless you're used to building
electronics to stand high vibration I should buy a standard item..
L # 5714 I have been trying to set up my Lucas MCR2 regulator over the weekend. I'm not sure I
understand how the cut-out works - the regulator controls the rate of charging, the cut out opens or
closes the circuit - what is it using as the control signal for actuation of the points? Battery voltage? The
Lucas manual says to set the regulator to the specified voltage (depending upon ambient temperature)
with the system in open circuit. It mentions that the voltage should be checked `when the volt meter
needle kicks'. Is this the same point as the cutout closes? Should I also be setting the voltage when the
cut-out points close in open circuit as well? I'm a little concerned as the needle is going off the scale on
the ammeter with the engine running. The battery ready 6.25V with the engine stopped.
# 5721 get something near 7.5 volts. cutout adjustment is experimental just make sure your amp
gauge flicks back to zero when motor is off or you'll burn out an armature segment. Believe me I’ve
ruined many a generator in the past out of ignorance!
L # 5812 A friend has a '46 MAC which is missing the battery attachment hardware. Does
someone have a Velocette parts manual for this model who would be willing to scan the page(s)
relevant to the battery platform and straps and send to me off list? I'd like to be able to determine what
is missing.
# 5826 Mark, I have a parts book for a 1947 MAC/MOV and it shows both the battery straps the same
as the later S/A model front strap, ie the one with the slot NOT the hole (Part No E9/5) but on the
MAC/MOV the front one is chrome plated and the back one is painted black. The trunnions ars also the
same as the S/A models Nos E51 & E51/2.
L #5998 Can anyone give experience with the readings for the checks to see wether a Miller
dynamo has gone down. I can check according to the book figures but need some experience as mine
does not follow the book. ie my Short one doesn`t and charges and my long one doesn`t and will not
charge. Is it such a black art that it is best left to the experts or are there checks that can be made to
ensure that a £140 or so rebuild is not done when not necessary.
# 6003 The simplest check is to motor the dynamo. Connect the field and live armature together and
apply a battery negative to this pair, and positive to the dynamo case. The dynamo should turn briskly
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in the direction it normally goes on the bike - ie anti-clock as seen from the pulley end. On the bike with
either lucas or Miller standard setup you can do this by removing the drive belt and pressing the cutout
contacts together - this also checks that the voltage regulator contacts are shut, which they should be
in this condition.. It's not 100% - a bad dynamo might still motor weakly - but a non-motoring dynamo
implies faults. Apply a finger to brake the motor - the torque should be constant. Any dead spot means
missing windings on the armature. Straightforward resistance checks - - the field coil should be about 3
ohms +/- 20% - across the brushes should measure a near dead short between each pair of
commutator segments. Are the brushes pressing firmly onto the commutator? Note the regulator should
be disconnected for these measurements to be meaningful.
# 6020 I sorted the problem with my dynamo after much checking and testing. I found that the stud in
the end cover which shouldn`t be earthed actually was. It looks as though it came about due to a not
very good rebuild job, having only a flat insulating washer on the inside with no insulation around the
stud where it passes through the end cover. Hey presto, earth leak. Reassembled with an insulating
tube round the stud. Above information might save someone else time when looking for non charging
reasons.
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C.4. Lights and Horn -
L #381 My recently acquired '61 Venom Clubman has original Miller electrics - all working v well!
But - it has a Cibie head lamp unit that has no provision for a pilot/parking light. It has a current MOT
but my local testing station is telling me that I need to have a pilot light. The Miller light switch clearly
has pilot and main beam positions. Any thoughts/advice??
#383 Change the sealed beam unit. Remember the pilot bulb assembly. Contact R F Seymour Ltd. 01
844 217 277. They will sort it
#385 The Cibie light unit makes a big difference to your headlight at night. I assume you have the
concave lens that was fitted in the seventies. I have a Cibie fitted with a pilot, but they are now have
convex glass. You should be able to get them from M & P in the UK cost £ 33. M & P part number 525
334.
#398 If you have converted to 12 volts I recommend buying a Hella H4 headlamp lens and specify the
one fitted to early Minis. This had a sidelight.
#399 In your case you will be absolutely correct, and this may be a way round the problem, but I don't
think that was the way the switch was intended to be wired up originally. I think you will find that the first
position was intended to be wired to the pilot light, but somewhere in the machine's past it has been
wired directly to the dip filament in the headlight instead. In this configuration the dip beam does in fact
become the pilot light, since it is independent of the dip switch and satisfies all the criteria of the test,
albeit a bit grey in terms of being a separate light bulb. When you move the switch on to the headlight
position the power is routed through the dip switch before going to the headlight, so you then of course
satisfy the criteria for the headlight. What you lose however, is the failsafe position that should the dip
filament fail (a very likely scenario!) you do not have the pilot light to enable other road users to see you
without being blinded by your high beam. I agree that we seldom if ever use the pilot light through
choice, after all what chance have you of seeing anything beyond the glow on the front mudguard, but
the general principle is that, as stated in the regs, "The light must be visible from a reasonable
distance," indicating that the idea is not to see, but to be seen.. .
#419 Miller lights in good condition are impossible to get hold of. If you are lucky you may be able to
get a NOS Lucas, the correct item should have the words “motorcycle” and “700 Headlamp” embossed
in the glass. If you want to use a halogen bulb (recommended) try your local Enfield India dealer who
should sell them to fit (they may even sell Lucas light units). The bulb is not the same as the modern
halogen bulbs. Alternatively buy a Cebie light, which are excellent and no one will notice. You can do
what I did on my MSS to keep it original; bought a light unit, smashed and removed the original glass
and used silicon sealant to bond the existing Miller glass into the unit..
L #553 want to get a few basic spares that do not seem to be available through the velocette
spares. 1. 24w/24w 6v SBC double filament bifocal. (pre-focused type) Lucas168 or Philips 6722 are
not listed any more. emailed Grove Classics 2 weeks ago but got no reply's, the bulb in the Miller
head light is a Stanley 6v 18w18w SBC which is a bit of an odd one?
#554 I fit a 6v halogen bulb which will fit strait in to the Miller / Lucas headlight unit. They are made for
Indian Enfield’s and I usually pick them up at auto jumbles for £5. Try calling +44 (0)1454 323434 who
sell them for £7. I would phone Grove classics rather than e mail, when you will receive excellent
service.
#557 A 30w main and 24w low beam is available from Walridge Motors. It is their P/N BULB 312. Lots
in stock $5.67ea Canadian. I do notice that my supposedly optimally functioning Miller dynamo still
does not keep up with the 24w low beam at low rpms. Thus the 18w Stanley bulb is an interesting
possibility.
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L #978 By the way does anybody have a horn for sale or know where I can get one.
#986 Try Taff Isaac at Swansea. He will advise you on which horn you should have, He prefers it if you
have an old one that he can restore for you but does have some that he has already restored. His email
address is found at www.velocetteowners.com/techinfo/electrics/electrics.html
L #2008 With the Miller headlamp shell and rim? Can anyone in the UK recommend a
modern(ish) unit that will accept car bulbs? I have an Alton dyno conversion and would like to fit the
best possible headlight.
#2041I bought a modern halogen unit, carefully smashed the glass and replaced it with the Miller glass.
A thin smear of my favorite silicone between glass and unit seals it from the weather.
#2072 I do not know the size of the headlamp on a MAC but for my Venom I bought a new Lucas
combined reflector and lens with separate 55/60 Watt bulb, Halogen I think from Goodman when he
was in business. I expect Grove Classics have them. The Lucas is an H4. I converted to 12volt with an
Alton too.
#2083 For many Velo owners the favorite headlight unit is the Cibie. Unfortunately they are difficult to
get hold of. However M & P sell them, go to www.mandp.co.uk/ then products, no need to register, click
on the catalog button and enter code 535334. I know it fits a Lucas unit, but I am not sure about a Miller
unit.
L #2118 Hello group, I'm looking for information on the type of horn my 1948 MAC would have
had when new. I'm not sure if should look for a Lucas or a Clearhooter or just what. I have a nice MAC
and like to show it but the cheap repo horn sticks out like a sore thumb. Anyone have such a horn to
sell or can point me in the right direction to locate one?
#2122 Look under horns, here www.croesus-consultants.co.uk/v-tec/ Velos around about this time had
all sorts of parts fitted, but I believe it was a Clearhooter.
L #2228 I am trying to ascertain whether I have the correct headlamp for my '50 rigid MAC. The
chrome rim is roughly 8" in diameter, and everything else on the bike is Miller, so I assume the ring is
an MIL118 (this number taken from Groves most recent parts list).The reflector and the glass are a
single unit, sealed together with a steel band of some sort. The glass itself is flat, and has a pebbly
texture (what we refer to in the States as bathroom glass). This assembly could possibly be a MIL148:
Miller 8" Light Unit (Glass and Reflector). Personally, I think it looks a bit odd, and people often ask me
why I have a piece of bathroom glass for a headlamp, but that's a separate issue. I notice that Groves
has a 138 Glass 8" domed, and a Glass 8" flat, but I could not find a corresponding 8" reflector that
would presumably be used in conjunction with either of these.
#2229 I have a 1950 rigid MAC, also, it came with no headlamp on the Dowty forks fitted to the "basket
case" machine bought a lot of years ago. Like you I wasn't sure as to the correct fitment. My
investigations revealed that at the very end of the rigid MAC production the factory used up a load of
"out of date spares" some of which were 8" miller headlamps. I've since fitted that size of headlamp to
my machine complete with the bathroom glass, it looks brilliant, 'need to find out how it performs on the
road. My glass and reflector came from separate sources and are therefore separate in their own right,
no steel band etc, so can't advise further on that bit
#2230 The Miller catalogue indicates that MAC 47 - 53 was fitted with a 7" lamp, that used a domed
moulded glass non sealed beam type reflector. The unit you describe sounds like a 7 ½" unit fitted to
later MAC/MSS, it too should have a domed glass. This unit came with both separate reflector and
glass, and as a sealed beam unit.
L #2340 Being a newbie and used to riding a Beemer, I'm wondering if the vibration of my
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Venom/Thruxton is the culprit. I've blown two H4 halogen bulbs in short order (at $10 a pop, I might
add!!)and now the taillight bulb has gone, as well. I replaced the halogen with a standard sealed-beam
headlamp and so far so good. Are there rough-duty taillight bulbs available? If not, any suggestions for
brands that have proved less sensitive?
#2341 Might be worth checking the system for excess voltage first - no more than about 15V with
engine running at or above 2500rpm or so - if over this then the regulator is up the Swanee. Bad switch
connections could be causing power spikes which bulbs won't tolerate for long, fitting a relay in the
system to minimize the arcing in the dip switch when changing between full and dip beam will help.
Also make sure the earth wiring is good and secure and that the lights are solidly mounted, not shaking
about in their mountings. On this side of the water several outlets are retailing a LED bulb which is a
direct replacement for the standard offset pin 12V 21/5W stop/tail light bulb. At around £9 a throw they
aren't particularly cheap but should last forever and if my experience is anything to go by their
brightness doesn't seem to be affected by fluctuations in voltage.
#2342 If I'm getting spikes with switch operation would I see that on a digital multimeter while I flick the
switch, or does it happen to fast to register?
#2343 I don't think a digital multimeter would show spikes particularly well - you might just be lucky to
see the numbers change momentarily but its unlikely. An analogue meter would be a much better bet,
but better still would be an oscilloscope if you can get access to one. The trouble is, you're looking for
something which may not occur until the machine is traveling, but strapping a scope to the tank and
trying to watch it as you ride is not a practical proposition. There is equipment available which can
record the performance of any movement or electrical signal - usually in use by most of the higher level
of racing teams nowadays for data logging if you have the contacts and want to take this route as a last
resort. But I would just try connecting an analogue meter across the bulb to start with and watch the
needle as you flick the switches on and off and between main and dip with the engine running to see if
it jumps excessively high.
#2355 I had a similar problem that resolved itself when I changed the piddley little 12v 3 amp hour
battery for two cyclones with a higher ah rating.
L #3856 'What is the "correct" Miller tail lamp face for a '54 MSS? I have seen the "STOP" and
"DIAMOND" available. Was the "STOP" ever put on bikes exported to the colonies?
#3863 The road test in The Motor Cycle dated the 15th July 1954 show a "diamond" type Miller rear
light.
L # 6384 Two questions for the group. The headlamp on the 1965 Thruxton that I am renovating
is a 'deep' type. Is this a Miller or a Lucas item please ?
# 6386 The deep headlight is Lucas, as are all VMT headlights.
# 6400 I think you will find only the earlier VMTs had the deep headlamp shell, later ones were fitted
with the normal depth Lucas chromed shell. The earlier ones also had the tickle 2LS front brake plate,
later ones had the "Blumfield"? one.
# 6401 The deep headlamp - Lucas - was fitted up to 1969. The 1969 to 1971 machines had a 'normal'
smaller headlamp. Exactly where & when the changeover came in 1969 ? Probably very early say
March. The tickle front brake was fitted until about 1968.
# 6405 I have a nagging doubt here, records show that "VMT 652 was supplied by Velocette to the
Southampton dealer Bennetts sometime between June 1967 and before October 1967 when it was
then passed to Smalls, another Southampton dealer. On the 20th of October 1967 it was registered by
Smalls who sold it on Nov 7th 1967. " the next owner rode it for some 6 months, presumably not
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changing the front brake or headlamp, the next owner sold it to me unrestored, ie a bit scruffy, but
entirely original. VMT652 has a "shallow" centre switch and ammeter headlamp and a Blumfield front
brake. I suspect that any definite dating must be also subject to the "what was in the parts bin at the
time" clause, particularly during the later years of Velocette.
# 6404 Yes - I recall delivery of various machines at the time. My own 69 registered Clubman had the
deep headlamp & tickle brake. Bryan Clarke's 70 reg. Clubman has the Blumfield brake & smaller
headlamp. The dates given in Rod Burris's book are a good guide - but remember Veloce always used
up whatever was in the stores at the time and I suspect that accurate change over dates didn't really
exist. Having said that, my Clubman also still had a K1FC mag and was probably built in 1968. The
smaller headlamp is more often fitted to coil ignition bikes also; what is yours? Another slight problem
(over here) is that many Velos sat around in dealers showrooms in the later '60s and were slow to sell.
The sales figures for example indicate that about 1 VM Clubman was sold per week in the UK! Hence
specification dates are a bit blurred. I have just looked at the Burris book and note that a 1967 VMC
has the Blumfield brake - which goes to prove my point about change-over dates.
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C.5. Electric Conversions -
L #23 I also converted the shaft of my distributor of my 1969 VMT to ball bearings some ten years
ago. Plus the fitting of Boyer electronic ignition and 12Volts by JG unit and careful stroboscobing, I
have not touched the ignition setting since 10 years and 15000 miles. It is clear to fit a sealed bearing
towards the CB room of course. If you use a Boyer (pre digital) ignition, be careful with the coils. I have
a collection of burned out coils. Especially the thin 12V ones ast only 1000 miles. Ernie Brandsen gave
then the advise to fit the genuine thick Lucas 6 V coil with a Norton Commando ballast resistor in
series. Till today it does the trick !
#27 I've had no luck with electronic systems, probably not sufficiently convinced to persist long enough
to clear up all the problems. Means going to 12v which I have on only one of my Velos. With my ballbearing
conversion, I couldn't find an oil seal which fits, so the outer bearing is sealed on one side.
L #88 am in the process of installing a Boyer ignition on my 1970 Venom Clubman, keeping the
bike at 6V. I'm wondering if there are any other electrical mods I should make at the same time to
improve reliability. Should I replace the original Lucas voltage regulator? How about the coil? Does
static ignition timing work well on these bikes, or should I strobe it? Also, I'm assuming this bike is
positive ground, since all the pretty red wires go to the frame :)
#89 You can stay at 6v, but if you intend riding much at night, why not look at alternators? There are
two on the market at least, my preference going to the one which looks most like the old dynamo. The
dynamo style one comes with control gear, as does the Lucas alternator version. You can use a cheap
voltmeter, a useful bike tool anyway, to check polarity. Personally, I have never had much luck with
electronic ignition systems, and still use points. As the Velo does not have a fixed mark for strobing, the
result you get depends on your skill setting it up. Which also applies to static timing.
#91 I have my doubts if you will succeed with 6V and a Boyer ignition. I have a Boyer on my Thruxton
since 13 years, but, as far as I am aware of, it only works with 12V. I converted the dynamo with a JG
unit to 12V and the system works reliable. If you convert to 12V here is one good tip (from Ernie
Brandsen, the electronic wizard himself) : Use the old 6V ignition coil with a Norton Commando ballast
resistor in series.
#92 I did purchase a 6v Boyer unit, so theoretically it should work. It's turning out to be a bit more
involved than I initially thought, since I need to replace the coil (the original coil is 2 ohms, and the unit
requires one in the 5 ohm range. I'm also going to switch to a solid state voltage regulator while I'm at
it
#93 Most electronic devices (semiconductors) need roughly 4.5 VDC minimum for function. In any
wiring system there is a voltage drop across each of the numerous connections. When you include the
effects of time and weather it is very unlikely that your Boyer will have sufficient voltage to operate
reliably in a 6V system. This is also one reason that 6V lights tend to look dim, even if the power rating
(wattage) is the same. OTOH, you could solder up all the connectors - but this makes repair a bit
difficult! I agree with Herr Patek, the JG has been 100% reliable on both my 60W Lucas (Venom) and
36W Miller (MAC) dynamos. The Venom has 30,000 miles and 12 years on this setup. I cannot think
of any good reason to stick with 6V. Also, both bikes have magnetos, and after towing a couple of
dead Velos equipped with coil or electronic ignitions I would not use anything else.
#99 I am very surprised to hear that Boyer offers now a 6V electronic ignition unit. Those Boyer guys
are excellent in technical respects, but quite bad in marketing their products. Who knows the exact
difference between a MkIII and a microdigital unit ? Instead of running their identical advert in all
magazines, they should describe their products closer. The only draw back I always had with all Boyer
units were the coils. An A65 twin worked perfectly with two 12V coils parallel, the Commando only with
two 6V coils in series. The 12V converted Thruxton, blew about six 12V coils of different makes on the
most uncomfortable places (single repair lane of motorway on top of a bridge with no escape lane, big
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fun !) till my desperate call to Ernie Brandsen revealed the secret of using the original 6V coil with that
mysterious Norton Commando ballast resistor in series. Why not telling the customer in advance ? I
agree with Tom Ross that the most reliable ignition is a magneto, and in this case a BTH. Once you
have a rewound armature and everything checked over, you should have no problems. On my Venom I
use a manual TT BTH magneto with a steel geared Lucas ATD and this offers the best of both worlds.
Reliable and smooth tickover, and the possibility to adjust at full revs when the engine pinks a bit. I
have 8 old bikes and long winter months (lay up periods) and compulsory daylight riding. So I converted
all magneto ignited ones to battery less systems, because I don’t want to buy several batteries each
year. I short cutted the cutouts and adjusted the voltage to about 7V at full revs. The light switch stays
permanently on, and from a little over 1500 revs, I have lights which can be seen, though this does not
say, that I see anything at night with a 6V Miller 30W system, for instance. One word to the praise of
the JG units. It seems they work perfect on Velos, but we tried four (4) on three different Goldstars, with
the effect of boiling batteries, burned bulbs and 3 exploding dynamos !!! A very expensive try ! It
appeared it has something to do with the high revs of the magdynos on the Goldies (the dynamo
rotates with 10500 rpm at full revs). We all reverted to conventional mechanical regulators then. Fitting
an electronic ignition to an original coil equipped Velo is the easiest (and cheapest) way to overcome
the sloppy distributor spindle. For the Boyer unit it does not matter if there is a bit up and down
clearance on the spindle once the rotor stays between the poles. But you always need to watch the
healthy state of your battery, be it 6 or 12V.
L #95 When my dynamo burnt out I was toying with the idea of fitting an alternator or converting
the dynamo to 12V. The Alton alternator looks more like a dynamo than the Criterion but I preferred the
bike to at least look original. I tend not to ride the Venom at night as the VFR seems much more
suitable for this. In the end I had the dynamo rebuilt (cheaper than an alternator) and replaced the KTec
(part of the reason why the dynamo burnt out) with a 6V JG regulator. The only modification with this
was to convert from a positive earth to a negative earth. Another useful modification was to replace the
dynamo V belt with the owners club tooth belt, which requires less tension and puts less strain on the
dynamo bearings. I have also had my magneto overhauled (extensively) and it seems to give a hefty
spark, so I am also in favour of points
#97 I got a dynamo rewound to 12v, and the fellow who did it wasn't happy. He claims there is
physically not enough room to put in as much copper wire as should properly be done. He also says
there will probably be some inferior rewinding jobs around. May be that he's a perfectionist. As long as
a modification is easily reversible, I have nothing against it.
#98 Electronic regulators (and 12 volt conversions) have been around for a couple of decades now.
The conversion requires no rewiring or other mucking about with the dynamo (assuming it is in good
shape to start). There were some problems with very early JG units, but they are quite reliable now. If
you run electrical accessories such as heated clothing, better buy an alternator. My vest draws 60W by
itself, which would not leave anything for the lights. Up to now I've toughed it out, but advancing age
will soon force me to install an Alton. Procedure: (tip o'the hat to FT and Ed G.): 1. Examine machine
for magneto. If found, proceed with step 2. If not, purchase 12V coil or (thanx Johann) Commando
ballast resistor. I am not sure if you need a 12V condenser, wouldn't hurt. 2. Purchase 12V JG
electronic regulator, plus suitable battery and bulbs. The horn will be fine unless you live in Cairo. 2.
Polarize dynamo per red book or instructions packaged with regulator. 3. Install above listed items.
VERY IMPORTANT - install a main fuse on the battery (10A should do it). Ride away. On my Venom
the ammeter shows charge at anything over 40 mph in top. The MAC (even with it's wimpy little 36W
Miller) performs similarly. The only dynamo problems I have had with either was when the screws
holding the mounting plate backed out (Lucas). Oh, and the brushes stick once in a while. Concerning
cosmetics, the JG is small and silver in color. It's not visible under the seat of the Venom, and on
ZUMAC I painted it black. This has not kept ZUMAC from earning a trophy every time I have shown it. I
use a full sized Yuasa motorcycle battery, wrapped in self-stick pebble-grained black vinyl film made
by 3M. It is used on auto bodies and a good paint shop should be able to get it. You have to be within
10 feet - and know what to look for - to notice it. Others have cut open an old black-case 6v battery and
placed a small 12V one inside. I saw a reference to a metal cover somewhere, too. And the sealed type
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atteries are black already, if a bit dear. There is one on my Honda XR650L - I think it's called a
Dominator in the UK. Personally, I like having lots of battery; the Venom has been used for campsite
illumination during late night work sessions on VOCNA Summer Rallys. This is the best reason for
sticking to a mag - battery condition doesn't affect engine operation. When it finally becomes so
discharged and sulphated that the dynamo field windings can't function (no charge even when revved),
buy a new one. Plus, if you leave an ignition coil powered up for very long without airflow for cooling it
can explode and spray tar everywhere. Happened to a friend's Clubman...
#100 To all of you considering of fitting either a JG or Ktec voltage regulator unit : There is one major
snag with all those electronic regulators. Once your battery is completely flat (after winter lay up) or
because the idiot riding it forgot to switch off the lights, the battery is not charged at all after a restart
(only possible with a magneto), no matter how hard you rev the engine. We experienced that there
must be sufficient voltage in the battery left to get the whole system working again. At least halve
charged ! No manufacture of the those units state this affair in their descriptions ! A mechanical
regulator instead also provides a charge to a completely flat battery
#101 I disagree that a mechanical regulator will charge a fully discharged battery. The field coils of the
dynamo must be energized first before the dynamo can function. However, the mechanical regulator
will function at a slightly lower battery voltage; the threshold voltage required by the semiconductors in
a JG (about 0.7 VDC) must be overcome. This means that a battery too flat to fire up a JG might still
work with a mechanical regulator. I remain unconvinced about no battery at all.
#102 I understand that the magneto system is much simpler, and when properly set-up is very reliable,
but, it seems to me that if the battery is kept up by regular running, and the coil(s) are of good quality,
and considering that millions of vehicles of all types use coil/battery ignition systems, if the quality of the
Boyer system is good, what would the problem be, aside from the dynamo being required for double
duty, ignition and lights? My Mac has the 12V JG unit in place with a B-B ignition system installed in a
K1F body by Dave Smith and seems to work just fine, though it has not had a great deal of usage as
yet,
#103 I recently converted my '56 MAC to 12V lights and ignition. It required rewiring the Miller Dynamo
to 12V, using the excellent JG Electronic Regulator, but I left the old regulator box on the dynamo to
look "right". I got a Boyer Bransden 12 V electronic ignition unit very nicely installed in a K1F Lucas
Mag body with new shaft and sealed bearings by Dave Smith Classic Motorcycles here in the US,
along with the required coil, a small German made unit that seems a good one. I got a 10amph battery
that is a bit small but works well. Except for the required extra wiring to be properly installed, and
retiming according to the clear instructions, that's it. The mag on my MAC needed rebuilding, so I
opted for the Electronic ignition and she starts up 2nd kick every time and often on the first if I do my
bit. Of course, you could just convert to 12V lighting and make sure the 6v mag is good shape for
ignition. My lower back is pretty bad, so any guarantee of less kicking over is happily appreciated
#108 I have tried JG's K-Tecs, dynamos with little success. I also have a Criterion type alternator
conversion. In my opinion the best solution is the Alton. It is easily fitted, well engineered, has great
performance and is aesthetically pleasing. I have had mine for 3 years, I did have a strange mechanical
failure outside the warranty period but they replaced the unit, just for the cost of the postage. Its
performance is superb - and even when you point out that you have an alternator fitted, the most
common comment is "I can't see one. I have uploaded the information files in the file storage area of
the group site, within the "Electrics" folder.
#117 The Alton was designed by a French Vincent owner, Hervé Hamon; For those who don't know the
Alton, it simply bolts on, in place of the Miller/Lucas dynamo and is belt driven as per the original. If you
wish later to go back to the standard instrument, this is simple, other than the rest of the bike being 12v
equipped.
#121 All the details on the Alton have been uploaded to the files section of the Velocette e group. Try
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this link. http://groups.yahoo.com/group/velocette/files/Electrics/
#124 Unfortunately you cannot use your JG with an alternator, as it was designed to regulate a
dynamo. There are sources within the UK that sell reconditioned KIFs but I have no experience of the
quality, so I could not recommend a supplier. If it’s just names and contact details you want I can
provide these
#341 I have run an Alton alternator now for about 4 years and have had no problems. It does come
with a hefty fully encased regulator unit and the strap will have to be changed for a more substantial
type. Their is a strong magnetic pull compared to a dynamo I also run it with a club supplied tooth belt.
The only criticism if any is the vents on the body (water ingestion maybe on the exposed position on a
Velo). Moreover, as it was designed for the Vincent some maybe supplied with a parallel keyed shaft
for a magdyno not a taper a la Velo. They are expensive but are a clever bit of design also by the time
you've had a dynamo overhauled bought a new electronic regulator you're half way to buying the Alton
with 150 watts.
#344 I purchased an Alton direct from the manufacturer in France about six years ago. My views are
as follows; The Alton is simple to fit; the most difficult task is removing the front engine plate to get at
the1/4 BSW bolt that holds the dynamo strap on. You need to do this to fit the substantial slotted strap
that comes with the unit. The rest of the installation took about 30 minutes.
#347 I have heard from a "reliable" source that the Altons are hard on bearings, and have a life span of
10,000 miles or so. How many miles do you have on your second unit? Even if true this would probably
not matter to most owners, but for a machine used regularly it could be a concern. I should also point
out that my Venom has needed new bearings in both dynamo and mag during its 33,000 mile history.
The screws backed out of the dynamo end housing, apparently a common complaint.
#348 I have completed just over three thousand miles with the Alton, and unless it stops raining soon I
won’t be adding many more miles this year! A friend has a Criterion and has had to change the sealed
bearings in that after approximately 3000 miles
L #530 Could you please tell me where I could purchase a 6 volt Boyer Ignition system for a 1961
Venom Clubman?
#532 I bought mine from Dave Smith Classics
L #743 I have just acquired a 12 volt 110 watt criterion alternator which comes with Zerner diode
and heat sink. the bike it came off used the mk one venom clubman/ mss/ viper type battery platform
which had a 12 volt 14 amp hour on it. I plan to put it on my bike which has a mk 2 toolbox come
battery holder. < same as thruxton > the problem I have is that the battery which goes inside it is quite
small, a lot less than a 14 amp hour. I am a bit concerned that the alternator might overcharge the
battery with dire results. should I look to relocate the battery and fit a decent amp hour size. any
feedback on this welcome.
#792 If the alternator/Zerner is operating properly, the battery will not overcharge no matter what size it
is. On the other hand use the largest battery that will fit and use a sealed one is even better.
Podtronics makes a good alternator cum regulator that should do better than a full wave bridge plus a
Zerner diode. Keep in mind that Zerners come in all limits and there are manufacturing tolerances,
even if the Zerner says 14 volts, the actual limiting voltage can vary by a few tenths. The state of your
battery will depend on the type of riding you do ( daytime, nighttime, fast and long, city trips, etc.).
Many problems can be traced to negligence of not keeping the battery topped up. That's why I suggest
a maintenance free type.
L #778 I have just fitted an electronic ignition on starting, the bike it stopped charging. I have sent
the dynamo for repair and I am informed that it is burnt out due to the electronic ignition and it has
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een suggested that I go back to Magneto. Have you any thoughts on the subject please, also any
thoughts on converting dynamo from 6v to 12v while it is in for repair.
#779 IMHO, I don't see how the ignition module could "burn out" the dynamo (generator). Those are big
wires in there. The only way I know a generator could "burn out" is through a massive short circuit, that
heats up the armature and the solder melts and is thrown out. The ignition module only draws a couple
of amps. You should have some seriously melted wiring if you had a short of that magnitude. BTW, I
would convert to 12V if you can. Much more efficient.
#780 The Boyer ignition module draws less than a tenth of an amp, it's the coil that uses two or three,
same as a regular coil/points setup. I'm with George, it takes a dead short to burn out a dynamo. I
have had excellent results from electronic voltage regulators made by "JG", even the little 36 watt
Miller on our '56 MAC maintains a charge at any speed over 40 mph in top, with lights on. We have
them also on Zuma's 1950 MAC, and my Venom. These regulators "trick" the dynamo into producing
12V by raising the cutout voltage. Although the '56 has a Boyer, I still prefer magnetos 'cause I hate
the sight of all those wires! Simple is best. But I would look for another specialist for advice re your
dynamo and ignition bits.
L #840 I've got a 1951 MAC, with a new 6 volt battery and bulbs - but it won't charge. I'd prefer to
hide the regulator unit in the old Miller case above the dynamo as it would be too visible sited on the
mudguard, (separate seats) I've got a 12 volt JG unit (which won't fit in the Miller case) and also the
converted 60 watt dynamo which worked perfectly last time I used them on my Venom - about 17
years ago. Is it best to use the 12 volt system although it would mean buying a new battery, bulbs and
headlight(and horn?). I've heard of K.Tec and now I hear about Pod Tronic. From real experiences,
which is best and where do I contact the various companies and how much do they cost?
#843 The Lucas MCR2 voltage regulator I have looks in good condition, but as indicated in recent
messages it seems like a 'Podtronics' item maybe a better long-term bet. So, where can these items be
found in the U.K., and at roughly what cost?
#845 SRM Engineering have recently started importing the Podtronics regulator. SRM Engineering
Unit 22 Glanyrafon Industrial Estate, Aberystwyth, Dyfed SY23 3JQ
#849 For anyone else interested in similar technology, here's the reply I received from srm1@s... :-
'We have choices of 6v & 12v conversion Podtronics, both available in pos. or neg. earth. Units are
wired in same manner (FADE) as standard regulators & so are simple to install; comes with diagrams
anyway. Units are(here I guess they're talking about the model I asked about) £64.88(incl p&p and
VAT.'
#867 I am uniquely qualified to give you advice on dynamos an voltage regulators. I have tried to get
them working on three Velos and failed every time. Having spoken to others 12v dynamos are better
than 6v, but they need to run at greater speed to maintain a charge. Anyway here's my input K-Tec -
cheap aprox £25, available from lots of classic bike dealers. I've never got one to work and there is
absolutely no technical support. JG - more expensive larger, and if you buy it from the right place you
should get technical support. Still need a knack to get them working. I have heard lots of good things
about the support and product made by CMES in Bristol, telephone number +44 (0) 1454 323434, but I
have never used them myself .
L #109 in nearly 15,000 miles of Velo rallies here in the US, the most common breakdown I've
seen is due to a non-standard coil ignition failing, due to either a flat battery or fried electronics,
followed by fibre gears stripping on Lucas mag's.
#110 Both my Velos have the original magnetos, and I have had good performance from them. Indeed,
the Venom's 35 y.o. K1F needed some work a couple of years ago - not the standard capacitor-andremagnetizing,
just new bearings and insulators. It was then demonstrated to produce a 1/4" spark
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when turned by hand. It's a shame that the Works couldn't get mags by the late 60's - I read
somewhere that toward the end they would send a runner with cash for one or two at a time. A coil
system is relatively "cheap and cheerful." The problems I have seen with coil and B-B type systems
have usually resulted not from faulty product but with the installation and maintenance. Bad
connections, batteries shorted from vibration, and not installing proper fuses result in being stranded.
Obviously this is not a concern with a mag. Most roads where I ride are very lonely, often lack mobile
phone coverage, and vultures circle overhead. And I am not eager to win VOCNA's booby prize - the
highly non-coveted Crock of S!#t Trophy awarded to the Chase Truck Queen on our Summer Ride. I
should point out that, unlike some areas, daytime lighting for old bikes is not a requirement in my home
state (California). All you need is a brake light. Also, I have several bikes and am constantly charging
flat batteries. Being able to hop on the Venom and ride off regardless is a real pleasure. As long as the
battery doesn't fall off onto my foot, as happened with a mate's Velo once! Also, the added current draw
from a coil or B-B will raise the rpm required for a dynamo to produce a charge. This could be marginal
on a 36W Miller on a slow revver like a MAC.
#115 I ride the MACt three times a week, for at least 20-50 miles per trip. The Miller is converted to 12V
so in effect it now puts out 72 volts, though that is a technical rating. It seems to charge up quite well
between 4-6 volts cruising along, but I will always keep an eye on it,.
L #337 Having had some mildly worrying times on dark country lanes due to fading Miller glimmer,
I have been wondering if the grass would be greener with uprated electrics. I have enough bits to
change to a Lucas 6 volt late model 60W dynamo and appropriate regulator as the BMS book suggests
Or.... The JG unit has been around for a long time but am I being over cautious in mistrusting electronic
boxes on vibrating British bikes? I am not keen on the Criterion alternator conversion, preferring the
appearance of the dynamo, so is the Alton unit the (expensive) answer? Is its accompanying regulator
just another electronic box? I have been a VOC member for two years so I haven't got the relevant
fishtail articles on Alton and 2CV alternator conversions. Can anybody give me their real life opinions of
these conversions and their reliability on wet winter nights.
#338 Re alternators etc. These comments are based on my own experience. I ran my Thruxton for
many years with a J.G. conversation with no reliability problems. The drawback was despite a first
class dynamo, with the headlights on the battery would eventually drain and the lights. (output
checked by suppliers of dynamo) I decided during a bike rebuild to convert to electronic ignition,
(Boyer). I had used it in the past and was impressed with its performance and advantages. Since the
slow running problems with the J>G> an alternator conversation was I thought necessary. I was
impressed with the unobtrusive looks of the Alton but thought the Criterion was a known, proven and
made in Britain. I ventured on the side of looks, but was unable to make contact with the manufactures
of the Alton so the Criterion was purchased and fitted some years ago. Initially I used a Zener diode
and rectifier with no problems. I later fitted a Boyer power box with does away with the Zener and
other ancillaries, this was several years ago and to date has given no problems. Electrics are not my
strong point but find wiring a electronic ignition system and the control box as simple as wiring a three
pin plug.
L #1120 The Miller DVR dynamo on my 67 Velo is shot. Is there a recommended source for
rewinding in the US or UK?
#1121 In the past I have used FTW in the UK 0114 233 6269, but perhaps the most knowledgeable
person I have come across so far is a Mr P Dunn, on UK 01782 856839. I have had good results with
both. But this sounds like a good time to buy an Alton to me......all my dynamos now sit on the shelf !
details from Paul Hamon in France, BP49, 29480 Le Relecq Kerhuon, Brittany FRANCE 00 33 298
283575. Paul speaks good English. Alton comes with 2 year warranty and looks very neat and
unobtrusive, and very much like a dynamo - and so doesn’t spoil the bikes appearance My only
criticism (so far) of the Alton is that it really needs a toothed belt rather than the std V-belt Toothed belt
is available from the UK VOC - a very simple machining job is needed to get it to fit. It would be
interesting to hear of anyone else’s experience with the Alton - mine has done over 10000 miles with no
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problems - it is one of the current models - there were some problems early on with these I believe.
#1123 A "usually reliable" source has told me that Alton bearings have roughly a 10K mile lifespan,
possibly due to the fact that they are geared to spin much faster than in a dynamo. This opinion is from
experience with older production. Has anyone else obtained more than 10K with one? And is your Velo
mainly used to putter down B roads or is it frequently on the motorway? The latter is an unfortunate fact
of life in my area. Many machines are ridden gently, perhaps only a few hundred miles per year, these
owners may not find a 10K lifespan a problem. I have obviously been thinking of getting an Alton
myself, but my dynamos have been more than adequate so far, running magneto ignition helps. Still,
our Boyer equipped '56 MAC ran 1000+ miles with all lights on last summer, and it still has its original
36W Miller, converted to 12V via JG.
#1125 I have owned an Alton for a few years now. My first Alton failed, in of all places France. Paul
replaced it free of charge (the shaft had sheared). The new one has been fine. I am a fan of the Alton.
My only complaint is the version I have has a steel body, painted black that has started to rust. I did
however have to change over to the Club toothed belt drive as belt slippage at high output was a
problem. Fitting the toothed belt drive was not a problem, all you have to do is bore out the centre of
the pulley and cut a keyway in it.
#1128 Hmm, your experiences really don't seem to indicate reliability equal to most dynamos. I've
never heard of one failing totally early on, yet you report this in 2 of 4 Altons. In around 50k total miles
on various Velos we've had one failure, when the screws holding the end plate on a Lucas came out
after 25,000 miles (easily prevented with a few drops of Loctite). I could have bodged it by the roadside,
but with magneto ignition all I had to do was remove the belt. Repair cost less than $100. IMHO, for 350
euros plus shipping the Alton should not rust or need machine work on a pulley to make right. Do
overseas customers have to pay French VAT? The order form includes this in the pricing with no further
comment. My "source" is a major U.S. importer and distributor of Tri/BSA/Nor parts, he based his
comments on the experience of his customers. Again, this was some time ago. Perhaps the tension
required by the v- belt accelerates the bearing (and shaft) failures. Andrew, if you had fitted a toothed
belt, what do you suppose would have happened when the brushes seized the shaft? Until California
starts requiring daytime "lights on" for vintage bikes, I think I'll stick with my dynamos for now. Unless
someone else weighs in with happier tales? One of our French group members, perhaps?
#1129 As I said I am a fan of the Alton. At a evening vintage bike meet, it was even commented on how
bright my lights were. (By the way, I recommend Zenon bulbs, c 30% extra output for no extra power
drain.) My first Alton was a very early version, Paul has constantly refined the design to iron out the
problems, e.g. bodies won't rust as they are once again aluminum. Regarding having to fit a toothed
belt kit, that was my choice as I ride with my lights on all day and only run a very small battery.
L #2196 I'm curious if anyone has experience with a self generating type ignition like a pvl on a
velocette? We've had problems with the magnetos on the racing Thruxton, and would like to upgrade
the ignition. any help appreciated.
#2198 I am using a self generating ignition supplied by Tony Harris of Rexton Ignitions and can highly
recommend it, although I am not into racing. It has the benefit of being able to power a strobe light and
is provided with slots rather than holes and an O ring instead of a gasket to allow adjustment with out
stripping the machine. (once timing marks are transferred to whatever.) The advance and retard can be
either fixed or electronic and there are no pick ups to fail. They only moving parts, I believe, is a disc
holding the magnets and two good sized bearings. It looks like a magneto and Tony insists it is a
magneto and bears the markings "BTH". He is into racing and can advise better than I can. Only down
side it the cost, but if for a Thruxton? Tony Harris can be contacted at www.bt-h.biz/index2.htm There
was little wrong with my Lucas magneto but I couldn’t resist his magneto.
L #2957 My Viper shows a charge of 8 amps on the ammeter going down to 3-4 with lights on, it's
a 1955 model with a 1961 engine fitted but don't know if a Miller or Lucas dynamo is fitted it's negative
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earth and I'd like to do away with the regulator and go transistorized i.e Podronics kit or whatever is
best, will gadget fit either a Miller or Lucas or do I have to get specific one? And is it a simple job to fit
or should I be looking for an expert, going to Bristol show tomorrow so hope to buy what I need there.
#2959 I'm sure a quick look will tell you if you d-mo is Miller or Lucas, 'cos it says so on them ! The
Podtronics reg works on either BUT... If you have a Miller unit it will need internal re wiring to "Lucas"
operation ( Not difficult ) It does sound as though what you have works ok.
#2960 There is an article on the files section of the site that explains all you need to know about
dynamos and regulators http://autos.groups.yahoo.com/group/velocette/files/Electrics/
#2971 I use CMS on my Venom (Miller)and 31CSR (Lucas) without problems so would recommend
CMS. Nice guy to talk to for info. also.
L #3022 I have recently purchased a 1955 MAC it has a good 6v battery (exide) which I have
charged and the charge has held OK for a week the ammeter shows discharge when the lights are
turned on. When the engine is running and reved the ammeter shows no charge. It has a miller dynamo
which appears to have the cut out removed at least that what I think should be in the space next to the
armature, the voltage regulator is a little black box on top of the dynamo and this has a little black box
within which doesn't look very Velo.
#3424 Sounds like someone has rewired the dynamo to look like a Lucas and fitted an electronic
regulator - there are several on the market these days.. it might be broke or there might be a wiring fault
or the dynamo may be faulty.. 'fraid you've got a bit of detective work to do 1) motor the dynamo - i.e.
connect the field and armature wires together and attach to a battery of the correct polarity with the
drive belt off - it should run as a rather pathetic motor. Check the brushes are in good order and can
move freely . Check the field winding resistance - about 3 ohms. Check the armature - should be near a
dead short. Does anything looks burnt? Is the commutator clean? 2) Check all wiring carefully - sounds
like it should be wired like a Lucas setup. 3) Check the little black box - who made it? Send it back to
the makers or find someone who can. K-tec's units are in a little black box, but there might be other
makers .... got any documentation?
#3427 I found the problem eventually (after buying a new regulator)the original was a K-tec so I bought
another one. The dynamo was wired correctly(Lucas style) after a fashion but the earth brush had
insulated it's self, believe it or not it had motored and on occasions I had measured 13-15v just above
tick over.....anyway after taking it all a part cleaning continuity checking all the contacts I put it back with
the old regulator and all is fine. I'll not send the regulator back as soon as I do the old one will go bang.
L #3818 Hi, Has anyone ever taken an Alton apart? Mine appears to have stripped an internal
reduction gear and I'm not sure if the drive-side alloy is a screwed or pressed fit in the steel body. It's
impractical to send it back to the factory from Australia so if anyone can help, I would be very grateful.
#3820 I have one of the first Altons that were available almost 15 years ago. It's screwed together but
LEFT threaded, i.e. opposite to a normal thread. Inside it there is a gear made of plastic with something
that looks like it is intended as a slip device, about the same as the slip device in a magdyno. It worked
for about 10 years until I installed the clubs toothed belt. Maybe the original belt was more flexible or it
might just have been worn out. Mine is still in pieces. If You find a supplier of a new gear/clutch assy
please make it known.
#3822 You can e mail Paul Hamon, I too had a similar problem and he was extremely helpful.
Otherwise call him on +33 2 98 46 57 74. Paul's English is better than my French, but like all French
British bike owners he is fluent in the key words of communication. (e.g. knocking big end, flooded,
misfire, clutch slip, leaking oil, etc.)
#3823 Interesting point about the toothed belt - I too have fitted one and I believe the damage may
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have been caused by the motor kicking back as it sometimes does with the electronic ignition on the
first attempt. Certainly there is no slip or flex in the belt so it could be a problem with the Alton drive
system as you describe it. Maybe Veloce knew a thing or two about driving dynamos? The Alton
requires a lot of power, hence my fitting of the toothed drive. Bruce, thanks for your kind offer - I will
attempt to unscrew the "gearbox" end and see what I require in the way of new parts.
#3825 Harvé Hamon is the one who does Vincents at 56 Aurey. His brother, Paul, is at Brest and does
the alton alternator, tél.02-98-46-57-74. Paul should be able to fix you up for spares.
L #4109, I've a sick 6 volt to 12 volt JG Unit electronic control. Might anybody on this list have any
technical knowledge about adjusting the parameters on this device or know how to contact the maker?
#4110 The JG Unit is still manufactured and therefore probably still repaired in England by Dave
Lindsley, 196 Pilsworth Road, Heywood, Lancashire OL10 3DY. Tel (00440 01706 365838 Fax (0044)
01706 627500
#4122 I used a JG unit many years ago before going over to an alternator. It seemed a bit fragile and
eventually failed. It does not like a fully discharged battery, a condition often met with classic bikes. My
unit was "potted" with a silicone substance that prevented easy repair, I don’t believe anyone would
offer a repair service. I was persistent and dug out the rubbery/silicone stuff. I found that the field coil of
the dynamo was controlled by a flimsy micro relay about the size of a small capacitor, and this is what
had failed, I replaced this with an external relay which kept me going until I got the alternator. Since JG
are still in business the circuitry must have changed as everyone I knew with one had this trouble
sooner or later. My recommendation would be to put your money towards an alternator rather than a
replacement, you will then have good lights and power to spare, Podtronic make alternator controls that
I have fitted and was impressed by, one box, three leads in (from the alternator) and two leads out +
and- just earth the one you want. This replaces the Zerner diode and rectifier (diode) pack at a price
less than the Zerner alone. Dynamos are getting old now and although many people will swear by them
60 watts (yes a bit more converted to 12volts) maximum output is just not enough. Criterion
conversions now have an outboard bearing under the pulley and are much better than the old overhung
ones that used to fret around the poorly designed tiny inboard bearing on the end cap. If you have
access to a lathe build your own, enrol in a college if not and use their machines, I have diagrams if
required but you can just buy a billet of alloy and turn it down until the stator fits. It certainly is not
beyond anyone who can tinker with Velos..
#4123 Largely agree. 12v dynamo conversions work, but you've a trade-off - either you limit the field
voltage to 7-ish volts, as in the original 6v electrotechnical regs, with a resultant cut-in speed of about
3000rpm - or you allow full 14v to appear across the field, over-dissipating it 4x causing overheating
and early failure.. I never stripped the gunge from a JG to find out what was underneath, but measured
one to discover it did the latter - as do the other 12v conversion controllers I've come across. Modern
alternators ought to do much better. But I hate the zener crude controllers that eg Criterion used to use
( do they still?) Dumping the full power of the alternator generates less whatever the bike uses as heat.
Wasteful, and if the Zener fails, burnt out bulbs and boiled batteries. I wrote to them offering to build a
decent efficient regulator for them for a commercial rate ( my trade is designing electronics) many years
ago, but no reply.
#4124 I was under the assumption that permanent magnet alternators (Lucas) had the same engine
load and output regardless whether the current went to the coil, zener diode or nowhere. I did see
something about an after-market Harley (permanent magnet, single phase) regulator that was able to
save engine power by regulating the current in some fashion (I think they called it a serial regulator). Do
the coils in the stator create a stronger pull the more current that goes through? Is the zener
arrangement just a cheap way of regulating? Do the regulators on permanent magnet Japanese bikes
work on the same principal? I've had a Lucas E3L 6v generator running with a 12v VW Bug mechanical
regulator ($20 at the auto parts store and available everywhere) for some years now. Had to convert
the generator from 'A' style to 'B' style by switching the brush wires around. It's never given me any
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trouble but I don't ride with lights on very often.
#4126 The Podtronic regulator that I fitted for a friend seemed just the job, price from memory was
around £24 but I know some places charge more. Ill dig up the source if anyone wants it. The
regulation was really good at around 14 volts, very stable. I shall convert mine soon and get rid of the
Zerner and rectifier, indeed some high output alternators call for two Zerners to be fitted, even more
expense and messing around with the wires. Has anyone used the podtronic in anger for extended
periods, I know this USA regulator gets good comments in the USA press
#4128 Permanent magnet alternators look pretty much like current sources - the faster they go the
more current they supply up to a limit set by their leakage inductance and the revs - the higher the revs,
the higher the frequency and the more the inductance limits the current. Above certain revs this means
they generate a constant current and the voltage is undetermined - could be quite high - 40 or 50 volts.
Unregulated lighting sets as used on bicycles ,cheap mopeds etc rely on this constant current designed
to feed their quota of bulbs correctly. But if one bulb blows the current remains the same and the volts
go up, so you'll blow the rest pretty soon. You're quite right about Zerner-controlled alternators such as
the old Lucas design - they generate power proportional to engine revs ( i.e. constant current and volts
proportional to revs) , and the power is distributed between the Zerner and the various bike loads. They
were cheap and simple, but wasteful of power and didn't control the battery volts very well- an old
triumph of mine always had to have it's battery topped up regularly. And of course if the Zerner failed
you boiled the battery thoroughly and blew the lights the moment they were turned on. Early Ducati
twins had a permanent magnet alternator like Lucas, but used a clever thyristor regulator such that
each cycle of the ac output was only turned on for long enough to hold the battery at 14 volts. With no
load this took very little time on, with heavier loads more. It's this style of reg I offered to design for
Criterion. I don't know what Harleys use(d). Might be a simple series pre-regulator but this misses the
point as the inductive reactance is lossless ( approx) . Don't know - can only guess. Modern bikes use
wound field alternators just like cars, with similar control units. Glad your VW regulator works OK - but if
designed for 12v it won't limit the field voltage and hence you risk over-dissipating the field and burning
it out.
#4130 Sounds a bit like the old Ducati thyristor-switching regs I mentioned in my previous. I properly
done should work very well. Less load on the engine, almost no wasted power so nothing gets hot.
regards.
#4132 A brief follow up on the JG Unit. I called Dave Lindsley this morning and had a long chat. The
problem I'm having is with a E3N 48 watt short generator mounted in a, wait for it, a 49 AJS. (the JG
Unit in my '66 VMT works Great!!!). The JG Unit will frequently fail to "wake up" and begin to charge
unless I blip the throttle and really boost the revs, like 4K RPM. Mr. Lindsley walked me thru the control
strategy and gave me great ideas for locating the problem. His view is the air gap may be too wide on
the newly rewound armature. Large air gap means the residual magnetism in the pole shoe man not be
sufficient to begin exciting the field coil unless the dynamo is spun faster than normally required. The
difficulty in correcting the air gap problem lies with either replacing the armature with a "newer"
armature that may not have been skinned after rewinding, or shimming the pole shoe. Either option
require removing the entire primary drive and tin ware to pull the dynamo out of an AJS. (I know, I
know, this a Velocette list). I've a PODtronics 6-12PE unit on hand and may swap out the JG Unit
before removing and stripping the dynamo. I'm seeking the path of least resistance! I've some testing to
do. In any event, I really appreciated Mr. Lindsley's patience with me and help in finding some
resolution. This is a vendor I will continue to support! One of his answers may be of interest to the
group. The JG Unit does send approximately 14 volts to the field coil but limits the current to avoid over
heating the field coil and the possibility of reducing the life of the field coil.
L #4161 My MAC is getting nearer completion and I have an Alton Alternator to fit. I have fitted
some neat little indicators and want to use a larger, more modern headlamp. I have a Honda
Superdream unit that fits OK but my query is, do I need the ammeter? No modern machine has one
and if the Alton is all it is cracked up to be, why would I need an ammeter at all. I am using the
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handlebar switches off a 1960's Honda CB250 and although I know it's not original, I want to be able to
use it in the dark. I have the original bits to refit if I choose. Can I ditch the ammeter?
#4162 It certainly wont hurt to ditch the ammeter, if you think you need an indication of charge then a
voltmeter will do the job just as well but will not affect the electrics, if it goes faulty, as its in parallel
unlike the ammeter, where you loose all your electrics as its in series. As you say modern cars and
bikes don’t have ammeters now and once you ditch the dynamo you can rest in peace with lights you
can see! My ammeter is more affected by vibration than the current going through anyway, it just fills
the hole in the headlamp.
#4169 Keep the ammeter. When, one bad day, it wacks over to 8amps full charge even when you know
that the battery is OK, then you will have the classic indication of regulator failure. It's happened to me
twice now. I guess that MCR-2s and RB-108s or whatever just don't like the vibes given off by 86x86
and yes, I have tried all kinds of rubber mountings. In the end I capitulated and fitted a V-Reg II - end of
all the problems.
L #4667 When I bought my '58 Venom 3 years ago it was running a coil ignition system with a
solid state regulator at 12v in line with the "Dynamo Uprate" article on the site. Last year I went back to
magneto ignition but left everything else alone at 12v. All went well for about a year until last month
when I noticed I had no charge. The cause is clear - the solid state regulator has a molten metal
"blister" on the side. I've checked the dynamo and all seems OK. My first thought is to simply replace
the regulator - I've read the various views on the different manufacturers. Then I had another thought. I
hardly ever ride at night, the only uses my lights get are if the day is particularly dull/raining and the
very occasional short trip at night and whilst it's nice to have bright, 12v lights I wouldn't want to do this
at the cost of shortening the dynamo life. I'm not an electrical engineer but I can't help but think that
running the "6v" dynamo into a 12v system will put addition strain on it. My choice is - a new 12v solid
state regulator or new 6v regulator, battery (probably needed soon anyway), and a set of 6v bulbs. Any
experience out there with running a "6v" generator at 12v for an extended period?
#4672 The big advantage of 12v is to be able to use QI headlamp bulbs which are MUCH brighter... but
if you don't ride much at night this may not be important to you. Also 12v bulbs are freely available,
whereas you have to buy 6v ones from a specialist. My ( homebrew) 12v conversion has run for 30
years and 160,000 miles without dynamo problems.
#4675 On my last Venom I ran thousands of miles at 12 v with a 60w Lucas dynamo and a JG 12v
regulator with no trouble. Soon after I bought my present Venom the 6v K-tec regulator went wrong and
the dynamo failed at the same time, coincidence? I fitted a re-con 6V Lucas 60 watt dynamo with a
CMES 12v regulator together with a small dynamo pulley. Running at 30 mph in top gear on standard
gearing I get a balance of charge showing with a 60/55w Q.I. bulb on dip. Speak to Sean at CMES
01454-323434, he is very helpful and will explain everything in layman's terms if needs be.
#4681 I'm also running the same lighting kit - 60w Lucas CMES 12v regulator - with no problems.
#4683 Does the JG unit work ok with a Lucas dynamo? If it does then it may be that the Miller dynamo
wires have not been altered to suit a JG as is required,
#4684 I converted the wiring myself, the whole system worked fine for a couple of days then stopped
charging. I thought a wire may have come loose so checked it over but every thing keeps pointing
toward the dynamo so I checked to see if it would motor, which it does, I then earthed then F and
connected D to voltmeter, ran bike voltmeter shows about 12 volts,
#4713 I have used V-Reg II regulators, and have had no problems whatsoever with them. They come in
neg or pos earth, and regulate at 6 volts as supplied, but are converted to 12 volts by snipping a small
loop of cable that sticks out of the epoxy surface of the regulator. They are small enough to fit inside
the miller regulator case. Look on www.AOservices.co.uk I speak as I find and have always had good
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service from them.
L # 4995 I need some information and this group seems a good place to get it. On my way to a
VMCC meet on Sunday 23rd Jan, VMT652 suddenly changed from an exciting, living thing into a static
roadside exhibit, that was it, no pops , no bangs and no crunches. Roadside inspection showed no
spark, the plug fine, very good colour in fact, but no spark on the lead, cap or plug electrodes. The bike
is a recent acquisition and I knew that the mag had been changed to electronic ignition, but have no
idea which type. Investigation some 4 hours later after collection and return home revealed a black box,
some 5"*1"*3" with PPPD 000014 stamped on it. This box is connected to a fairly small ignition coil.
The black box has a 4 wire (only 3 appear used) connection via the mag breather pipe and fitting to an
optical trigger unit which can be advanced/retarded by the normal handlebar lever. The PCB has PD
Electronics and a phone number on it, the phone no. no longer works. My questions are: a)Does
anyone know who made this stuff? b)Do they still exist? c) Has anyone any details, installation notes,
or setup info for it? d) Would I be better to forget it and get the K1FC rebuilt properly? however the
engine has always started very well (2 kicks max) hot or cold aand can be relied on with just a whiff of
throttle (on a GP) for traffic lights aand first gear selection so I would like to get the same from a mag.
My memories of LAP123E, my first Thuxton in 1967 are of much more erratic behaviour, even for those
days. e) If the mag is to be rebuilt, who by? Sorry about the mega mailing.
# 5008 The fault in my system is the trigger unit mounted in the mag, has anyone any old wiring
diagrams, installation notes, specs etc. for PD Electronic Ignition, from which I can identify the sensor
component? I have been recommended to go to FTW in Sheffield for the mag rebuild, has anyone any
knowledge/experience of this company?
# 5012 What makes you sure it's the trigger? There are three basic sorts.. opto - an infra red emitter
and detector looking through a slot or similar. A hall-effect device - Sprague were the main makers of
these, now called Allegro - UGSxxxx typical part numbers - in a TO92 package - with either a spinning
magnet or steel occludor with a slot and a fixed magnet. MZ used this system. Or a coil with spinning
magnet or occludor/fixed as above. All are intrinsically very reliable if used properly.
# 5049 There is only one opto switch, it is larger than mouse switches and is embedded in araldite so
numbers are hidden. Thanks for your offer, I have decided to junk the electronic ignition and have now
removed the mag to go away for a checkover and have the missing parts replaced, I will report back on
completion of this exercise.
# 5034 The PD stuff consists of the black resin encapsulation box with 6 wires exiting. 3 are fairly
heavy gauge and are the Pos and Neg from the battery supply and the connection to the Coil. The
other 3 are fine wires wrapped in a shielding sleeve and protective outer which go via the points cover
breather on the mag to a slotted optical switch, 2 go to the infra-red transmitter LED and 1 returns from
the phototransistor. I suspect, but cannot be certain, that the cold side of the phototransistor is
connected to the cold side of the LED. The sensor is soldered to a pcb which is in turn araldited to an
aluminium ring which replaces the cam ring and is rotated partialy by the hand advance/retard
lever-cable-sliding connector to enable retard for starting and advance for running. The points have
been removed from the armature shaft and an occluder fitted which has a deep trigger slot and a cutout
to give TDC (I think). When the occluder triggers the coil an LED embedded in the black box flashes.
Diagnostics completed so far, The coil has a resistance compatible with a large winding and when the
return side is flashed on the battery, a spark is generated at the plug - so far coil passed as OK The
black box when powered by battery voltage, responds with a high voltage short dwell pulse on the coil
feed wire when the switch LED feed wire is grounded. - Hmmm!! The LED on the PCB in the sensor is
open circuit on all connections in all directions as is the phototransistor and the track on the PCB
appears to be missing between the receptor output pin and connecting wire. Here I am at a loss, should
there be a reading across the LED in any direction? is the phototransistor linked to a common with the
LED?, there is battery voltage on the feed to the LED (ie 12.5-13.8) looking at RS Components sites
most slotted optical switches run on only 5v. seems rather high, only 5 wire logic switches seem to run
at 12 - 14 volts, this kit is far earlier than that and only 3 wire anyway. Anything you can suggest, throw
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light on, etc would be very useful, the bike ran so well on this kit I am very loathe to just throw it away.
John PS I don't know if you read your off-group mail so if you do receive this please respond simply to
confirm, if i hear nothing within a day i will re-post on the group and risk boring everyone.
# 5013 I have used FTW for some years and find them OK. You can also try Tony Cooper 021 559
2405
# 5030 I have been talking to FTW and Tony Cooper, Tony is nearest to me and he seems to be just
the man should I go the rebuild route. I have a lead to follow up yet on the repair/rectify of electronics
route yet before deciding. Once again many thanks, this group is a real asset to Velo ownership isn't it?
# 5032 Surprised no-one has suggested Dave Lindsley to do your mag overhaul - definitely one of the
main players in the magneto game, he did my mag a few years ago and I've had no trouble since.
Based in Heywood, Lancs, you'll get him on 01706 365838.
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D. The Carburetor and Fuels
D.1. Carburetor -
L #152 I am thinking about fitting as one inch and a half carbs to my Thruxton which has been
stroked to 580cc. I will be boring out inlet to suit and have been given a MK2 concentric to try. Has
anyone fitted a larger carbs to a Thruxton? If so what was the benefit if any?
#155 I have alternated between 1-3/8 and 1-1/2 GPs on my Thruxton (709cc). I have not opened up
the intake port in the head as flow bench testing revealed that with minor work around the guide area
and the best valve tulip shape netted 50+ hp flow potential with the 1-3/8 port. I would guess that
opening the port would only slow velocity and weaken the midrange (although some other 2 valve
street singles did come with the larger port, most in my experience will not outrun a good Thruxton,
particularly off the corners). Instead I have the 1-1/2 inlet manifold tapered down to 1-3/8 at the head
which is common practice on newer long inlet tract designs. I tested a bunch of carbs (GPs, Mikunis,
Delortos, Concentrics, etc.) and couldn't find anything with a needle in the middle that would match the
GP for all out flow. Others may help mid-range though with better part throttle metering than the broom
stick that the GP uses for a needle. I believe there are two different Mark 2 Amals, standard and
smoothbore. I think you will find a standard 38mm (1-1/2) Amal will not flow any more air than the stock
1-3/8 GP. The smoothbore might a bit. The stock Velo exhaust port is terrible, you should concentrate
more effort there.... The seat of the pants difference between the two GPs on mine is negligible. I'm
going to be trying a 40mm Mikuni flat slide in the near future but the sight of that thing sticking out the
side where a GP used to be doesn't excite me any! Maybe the power will.
#156 Re: Stewart's question on larger carbs on Thruxtons. Paul Zell has a 1.5" GP carbs on his 720cc
monster Thruxton, and it works just fine thank you. Mind you, his engine is a lot bigger than your
measly 580cc (MSS crank?) item - and as a consequence he's done a lot of work beefing up the drive
side of the custom cast crankcase. But not even a Manx used a GP that big, and made plenty of
power. But then again, Italian racing singles use monstrous carbs for top end breathing - they must
have been useless at low rev's. Don't expect a big increase in the top end unless you have a very good
tuner doing your porting!
L #212 I would really like to set up an airbox/filter for my '56 MAC which has the usual short open
bellmouth on the 376 Monoblock. Putting any kind of even light foam over the bellmouth breaks up
airflow and causes the bike to run lumpy. I live in the desert area around Carson City, Nevada, so an
airbox would probably add considerably to the engine's longevity. Any suggestions out there?
#213 I have a foam sock on my 52 alloy MAC, bought at a dirt bike place. Works, but you may need to
rejet. There is not a lot of room between the carbs mouth and the oil tank. The original Velocette air
cleaners had a rubber tube leading to the air cleaner between the back of the oil tank and the battery. I
don't see that this would give any better air flow to your mono block than a sock, but it would probably
look a lot better. I have seen variations on this, a rubber tube with a sock on the end.. I also have a
K&N flat round filter on my Endurance which is perfect.. just fits with some force between the oil tank
and the carbs. I had to reject for it as well, but it is like other K&Ns.. not much restriction. I understand
that these are no longer available, I got it with some parts I bought. I have seen modified Triumph style
filters fitted to Velos.... if you are handy with body work.. I think you need to start with one with hole for
the carbs in the middle. Mike Jongblood has one on his 500, you may have seen it.
#219 Thanks for the air filter info. I will be at the opener. I have come across one of the BSA/Triumph
pleated paper air filter elements, about 4 ½ inches by 2 1/4 inches. I have some great firm plastic
sheeting to adhere to both sides of the element, cutting an opening for a short rubber spigot to apply to
the 376 Monoblock after removal of the dinky bellmouth, which, aside from protecting the threads on
the carbs is probably technically useless on the MAC at it's normal driven speeds. I think it will breath
quite well, but we shall see. Need a project right now, anyway. I have already dropped the main jet to a
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180 from the stock 200, which at this altitude of about 4700 feet cleaned up the mixture nicely. Now, If I
choose to open the throttle to the 3/4 to full open position, the engine doesn't bog down. Must
remember to rejet when I get closer to sea level. Running a B7ES.
#219b I run a small foam air filter on my Venom, yes it required minor rejetting. I run a main one size
down from the 270 specified for my Concentric. It has the spring. The light green Uni's filter better but
flow worse; I'm using a dark grey one. If you have never seen a stock air filter like the one Paul has
offered you would not believe that it actually flows enough air. There is a short rubber adapter (

#746 Spitting back in the carbs can be a sign of a weak mixture, although you do say that there is
flooding which would perhaps indicate enough fuel is getting through (unless there is a restriction in
the pilot jet leading to weakness at tickover, and the main jet / needle is oversize leading to flooding
when the throttle is opened ?. I would think that by checking the state of your plug immediately after a
run i.e. not letting it tickover before you check it, would indicate whether or not it's running rich? What
is the engines performance like when it's running above tickover?
#749 I was led a merry dance by a carbs spitting problem at kickstart/low revs. The culprit turned out to
be the ( peripheral ) slip ring in my manual BTH magneto; there was a section missing! Presumably, at
higher revs the points operating arm jumped the gap.
#752 The Plug was black and the engine runs very well past the tickover speed. The tickover passage
in the carbs was cleaned out thoroughly. In general should the VMT have a compression plate added to
reduce the chance of a holed piston?
#753 My Venom runs an optimized 8.75:1 compression ratio (measure the volumes to make sure), the
same as a Thruxton. Cams are M17/8 but with standard Venom followers, head and valves. Carbs is a
30mm Concentric Mk1 with a 3" long velocity stack (proper Amal turned type, with a blended venturi).
Getting the carburation exactly right was a bit of a pain, but it now runs quite happily at all speeds and
loads, with no more pinking than I would expect on a Velo (I do believe that they can stand more than
people realize). I run on either Super unleaded or Optimax (not yet sure if there is any advantage to
Optimax due to my experiments with carburation overlapping with the introduction of this fuel to the
marketplace), in either case Nominal RON value of 97/98. I always felt that the motor ran more happily
on unleaded than on LRP.
#762 Just fitted a 1036 Concentric recently, the air correction orifice (the center of the 3 holes) needed
to be opened from .080 to about .135. Make sure you have the 4 stroke siphon tube, the one that is cut
flat across the top. thanks for the info . Can you tell me why the air correction orifice has to be opened
and how? Also what is the 4 stroke siphon tube?
#770 The air correction orifice performs the same function as the air correction lever on a GP, it allows
some air to enter in the mix at the siphon tube, the brass tube that needle enters into first. Two strokes
need lots of fuel at low rpm so the air correction is small and the siphon tube is usually slash cut
across the top, four strokes are flat cut. To convert to four stroke use take the siphon tube (along with
the needle, needle jet and jet holder, also different, and whatever main you want to start with) out of
most any smaller four stroke Concentric. While you have the siphon tube out of the 1036, match the
size of the air correction hole (the center of the three that leads to the siphon tube area) to the four
stroke carbs you just cannibalized from about .080 to .125-.140 I believe, or you can see how it runs
and gradually open up the hole. You will probably need a 3 or so cutaway on the slide, you can file it if
it's a 2.
L #790 I am also trying to source an air filter.
#791 Grove Classic Motorcycles on +44 (0) 1582 873066, e mail mike@g... has loads of original air
filters at a reasonable cost.
L #1143 I am having difficulty staring my Venom. The magneto has been overhauled and there is
a fat spark on kick-start. I think the Mk1 Concentric is suspect. There is noticeable play on the slide in
the body. I am looking at the tolerances and possibility of replacement slide . The literature tells you
how to set it up for running but mine is OK once going. Is there a procedure to set it for starting? I am
also considering a new carburettor. Has anyone any experience of modern alternatives. I know a
Mikuni has been used and a Del Orto. Any first hand experience of these, later Amals or others
welcome.
#1144 Usually a well-tickled carburettor will start just about all the time, a worn slide will produce an
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erratic idle and the engine seldom settles down to the same idle speed twice. If you're still considering a
carbs change, though, I've had good luck with Mikuni slides dropped into suitably bored and modified
Amal concentrics. Here in Arizona I go through AMR in Tucson - couldn't tell where you are, but they do
mail order if you're on this side of The Pond. Personally, I like this approach because you still have a
tickler on the finished product. Nothing like the smell of raw fuel in the morning to get the day started
right.
#1145 Essentially all carburettors have two circuits as part of their design. The idle circuit is in play up
to about 1/8th throttle. Beyond 1/8th, the slide cutaway, the position of the needle in the needle jet and
finally the main jet all come into play. Getting all of these components to work in harmony and in
sequence is a bit of a chore if one starts from scratch. In so far as AMAL has published great amounts
of data, as have Veloce on the specs for a give model, switching to a Mikuni or Del O'rto may cause
you to become very frustrated, unless you have reliable info on how the brand X carbs should be setup.
You email does not state which model Concentric you have, or any of the specs. I can only assume that
the carbs is one Veloce recommended and is properly set up AND the bike has been reliably started on
this carbs by you or a previous owner in the past. Reliably started is defined by me as "the bike will
start with 2 or 3 kicks regardless of ambient temp or engine temp. Have you ever had this degree of
reliability with this bike? If the answer is no, two factors come to play. All bikes, most notably English
single has a "combination" in the starting sequence. Learning the sequence, and it can be different for
each bike, can be a bit tedious, but adds to the charm of the breed. When properly set up, an AMAL
concentric should readily start your bike on the idle circuit and require almost no throttle till the engine
lights up. Would you please tell the list the model of the carbs stamped on the side, and the variables
such as jets, slide cut away, etc. Is this a two stroke or four stroke variant. There are distinct differences
between the two carbs variations. I'm confidant someone here can help you get this machine running in
short order.
#1146 Having torn my cartilage trying to start my KSS with a worn carbs. I replaced it with a new one,
result starting first kick. Obviously you could still have problems with your magneto, starting drill, etc.
but a new carbs sounds sensible. In a discussion with Surrey Cycles who sole line of business is Amal
carbs, they recommended the Monobloc as better than the Mk1 concentric. You could fit a MkII
concentric, but you would probably need to have your oil tank moved back. New Monoblocs are
available.
#1147 The carbs is a Mk1 Concentric marked R29/930. The needle jet is 106,main jet 270 and air
screw out 21/2 turns. Jets and needle are all new. Float needle is new. These numbers agree with the
list from Frank Stafford in FT and printed in the batch of tech docs last year. It used to start in 2-3 kicks
but has not been used for some years. I had a long spell of working away from home and other less
acceptable reasons for not using her till I took early retirement and carried out a refurb, mainly to cycle
parts and new electric's. Apart from the Magneto I have not touched the engine as the last major work
was to the head and valves. I cleaned the carbs several times and soaked overnight in fresh petrol to
remove internal deposits, but some passages cannot be reached. Performance when running appears
good and progressive, although I have not tried extended full throttle yet
#1150 I had the same starting problem with my Gilera Saturno 500cc which for some reason is fitted
with an Amal Mk1 Concentric virtually brand new so no wear in it at all. This problem occurred after the
bike had been standing unused for some time. I ended up soaking the entire carbs in carbs cleaner for
about a couple of weeks & it seemed to solve the problem...as you rightly say in your later posting,
there are passageways in that carbs. which are inaccessible & you just have to rely on solvent doing its
job + a strong jet of compressed air. At the best of times Amal Mk1s like a lot of flooding for cold starts
as I've found out after fitting one to my Thruxton!
#1151 I bought a Mikuni kit for my Venom about 8 years ago from Phill Allen. The kit consisted of a
jetted carbs and an adaptor. I have used it since although I fit the correct carbs for special occasions.
My magneto and other related components are in good shape. The starting is extremely reliable. The
only way to not have a first kick start is to forget the fuelcock or completely ignore the Hall Green
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procedure. I use my Velo almost daily and last summer it missed first kick 9 times (I keep count) and
that was my fault because when used to reliable starting you get sloppy, and it still needs a boot, but
not more than an ordinary moped. The tickover is reliable as a steam engine. The drawback with the
Mikuni is that it gives lower top end performance, the top speed is in the low 90s and if rh knee is not
tight to the tank it slows down to about 75. There seems to be an unfavorable airflow around the carbs
inlet on a standard Velo with a standard oil tank, of which Phill warned me when I bought the kit.
#1155 AMAL lists the R930/29 in their 1969-1972 carburettor Settings List as being the right carbs for
Venoms from 1970 on. This variant of the 930 differs from the R930/15 specified for the earlier
Venoms. The difference being the R930/29 does not have a replaceable pilot jet, like the number 30
specified for the R930/15. AMAL initially released the Concentric with a replaceable pilot jet but later
decided to build all 4 stoke variants with a pressed in bush for the pilot jet, while 2 stroke versions
retained the screw in pilot jet. This change made things difficult for folks wishing to tune Concentric
series for applications AMAL had not considered. I found that modifying an existing 1000 series to fix
my '60 Gold Star required changing it from a left hand model to a right hand model and drilling out the
pressed in bush. The change out to a replaceable pilot jet was a rather simple drilling and taping
operation and has made the Gold Star an easy starting and tractable bike. I've since made this
modification to other fixed bush Concentrics and am quite happy with the change. In your case, as this
carbs used to work fine on your Venom, I'd recommend you remove the float bowl, and the pilot air
adjusting screw and direct a stream of compressed air into the passage to blow out and obstructions in
the pilot jet bush. If the carbs is gummed up at all, some carbs cleaner squirted into the passageway
several times a day for 24 hours and then blown out may provide the cleaning required to return the
carbs to its easy starting ways.
#1149 If you are obtaining a good idle with the pilot screw 2 ½ turns out my guess is your slide is OK,
my experience with worn slides is they require the pilot screw be turned all the way in to compensate
for the extra air. Easy to put some grease on the slide to test though, see if it starts better. The Mikuni
slide is about .040 bigger than the Amal and a good fix, done it a few times. It's made of dissimilar
metal too so doesn't wear out the bore so fast.
L #1163 Does anyone know what a 1 3\16 GP carbs would have been used on, I happen to have
one. I picked it up thinking it could be put on a Venom.....any thoughts.
#1171 GP carbs were fitted to some Clubmans in the mid 60's both VR & VM then later on all had
Monobloc and lastly Concentric carbs. The GP is not so nice on the road as a TT though. (and the
Monobloc works just as well as a TT - even on the track!)
#1180 I guess I was attracted to the looks of the GP. I have to agree about the Monobloc they do the
job very nicely. I'll leave the small GP off the bike.
#1168 I have a 1 3\16 GP carbs which I picked up in the hope it may fit on a Venom. I didn’t know that
they could be used for that. DO you have any settings that might apply to a Velo that has a Thruxton
head but other than that is still a Venom well actually viper.......long story.
#1195 The settings given in Burris for 1 3/16 GP are for use with a Venom with megaphone, so prob no
good to you. The Thruxton normally uses a 1 3/8 GP, not sure what effect a 1 3/16 GP would have but
doubt it would be beneficial, I have always stuck to the book with Thruxton motors since they go well
enough for my humble purposes that way.
#1251 Well, I promised to give the settings for my Thruxtonised venom racer ... Amal 1038 with 4 inch
manifold and 3 inch trumpet. 380 Main #3 slide 107 needle jet needle in the middle groove 30 Pilot
CR is approx 10.4 It goes very well, and idles reasonably
L #1616 On the newer Amal Concentric MK1 carbs the pilot jet is pressed in and not accessible or
even visible. How does one know what that pilot jet size is? Also, I notice that Monobloc's are available
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new. Is there any reason to switch a '60 Venom back to a Monobloc?
#1618 Isn't a Monobloc the original fitment for 1960? My '69 had one but I suspect that my Dad fitted it,
as it was considered superior in design and manufacture back then. Recent postings have stated that
they flow better than the Concentric, too. There is a "new" (Spanish?) Monobloc on ZUMAC, it seems
to work very well. The offset float bowl is an interesting feature; when you lean it onto the side stand the
revs pick up, this can be useful at times.
#1620 Yes, Monobloc is original fitment for a '60 Venom but this has been replaced with a concentric
prior to my acquiring the bike. I'm therefore working with what I have. There seem to be a number of
monobloc's for sale on ebay. Can someone explain the numbering nomenclature to me? I wouldn't be
adverse to buying one and rebuilding it even if I needed to get it sleeved.
#1622 Don't waste your time - buy a new one from either Grove, Hitchcock's or Surrey Cycles. By the
time you have reconditioned a carbs it will cost you nearly as much as a new one. Incidentally the
numbering system defines the carbs body (first three numbers) and the numbers after the / define the
application i.e. the bike it is designed for with specific jets, slide, needles etc. If you speak to Grosvenor
Works (as was), Hitchcock's or Surrey Cycles they will tell you that the Monobloc is a much better carbs
than a Concentric, which was built to a price. Size for size its flow is only about 4% better than a TT.
L #1665 I have freshly rebuilt Venom in second overbore, with Viper head (8,5:1 CR) and Amal
MkI1/2 Concentric (lever choke, no plunger) 30mm with air filter. What do you use as settings (needle,
jets...)? I know these are found in tech data base but do you use those? I set my carburetor according
that in data base but I think she runs lean and spits back when idling and dies and accelerates poorly in
my opinion. Maybe I just have to fiddle with pilot air adjustment. But I`m interested to know what
different settings do you use. Exhaust is Clubman style.
#1691 It's commonly said that the carburettor settings that were indicated in the Haynes book and other
technical books are now obsolete since we're all using lead-free petrol. It is recommended to ride with a
richer mix. I'm doing this with a MSS which has been equipped with the same carbs as yours (pilot jet
270, as for a Venom), the plug is always OK and cold starting is second kick. If you don't do this, you're
at risk of overheating.
L #2013 I'm doing a tune up and other maintenance on a friends Venom Clubman. It has a worn
monobloc and my friend is interested in replacing the carbs. I had a mk1 concentric on my VMT, and it
was ok, but... Can someone suggest the best replacement carbs model and size and recommended
base jet sizes and settings. The machine has stock exhaust, 9:1 CR, BTH mag with manual control.
We'd like something that will enhance starting and slow to mid range running, not WOT.
#2022 A non-technical response based solely on lots of miles on Velos / learning from my own
mistakes. Either new Monobloc or new Concentric Mk1 will give good performance for the road if set up
properly and the machine is otherwise OK etc. Set-up info, jet sizes and so on are readily available in
most Velo books - and prob in the archives on this site. The Rod Burris book on the M series is not
without errors but is readily available and gives a useful table of carbs settings etc. I’ve had a few VM's
VR's and a VMT over the years and find they all run slightly differently/better/worse on slightly different
settings - really I think it depends on just how worn out things are ;-) Best advice is to stick with std
factory recommended monobloc/concentric settings to start with and then fine tune to suit your machine
/ your riding requirements - jets, slides etc relatively inexpensive. I think if I were starting from scratch
and had to choose one carbs only I might go for a new Monobloc but for real world use I doubt there is
much in it. (Make sure you’ve got a plug to suit the type of riding you do and of course get that ignition
timing spot on).
#2039 A number of the carbs settings in the Burris book are incorrect. I believe, but cannot confirm that
those on the technical site are correct. I have cross referenced them against original Amal lists. I spoke
to the technical manager at Grosvenor Works when they manufactured Amal carbs. He confirmed the
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monobloc was the best all round carbs, providing you are not using it at silly angles.
L #2071 I have a 1961 Venom Clubmans fitted with an Amal Mk2 Concentric and I am unable to
determine where the hand lever should be for enrichment, should it be under tension or fully forward for
enrichment? Alternatively what position is off?
#2079 The Mk2 Concentric has a cold start system similar to most modern Japanese carbs, not an air
slide in the main throat of the carbs. The choke on these carbs is ON when the cable is pulled, i.e. the
choke plunger is lifted. For normal running the cable should be slack. This is opposite to the Mk1
instrument but similar I believe to the "Mk1½" which has no tickler but has the Jap type sold start circuit
in its place.
L #2209 Another very useful chemical available from Yamaha is their carburetor cleaner, P/N
ACC-CARBC-LE-NR. This is a powerful liquid cleaner that is diluted 1:3 with gasoline and placed
directly into the float chamber via the fuel line, then drained after one hour. It removes varnish and
other dried fuel residue. Also paint, etc.; I use a 50cc catheter syringe to minimize spills.
L #2303 My Mk I LE "Carburettor of Many Jets" has lots of brown discoloration on the outside.
Can anyone suggest any way of getting it back like new? It's a very small carbs with lots of crevices.
I've heard about some liquid cleaner you can buy. You drop the carbs in and let it bubble away for a
certain time. Another option might be to paint it. My MAC carbs is painted a sort of silver-grey. I didn't
do this so don't know what kind of paint it is. Is there a special paint for this kind of application? (Looks
like the same stuff that's on the cylinder.)
#2307 Here in the states we refer to it as "boiling" a carbs and you can pick up a carbs cleaning kit at
any auto parts store. It consists of a lidded one gallon can with solution and a parts basket. Costs less
than $10.00. I purchased one years ago when I was restoring a very grungy BSA M20 and found that it
was great for general parts cleaning, although I would be very hesitant to put a carbs back into it after it
was used for other parts. Stay away from any cleaners that contain phosphoric acid - you're carbs will
turn into something that resembles gelatin.
#2309 I have seen carbs that have been boiled in water with Ariel Biological Washing liquid (aka:
enzyme detergent), the result while not perfect was good. Vapour blasting is the only way to getting
your carbs to look as new.
#2317See below - its from somewhere on the great WWW: Acid Cleaners Acids help remove hard
water deposits. Some acid cleaners help remove discoloration from aluminum, brass, bronze, and
copper. Other acids remove iron rust stains. Acids are typically found in toilet bowl cleaners, rust
removers, metal cleaners, and kitchen and bath cleaners that remove mineral products. White vinegar,
a weak acid, is about 5 percent acetic acid. It may remove hard water deposits from glass, rust stains
from sinks, and tarnish from brass and copper. b.. Lemon juice, another weak acid, contains citric acid,
which can be used in much the same way as vinegar. c.. Oxalic acid is effective as a rust remover. d..
Phosphoric acid is often found in cleaning products that remove hard water deposits. e.. Hydrochloric
and sulfuric acids are sometimes used in diluted concentrations in toilet bowl cleaners. Rust stains
present a special problem on plumbing fixtures. Commercial rust removers contain oxalic acid. If you
purchase oxalic acid at full strength, dilute it with 10 parts water. Follow all precautions when using
oxalic acid, as this is a highly toxic product. A commercial product like ZUD may be effective on rust
stains because it contains oxalic acid. When surfaces have become rough or pitted from repeated
scrubbings with an abrasive cleaner, ZUD or a similar product may be mixed with water to form a paste
and left standing on the stain for several minutes, then rinsed off. For fixtures that are not acid resistant,
clean with trisodium phosphate to remove the rust. Cream of tartar, a mild acid, may be mixed with
water to form a paste rust remover.
#2329 "Wonder Wheels" sold in motor accessory shops works well on aluminium carburettor bodies
(tried and tested) but works best if all oily deposits are removed first. Oxalic acid is very good for
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emoving rust stains even on cloth, but chemists won't now sell it to the public. However a good source
is Teak Brightener/Cleaner which normally contains oxalic acid in enough concentrate for most tasks
(find in boats' chandlers or hardware stores- check contents on bottle)
#2306 The discoloration on the outsides of carbs, taps, & petrol things in general is easily removed by
using methylated spirits. As it evaporates quickly, apply liberally with a small piece of cloth. it is not
always fully effective on the internal parts. An old toothbrush is the obvious choice, but some electric
shavers have small bristle brushes, used for cleaning, an old one of these is good for getting into the
crevices.
L #2386 What does the number after the slash on a monobloc carb refer to? Say a 389/96. What
does the 96 refer to?
#2387 A code about the slide/needlejet/main jet that was originally fitted from Amal-factory.
#2388 So who has the code? Is it available? I see various motorcycle manufactures specifying say a
389/46 as original equipment. Is the code published?
#2389 Yes, an AMAL bulletin from the period will list all of the machines covered, and the specifications
for each one of the /numbers. Bruce Main-Smith and the usual suspects may have these bulletins. A
389/46 will have been fitted as: original equipment on BSA A10 Super Road Rocket, for 1960 & 61
using a 389/003 mixing body, 1 5/32" choke, 389/057 jet block, 420 main jet, 25 pilot, #3 slide, needle
in position #2, .106 needle jet, and tun less air cleaner. Date from AMAL list No. 601/3 for 1955 - 1961
motorcycles. Please note, any 389 carbs with a 1 5/32" bore, fitted with a 1 5/32" jet block can be
assembled to become the same as the 389/46 as manufactured. For example, a Matchless G80 built
between 1955 - 1961, was fitted with a 389/1 with the BSA sized mixing body and jet block, I.E. 1 5/32".
In this instance, the G80 carbs with only a few parts changed would work on the BSA A10.
L #2521 Does anyone on this list know where to get Gardner carbs, info, parts, etc?
#2522 Try Summerfield Engineering, they should have contact details or poss supply direct
(UK) 01773 835977
#2557 I have just arrived back from the Australian Classic Racing Championships and spotted your
request. You can contact Ron Gardner as follows: The Gardner Carburettor Company Limited 12
Slimbridge Road, Burgess Hill. West Sussex. RH15 8QE. UK Phone : (44) 01444233485
L #2864 Hello, I am trying to complete my Velo project. I started with a 59 swing arm frame a 68
endurance engine, I bought a thruxton head and intake new amal con. carbs. I bought the correct
pushrods, set up the engine for 9to1 compr. did the valve timing following advice from dave smith. He
sold the carbs to me and said it was jetted very close. I have converted to electronic battery ignition and
timed to dave’s advice. This carbs is a 1036 on body of carbs. I have a correct velocity stack on carbs.
Starting the bike is quite the project, when I do get it running it runs very rich I took the jets out of my
500cc bsa single and tried them in this carbs same thing. Any ideas would be helpful. Next problem oil
from engine fills the primary. I have Bought thruxton oil tank new lines filter conversion. I have very
good flow on return. In 5 miles of running it fills primary with 1\2 pint of oil. This bike project is driving
me nuts. I have worked on bikes for 30 years, I am a mechanic by trade and I always figured things out
this bike has me at a disadvantage. Any ideas?
#2877 Original Thruxton Conc 1000 series carbs should be R1036/4 (D Gibbison) Main jet 320, pilot jet
30, slide #3, needle pos #1 and needle jet 106. Common reasons for rich-running are incorrect idle
mixture and worn needle/needle jet. When carbs gets worn it also affects the needle/needle jet with
resulting rich-running at part load. Countermeasures are dropping the needle (step one), and replacing
needle/needle jet (step two). Check that carbs doesn’t vibrate which might upset the function of the
floater needle and cause high level/flooding.
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#2884 My VMT ( 519 )is fitted with a Mk 1 concentric stamped 1036 R1 on the body that came fitted to
the bike . I have the GP but have never tried it as I figured the Concentric would be easier to set up . It
has 320 main and 30pilot jets . a 2 ½ slide and 106 needle jet . There's no choke . I adjusted the
needle position to give the best pick up as in pos 1 it was hesitant under acceleration ( I have a feeling
it is on pos 3 , it's a new needle ) It was difficult at first until I found the 'knack ' to starting . From cold I
have to flood it really well and with Ignition retarded just a tad it will start easily . If it doesn’t fire I have
to flood it up again . Warm it starts first or second swing using the velo 'ritual '. In deference to my age
and maintenance , I fitted a center stand and put it on the stand to get a good swing . I've always felt it
is over rich at tick over/ just opening settings , and it took a while and riding adjustments to get it to a
setting where I'm satisfied .It ticks over OK if a little faster than a std Venom and if I set it to a too slow
tick over it will sometimes stop which is inconvenient. The Thruxton was meant to go , so I'm happy to
trade mid range performance against a good tickover.
#2886 If you open up the size of the air correction jet, you'll get rid of that slow speed richness. The
1036 carbs was made in Spain specifically for use on the big two strokes, which require richness at that
point. The air correction jet is directly under and parallel to the main 36 MM bore, the middle of the
three drillings, and you'll find that it is about .075" in size at the inner end and should be .100"-.140" in
order to allow more air entry to the upper end of the needle jet, thereby leaning it out. Go slow with a
set of number drills until you reach optimum results, as it's hard to replace metal that you have been
drilled out. This adjustment variably affects the mixture from barely above idle to about half throttle with
nearly the entire effect at the closed throttle point. It works in similar manner to the pilot jet in that the jet
is sized for a slightly rich condition and then air is added to adjust the mixture to a more correct ratio, it
being easier to moderate air flow than fuel flow.
#2901 Not only the air correction hole must be increased, also the following changes are necessary :
Spray tube must be of cylindrical type without cutaway, needle jet must have bleed hole, main jet holder
must be of longer 4 stroke type, jet needle must have 2 identification grooves at the top. The story goes
that there were never any 4 stroke 1000 Concentrics made. As I never found a 4 stroke 1000 series
Concentric either, only 2 stroke types, I really wonder if the Velocette factory on their own converted the
2 stroke types into 4 strokes. Was there a guy drilling by hand all the air correction holes and changing
all the internals?? Or did they get them converted by the Amal factory ? Any info would be appreciated.
#2907 Is this of any help? www.ingfatrygg.se/amal.html
#2911 A useful reference guide on Amal carbs. www.britishonly.com/tech/tips/mark1.asp
L #2921 I was reading the article in Classic Bike Jan 04 regarding carburetors. In the article it
recommends "where the flange has been bowed through over tightening .. then grind it flat on a flat
plate". It also says that if the body is distorted "bore oversize and sleeve". Well my Mk1 concentric was
suffering from bowed flange and distorted body making the slide stick. I took it to Rabers in San Jose,
and they were able to "straighten it" so that the flange was flat and the slider also moves freely. It turns
out that in many cases the two problems are linked. Rabers have very simple jig to correct this. They
charged a nominal amount and it took less than 30 minutes. I took a look at the jig and it consists of two
parts. One piece is an almost flat plate with a 15 thou concave dip with a hole through the middle
(about 3/8inch). This goes up against the carbs flange. The other piece is a round bar that just fits fairly
tightly within carburetor body. This also has a hole through which allows a bolt to be pushed through
throat of the carbs and though the hole in the middle of the flat with the concave surface mentioned
above. The procedure is to tighten the bolt and leave it for a few minutes – and magic the whole thing is
straightened. I hadn't heard of this before. I thought other might be interested. The trick I should
imagine is making the plate with the 15 thou concave. I have no idea how this might be done, but I am
not a machine shop expert.
L #3331 looking to fit a new carbs to my standard 62 Venom. Do I fit standard Monobloc or as
someone recommended a Concentric. Observations appreciated.
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#3332 I fitted a new concentric and it transformed the bike! However a new Mono might have improved
things also because the old one appeared very worn on inspection. I suppose it depends on finances(
new concentric is cheaper) and how original you want things!
#3334 Common consensus is that a Monobloc is a much better carbs than the Mk 1 Concentric. This
was also supported through various conversations I have had with a number of people in the know,
including a one time Technical Manager at Amals.
#3345 I always figured that the Monobloc had to be jetted richer than the Concentric, by about ten
sizes, due to the greater distance that the fuel must be lifted from the bowl to the discharge nozzle.
L #5290 My Venom has a monobloc carbs with standard Venom set up. The bikes performance is
good with no problems running or starting etc. I'm using a Campion N3C plug, which is the same as
when I purchased to machine. The only thing is that each time I have removed the head (for various
reasons) there has always been a heavy build up of carbon. The plugs general colour would indicate
some richness in the mixture, but not excessive. I would think that only a small adjustment somewhere
would improve combustion. Should I drop the needle a notch (currently set at fourth notch) or would a
different plug help?
#5291Which kind of carbon is it? Hard carbon from Petrol or Soft carbon from Lub. oil.
#5293 Most definitely hard (used a needle gun, cold chisel and lump hammer etc. to get it off). The bike
doesn't smoke at all and the bore is nice and clean.
#5294 Suggest leaving the needle and using a N0. 4 or 4 ½ Throttle slide. We are on a 4 and have a 4
½ available. We also run with a 330 main jet as the book.
L #3688 I live at the beach/ocean in Southern California and want an air cleaner. My automobile
air cleaners trap LOTS of sand and I don't want sand in my bike intake. I can't find any standard air
cleaners for a '55 MSS Velo. Suggestions? I would prefer a 'standard' look but want to ride the bike.
#3689 Grove Classic Motorcycles had a number of these in stock a few months ago.
#3690 There were two versions of the Velo-built filter: "gasworks" carbs (i.e. pre-Monobloc) and
Monobloc. I've been told the pre-Monobloc fits the Concentric. Can anybody confirm this?
#3691 I have an Amal 276 type carburetor with the side float.
#3693 The 276 side float ("gasworks") carbs was normally not used after 1954, unless maybe Velo had
shelves to empty. So far as I know, the later Monobloc filter doesn't fit the Gasworks- I talking about
Velo-made filters which maybe aren't the best for fine particles. The Monobloc filter doesn't fit the
Gasworks. Nor (I think) does it fit the Concentric, but maybe perhaps the Gasworks filter fits the
Concentric.
#3704 I ran a K&N air filter on a 1036 concentric fitted to a VMT. The filter worked well. K&N make
many many sizes, and you should be able to get one that has a inlet flange that will clamp to the inlet
threads on the carbs. On the VMT the carbs is set quite a ways back from the head, and as a result is
close to the frame tube near the front of the saddle. I looked at a number of filter sizes and offsets and
found a tapered cleaner that fit nicely. The K&N is a modern device, designed for periodic cleaning and
reuse. If you find one with a black end, rather than the chrome ones, it doesn't look too bad on a Velo,
and will do wonders versus no filter at all. A good solution for a bike to be ridden.
L #3860 I have received my Thruxton just a month ago, and the mixture is much too rich the bike
is running with a GP2 carburettor. I have checked all the jets no: 25, 109 and 280), needle (position 4)
and slide no: 3) for correct size and also adjusted the float chamber to a little below the recommended
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position. What can be the problem? The ignition should be a little higher, I believe. What is the correct
setting (timing). What is the correct position for the air control level on a hot engine? It seems that the
handle in forward position is giving the best result.
#3861 You may find that the carbs is weak not rich. If the air slide is closed (forward) this indicates
weak mixture. Is the slide worn? Ignition should be 38 degrees BTDC as book, probably 36 degs.
would be better on current fuel. Your carbs settings are as book. Check the float chamber level
carefully, this has a big effect.
#3866 When supplied new in Sydney Australia in March 1967, VMT457 and VMT458 were both fitted
with no3 slides. Dennis Quinlan, first owner of 458 soon changed to a No4 slide and the running rich
problem was solved. My Thruxton, VMT457 has run a No4 for the past 30 years of my ownership.
Dennis wrote to the factory and advised them of the problem but I don't know if they corrected it in later
bikes supplied with a GP carbs, or in any updates to the red book - apparently not. So I don't
think the carbs is weak - change the slide to a No4 by filing away the leading edge by 1/16" (I think! can
someone in authority please confirm) and the problem should be solved.
#3867 I agree it is 1/16, so a 4 slide has 1/4 inch cut away. My VMT would never run with a 3 slide
either, 4 and even 5 needed. Also too rich with the rich needle (has about 3/4 inch of taper) even on the
leanest setting and new jet. I used the lean needle which is straight for all but the last 1/4 inch. This on
US petrol.
L #4140 I am thinking of fitting a Mikuni carbs to my Venom. Information I received from the
supplier stated that the 3 gallon petrol tank needs to be raised by an inch and a half at the rear to fit it.
Has anyone carried out this modification and could they detail how the tank was raised and did it spoil
the symmetry of the bike ? Also was there a noticeable improvement in performance ?
#4146 I have used a 30mm Mikuni kit for 6 years on my Venom Clubman with the big tank. There's no
need to change the tank in any way if a standard Venom head is used. I had a problem with the airflow
at the inlet, it's a known fact I think that the performance is dependant on the driver holding his right
knee to the tank. I fixed this with a homemade inlet extension of about an inch which is not conical but
cylindrical. The top end performance was not improved but it's always a first kick starter and the idle is
reliable as a steamboat.
#4149 I have just fitted a Mikuni, supplied by Allens, to my Thruxton. The bloody thing doesn't really fit
at all. I have had to squeeze it in and it presses with great force on the oil tank and underside of the
Thruxton petrol tank. It WOULD fit if the finned aluminium inlet spacer was not the full 4 inches long
that it is. Does anyone know how I can get hold of a slightly shorter inlet piece (say 3 inches?) Also, at
a standstill the petrol pours out of the little plastic breather pipes. Oh woe is me!!
#4158 4 inches - thats ½ inch longer than standard. (size matters) Not sure of the mikuni fitting but I
have a 3.5 inch inlet manifold going spare for a stub fitting Mk2 Concentric (i.e. rubber mounted as I
expect the Mikuni is) for a Thruxton. Its not an original cast item but a 'machined from solid alloy'
modern thing.
#4143 Now, raising the rear of a small tank and inch and a half would be atrocious! Fortunately that's
not necessary. My Venom had a 38mm Mikuni on it for some time that fit (albeit snugly) under the small
tank without raising. I have a 36mm (1036) Amal Concentric on it now which also fits fine.
L #4430 I recently bought a 1936 rigid mac now need to set the carbs (a new concentric) up as it
did seem to be running lean going by the colour of the plug, I had replaced the old mk1 concentric fitted
with a new one and need to set it up correctly this time!! jet size is 170 ,the new needle seemed to be
too short so replaced it with the original one but I do not know what the correct length should be any
advice on setting up would be appreciated thanks.
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#4432 Be sure to use a .106" needle jet and a needle with two identifier rings above the three grooves
for the needle clip.
L #4416 I have a Venom fitted with an Amal 389 carbs of uncertain age (old). Whilst the bike goes
really well, tickover speed can vary and be a little unreliable when the engine's hot. I have toyed with
fitting a Mikuni to it, but am put off a little because the information supplied by Allens Ltd state that the 3
gallon tank has to be raised at the rear by one and a half inches to clear it. Can anyone confirm that ? If
the Mikuni is not possible then I will fit a new Amal. What's the best advice-a Monobloc again or a Mk 1
or a Mk 2 Concentric?
#4417 Just checked with a friend who has a Mikuni carbs fitted to his Venom that has a 3 gal tank. He's
had the underside of the tank modified rather than jack up the tank to provide clearance in order to fit
an air filter on his carbs. He reckons that if you are intending to use just a bellmouth then you should
get away without any need to jack up or alter the tank. I've used a Mk 2 concentric on my Venom with
very satisfactory results, but never tried a monobloc or Mk1 concentric, just that the Mk 2 came my way
very cheaply, so I bought it.
#4419 I have used the Mark 1 Concentric carbs on my 1963 Venom Clubman for years and have
absolutely no trouble at all as long as the timing is spot on.
#4420 I recently rebuilt the carbs on my Venom which was the 389 type. I initially tried to cut the cost by
replacing jets and slide but this didn’t prove 100% successful as it continued to run on the rich side.
Eventually I succumbed and replaced the body and jet block too which basically meant I had a
complete new carbs which transformed the running. The only problem I found was that to get it to run
OK on pilot I had to reduce the jet from a 30 to a 20. 25 was still too rich. Once this was done all
appears OK and it runs well now albeit I still think slightly rich on the needle. I am loathed to lower the
needle a notch as I have read with interest the cases of holed pistons and weak mixtures. I do note that
the small red Owners Handbook, mine being the 10th edition dated August 1967 says "Normally the
needle clip is in the middle groove" All my other publications including the official Service Manual state
the No4 groove. Starting is not a problem, second/third kick, sometimes even first
L # 4922 Can someone please tell me the difference between a smooth bore Mk II Concentric
and an 'ordinary' Mk II Concentric? Surrey Cycles tell me that for quick indentifcation the smooth bore
does not have a throttle stop screw and that inside the smoothbore there is a jet block and hollow slide.
But what is the difference in terms of performance and suchlike? Is there a good practical reason for
fitting a (more expensive) smooth bore?
# 4923 If you're going to race the machine the gas flow through a smooth bore is much improved over
that of an "ordinary" carb at wide open throttle so you can expect a small improvement in performance,
but for normal street use you are unlikely to notice any real difference.
L # 5342 Can someone out there that has a Mikuni carb let me have some details. I phoned
Allens who will supply a 30mm VM Mikuni jetted for my Venom but only offer a 5" round pancake filter.
Has anyone fitted this carb with a K@N type airfilter? I have the late Clubman's tank that has the
clearance for the GP but without the cutout on the side. Your experience of the carb would also be
appreciated.
# 5347 I run a vm30 mikuni on my Venom. It's very good. Much much better then a concentric, which
is only suitable for the scrapbin. Biggest mistake of my motorriding carrier fitting a concentric. Idling is
fantastic with the Mikuni, never misses one revolution. Throttle action is very light without jamming
(thank god, I had a few narrow escapes with amals on that front) and top revs are there plenty and easy
adjustable. Its is light of weight being aluminum instead of mazac and not too expensive to buy. It is a
tight fit underneath the tank but possible. I run a 175 main jet and a 22.5 pilot ( I used a 25 pilot for a
while which is also satisfactory but was more difficult starting in my case, because for the choke to work
the slide has to be almost closed, although snap action response is a little better). Needle on 4th
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groove. If you like to know which slide and needle etc it has, I have to take apart. So that will take some
time. Let me know if you want to.
# 5372 I'll take the scrap-bin concentric, but shouldn't you have had a Monobloc on that instead of a
Concentric?
# 5849 If it it at all possible could you let me know the slide and needle that you use? also the position
on the needle. It would make the initial set up easier with this information. Did you know you can get
the Mikuni VM carb Tuning manual off the net for free? www.mikuni.com/pdf/vmmanual.pdf
# 5868 I use on my Venom a Mikuni VM 30 with: Slide: 2.0 Needle: 5FL14 Needle position: 4e from top
Main: 175 Pilot: 22,5
# 5979 Is it possible could you let me know the needle jet "size & type" you use with your needle
5FL14, on the VM 30? I bought a Mikuni VM 30 from Sudco in the US some time back, asked it to be
jetted to Velo venom specs. I didn't find them very helpfull. In fact a friend ordered from them about
same time - the jet specs were completely different to mine! Mikuni needle jets for the VM 30 come in
two basic types: (a) series "176" (bleed type, with a group of small air holes drilled down the side)- used
on 4-strokes and (b) series "159" (primary type, (no side holes, but has a raise shield on top, which
protrudes into the main air flow) used on 2- strokes. The jet size is a alpha-numeral system, eg:
N-0,N-2 to.... R-6,R-8 So the jet should be marked something like..."176 & O-4" Sorry if all this is boring
for everyone, but I thought it might be helpfull. (It was to me when i found this out.) Someone asked
about K&N filters for the Mikuni, try these: www.knfilterchargers.com/
# 5980 A friend has fitted a Mikuni supplied by Allens. He has played around with the settings and
ended up not knowing how the carb was supplied. He requested the original setup from Allens, the
Mikuni supplier for classic bikes, especially Venoms, his reply follows."I have listed the settings we use:
Main jet: 300-330 Pilot Jet 40 Needle Jet 176-P-0 or P-2 Jet Needle 5L1-4 Thottle Valve 2.0 "
# 5994 The following are the standard settings for the Venom: Needle Jet 176-P-0 or P-2 Jet Needle
5L1-4 I assume this to be the 5FL15 though it was listed 5L1-4.
# 5995 Interesting that you have main jet at 300/330 and pilot jet 40 and both the others have 175 and
pilot jet 22.5 Both wide differences eh? My setting are: (from Sudco) Main jet: 240/250 Pilot jet: 35
Needle jet: 176 - O-6 jet needle: 5L1 Throttle valve: 2.0 Needle position: 3rd from top
# 6001 Are you sure the other carb settings were for a VM30? Allens say that they supply 240-260
Main jet and 25 Pilot jet on the VM36 used on the Thruxton, but use the setting listed above for the
Venom using VM30.
# 6075 The needle jet is: P-5, type 159
# 5357 I have a K&N filter on my Velo/Mikuni. It is a model R-1260 which is about 4" long which
probably won't do you much good. I have the gas tank with the cutout. My oil tank (not a Thruxton
variety) has been moved slightly aft and down when the m/c was fitted with a screw off oil filter. This
gave me the room to fit the long filter. I spent some time with the local m/c shop at the time and their
catalogs going over sizes and shapes to find the largest filter I could find. On a side note with K&N's. I
did the same research when I was looking for filters for my Honda CB160 race m/c 10 years ago to find
the largest ones again. Then I built a second race m/c for my wife and used a different filter that was
smaller and tapered rather than straight. This was due to availability and the next race date. Both m/c's
ran the same on the dyno and on the track.
# 5358 I have used a Mikuni, it is functionally superior in many ways. The heavy slide, spigot mounting,
and enrichening circuit are good examples. With the standard late Venom fuel and oil tanks only the
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smallish Triumph twin style K&N will fit. It is a bit short on filter area. I use a Uni foam filter, this is
flexible and fits easily. They are available in diameters in 1/8 inch increments to fit virtually any
carburetor, including the sleeved and bored Concentric on my Venom now. I even fitted one to our '51
rigid MAC. Ran an "S" shaped piece of radiator hose under the seat from carb to filter for the ride up
Pike's Peak. Didn't hurt performance, even at 14,000 feet.
L # 5392 I've been reading the discussion of Amal carbs. My Venom Clubman has a 930
Concentric, and I now experience the dreaded "stuck slide" on occasion. This is quite inconvenient,
with no kill switch fitted, and the ignition key somewhere behind my left knee. As mentioned in one of
the posts, I attacked the slide with emory cloth, but couldn't really find the high spot. Now I realize that I
probably have a distorted bore, so what to do? I bought a new Amal, but it doesn't look right to me, with
plastic parts, and appears to be even more primitive than the original. So what is my best course of
action? I've heard of folks that will bore the carb and sleeve the slide. Is that the way to go, or should I
just pop the new one on and hope it looks vintage after a time?
# 5393 Get a new monobloc, its more original and you will not suffer from the sticking slide problem. I
had two concentrics sleeved for a bike I was building and eventually went back to two new monoblocs
with better results The concentric was made "down to a price" on the behest of the BSA group.
# 5396 The monobloc was fitted to Venoms until what year? I have a later one, and it came new with
the concentric. How come the monoblocs don't succumb to this problem? Heavier casting? I confess
I've likely been guilty of overtightening the flange nuts over the years... parts on singles do tend to
vibrate off now and then.
# 5401 Triumph Bonnevilles were first fitted with concenmtrics on the 1968. Therefore I suspect they
became available from then?. I swear by the monobloc over theMk1 concentric for all the previously
stated reasons. The Mk2 is much better made but I stil prefer the simplicity of the monobloic, ease of
tuning and spares availability over ANYTHING else
# 5455 Mk I concentrics were launched by Amal in August 1966, however in reality they probably didn't
start to ship on bikes until existing stocks were used up in 1967. Regarding which is the best carb, I
spoke to the Technical Director of Amal a number of years ago and in his opinion the Monobloc was a
much better carb than the Mk1 concentric, providing you weren't trying to use it on a two stroke (which
along with cost was the reason they introduced the Concentric). The Monobloc only flowed 1.5% less
than a TT carb (but aesthetically looked 98.5% worse). We didn't talk about the merits of the Mk1 vs.
Mk11.
# 5466 Just one thing to check when you fit a Concentric to a Velo is that you have a 3/8" thick
insulator between the carb and head. Not only does this provide the necessary heat insulation but it
also keeps the top of the carb body clear of the head. If omitted, the carb is just close enough to cause
a small amount of distortion when it's secured, which of course causes the slide to stick at full open.
# 5495 My Venom just has a thin gasket, and, in fact, the carb does touch the head, so I'm guessing
this is my problem. Is this insulator a generic Amal part, or do I make one?
# 5498 You can buy them from about 1/8" to 1/2" inch.
# 5394 Put your slide in the carb and pull it in and out a few times and make a note of where it is
picking up in the stack. You will see where the slide is picking up and marking the slide. Mark the
outside of the carb with a felt tip pen where the slide is picking up. Bring the slide up to level with the
top of the carb and using some alloy protectors in a vice, put the top of the carb in the vice with the
slide in it come in sideways on the vice and where the carb is picking up, put the carb in the vice and
gently tweak the vice. Take the carb out of the vice and see how the slide comes out. if it is still sticking,
you will have to repeat and tweak the vice a little harder. What you are doing is putting the top of the
carb, back into shape. You should end up with a slide that just falls out of the carb. emerying the slide
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is a waste of time, because you are not sorting out the stack distortion, and this is where the problem
lies. I have done this repair a few times and it works well. Take care not to overtighten the flange nuts
when refitting. Take some good advice and fit a stub and fit a rubber mounted stub fitting carb. who
gives a toss if its not original. I have a 30mm mk1 and a half stub fitting carb on my clubman and it
starts and runs, spot on. I fitted a amal velocity stack and I filed a flat on the bottom of it and I put a pad
of formica on top of the oil tank, and it rests on that and it looks great. plus no tickler to spew fuel and a
choke that is on for on and off for off. i.e. slack wire off.
# 5395 I had a Concentric Mk1 straightened by Rabers in San Jose. The jig they use to straighten the
carb basically straightens the bow in the flange which magically removes distortion from the bore, and
the slider then becomes free. The problem of a sticking sliders is as a result of over tightening the
flange nuts. The rule of thumb is that you should still be able to move the carb after tightening the
flange nuts. I was told that the jig was made by someone in the US Midwest, so there are probably
more of them out there. If you cant find someone who can do this, make sure when you install the new
carb do not fully tighten the nuts or you will end up with another piece of scrap
# 5496 The Velo parts book calls up part number M180/2 - Carburettor flange gasket, (heating
insulating). I don't know whether this is the proper item though. The description would hint that it is, but
the club spares list it as a "Gasket, carb to cyl head" which suggests that the item they sell is a plain
gasket. You would have to check with the club. I couldn't find it in Grove's list. I actually made my own
from a piece of Tufnol 3/8" sheet. Simple enough to bore three holes and shape to suit the outer
contours of the flange, then carefully blend the main hole to suit the carb and cylinder head perfectly on
either side. You will need a paper gasket on the head side unless you have the facility to cut an O-ring
groove on that side of the insulator, the carb has its own O-ring of course.
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D.2. Fuels -
L #180 I have not used my 1947 iron MSS (called "Eugene", after its designer) much in the last
three years or so since leaded fuel pretty much vanished. On pump unleaded (95) it seems to run
ragged at revs and much hotter (straw exhaust pipe for the first time ever - I do not thrash it as a rule).
Does any one out there have any experience of carburation with UL fuel? Do I need to re-jet? The
valve seat recession thing can be dealt with by additives and I cannot believe that I need an octane
booster with the MSS at around 6 to 1 CR! All ideas gratefully received.
#183 We Veloist here in West OZ have had all sorts of problems with the lead replacement fuel which
replaced the old "Standard" fuel. Plugs foul after only a couple of miles, engines run roughly,
impossible to time the engine - Yech! The only solutions we have found to work are either using the
combined octane booster/upper cylinder additives in conjunction with the highest octane rated
Unleaded fuel we can get, called Premium Unleaded down here, which works well. It certainly does not
work using the additives with "ordinary" unleaded fuel. The best solution and one that makes the old
girls run as sweet as can be is to use Avgas (100 Octane aviation/racing fuel) at a ratio of about 25%
Avgas to every tank of unleaded fuel. This has worked for all our machines from pre-war to Thruxton
#184 RE; the unleaded fuel debate. We in the USA have had unleaded fuel for about 12 years, and I
am happy to report that it required very, very few changes to jetting or valve seats. There was as much
fuss here at the time of the switch as you are experiencing, which all pretty much went away with time.
Yes, the octane is lower, so no more 10:1 pistons, we find 9:1 the limit on a Velo. Some (VERY FEW)
bikes have had problems with valve seat recession, in fact the only bike I ever consistently heard with
this problem are BMW R 100's of a certain year. I don't see why a bike with an iron head and 7:1
piston would need Avgas, it will run hot certainly. Some unleaded fuel has extra alcohol here, which
can make some bikes run lean, a simple adjustment is all that's needed. Don't panic, everything will be
just fine.
#421 fill up with Shell Optimax, they make some ridiculous claims - however it has transformed my
Venom, no more pinking the acceleration and performance is back to what it was on 5*.
L #438 It’s a well known fact that petrol does go off rapidly, I find even two month old petrol will
hamper starting. There is even an additive to add to lawnmower petrol to stop it going off.
#439 Thanks for the note. I've often heard people say that petrol `goes off' but have never experienced
this. Even when the bikes have been sat in the garage over the winter they don't seem to have any fuel
problems. Maybe in the colder weather the volatiles don't evaporate so quickly. Anyway, I'll get a fresh
gallon tonight and see what happens.
#440 Don't know if it is available in the U.K., or if you have your own version there, but there is a fuel
stabilizer here in the States called Stabil, which works well in diesel and pump gasoline. I have literally
used 6 month old gas that has been treated with it, and the vehicles ran fine. Might be worth looking
into. I have the feeling the quality of pump petrol in your geographical location is poorer in quality then
what we have here. My impression, at least..
#443 Here in the USA, if fuel is in a vented tank, such as a motorcycle tank, and sits a year of so, you
can't light it with a match! Fresh fuel and a new plug should do it.
L #908 In USA, and probably in Canada too, the quoted Octane number is (M+R)/2. Therefore
what is 92 octane in USA is probably a close equivalent to 95-96 RON= in UK, and the 97 (R+M)/2
must be around 100 RON or so. I thought you'd like to know that! It does cause confusion.
#909 If that is correct then North American 97 grade fuel should be the stuff to use without a doubt. If
Michael has been running on the lower grade option without backing off the ignition timing then this is
highly likely to be the cause of his holed piston don't you think?
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#916 Quite right. The top grade should be used in Vipers and Venoms. Lower grades are OK for MACs
and MSSs in standard trim, but their use with the higher CRs will cause pinking and eventually holed
pistons. Using the wrong spark plug can do this too, by causing pre-ignition. NGK B8ES or harder is
necessary for VM etc.
#919 I always run Sunoco grade 94 (they claim is the highest available in Canada) Is Aviation fuel an
option?
#926 Personally I wouldn't recommend using Avgas. Although the normal rating is 100LL (100 Octane
Low Lead) my experience with an Aprilia 250 GP bike demonstrated that this is not a cure all for
detonation problems. This machine was bought new direct from the factory in '90 for use in the British
and European championships and came with the usual amount of technical documentation and help
that one gets from an Italian factory - not a lot! Believing that we ought to be running high octane race
fuel which was unobtainable in the UK at the time and since the rules on fuel were being tightened up,
on advice from BP we began running the machine on Super unleaded 98 RON pump fuel (BP claimed
at the time that their pump average for this fuel was 99 RON). Since this was a two-stroke machine we
mistakenly believed that the lack of lead shouldn't be a problem. Within a dozen or so laps of Cadwell
on the first time out we had a holed piston. Consultation with people in the know suggested that
perhaps we ought to be running leaded fuel so the next time out we ran a 50/50 mix of 4* leaded fuel
and Avgas, a common brew in racing use at the time. This stopped us holing pistons but we continued
to have a small amount of detonation erosion on the top of the pistons and the rider always reported
poor carburation whatever jetting settings we ran. I gradually increased the proportion of Avgas until we
were eventually running 100% of the stuff but never completely got rid of the det damage and it
appeared that the carburation problem was getting worse. Eventually frustration led me to go to the
other extreme and I tried 100% 4* as a last resort and - hey presto! - no more detonation and perfect
carburation! This led me to believe that although Avgas is rated at a high octane it is not designed for
use at ground level but at several thousand feet up in the air where the oxygen content of the
atmosphere is lower. The "Low Lead" tag is misleading too, in fact Avgas has a higher lead content
than 4* leaded gasoline. However, as the regs regarding fuel have changed over the last few years,
most of the factories have produced racing machines which are designed to run on Avgas and have
combustion chamber shape and ignition advance curves altered to suit the burn characteristics of the
fuel. My conclusion was that in general Avgas was no help in tackling det problems in engines unless
those engines were designed for it in the first place. Better to alter the timing to suit the available fuel,
particularly when you can't get Avgas from your everyday petrol station. What would you do if you went
for a touring holiday on the bike - have someone follow with a tanker full of special fuel?
#932 In the USA Sunoco sells a variety of race fuels, their website is www.racegas.com There is a
dealer close to me that has 110 octane (R+M/2) leaded, they also offer unleaded up to 104. And
leaded up to 117! Also methanol if you are racing speedway or sprint cars. With a 50/50 mix of the 110
and the 91 octane U/L "premium" sold in our local gas stations, my VMT starts first kick, no pinking.
Since this bike is not intended for long-distance touring (rather for 100 - 200 mile rides on Sundays),
this works for me. All other Velos in our garage are timed at 36 - 37 degrees and run 8:1 CR or less.
30 years ago I thought my Venom had a rod knock, took it down to the crankshaft looking for a nonexistent
problem, realized years later it was pinking.
L #934 What about so called octane boosters? Is any one brand preferred over another?
#940 Octane boosters are a waste of space.
#942 Warning! Anything potent enough to raise octane significantly in small amounts will likely be so
poisonous and/or carcinogenic that you wouldn't want it in your garage, much less toolkit or tankbag.
Remember Dave Allcock.
#944 I have spoken in the past with a fuel chemist, and he recommended adding xylene at NO MORE
THAN 10% to gas if octane boost were needed. Toluene I would imagine is much the same, but I
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wouldn't add 20% as this might bring new problems due to altered burn rate and excessive heat.
L #1035 On the question of petrol in the UK as an owner of a Lotus elan for the last 30 years until
recently. The Lotus twincam engine with 10.5 c/r & webers carbs, the drop in octane in UK petrol has
been a real problem! in starting & pinking. 95ron & 97 ron is not the same as the old BS octane figure,
that use to be on the British petrol pumps the MON octane is lower than RON, & LRP has not even got
a British Standard!! The FBHVC lead replacement testing was only carried out on a Rover A series
iron head low compressions engines @ 4 deg advance for VSR measurements, which is no criteria for
a high compression engine. But in the Lotus world we do know QED with Miller oils had done engine
power tests with QED dynamometer with Millers CVL. (Competition valve lubricant) on the twin cam.
Test showed that it produced considerable power increase using 95 ron unleaded fuel at 300ml x 20
ltrs further inquires with Miller oils tech dept confirmed the results that CVL produces a rise of 3 octane
& Millers VSP a rise of 2. I used VSP in my Lotus for two years before I sold it to great effect that I
was able to advance the ignition back to 12 deg. from 10 deg which most of us had been running at
since the loss of 5 star petrol in the uk, I have been using it in the Velocette although the MAC is not a
Performance engine. I think it improves starting? The only problem with using octane boosting
additives is Millers is manganese, Castrol valvemaster is phosphorous and LRP is generally potassium
although individual oil companies will not confirm this? But what ever you use you must stick to it as
they do not mix, the other unknown factor is long term corrosion if any? Only time will tell. Which as
somebody has already said, makes Gordon Jennings, thesis on Plugs, a bit old hat nowadays.
L #1732 My 1958 Venom has a manual advance/retard. I've set the timing at 38 degrees BTC at
full advance. I'm running on normal unleaded with Shell Valvemaster and Octane Boost. The problem is
that I cannot find a "balance" between loss of power and excessive pinking. Keeping the engine "on the
boil" by using lower gears helps to a large extent but doesn't solve it. I haven't looked inside the engine
since I bought it about 6 months ago and have not measured the compression ratio. The only indication
I have is that there are no compression plates between the cylinder and the crankcase and the
previous owner (who is not contactable) had a bit of a reputation for "warming up" engines. I've read
previous postings and the options about mixing avgas/petrol etc really aren't practical for me. I need to
be able to fill up with what is easily available when the tank is empty. I've used Optimax and this does
seem to improve things, though it's not necessarily available in the wilds of Cumbria where I live.
Normal unleaded and LRP are often the only things on offer. I've heard good things about the Broquet
catalyst but wonder whether anyone has any experience of it. www.broquet.co.uk/ for anyone who
hasn't heard of it and is interested. Any experience out there?
#1736 It might be worth trying genuine 4 * petrol. I don’t know where abouts you live in Cumbria but
there is a garage at Thursby (West of Carlisle) that sell it. It is rather expensive though.
#1738 Might simply need a decoke. I just done mine and it cured a not dissimilar problem. On additives
- I have had good results with Tetraboost - which contains real tetra-ethyl lead. Dose is 100ml
Tetraboost to 6.5 litres super unleaded (97 octane) - gives 5 star (100 octane). Not very
environmentally friendly though. Tetraboost are on 020 8870 9933 see also: www.tetraboost.com If you
want to try it I have plenty spare - comes in 1 liter bottles - let me know (or ask James Jacques who I
think still has a drop or two I 'lent him for experimental purposes')
#1996 Mine is running an optimised 8.75:1 on Super U/L or Optimax preferably, 38/ ignition timing
without any form of octane booster or other additive. It pinks slightly at high load/low revs as one would
expect, but is quite happy otherwise. Pinking tends to increase slightly as it begins to run low on fuel
and the level in the float chamber drops - a useful warning to switch to reserve before it slows up
rapidly with someone on your tail!
#1998 1) you have stated THE most important thing to remember ... 'It pinks slightly at high load/low
revs as one would expect, but is quite happy otherwise.' 2) BUT, also remember that a weak mixture
will pink more than a rich mixture. My venom and viper racers both run approx 10.5:1 compression, and
I run them both on super u/l, no additives (which is just about the only thing you _should_ be allowed to
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un according to how _I_ read the acu regs) They don't pink 'cos they don't get run at low revs ...
Pinking is an issue with 'lugging' your engine, if it pinks, just change down a gear. BTW - Shell Optimax
does _not_ have a better octane rating than other manufacturers any more (if it ever really did have).
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E. The Drive Train
E.1. Primary Drive, Chainwheel and Clutch -
L #151 The large clutch ballrace assembly C26AS is an interference fit in the chainwheel
assembly, although the same problem would also exist for the clutch thrust bearing if there was no oil in
the chaincase, as you point out. I have converted my clutch thrust bearing assembly to rollers also. I
would be interested if anyone else sees this as a problem and also if anyone knows of a cheap source
of the large ballrace assembly. The last one I purchased was about £90 so I would not want to replace
it too often.
#154 I got mine from Grove Classic Motorcycles in Bedfordshire U.K. (+44 (0)1582 873066) as mine
was cracked and loose in the chainwheel. I checked the price list and they are currently listed at £95
#156 Re: clutch chainwheel bearing (not throwout bearing) life with a belt drive. There will always be
some oil in the primary from the engine breathing through the main bearing. I think we should ask
someone who's put some miles on this system, though, to find out if it's enough. Those bearings
sometimes are in short supply! And as a sidebar, on the throwout bearing, rollers are the only way to
go. Two sets of the ball type wore out in 3 years on my VMT before I got wise, and have never had to
change them since (this is 12 years ago).
#157 Some new chain wheel bearings are a thou or so undersize (not necessarily those from Grove
Classics), and have a habit of dropping out of the chain wheel. Check the OD of the new bearing
against the old before you fit it.
L #160 My Venom has traveled just about as far in 13 years with the original ballrace release
bearing. It is adequate when properly lubricated. I was slipping the clutch like a mad 125 GP rider on
the way up Pikes Peak last summer! Stinking SUVs... Simple geometry says that the roller setup needs
good lubrication too. If the heavily loaded rollers on a crankshaft skidded like they do in the release
bearing they would not last a minute. I agree that someone with experience with running a "dry" primary
should give us some hard facts about bearing life. Race bikes probably don't see the long-term clutch
abuse that a street Velo does. Perhaps
#161 Reference the clutch release bearing saga, I modified the brass cage on the bearing by filing it to
take 3/16th" rollers after reading about the mod in Fishtail in the 70's and never had to change any of
the parts despite using the bike as everyday transport for years
#162 When I had mt first Thruxton back in the late 60's early 70's it seemed to "eat" thrust race
bearings of the ball type. I now use the roller type and find in the 10 years of ownership of my second
Thruxton I am still using the same bearing
#164 I have been using bonded clutches and better quality steel plates for about 3 years now and find
them a great improvement. I find that neutral is easier to select, the gear change is smoother, also
when abused the clutch will go out of adjustment but return to its original settings when "rested". I
have found that the chainwheels made in Germany do not last long and seem to wear very quickly. I
have just had them relined at Safetex in Yorkshire, but to date have not had the time or the weather to
used them, has any one else used Safetex relined chainwheels or plates?
L #423 I have a 1954 MAC and I want to rejuvenate the clutch. I have a few bags of inserts from
Martyn Bratby, enough to do all of the plates and the chain wheel. Is it as easy as popping the old ones
out and bunging the new ones in? Or are there other things I should do as well?
#424 Plates must be reasonably flat. Tabs to be deburred, insert new inserts, put every 2nd one in then
reverse plate, and finish off. I have found that a dab of araldite holds the inserts in place , they tend to
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ecome sloppy in use. finally , a gentle sanding,( 250 grade wet and dry on a flat peace of glass). The
main thing is to use FLAT plain plates, most become dished with use. A little extra throw at the lever ,till
the clutch is bedded in will help eliminate the drag.
#425 I agree with Chris replace them alternatively from opposite sides; you will need to file the inserts
with a taper to make them fit the holes. (Use gloves and a mask). Inserting them will require some form
of press, I used a fly press but you may be able to do it in a vice. You will need to find a spacer so that
the insert can protrude through the plate –some people use wire. To calculate the wire thickness, take
the thickness of the plate away from the insert thickness and halve it. Remember there is two thickness
of inserts 0.195 thick for the seven-plate clutch and 0.155 thick for the nine-plate clutch..
#428 Why not send them to Saftek, 1 Rawfolds Ind Estate,Bradford Rd,Cleckheaton, West Yorks.
BD19 5LT.Tel 01274 862666 Web site www.saftek.co.uk and have them bonded, saves a "pig of a
job"
L #451 I do have a running long term test question; I have had two of the new 'Canadian'
clutches (with bonded linings from an automatic trans - I think Goodman makes a version now) in my
bikes. They have failed within 3000 miles each, with proper adjustment even. Anyone else out there
have the same experience? My Thruxton, a week before our annual ride, has terminal clutch slip.
Time to go back to standard
#480 I think you will be surprised to find that the 'demonish' clutch you took apart is identical to the one
in any Venom, MAC, KSS, etc! All Velo clutches work beautifully if they are set up according to 'the
book', and in this case you could use the Red Book (factory service manual for Venom etc) to set up
the clutch, or ask any knowledgeable Velo enthusiast; they could help you set it up in a trice, as
undoubtedly they have done it themselves many times. There are several sources these days for
improved clutch parts, i.e. bonded linings on the friction plates, slotted plain plates to obviate warping
(not so likely with such an, er, understressed engine as the model U), most of which were developed
to handle the power of a Thruxton engine on that same little clutch. As for you overhung crank, many
prewar two strokes used them, including Scotts, and while yours will likely do an 'end to end' run with
no problem, the advantage of this design is the ability to replace the rollers without removing the
engine! That's what that round door on your crankcase is for. Not your grandson's Yamaha... By the
way, after surfacing my plain and friction plates on my Thruxton's 'Canadian' clutch, it has improved
dramatically, and after some adjustment on the first day of our annual Velo rally here in Washington
stage, went perfectly the rest of the week/1100 miles or so
#481 I agree with Paul, with the exception of the thrust and chain wheel bearing you cannot use any of
the modern parts as the clutch while operating on the same principle needs components of different
dimensions..
L #529 I have a 1970 Venom Clubman, and could use some advice about the clutch. I've done
the clutch adjustment drill as carefully as I can, and my clutch still slips under power. Should I dig in
and take the clutch apart to see what's going on, or should I try adjusting it further to increase drag?
Since this is essentially a new bike, with just 12 miles on the clock, and sat for 30 years, could it simply
be that the clutch springs are sacked?.
#531 Now I don't know if this will help but I had bad clutch slip on my MAC after replacing the main
bearings (I also took the clutch apart). Turned out that I had replaced one of the plain plates the wrong
way round. That’s all it was. It was preventing the plates being sandwiched together.
L #1041 In this cold period, I decided to keep my sundays busy in replacing this felt seal on my
Venom, you know which I mean. Opening the primary case, I saw the following problem I never
experienced : The primary chain has seized links, some rollers are broken. The chainwheel is out of
alignment, outside 2.5 or 3 mm. There is no sensible end play on the sleeve gear. I'm puzzled as there
is no provision to shim neither the drive pinion nor the clutch or the sleeve gear. Where could this
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trouble could come from, and how to cure it ?
#1042 You have got something wrong. There is no way that the chain line will be out if all the parts are
as they should be. Is the chain wheel on the clutch the right way round? Which way is the chain out? Is
the tubular spacer behind the clutch the right length? Do you have a Venom engine sprocket? Did the
machine work OK before you noticed the damage? A bit more investigation will find the cause (I hope)
#1045 That's why I'm puzzled !!! The chainwheel is too much outside; yes it was in the right way (two
friction plates inside, one outside), the spacer on the sleeve gear is the original one I use for years, as
well as the engine sprocket. Engine and gearbox have been rebuild, and the machine ran perfectly well
! If no other idea, next step could only be to take the sleeve gear off, which I should have preferred to
avoid.
#1046 If everything in your clutch was fitted the right way, my suggestion is that the big threaded ring
that secures the main bearing loose and the whole clutch moved away from the gearbox because of the
force you put on it when operating the clutch. If the bearing sits relatively tight in the housing, you won't
feel any play. Anyway, if this is the case you should have encountered some clutch drag. Maybe you
adjusted it and some time later it occurred again and so on.
#1051 Regarding primary chain alignment, they are usually out of line by about 4-5mm my friend from
holland has encountered this problem and I have fallen foul of it as well. The standard primary chain is
a bit weak if you tend to give the bike a bit of stick. you can fully stretch a chain in 1500-2000 miles if
you ride a bit hard. I was told to fit a 428H DID primary chain which has thicker side plates and is a
heavy duty chain. It’s a tight fit to the primary case but they are ok. I fitted one and ran the bike. I had to
take the outer chaincase off and to my horror the chainwheel was eaten away on one side very badly
where the chain was trying to align its self and pulling into the chain wheel because the sprockets were
out of alignment. It hadn’t done it with a standard chain but the heavy duty chain showed up the
problem. the chainwheel is a fixed item so any adding shims has to be done at the engine sprocket
end. if the engine sprocket is too far out, you can always let it down by using grinding paste and a
mirror. Remember that a mirror is flat because it is ground and a pane of glass is not. it seems that all
the bikes that were made were not too well aligned on the primary side. He has checked a lot of
Velocettes and they all needed aligning on the primary side. I hope someone can use this information.
p.s. remember that if you do decide to fit a heavy duty primary chain always rivet up the link as split
links are a definite no no.
#1053 I mentioned about primary chain alignment and I said that you either had to shim or let down the
front engine sprocket. I was lying in bed when it dawned on me that I should have said shim or let down
the inner cush drive, as that will determine the alignment and not the sprocket. my mistake. I will give
him a ring and ask him for some more input into this subject..
#1057 I have taken the bearing ring nut out, it was ok, and the bearing is snug fit in the case, so any
end play would have been noticed. Do you mean that's normal to have 3 mm or so out of alignment,
and is not why my "normal" chain has been destroyed ? The outside of the chainwheel teeth is worn too
(the chain wheel is outside alignment). So the only two other possibilities I consider are lack of oil (there
were very few in the case), or too tight a chain. It was ok when I opened the chaincase recently, but I
remember last year I found it over-tightened once. Just in order to check the sleeve gear bearing, is
there a way to take it apart without opening the gearbox ?
#1060 I have done quite a bit of primary chain (well belt in my case) alignment work. One thing I have
noticed is that if checking with a straightedge across the chain wheel the state of the trans in the
mounting plates has a significant effect on alignment measurements. This applies to rear chain as well.
The effect riding the bike has on the trans (notice how when you adjust the primary chain, making sure
to leave the jack screw pushing the trans forward, then go for a ride the primary chain still tightens up
as the trans gets pulled back on the drive side only) will change alignment. So you might try moving the
trans in the plates and see if there is any change. Also main bearing shimming will of course change
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alignment by a small amount, as will clutch plate thickness.
#1061 The inner 'cush' drive IS the sprocket! There is also a spacer on the sleeve gear against which
the clutch backplate abuts. This may be the wrong length, causing chain misalignment. Different
models had different length spacers, and sometimes the wrong one is inadvertently used.
#1062 PS: It is also possible that the clutch chainwheel bearing is worn, loose or missing (yes, I've
seen it missing!). Also, of course, the sleeve gear nut not being fully tightened would cause
misalignment.
#1063 Have you checked the mainshaft nut under the cap on the gearbox cover? That could allow the
clutch to slide over to the left, wearing the outside of the clutchwheel's teeth.
#1064 The final drive sprocket is mounted on the mainshaft, not the clutch.
#1067 Just one observation that you probably knew about. When you checked your primary chain did
you check in five or six different places on the chain. Every primary chain I have checked has variable
tension depending on the concentricity of the chain wheel. If your unlucky it can vary between tight to
flapping about. It's also interesting to check (with a gloved hand) when everything is hot, I am surprised
how tight it gets on expansion.
#1068 When you stripped the clutch to check on the sleeve gear bearing was the chainwheel still tight
and central on the large bearing? I think he has the right idea when he refers to the clutch plates and
inserts wearing and misalignment taking place. Have you measured the inserts and the steel plates and
compared them with the thickness of new items? I have seen Velo clutches where it is possible to rock
the chainwheel even when the clutch has been adjusted perfectly, due to worn inserts. A combination
of the above and your own observations of little oil and tight chain could have caused overheating
leading to seized and broken rollers, culminating in the wear you noticed on the chainwheel. As Geoff
states the mainshaft nut in the box shouldn't affect the clutch, which should still work and rotate even if
the mainshaft is out of the gearbox, but don't try it too often as the pressure exerted is taken by the
unsupported clutch and bearing and may distort or crack the alloy of the gearbox shell. you stated in
your second reply that the bearing spacer was the original and the gearbox bearing was still tight so I
can't see what else could cause such misalignment other than the above.
#1069 Yes, I always check the chain tension in different places. For years, I always had it on the slack
side. But last time, I remember I tightened it more than usual, to the specified value (red book) ½ or 1"
free play cold, thinking it would get some more play when hot. This, added to dry case, could explain
the chain havoc. But this doesn't explain chainwheel misalignment. I checked all the clutch parts :
Chainwheel was true on the backplate, as well as on the sleeve gear. Thickness of all plates is right, a
bit less than new parts, a bit more than used ones. Some plates are not perfectly flat, but as far as the
clutch worked properly and didn't drag, I do not think this could cause a real thickness excess of the
assembly. Anyway, even without any friction and plain plate, i.e. assembled with backplate and
chainwheel alone, the later is still outside about 2 mm. The alignment was checked with a ruler on the
outer face of the engine sprocket (in different positions of the engine, and sprocket). The edge must
point at the outer face of the wheel teeth. It does at the middle of the tooth instead. I reckon this
measure must not be affected by the position of the box in the mounting plates, as far as the shell is
tight between them. Misalignment could be due to wrong spacer length. Maybe it has been like this for
the last 35 years (never checked it before), and the oil + tension revealed the prob. This would mean
such a misalignment is acceptable.
#1070 Venom Par no. B35/3, length = 11/16 inch. MAC/MOV etc. B35/2 length = 5/8 inch. The primary
chain normally tightens when it get hot.
#1071 Maybe your problem is due to warped gearbox mounting plates. During several decades of hard
work this might happen. At least my plates were warped when I stripped the bike although it was fitted
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with the double plates at the drive side.
#1072 Both my spare parts list for MAC (spring frame model) list B35/3 sleeve gear distance piece for
the MAC. not B35/2 ? could this be the problem
#1075 I used the designation MAC/MOV etc. to relate to rigid gearboxes. You are correct B35/3 was
used on "Springer" MACS. Also check that the inner end plate, i.e the one closest to the gearbox, has a
2 5/8 inch diameter recess that is 9/64 inch deep. This information comes from a Fishtail article written
by Dave Childs, which if you own a Velo is an absolute must.
#1087 The B35/3 is the right one, the inner clutch plate has the correct 9/64" recess , the mounting
plate doesn't seem to be bent, as far as I can check it in the frame.
L #1608 I bought bonded and plain clutch plates from Simon Goodman some years ago, which I
think are the same as offered by Grove. I seem to remember him telling me that the bonded plates
were thicker than standard, and the plain plates thinner, making the overall clutch the same width as
standard. Regards
#1689 I dismantled the clutch on my recently acquired Venom (which came with receipts for a new
clutch)which has Goodman's bonded plates and Goodman's plain plates together with a standard
chainwheel. As the inserts were very loose I had the chainwheel lined with bonded material by Saftek. I
fitted a new engine sprocket (same dimensions as the old one)together with a new Reynolds chain.
The result was a mis-alignment of the chainwheel and sprocket of about a sixteenth of an inch. The
engine sprocket was being pulled away from the engine. also the outer chaincase was now being
fouled by the clutch, so my conclusion is that the clutch is now appreciably thicker. With no oil in, it is
easy to here the chain clicking over the engine sprocket as it runs out of line (turning by hand of
course). It appears the only answer is to decrease the length of the spacer behind the clutch but there
is not a lot of room, or put a spacer between the sprocket and the main bearing. I have looked at the
last option and cannot see a problem. It wont seem to mask the breather (it has a crankcase breather
as well)but it will increase the shock absorber spring tension.
L #1140 In rebuilding the 7-plate clutch (inner end plate, outer end plate, chainwheel, two insert
plates, two plain plates) on my '50 rigid MAC, I came up with a few questions. For reference, I went
through David Childs' article, "Identifying the Right Clutch Parts," and the measured dimensions of all
the components agree exactly with his list. On that basis, it would appear that I have all the correct
parts. 1) Dai's list states that the correct clutch springs are C12/3. The free and bound length for these
springs are specified as 7/8" and ½," respectively. My measurements indicate that when the clutch is
fully assembled, the free length of the springs (i.e. when the clutch is engaged) will be on the order of
0.600." I measured the full travel of the thrust bearing (when the clutch lever is pulled completely up
against the grip) to be about 0.070." Therefore, the compressed length of the springs (i.e. when the
clutch is completely disengaged) is 0.530." The amount by which the springs are compressed is a bit
more than I expected. The processes of assembling the clutch compresses their initial free length of
7/8" by nearly 31%. Further, when the clutch is fully disengaged, the springs are only 0.030" longer
than their bound length of ½." Is this really how everything is supposed to be set up? 2) I replaced the
original ball-race type thrust bearing with the redesigned roller-type. The original bearing was badly
worn, so it is difficult for me to assess whether the grooves in the races are purely a result of wear, or
perhaps a groove was intentional when these thrust faces were originally manufactured. The end result
is that the new thrust bearing assembly is about 0.020" thicker overall than the original. When I pull the
clutch lever hard up against the grip, the front face of the new thrust bearing actually touches the
surface of the clutch inner end plate. I don't believe this situation would damage anything, since the end
plate and thrust surface would already be rotating at the same speed. Is there typically some amount of
clearance between these two surfaces? I haven't checked the alignment of the engine sprocket and
chainwheel, but I suspect I could install a small shim between the distance tube and the clutch inner
end plate to add a small amount of clearance if it is advisable.
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#1141 Your message re the 7 plate clutch had me checking my K model clutch which happens to be in
bits at the moment! The spring C 12/3 is .875" free length and .485" coil bound. The amount that the
spring is compressed when the sleeve gear nut is fully home is .300" Therefore the spring length
installed is .575" The maximum lift on the clutch is .125" which as 'on the tilt' and so equates to .0625"
at the centre. All the above works OK. Remember the clutch adjustment method is based on only a
slight increase in pressure above the 'just slipping' point. Therefore only a slight reduction in pressure
will let the clutch free. Now to the thrust bearing. The grooves are wear and the inner and outer rings
should be flat when new. How do you know the thrust bearing touches the clutch inner face? I would
suggest that you check the length of the thrust pins which should be .391" also check that the sleeve
gear nut is fully home. I would not fit any shims in the clutch assembly. If all the bits are correct it will
work properly. Dave Child's list of clutch parts is correct in all important respects and is the clearest
guide available.
#1142 I appreciate your response. As you observe, the length of the springs when the clutch is
disengaged is only on the order of 0.030" longer than their bound length. I found this a bit surprising,
hence my motivation for soliciting input from those more knowledgeable than myself. It appears that
everything I have is set up properly. As I stated previously, I checked the dimensions of all parts
against David Child's list (if no one has ever thanked Dave for compiling the list, I would certainly like to
do so). This included the thrust pins, which are 0.391" as you indicate. I know that the thrust bearing
touches the clutch inner face [when the lever is pulled hard up against the grip] for the following reason.
I made an aluminum cylinder that fits over the sleeve gear, and has the same O.D. as the thrust
bearing. It is also the same thickness as the clutch inner end plate (not the total thickness of 0.875" as
shown in David's specifications, but rather the thickness from the indent in the back face, to the surface
against which the sleeve gear nut comes to bear. For reference, I measured this to be 0.603".) This
cylinder slides over the sleeve gear, and is trapped hard up against the distance tube by the sleeve
gear nut, just as the actual clutch inner end plate would be. When you pull on the clutch lever, you can
measure the resulting clearance between the face of the thrust bearing, and what is equivalent to the
plane of the inner clutch face. In my case, this clearance is zero. When the clutch lever is pulled fully to
the grip, the face of the thrust bearing just touches the back face of the clutch inner end plate. It's
possible I do not have the original clutch lever, and may have slightly more travel than originally
intended.
L #1185 The clutch action on VM1958 is very heavy. I first fitted the clutch cable before I fitted the
petrol tank and when the cable was run freely between the lever and the gearbox (no petrol tank) the
action was light, so it's not a problem with the clutch itself. When I fitted the petrol tank the clutch action
became very stiff. I concluded that the run was wrong but I have spent a long time today trying different
runs without making things any better. Without the tank the action is still easy so I'm certain that the
problem is to do with the cable routing. The cable is new. Any ideas? Is there a "correct" route?
#1186 I've found that the larger the curve of a cable, the easier it is to pull - clutch, throttle, brake, etc. If
the clutch cable is routed to pass under the tank on the left side of the steering head with one curve
and the other portion arcing down behind the engine it should be a smooth and easy pull. Of course
things get in the way. Monoblocs with float bowls on left or right (I've used both), concentrics with single
fuel feed or both can have fuel lines get in the way. Up at the top the back of the headlight can push the
cable out of the desired path, as well as other cables too. Keep at it, you'll find a way. An addition to
the previous thought is that a cable can also be too long. In that case it will kink in the middle of its
curve and be hard to pull, too. There's always something else to check.
#1189 Re- clutch cable. I had exactly the same problem (& also with the valve-lifter cable).I daresay
there is a proper way to lead them, but I took the easy option & bought new ones from Johnson's (Ads
in OBM).Just ask for whatever extra length you require, how much free play on the inner cable, and
where you want the adjuster situated, and they'll oblige - all for £12 per cable. Just remember if you
want the clutch cable adjuster situated where it's accessible, you may also be allowing easy entry for
water into the cable & thence the gearbox.
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L #1331 My clutch ballrace is bit wobble I suspect wear on the ball. Some one know the exact
size of balls and is it easy to obtainable?
#1332 It is normal for the ballrace to be a bit loose. It is likely the race itself that is worn, as the balls are
very hard. I have one that a local expert filled with balls from a Triumph's similar assembly, it is really
tight. I don't think it makes much difference in operation, this bearing only keeps the chainwheel
centered in the clutch assembly and a few thou of movement should not cause concern. It gets most of
its loading from primary chain tension, when the clutch is disengaged. Check the race closely for
cracks, I had this happen once. Unless they are seriously worn, the balls are easier to install than
remove, so perhaps you could measure the ones in your race and try to find some a thou or two bigger.
L #1322 I have a 1953 MAC which is experiencing clutch drag after about 5 - 10 minutes riding.
Once the dragging has begun, it is impossible to move away from stationary and all I can do is to limp
home. I have adjusted the clutch according to the book, but to no avail. It feels as if something is
expanding or warping when it gets hot. Could it be the plain clutch plates warping? The clutch is the 7
plate type for which Veloce Spares Ltd do not sell a replacement. However, would the individual plain
plates from the 9-plate type clutch fit?
#1325 Are all the clutch bits in good order? Thrust bearing OK? The clutch plates on the 9 plate clutch
are thinner - on the friction plates - but the plain plates are the same. Try some new ones as they are
likely to be the source of your problem. Even the thinner friction plates will work if you don't have the
correct 'thicker' type. Have you got a clutch lever with the right amount of lift? with standard levers there
is precious little lift and hence the clutch will drag more easily. Check for lost lift through the system as
wear can reduce the effective lift too. With a MAC you should be bale to achieve the sweetest easiest
clutch which will work easily and last too.
#1334 The brass that contains the balls is high tensile brass. If you fit a replacement bear this in mind
because if it is just ordinary brass it will give problems. some replacement parts today just don’t cut the
mustard and are dubious at best.
L #2166 Can anyone tell me the exact dimensions of a clutch back plate thrust pin ( part no. C6/3
I believe) as fitted to a Venom please ?
#2167 Follow the clutch link on this page www.croesus-consultants.co.uk/v-tec/
#2168 These are 3/16" diameter 0.453" long.
L #2758 I have just stripped my clutch to investigate movement in the clutch chain wheel. I have
found approx 9 thou clearance between the clutch ballrace assembly and the backplate. According to
the manual this should be a light push fit. Has anyone else come across this problem ? If so how did
you overcome it? Will I need to weld up the back plate and then turn it down to size? What should be
the measurement for the ID of the bearing? Mine measure approx 2.927 inches.
#2759 That bearing is pretty much free of any load, as it only moves when the clutch is disengaged.
Later Velos used only a skinny bronze bush in there, so make one up and use that, pressed into the
wheel. Or affix it with two part epoxy such as Devcon or J B Weld or a few tacks of arc weld.
#2763 While not sure of the exact damage (?) to plate, I can suggest 3 small bits of 4-5 thou. shim to
stabilize the race in position, then use LOCTITE, I have used the 'WICKIN' grade for all sorts of things,
including really sloppy gear fits on shafts on stationary engines, also substituting it for silver solder
when fitting ends on Veteran guard stays etc. It's Bloomin Marvellous stuff & I have never had it let go,
& I can assure you that the only way to unstick such a joint is to heat it up to a considerable
temperature at which point it can be pulled apart, (if you are lucky ! ) It should be an easy certain cure
to your problem, definitely better than center punching the inner surface of the plate, (which is common
!) although this would be an acceptable way of stabilizing the bearing into the correct position instead of
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the shims. Assuming that you are going to use LOCTITE, it is imperative that the ball race is sealed off
with light grease, it is best to do this before fitting bearing, & then cleaning off the outer mating surface
with petrol/cleaning solvent to ensure a good bond with the Loktite. When you get everything set up, lay
a piece of light plastic sheet, (a good shopping bag will do ) on a flat steel surface, then tap the bearing
& plate flat to the plastic to get a perfect alignment, then use the LOKTITE, failure to use plastic will see
the assembly stuck to the steel surface!
#2765 The inner diameter should be 2.922 +0.001"
#2769 Beware the "light push fit" with the chainwheel bearing. In my experience this needs to be a
loose fit on the back plate otherwise the inner part of the race binds on the backplate when you operate
the clutch (due to the initial tilting action) and the big bearing ends up working its way out of the
chainwheel assembly in short time. Many of those that were a good press fit in the chainwheel but too
close a fit on the back plate have ended up being tack welded to the chainwheel to keep them in place,
whereas the solution was to find a friend with a bin full of old ones and swap him your new one for a
serviceable used one which is sloppier on the backplate (as I did over 20 years ago, and Peter's
bearing is still in my VMT). Check for cracks at the notches if reusing an old one. The notches are only
good for assembly of ball bearings - I've never met anyone who has been able to get the balls out to
renew them. My 69 Clubman has the bronze bush that Frank referred to - the factory used a bronze
ring on the backplate as well as the ring in the chainwheel so that it is a 2 part chainwheel bush. It is
renewable at a fraction of the cost of a "pattern spare" chainwheel bearing, and far less trouble!
L #2761 I have seen for sale recently by a dealer, clutch back plates featuring 6 thrust pins
instead of 3. Has anyone tried 6 pins. Was there any difference/improvement to clutch operation?
#2762 Fitting 6 pins was a suggestion from many years ago. In the Velo design pulling in the clutch
lever pushes the "frying pan" against the pins. They push the spring carrier, which starts to free the
plates which supposedly separate in one complete revolution of the back plate, a form of self servo
action apparently. It was believed therefore that drilling the back plate to accept 3 extra pins would
speed up the process of clutch separation even more. Don't ask me if it helps, mine has only been
modified like that for the past thirty odd years! I never could find the time to try three pins against six
with all the hassle of refitting etc, to test the theory of which was better. I've still got 6 pins in my Venom
racer and it works beautifully in the Manx Classic race, but I haven't bothered to alter the back plate in
my MAC! For Lords sake don't let him charge you extra for one with six holes, he'll make a fortune
selling less back plate and 3 extra pins!!
#2766I drill my back plates out to accept three extra pins, the theory is that the clutch disengages and
engages more evenly. The logic is sound, but I am not sure in practice whether there is any significant
improvement in clutch action.
#2767 I think that the logic is NOT sound, but I don't see that the use of six pins will injure anything. If
you examine the cross sectional drawing on page 28 of the Red Book for 86 X 86 Velos, you will see
that the pins (3 or 6) do nothing but hold the inner surface of the spring holder parallel to the outer face
of the thrust race such that these parts collectively function as one unit. There is no rotational
movement between the two flats separated by the pins, (3 or 6). This can be verified by examination of
the flats upon which the pins press, which will show no wear. The lifting of the thrust cup does appear
to apply lift to one side (forward) of the front plate, which would cause axial movement of one, or
possibly two pins followed by the other(s) during the first rotation, but the pins always remain in parallel,
as do the flats on which they press. The initial movement would create a 'diamond' cross sectional
distortion of the normal rectangular configuration of these components, but there is no other relative
movement. During the first rotation the rectangular configuration is recovered as the spherical interface
between the thrust race and thrust cup moves and aligns. Similar to a three legged stool, the addition of
three more legs would do nothing to change the relationship between its top and the floor.
#2768 There is a nice feeling about the 6 pins, but wishful thinking I am sure, but if so go for it.
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However the reasoning (?) behind it must go back a long way, & to be honest I was quite surprised to
note that in later years, 6 pins were actually used (?) , of course I am not very familiar with anything
past '46 having only once owned a Thruxton for a very short time, & the only late model stuff that I
possess is included in my 53 framed & gearboxed , 48 'Cammy' special. - But , for years I have owned
a NOS plate of a smaller diameter that only relates to the earlier models, possibly early 'K' series, but
certainly also of the early two stroke era. I have always viewed this as a bit of a curiosity, it is certainly a
genuine early NOS part that could have lain on a dealer's (Frank Mussett) shelves for years, so what
was this intended for, a KTT possibly ?, Frank certainly had a lot of KTT stuff over the years. maybe
Ivan Rhodes or someone out there knows the full story ?
L #2820 Laying in bed last night after closing down my PC, I realized that I had assumed that all
Velo owners are fully conversant with the workings & correct adjustment procedure of the Velo clutch,
the fact is that some of the inquiries that the site gets, may well be from first time Velo owners, - even
some who have bought a completely dismantled machine, & with a good chance of a clutch that has
already gone through all the stages of neglect, maladjustment & ruin. As long time Velocette owners, it
is our duty to make sure that these newcomers to our marque, fully understand what goes on inside the
clutch at all times. Les Diener used to say, 'The average clutch is usually simple, but a Velocette clutch
is an engineering device, & it takes an engineer's reasoning to keep it in good order' There is no
guarantee that a newcomer has engineering expertise, or the instruction book with the full detailed
adjustment procedure ! So I say, if this is your first Velocette, get good detailed, on the spot instruction
from a LONG TIME Velocette owner, and DON"T interpret slack in the clutch cable, as the necessary
running clearances inside the clutch !!! this is almost certainly the biggest trap, the start of clutch
problems, & the ruination of countless thrust races. Probably 99.9% of the site readers know all this,
but if you are of the .1% you really have to know it ALL! This sounds like mindless repetition, but we
cannot assume that all new owners know the score !
#2831 You are right to assume that I am a first time Velo owner. Though I have had the bike nearly 18
months this is the first time that I have had the clutch off. When I bought the bike the clutch was almost
OK but dragged a little. A new cable and re-adjustment of the clutch as per the manual solved this
problem. The reason why I stripped the clutch was to investigate the chainwheel movement which was
causing a variation in primary chain tension. I noticed this shortly after buying the bike but don't think it
has got much worse in 2000+ miles I have ridden it. It does mean the I have to run the primary chain a
little slack though. If there are any LONG TIME Velo owners within 50 miles of Carlisle that would not
mind me bringing my clutch for a second opinion please let me know.
#2838 In mentioning that the clutch 'dragged a little', you have described the initial symptoms that leads
to the Velo's, (or any clutch for that matter) downfall, the difference is that agricultural, ( BSA, NORTON
etc) clutches can withstand this sort of abuse, a Velo clutch cannot !. This is the price you pay for
having a lightweight clutch , that when properly set up will remain perfect for ever. One rule with Velo's
is that you should never just pull the clutch in & chat to your friends, everything goes down hill from
there ! You have to educate yourself to snick into neutral at all times before stopping, - even for the
traffic lights if it looks like being a long wait. To this day I do this on any bike that I am riding, & also
when driving a manual vehicle, it's a GOOD habit for many reasons, not all to do with the Velo clutch!
The dragging clutch is , assuming that all outer clutch components are in good order, almost certainly
the end result of lost movement between the clutch lever & the little pin coming out the end of the
gearbox, but one must be sure that the springs are of the correct length & not stuffed to the point where
they cannot give full compression movement, & are 'bottoming'. As for the internal components, I have
variously filled the worn & elongated pivot hole in the crank lever with bronze, & re drilled it, or found a
better one in the old spares box. There can also be the result of the pivot bolt not being adjusted 'snug',
& the lever kicking to one side has the pin off centre, & wearing the side of the contact point - I have
made new pivot bolts, the old ones which I have seen worn almost half way through. There is also the
problem of a clutch outer casing that has been pinched at the steering head, & has a small section that
springs in & out under the pressure of clutch lever useage, this must not be ignored ! Non standard
clutch cables can also be a problem, no hint of stretch can be tolerated, the reason why Velocette have
always had their own heavy duty cable assemblies, which can last virtually for ever. I have made up
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cables using modern Japanese clutch cable assy.s & they work really good if properly made up. All the
above needs a thinking approach at every point, don't ignore even the smallest indication of lost
movement.
L #3653 I have a small bag with 88 clutch plate inserts (C25-2) that I bought from Lou Branch in
Los Angeles in 1974 (?). Price marked on the bag is $11.44 :-) The material is not cork, looks like
Ferodo and in great condition. What dimensions should I size them to before pressing them into the
clutch plates? Any suggestions on how to size them? I plan on running a dry primary case.
#3654 If these are the original parts, they will be only slightly bigger than the square holes they fit into.
Just press them in to alternate holes, turn the plate over and fill in the gaps. This helps to keep the
plate central as the inserts are then slightly oversize on alternate sides. When all in, assemble all the
plates in your hands, then squeeze the whole lot in a vice a little at a time turning the clutch in the vice
as you go. This will get all the inserts level with each other. It may pay to wear a face mask as I don't
know if these may contain asbestos. Should be OK running dry, but don't expect too long a life from the
chain ( or have you belt drive?) Good luck, Bob PS older clutches with 3 friction plates had thicker
inserts, The fact you have 88 suggests yours are the thinner 4 friction plate sort.
#3658 Yes they are slightly bigger so I'll just press them in (I'm sure easier said than done!)....I'm
refurbishing an MSS for city use and feel good chain lube should be sufficient for the lower speeds and
short trips.
#3660 In years gone by when Velocettes were in daily use, we had the ' 88 inserts' & they were
seldom replaced in normal use, as to chain lubrication, the primary case always seemed to be filled
with oil from the engine mainshaft leakage, & at times lubricating the rear chain with the surplus, rather
than needing more oil ! This situation varied with the model & the amount of wear/use. There was also
the problem (?) of washing the model every Sunday morning with the kerosine brush & the garden
hose, & this procedure invariably introduced water ( & kerosine), into the chaincase via the openings ,
the result, after a few weeks there was certainly a pool of watery gunk at the bottom of the primary
case, with the lube (?) floating on top ! - If you were into riding through shallow creeks or flooded
roads, I had a local main road that often had 6 inches or more of water running across it after a Winter
downpour, - there was also the water intrusion problem. The answer to this was to fit a drain at the
lowest point of the outer primary chaincase, & I don't doubt that many of you have bought a Velo with
this drain already in place. (did any later models have this fitted ?) This meant that you could drain the
case at intervals & at least give the chain some good fresh oil ! As for clutch slippage problems with the
old type inserts, I can't recall ever having any, the clutch seems to keep itself free of oil by centrifugal
action, even if it became overfull, maybe we were lucky in those far off days, or the oil & the (asbestos
?) composition that the designers had arrived at from the 'suck it & see' method was quite efficient,
whatever, in years of Velo riding, - & side carring I can't ever remember having clutch slippage
problems that related to oil in the primary chaincase, - Maybe I was just lucky?
#3714 What is the trick to removing the ball bearings from the clutch ballrace assembly? Is the opening
crimped in any way once they are all installed or do I just need to apply more pressure when removing
them. It feels like a piece of foreign matter is caught in there and flushing doesn't remove it. Any
suggestions are appreciated.
#3716 I have never found a way of getting the balls out of the ballrace, after all, they're designed to stay
in there! I would suggest however that if you can't sort out the problem by flushing and blowing out with
an air line, then the chances are that the races themselves are damaged and the only solution will be
replacement.
#3731 I have stripped a big race bearing. It was a little loose, and the problem was to line up the two
half-holes on one ball. I don't remember how I did it which normally means it wasn't too difficult. If the
balls are 3/16", this is 0.1875". An oversize 5mm ball would be 0.19685" but I don't know if you would
go through the hardening at that figure. A friend did grind oversize, just a touch, but used the original
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alls. He Loctited the bearing into place hot, which tightened it up, but either he calculates better than I
do, or he was lucky. Seems it worked. I could get oversize balls but the price could be horrific- how
much does that bearing cost now?
L #3742 I have a Venom with the bearing in the clutch plate which refuses to stay in place. The
last attempt to Loctite it in using "bearing fit" did not work. I have measured the bore of the chain wheel
and the outer diameter of the bearing and these are size for size at 3.812ins. i.e. no interference fit. I
am loathed to purchase a new bearing or chainwheel as I don`t know which part is incorrect. Does
anyone have the correct dimensions for both parts? Is there an accepted "fix" for my condition other
than the one in the BMS book by tack welding which is rather over the top as it buggers both parts up
for the future. The brass bushing solution seems a way out. Does anyone have information on this?
Was it a factory solution fitted to later models and does it fit in place of the ball bearing and does it
work? A brass bush will be considerably less expensive than an £80 ball bearing. Here`s hoping for a
solution to get the bike back on its wheels on the road.
#3745 You say that tack welding buggers up both parts. Here's another thought: With an OD size of 3.8
inches, the bearing/bore interface has about 12" of circumference. A tack weld has about 1/4" of length,
so four of them will use up about one of the twelve inches. Given that later removal of the bearing likely
would destroy that bearing, OR the chainwheel, and given that the chainwheel sprocket is normally
subject to damage from wear, what do you have to lose by welding? If not welding, how about a two
part epoxy such as JB Weld? I was told by Ed Gilkison that the OD of the bearing was tapered such
that when the smaller diameter was pressed in to the chainwheel it would tighten up.
#3750 Between the chainwheel and the bearing, I'd say that if one is worn, it is more likely to be the
chainweel, as it is softer. As you probably know, if you suspect there is a taper, try fitting first from one
side, then from the other. The taper would be more likely to be on the chainwheel, if there is one, but in
mechanics no possibility can be neglected.
#3752 Check for adequate clearance between the ID of the inner and the OD of the prongs of the back
plate - I tell you if it is too tight here the bearing will work out of the chainwheel no matter how good a fit
on the OD. Don't know if Dai has the factory tolerances but the inner needs to be a sloppy fit (excuse
the technical jargon) on the back plate. As to the big bush in lieu of expensive ball bearing option, I
suggest you find a friend with a late model machine and measure up - I loaned the chainwheel and
backplate from my 69 Clubman to a friend last year and for about AUD$25 he had a bronze sleeve for
the backplate and a big bush for the chainwheel manufactured to the same sort of tolerance as my
partly worn example. When I got the bits back I threw the clutch together and the original 1969 big bush
is still there and working fine. I'm not aware of it causing problems after the factory changed from
expensive ball bearing to cheap bush - the only time it does any work is when the clutch is disengaged
anyway. I know of another 69 Clubman that has never had the clutch apart, and it would certainly have
the same clutch parts as mine, being only one engine no. apart.
L #3927 My 1970 Venom Clubman clutch slips, so I need to adjust it. I made the proper tool, but
the inner and outer race both turn together when I rotate the rear wheel. The manual describes a
technique where you place the trans in gear, and rotate the wheel the opposite way. This seems to take
advantage of differing rotation speeds of the two parts. My question is this: How fast does the clutch
adjust with this technique? In other words, using this alternative technique, what is the ratio of wheel
turns to the standard technique (when it works). Also, my bike only has about 200 miles on the clock
from new. Should I pull the clutch apart to see what's going on? (I'm not anxious to, but will if
recommended.)
#3928 Initially, depending on the degree of mal-adjustment, you may need to engage top gear and with
engine turned against compression a complete rotation or two of the rear wheel may be required. (for
safety sake, remove the high tension lead from spark plug). After clutch has been properly adjusted,
some miles racked up, and you are making a new adjustment to correct for settling, etc., 1/8 - 1/6 of a
turn of the rear wheel will be sufficient find that I must turn the wheel forcibly and swiftly to move the
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clutch sleeve without pulling the engine thru compression. I've a 20 spring clutch in my Thruxton.
#3929 The adjustments are made in neutral. Make sure the clutch cable is removed from the clutch
lever. We pull (or push) a sidecar and do not have clutch problems or the need for frequent
adjustments.
#3931 Select an intermediate gear- 2nd? - not top cos then the clutch and final drive move together.
Put peg through final drive sprocket into a notch on the spring carrier - you may have to push back and
forward a bit till they align . ( Pull in valve lifter so the engine can turn freely .) Push forward maybe half
a turn of the rear wheel. Remove pin and try to see if the clutch grips. Repeat until it does, then do
adjustment as normal.
#3932 The lower the gear the greater the differential movement between spring carrier and outer plate
of the clutch - in top gear there is no differential movement. Except I'd take the plug out during this
operation as I find it hard to reach the valve lifter from a position squatting behind the back wheel. If
reading from the Haynes Manual, beware - the edition I have gives the wrong advice on which way to
turn the wheel. If doing it in neutral turn the back wheel forwards to create greater clearance between
thrust pins and spring carrier and hence cure a slipping clutch. If having to do it in an intermediate gear
then turn the back wheel backwards to achieve the same result. It's possible that after you adjust it you
can do future adjustments in neutral because a clutch that is badly slipping won't have enough friction
to hold the front plate still while the spring carrier turns. But in other cases the damn things are just tight
and you have to use the intermediate gear technique all the time.
#3934 Had exactly the same problem last night on my Venom after reassembling the clutch. I found
about half a revolution of the rear wheel with the transmission engaged took care of both parts turning
then I could adjust in the normal manner, i.e. out of gear. Remember the cable.
#3968 Thanks to all for providing advice on the clutch adjustment. Once I used the "in gear, rotate tire
backwards" method to break it free, I could adjust it as normal in neutral. I was amazed that 1/8 turn of
the rear wheel produces nearly 1/4" of cable play, so it doesn't take much once your in the right zone
on clutch adjustment. In any event, the clutch doesn't slip or drag, and shifting is great.
L # 5269 Can anyone explain what the clutch adjustment tool does when the wheel is turned?
Also which part does the flat end engage? Is the 1/4" DIA critical?
#5270 The 1/4" is nominal but must fit through the holes in the final drive sprocket. The "Flat" is
required to fit the castleations on the Clutch thrust nut. The adjustment works by the differential
movement of the sprocket (don't worry). Set the clutch as required in the red book. Our clutch has
remained in full working order and without adjustment for over two years from being "set-up" and we
pull (or push) a sidecar. Disconnect the clutch cable as required by the book.
# 5272 The "tool" just effectively screws the castellated spring holder (which is threaded into the clutch
outer plate) in or away from the operating pins. By following the red book instructions you will end up
with the correct clearance. The misconception is to compare it with other British bike clutches. On the
Velo the spring tension/pressure remains fixed by the centre nut screwed tightly to the sleeve gear and
has no adjustment.(Despite this you often hear Velo owners of long standing saying they have
increased the spring pressure by adjusting the spring carries with the "tool"! it simply cannot be done
except by packing out the springs under the shims, using stronger springs or by using more springs as
the Thruxton does.) You just move the spring holder to set the clearance with the operating
mechanism, followed but setting the clutch cable for its clearance. On other British bikes you can
increase the spring pressure with the adjusting nuts (normally one per spring)and then adjust clearance
to the operating mechanism by the clutch cable. Just a reminder, watch out for the Haynes manual, it
describes setting up the clutch clearly but tells you to make the final turn of the castellated spring holder
the wrong way, if I remember correctly, may have been changed in the latest print but I doubt it. regards
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# 5273 Unless I am mistaken turning the spring carrier in or out (adjusting the clutch) does change the
spring tension as the distance between it and the sleeve gear nut is altered. Not that it is to any degree
that would affect performance however in the case where the dimensions of the thrust pins, throw out
bearing, clutch plates, etc. are improper, using the spring carrier to compensate may result in incorrect
spring pressure.
# 5275 Correct, except screwing the carrier in to take up free play will increase spring pressure, 'in
theory'.
# 5276 I rebuilt my clutch assembly in its entirety last year and learned a number of interesting things
about this infamous assembly. In the present context, the first point relates to the relationship between
spring tension and clutch adjustment. In fact, the free length of a new set of springs is significantly
larger than the length when compressed (I actually measured all this stuff in exhaustive detail if anyone
wants the exact numbers). In comparison, any changes in the compressed length resulting from clutch
adjustment are extremely small, and effectively irrelevant in terms of the effect on the resulting spring
tension. It's actually more fundamental than that. When you are adjusting the clutch to compensate for
wear in the friction plates, in actuality the adjustment process precisely moves the spring cup back to
the position it was in before the wear occurs. Stated another way, wear in the clutch causes the springs
to lengthen very slightly, and adjusting it restores them to the length they were before. The various
subcomponents (e.g. the actuating pins, spring cup, sleeve gear nut, frying pan, fixed and friction
plates) come in different varieties, and using the correct versions in combination is critical. I apologize
for forgetting off hand the name of the individual who put considerable effort into cataloging all of the
dimensions of all of these components, as well as listing what versions correspond to what model and
year. Again, I don't remember the exact issue, but this list was reprinted in its entirety in FT. It is
extremely useful. I combed through his dimensions, made sure each and every component was exactly
as he specified, and it now works superbly and reliably. Unquestionably, certain combinations of
incorrect components would spell disaster (for example, a certain vendor sent me actuating pins which
he insisted were correct, but would not have worked at all). For my MAC, I also calculated the ratio
(shown here as "K") of the angular rotation of the spring cup as a function of the angular rotation of the
transmission output drive gear. The second column factors in the final drive ratio, and is thus the
angular rotation of the spring cup as a function of the angular rotation of the rear wheel. It can be seen
that using 3rd gear provides the greatest adjustment sensitivity (large amounts of rotation of the rear
wheel producing comparatively small amounts of rotation of the spring cup). Using 2nd or 3rd gear also
guarantees a fixed relationship between the angular rotations of the spring cup and output shaft
(although in the opposite sense). In contrast, if the spring cup does not rotate easily in the front clutch
plate, adjusting when in neutral can cause the entire assembly to slip as a unit (i.e. no change in
adjustment occurs). Adjusting while in gear eliminates any guesswork.
K K x 1/final drive ratio* Neutral 1.0 2.7368 1st gear -1.5278 -4.1813 2nd gear -0.7501 -2.0529 3rd gear
-0.3300 -0.9032 4th gear 0 0
* Minus sign denotes opposite sense of clutch adjustment relative to neutral. Clutch mechanical
advantage and adjustment: As measured, 0.5" travel in cable produces 0.040" movement at centerline
of thrust cup (12.5:1). Measured clearance between thrust face and back of rear clutch plate # 0.060,"
implying a total available travel of the cable at the clutch lever of 0.75." The exterior of the spring holder
is 24 tpi (= 0.0417"/revolution)
# 5284 Not to beat a dead horse, but again, it is precisely the process of wear in the clutch that affects
the length of the springs (and thus their pressure). Adjusting the clutch restores them to the length (and
therefore pressure) that they were originally.
# 5328 The clutch article you mentioned was published by Dave Childs. Dave allowed me to publish
the details on the technical website - look under clutch here www.croesus-consultants.co.uk/v-tec/
# 5286 I'll take one more swing at this horse, but first I must say you have taken Velo clutch
adjustment wisdom to an entirely new level with your angular adjustment calculations! If you ever get to
setting the bevels on a cammy Velo I'll look forward to reading that novel. You are of course spot on
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with the adjuster compensating for spring pressure loss due to clutch plate wear. I have, however, a
box of old throw out bearings that have grooves as deep as .050, a common occurrence (I use the
roller type). This will not be compensated for by adjustment, in fact adjusting to take up slack would
lengthen the springs .100 (both races, same goes for worn pins etc.). On my Bonneville and B50 (I
keep these around to remind me how good Velos really are and to lend out) just one turn of the clutch
spring nuts (.040?) has a noticeable effect on grip and handlebar feel. Also on my hot rod VMT, before I
went to an updated clutch, I had to run a spring shim of about that size to avoid slippage. Two years
ago I updated the clutch on my MKIII KTT (yes, with the old VMT clutch) and in doing so ended up with
a very soft clutch that wouldn't even hold for starting. What I neglected to realize was that the three
thrust pins were of different length, so I had just the scenario above. I should have realized this when
the center nut went on without the usual push and twist motion. Point is that in a perfect world all is well
but over the years many bikes get 'massaged'.
# 5271 The most difficult bit about the procedure is defining “and only just slip”, it’s a bit like saying
slightly pregnant.Although Veloce made the large thrust pin in 2 lengths,next time you have the primary
side apart,you may find that with the gearbox operating lever at its lowest position (clutch cable
removed),there is room for a longer pin,make one up out of silver steel(drill rod)so that it is flush with
the face of the g/box, we need all the clutch lift available particularly with new plates fitted.A few years
ago there was a tip in Fishtail no37. for a Clutch oil seal convertion, I made one up & have been using it
for about 5years it works well, much better results than the felt or neoprene seals I have tried.
L # 5296 It appears to me that the advent of the World Wide Velocette chat room has buried the
Velo clutch bogey once & for all ! There is so much instant help out there, that the newcomer only has
to follow the plentiful advice given, & those first agonizing weeks of getting sense out of your new
acquisition that has this clutch that you were warned about, are in the past ! On the other hand, we of
the earlier generations still remember it all only too well ! It's been said before, -- but how many happy
Velocette owners realize that one of the reasons that we eventually have a silky smooth, light clutch, is
because the system has a sneaky inbuilt servo system ? The whole clutch operation system came out
of necessity after Veloce decided to put the clutch inboard of the final drive, - but did the guy on the
drawing board realize the full extent of his genius ? - I doubt it ! For those newcomers to the Velo
mystique, the fact is that due to that rocking plate that operates the clutch thrust race, the effort needed
to release any given spring pressure in the system is pretty much just half of what it would be in a
normal (?) clutch. Think of it this way, without the motor running, & everything static, when you pull the
clutch lever in, you really only lift (or push) , - & release, one side of the clutch assembly, this is not
generally noticeable, but if you care to observe the action without the primary case fitted, the movement
will be obvious, - the back (rear) part of the clutch opens like an ocean clam, - but the front part remains
pretty much firmly closed, ( same as the ocean clam ). Yes ! there will be some movement otherwise,
via the radiused surfaces of the thrust race assembly , but basically that is what happens. ----- So ,
where is this servo concealed ? ---- well, ----- start the motor, & the whole clutch assy. will then stabilize
itself immediately upon clutch release, & this is brought about simply because the action of the motor
rotating the clutch, is actually using a tad of it's effort to drive the balls (or rollers) up an inclined ramp
that is formed when the rocker plate, ( What the hell is the official name of that thing ?) is tilted. The fact
is, that it's a little easier to release the (whole) clutch with the engine running. Re. the push pin in the
gearbox that transmits this effort, -- it's nice to see that it has been recognized that minor wear over the
years in the gearbox internal clutch 'bits', makes it imperative that the length of this pin is increased just
enough to compensate for the wear. I have had a (mostly) losing battle for years trying to point this fact
out, & the consequence of ignoring it, & fitting a 'GENUINE' original length pin in a gearbox with a string
of worn components inside the box, - ignore this fact, & you may well be making things much harder for
yourself.
# 5297 The name Veloce gave it was Thrust Cup. When you remove one from a machine, examine it
carefully, they can wear thin in the spherical recess & some develop a warp, may be something to do
with stresses of heat treatment working out of ageing metal. I had a useless clutch under the bench,
might still be there, it had what looked like bonded on neoprene, never could get it to work. As clutch
chainwheel bearings are expensive, & hard to find,(beware there are some out there that are small on
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the O.D. not much, just enough for it to work its way out & ruin your day),I thought about making up the
2 piece solid bearing Veloce tried towards the end, I understand some ended up in OZ, any info
available? RCP ps The useless bearings to which I refer, were not supplied by any usual Velocette
spares supplier, it was a bearing specialist.
5298 Keith, I was always told the clutch takes one revolution to open, much like a slice of bacon
coming of a joint on a slicer.
# 5303 Yes, theoretically at least one turn, (possibly less) does the trick, As for the thrust cup, it has
been theorized, (possibly proven) that it actually flexes under the load of releasing the later multi plate
clutches, -- quite possible I guess, one has to admire the design & construction of this 'jigger', I
personally would have made it a bit more robust, but it has stood the test of time, I have never heard of
one breaking ? One has to admire the design expertise that existed at Veloce, -- just a group of family
& friends, that seemed determined to tell the rest of the industry that they would do it their way, one can
only wonder what sort of discussions went on over the drawing boards in what was probably a pretty
dingy corner in the Veloce establishment ? As for the 'solid' chainwheel bearing, -- well in the first
instance it was just hardened steel on steel, & I guess it worked OK on the early two strokes, but they
soon decided to machine & harden a 'race' in the chainwheel & a heap of balls ran free in there on the
flat inner bearing diameter which was a part of the hardened back plate of the clutch. I have often
wondered about the theory of the 'modern' race, it had to move 'illegitimately' somewhere, I guess it
was just one of those ideas that worked without causing too many wear problems, I doubt that it ever
has any real stresses applied to it under normal usage, - if they did, they would have flown to pieces in
their thousands I am sure. - I have never replaced one for what it's worth, in fact I have always
considered that if the race was worn, but still serviceable, it possibly worked a little better than a brand
new race because there was a bit of clearance involved, --- an interesting feature really, it is no wonder
that the race does tend to become loose in the chainwheel, in my experience it was far less inclined to
do so in the early 'single' plate clutches for the obvious reason that it didn't have the need to move so
far when the clutch released . In one case on a very badly rusted early chain wheel, I just built the
chainwheel bearing surface up with bronze rod, & machined it to an easy fit, & it worked OK. I even
considered the possibility of machining a bronze ring to replace the ballrace in a case where the
chainwheel had worn & been centre punched countless times, -- can't remember what I did eventually ?
I think I may have mentioned it before, but I have a stack of N.O.Stock clutch plates (no chainwheels)
of various dimensions, including one plate with 6 push pin holes. ( I wonder who came up with this idea
?)
# 5299 Hello. I have tried one of the solid chainwheel bearings. It was 2 metal rings and a band of a
plastic material (teflon??) in between. It did not work any good. There seemed to be more friction than
in the ball bearing. It was brand new when installed, maybe it could have worked if the clearance for the
plastic were bigger. What happened was that the whole assembly rotated on the clutch backplate. I
fully agree with those who claim the Velocette clutch to be an engineering masterpiece. In fact it is
superior to any other motorcycle clutch. The light handleforce required, the size, the way of adjustment
without changing the spring tension and the quality of the parts included compared to the flimsy, rapid
wearing clutches of other makes from the same time. But there is one major design flaw. It concerns
the chainwheel bearing. On my bike, a Venom, there are 2 friction plates inboard of the chainwheel.
This means that in order to declutch, the chainwheel must move outwards, so the whole ball bearing
must move outwards on the backplate. There should have been rollers in a cage there, wide enough for
the chainwheel movement. If anybody out there can manufacture such a bearing please let me know
and I will buy immediately.
L # 5738 I've just rebuilt the clutch in my venom ( VM3211). I replaced the friction plates with
bonded ones from Seymours, and 2 of the plain plates with the slotted ones, also from Seymours. I
replaced the inserts in the original chainwheel. They assured me that there would be no problem
building a clutch with slotted and non-slotted plain plates in it. About 50 miles later, and with frequent
adjustments necessary as it bedded down, CLUNK! It wouldn't disengage any more. I've just stripped it
back down, and one of the slotted plain plates has disintegrated, sending shrapnel all over the PCC.
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One jammed the chainweel to the backplate, explaining the symptom. Thankfully the only parts
damaged were the two bonded plates on the offside of the chainwheel and the other plain plate on that
side (also slotted). Has anyone else ever had anything like this happen? What could have caused it?
The only thing I noticed, on taking the clutch apart, is that the chainwheel had detached from the large
bearing, although I don't know if this was before or after the slotted plate disintegrated. Could this have
caused it? Or just a one-off dodgy plate? Any suggestions would be appreciated, as I am just going to
rebuild it exactly as before (only with normal plain plates), which doesn't leave me very confident that
this won't happen again... Also, is it acceptable to bond the chainwheel to the bearing's outer ring to
keep them attached?
# 5742 The bearing was original, and had been in the clutch with no problems for years previously,
according to the last owner. So I don't know what to blame the detachment on. Fortunately, there was
no damage to the chainwheel or bearing, and the fit is still fairly snug, but I've put a layer of loctite on it
for good measure! This is what makes me think it was not the bearing detaching which triggered this
whole explosion.
# 5744 Had the same problem of the bearing moving from the chainwheel. When measured, mine was
a size to size fit. ie no interference. Tried loctite bearing fit which didn`t solve the problem, the bearing
still moved out of position. Didn`t fancy the welding solution so I had my local plater deposit some
nickle on the chainwheel which to date has cured the problem.
# 5743 Suggest you line the bearing up carefully and weld it in place - perhaps short bursts of MIG to
avoid overheating it. regards
# 5745 You can also (carefully) whack the chainwheel with a hammer to improve the fit1 - Yes it does
work!!
# 5746 Perhaps I'm a bit of a reactionary but I don't like the idea of the slotted plates; plain plates can
distort - only as a result of squeezing too many into the clutch (9 instead of 7 plate clutch) - but a slotted
plate seems too similar to a circular saw blade for my liking!
# 5747 Actually, that's how I've reconstructed it in my mind. The chainwheel disengaged from its
bearing, and started flopping about. One of the inserts detached itself slightly from the wobbling
chainwheel and lodged itself in a slot of the plain plate, tearing it to shreds. Catastrophic failure, whilst a
smooth plain plate would have just felt like a soggy clutch for a while, before falling, uneventfully, to
pieces.
# 5750 Get the proper ones from the Club. They have the original bends for the tangs and are the
correct thickness which is quite important in such a compact set up. r
# 5761 The failure ofyour clutch raises some interesting points on the design, construction and
assembly of the Velocette clutch. Although of unusual design, provided it is assembled correctlythe
clutch will give thousands of miles of service without trouble or adjustment. The problem is you have to
understand the beast and to a non-engineer this may be the problem. He gives the clue for his clutch's
failure in one sentence. To quote:-" About 50 miles later and with frequent adjustments necessary as it
bedded down, CLUNK.". No clutch should need adjustment several times within 50 for 'bedding in'.
After assembly and initial adjustment it should normally only require a 1/4od a turn of the spring carrier,
usually to prevent slipping,to get the clutch operating properly. After that the clutch should be good for
thousands of miles. The symtoms described indicate that the centre bearing was working its way out of
its housing until the final catastrohpe. Nothing to do with fact that slotted plates were used. In defence
of one of our respected suplier/dealers, Seymours were quite correct in advising that slotted plates, and
also fully bonded plates, can be used with other Velocette clutch components. If one assembles his
clutch without attention to the security of the centre bearing it is almost certain that the same thing will
happen again whatever type of clutch plates he uses. There has been several suggestions on how to
secure the centre bearing in the chainwheel but the only one which has any credibility is to plate the o/d
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of the bearing to give the correct interference fit. This type of failure could be avoided by a slight
modification to chainwheel. This consists of providing a small flange to the bearing housing to prevent
the bearing working its way out. Perhaps the procurers of Velocette spares could ask the manufactures
of chainwheels to provide such a flange. This modification does work and has been incorporated on my
belt drive clutch drum for years. It was also remarked that slotted plates are like circular saws is halfway
true. Circular saws do indeed have slots in their periphery to prevent distortion when they get hot.
The same principle applies to the slotted plates. They are flat when you buy them and they remain flat
when they get hot, minimizing drag. The reliability of the slotted plates is well proven by the number of
vintage and classic racers, of Velos, who use them. So. to the critics I would say get 'slotted'. The
remarks could be taken as implying that the 'bends' and thicknesses of the slotted plates and fully
bonded plates might not be correct. Not so,the bends and thickness are indistinguishable from
Velocette parts and have been for years.
# 5764 The 9 plate clutch uses thin plain plates in order to squeeze more material - friction plates - into
a thin assembly. The thicker & plate type plain plates do not distort anywhere nearly as much. The 7
plate clutch will take much more abuse than the 9 plate without distress. I would like to know if anyone
has played with the idea of a three plate clutch - similar to Francis Beart's Manx Norton design. I know
Geof Dodkin had started on this years ago. As I recall it had a sudden take-up and probably not ideal
for road use.
# 5766 Last summer I made a very crude prototype to a 7-plate clutch where the chainwheel was
moved so all the plates were outside of it. My workshop facilites are a welder and handfiles so it was
not suitable for daily use but as I use a beltdrive from Kevin Thurston chain alignment was a minor
problem. Anyway it worked brilliantly. It retained the light operation of a Velocetteclutch and the grip
was the same but as the chainwheel (beltwheel) did not have to move outwards it declutched faster
and better. Absolutely no drag at all when declutched. If anybody out there is able to make a clutch like
that it will be a success. The backplate needs to be modified or manufactured, the frontplate must
probably be manufactured as the tangs must be quite longer (the welding broke on my primitive
prototype when heavily loaded) and if a chain is used an offset chainwheel must be manufactured.
(Actually the same goes for a beltwheel as a good part of the belt ran outside of the wheel.)
# 5768 When it became obvious that the original, blued, dished plain plates on my Venom had
reached the end of the line (they were more like swashplates), I fitted a set of John Watson's slotted
plates. I could have bought the VOC Spares items but John was there at the Annual Rally and it was
convenient to pick them up on the spot. Since then and for over 3000 miles, my clutch has behaved
faultlessly with silent engagement of first gear and easy selection of neutral when stopped. Bearing in
mind that, being a skinflint, I used my original friction plates and chainwheel, I could not have been
more satisfied. Consequently, I would not now consider buying/using secondhand plain plates on any
future restoration. Of course, being a Velo Owner, I will never throw my old plates away and my
conscience will not allow me to try and offload them onto anyone else. So they will sit there in an old
box until I fall off the twig and my heirs call in the house clearance vultures. Trouble then is: they could
find their way to a bike jumble.
# 5771 One of the quirks of the Velo clutch the I have experienced, is the problem of the plates sticking
together when the machine is returned to the road after laying idle for a few weeks, this leads to drag &
rough gear changing for a few miles, also during these miles you may also find some slip. Don't be
tempted to reach for the adjusting tool, you will find the clutch will settle down as soon as the oil has
had a chance to warm up and find its way around & the plates will sort themselves out. The slotted
plates are an excellent way of preventing "sticktion".
L # 5875 As part of the cylinder head holdown stud upgrade from 5/16" to 3/8" I was given four
skinny o-rings for cylinder stud to head seal and told I should chamfer the head before installing them.
Any particular angle or depth for the chamfer? Are these seals effective? Anyone need a set of 5/16"
crankcase & cylinder head studs? Also, how many and how thick are the sleeve gear shims supposed
to be? The parts book shows two shims but upon tear down I found 6...4 at .050" and two at .020". Is it
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a practice to add shims for a slipping clutch? The clutch springs all measure the correct length so I
suspect it was a jerry rig (a bodge?).
# 5878 You can use a standard 90% countersink tool,(do not use a large Drill instead) to get an even
depth I found it best buy one fitted with a handle. It is easier to use a hand held one rather than one in a
hand drill. A drill press however would also be OK as you can adjust the depth accurately. I accept
what the previous answer said but I preferred my chamfers to be a small amount bigger than the O
rings. How skinny is skinny? the O rings I use are 68 thou thick, best not to use ones much thinner.
They should also be a tight fit on the studs. Use nylock nuts as they also help to prevent oil migration
down the studs..
# 5880 Your O rings should be fine. You should not have any problem starting the nut unless the
sleeve gear is pushing back in the bearing, you can check this by hand pushing and pulling it into the
gearbox. If it is moving assemble it in gear, I was always told it should be 4th gear but try each gear
until you find the best one that prevents the seleeve gear moving into the box. Use a proper tool to get
it started, I do not believe the nut and bent piece of metal like the Haynes manual suggests is any good
as it can push the sleeve gear through the bearing. If you dont have one ask around and borrow one,
I'm in Essex, near Dartford crossing, and you could borrow mine if you are reasonably local. Regards
Dave.
# 5881 The proper tool is available from Mike at Grove classics.It makes the job easy!
# 5884 I believe my problems with getting the sleeve gear started are associated with the new inserts I
installed...the thickness of the total clutch assembly comes into play when installing the sleeve gear
and you must temporarily bottom the spring holder to get the nut started and move the holder out as
you compress the clutch springs. Which brings a new question...how much should the sleeve gear nut
be tightened? You can't bottom it since the compressed length of the springs is more than the available
space in the holder (by 1/16").
# 5894 The oil retaining shims were originally 0.010" thick
5883 If the extra shims under discussion are located between the sleeve gear and it's large bearing,
the purpose is to increase the engagement of the top gear driving splines. This is a good thing, as
tighter engagement means that it is less likely that the collection of 'factory assembly tolerences' will
allow the box to pop out of top gear under load. It has also been reported that if the sleeve gear is
located too far to the left side of the machine, the drive dogs on the sleeve gear can be chipped by the
matching gear on the left end of the layshaft. This last comment does not apply to the Series 14 (MSS)
gearset. The Velo gearbox as delivered had occasional poor dog engagement in any of the gears,
especially 1st, due to assembly tolerances. This is what leads to the gears disengaging under load and
the subsequent wear of the shift forks and tapering of the engagement dogs. When I assemble any
gearbox, I do what I can to tighten up the gear and dog engagement with the use of shims or spacers in
order to have a sweet shifting box.
#5885 No, they are between the sleeve gear nut and the springs. Part C8. I can't figure out why any
extra shims were put there at all. What's their thickness supposed to be?
#5886 I can tell from your statements that you have not read the 'Red Book' repair manual or the article
by David Childs on the various different clutch parts. The physical sizes of clutch parts can be found at
the Velo tech site http://www.croesus-consultants.co.uk/v-tec/ . The shims between the sleeve gear nut
and the springs are not for the purpose of spring preload, but are to be greased to allow the sleeve
gear nut to be tightened without bending the springs over, kinda like plain thrust bearings. There are to
be two shims P/N C8, (about .015" thick) and the sleeve gear nut must be made up tight, as otherwise
the clutch hub (or back plate) will be free to move around, wearing the splines, allowing primary chain
misalignment, and upsetting the operation of the clutch throwout mechanism. If your springs are
coilbound with the sleeve gear nut made up tight, you have some inappropriate parts in the mix. A
210

study of the 'Diagram of Clutch Operating Mechanism' on page 69 of the 'Red Book' and the five pages
of text will help to make the operation clear. As to the use of the sprocket nut and bent piece of steel to
start the sleeve gear nut, it has always worked well for me. The sleeve gear must be tight, and the
locking plate keeps it there.
# 5889 Some years ago there appeared an article in a defunct magazine titled "Classic & Motorcycle
Mechanics". The article was by Peter Dobson & the Consultant was Martin Arscott. This illustrated
article was one of the best I have seen explaining the reassembly of a Velo clutch as it shows one or
two tips not to be found elsewhere. Ref the Sleeve shim C8. I have just measured one at, 0.015".Use
both together & apply thin grease to both sides & under the sleeve gear nut flange, also grease the
springs & the spring holder assembly. Sometimes the clutch goes together so easy you wonder what all
the fuss was about, at other times it would try the patience of a saint. Life with a Velocette in the
workshop is definitely not boring, frustrating maybe, but always interesting.
# 5896 Lets not get confused here, Sleeve Gear Shim C8. =2off at 0.015"Thick. & Gearbox Housing
Oil Retaining Shim B31/2. =2off at 0.010"..
# 5902 Have to have my a'pennorth in here, though most of it seems to have been covered. The 2
shims under the spring nut face must be .015, quite often over the years I have found them to be
thinner, which just isn't good enough. Another problem with new springs can be that while they are the
correct length, the facing of the ends has left an extremely sharp edge which can bite into the
corresponding shim face, as soon as the assembly screwing pressure comes on, a sharp edge will
grab straight in to the shim if things are not exactly right ! I always check all the springs, & touch off the
slightest sign of a sharp edge on the bench grinder, -- but just a touch ! the spring needs the full contact
face to help it stay in place properly. I discard any shims that show signs of previous 'grabbing', & I
grease all shim faces with 'moly' grease before assy. It is also a good idea when tightening the nut to
back off every now & then. Sometimes a problem spring can be reversed to overcome the tilting
problem. I always keep a close watch on all springs as tightening progresses & nip any problems in the
bud so to speak. Inferior quality springs need to be avoided. Although it doesn't occur in a well fettled
machine, the condition of the nut needs to be checked, in years gone by it was common to find that the
holes in the 'nut' face had been bodged by the use of a punch, & this had also carried through to the
shims. I have old 'nuts' in my junk box where the holes have been punched into horrifying hole
dimensions, --- even right out the side of the nut ! ---- probably a lot of you fellows have similar
collections ?
# 5914 If you feel that the assembly cannot be tightened fully without the springs becoming coilbound
you almost certainly have the sleeve gear pushed into the gearbox. Try to assemble without the
springs, do the spring carrier flange nut up tight and see if it pulls the sleeve gear back out. Once this is
done assuming you have assembled the clutch components together so they fit properly you will have
enough thread to start the flange nut unless as previously stated the sleeve gear pushes back in. You
wont need lots of force, if you do, go back to the length of the sleeve gear. If someone has their clutch
apart perhaps they could let you know the length of the sleeve gear shaft that should be protruding. If
not I will dig out my other gearbox and post the measurement. New clutch plates will not prevent the nut
starting if you have the correct chainwheel.
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E.2. Gearbox -
L #9 Being new to my 1956 MAC, what are safe max upshift speeds on this machine? I have
been shifting at about 15, 30, and 40 miles per hour, taking into account the relative accuracy of the
Smith's Chronometric Speedo.
#10 Proper shift speeds for a MAC are 'before the valves bounce', preferably. The mph would depend
on your gearing. As Velo's are fairly unburstable, I don't think it's much of an issue to worry about. I
usually shift when the model is no longer accelerating under full throttle. just one man's opinion.
#12 Torque is fairly low down on the MAC, and on the wide-ratio gearbox, buzzing it won't do a lot. 3rd.
is at 75%, remember. Always remember, don't slip the clutch
#14 The ratios are as follows with the standard 21 tooth final drive sprocket: 1st- 14 to 1, 2nd- 9.6 to 1,
3rd- 7.3 to 1, and 4th is 5.5 to 1. These don't seem to be particularly wide ratios. I do find, though, that
when I shift at an indicated 40 mph, speed drops enough so that I need to run a fairly wide throttle to
build up acceleration again to cruising speed.
#16 Over here, we work out gear ratios as percentages, so what you have is the 10- box, which has the
wide-ratio gears the same as the MSS. I don't think the actual pinions are the same, I think the box is a
bit lighter being drawn from the MOV rather than the "heavy" bikes. This on the MSS is called the 14box,
and not all MSS had it, some had the Venom 12- box A 5.5 ratio on a MAC is unbustable, that is,
you can rev as far as you like, you are not likely to get into the red zone. But on a 7.3 third, 70 mph is
already too much for sustained use, 50 in third the same, and 40 in 1st. is about 7,400 rpm- we are
talking racing speeds here. You tell us how many rpm you consider reasonable. To give you an idea of
how wild a Thruxton is, the high 4th. gear (4.4 on a 20 tooth sprocket) is to try to limit revs in 4th. gearusually
we can get to the maximum allowable, 6,200, in all four gears without trying too hard, which is
about 105mph in top. On the Mac, you could go to 20mph in first, 30 in 2, 40 in 3 and you would be
revving to about 3,800 or so in each gear. I don't know peak power on a MAC, but it is likely to be
around the MSS figure of 5,000 rpm. You would have nothing to gain revving beyond 5,000.
#288 Judging from the way that ZUMAC ran up the hills in top, I think that a 20 tooth gearbox sprocket
would improve things on both your S/A MAC and Zuma's iron head rigid. The Book says yours came
with a 21, ZUMAC with a 19. BTW Dai Gibbison’s spec page lists all 86mm 500 Velos as having 18T
gearbox sprockets as standard - the Red Book sez VMTs came with 20. Of course, it also lists no
standard sprocket at all for scramblers.
#576 A 21 tooth sprocket is very very tall, and a bike would struggle to pull it. my venom has a 19 tooth
fitted and it works spot on. I fitted a 20 tooth and it was too tall. fitting a 21 tooth would be way too tall
for a 500 and a 350 would never pull it. I guess the demand for a 21 tooth is next to zero, that’s why
they are probably not listed.
L #197 Just a quick comment on the use of 80/90 gear oils in Velo gearboxes - DON'T!!!!
Especially if they are Hypoid type oils - REALLY DON'T!!!! The recommended oil for a late Velo
gearbox is a 20W50 multigrade engine oil - Hypoid oils will attack the bronze bushes in the box and
cause eventual seizure - the sort of increased friction you can do without.
L #199 First comment is to correct the statement re non-listing of c.r. gears for pre-war
MAC/MOV. When iron MAC first came into the family in 1978 I copied a parts book from old Joe at
Allparts, Sydney, (sadly no longer trading, although sister company, Modak, in Melbourne is still going
strong and does excellent mail order service for things like 3/16"x3/16" rollers for clutch thrust race
conversions, .001" oversize rollers to revitalize tired drive side mains on pre-war Velos etc). Anyway
this book is marked "12/39 G.D." and lists B6/2AS sleeve gear (bushed) 16T (standard ratio) & below
that B6/3AS ditto 17T (close ratio). These pair with B86 layshaft driving gear 28T (standard ratio) and
B86/2 ditto 27T (close ratio). Now, Mick T's MAC definitely has the 17/27 combination (I counted the
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teeth when he had the layshaft with the broken 2nd gear on the table at the January Club Meeting here
in Perth) and they are as rare as... easiest way to go close ratio is to get a standard ratio MSS sleeve
gear and driving gear, grind down to suit MAC/MOV width, then make suitable changes to the various
spacers, sleeve gear nut etc of the clutch so it will still operate correctly, as I think the protruding
threaded portion of the sleeve gear will be different length to a MAC. Oddly enough, the MSS parts
book of that era lists 2 ratios, the 17/27 (BK8/2AS & BK86/2) being "standard ratio" and the 16/28
(BK8/3 & BK86) being listed as "wide ratio"!!! At least this explains why there are a lot more 17/27's
around for MSS gearboxes. Only other source of new c.r gears for Velos I've found are the 18T KTT
sets available from Bob Jolly in Adelaide, but these would need grinding to fit a MAC and I'm not sure
we need 3rd and top to be THAT close. If enough of us got together we could have sets made in Perth
from EN36 - enquiries have been made with the man who makes the gears for most of the V8
Supercars (Ford and GM Holden tintops), but price for only 2 sets is prohibitive. If I'm swamped with
positive rehouses we'll include 2nd gear layshaft in the order as well, to help get Mick back on the
track and to fit to our racers to ensure that bogey stays at bay.
#207 I for one would be very interested in c.r. gear set for MAC. To be viable I guess they need to cost
less than the swing-arm grind-down method. I haven’t been able to check how easy(how hard?) this
would be as I don’t have a later g'box to look at...(I have owned three different swing-arm 500s but now
there's only the wee-mac). Maybe someone happens to have both types in bits and could compare
dimensions. Many years ago when I first had the Mac, someone told me that c.r. gears were available
in Sydney. I wonder where they ended up, or if the info was even correct, seems it may have been if
the parts were once listed. I cant imagine many Macs would have been other than 'standard' ratio at the
time when they were new, as for a general- purpose machine and perhaps with a pillion as well they
would be struggling with anything else. I'm not under any illusions about making the Mac into a 'racer',
but for the use I give it, the c.r. box would be a real improvement.
#208 CR 27T layshaft gears (B86/2) are available new old stock from the UK Velocette Owners Club
spares scheme, cost £ 8.30 plus postage. I have just bought a new 17T B6/3AS sleeve gear for £ 36.00
plus postage. The Velo dealer that I bought it from probably has more; if any one is interested please email
me direct (not via the group) and I will check this out and get back to you.
#209 Strangely enough I think you will find that B86/2 and B3/3AS was originally listed for the GTP as it
appears in the GTP spares book but not the MAC spare parts book.
L #556 During a discussion with Don Chesson this morning the subject of a weakness in the
normally robust series 12 gearbox came up. Don is Perth's elder statesman of Velo folk lore, having
begun his racing career on a Velo just as WW2 was ending. If you refer to any list of bearing numbers
for Velos you will see that all the sleeve gear bearings B22 are the same from MOV to MSS to VMT.
Same for the layshaft bearing B22/3 or BK22 for cammies - one bearing fits all. But when it comes to
the mainshaft end cover bearing the series 12 shares its bearing B23 with the MOV/MAC whilst the
iron MSS and cammies use BK23, a larger bearing. Consequently it has been known for this bearing in
the series 12 gearbox to fail or for the relatively thin bearing housing to crack, with disastrous results.
Don has recently obtained a butchered series 12 end cover and is presently using it to make a pattern
to cast a few series 12 endcovers with enough meat around the main shaft bearing to take the BK23
type bearing of the iron MSS and cammy style. The strange thing is that I can't recall ever reading of
this weakness in the design and have personally never had a problem in over 25 years of flogging
VMT457 around the best biking roads in Australia. But I've seen the results and know of a couple of
people who are currently looking for series 12 endcovers to replace broken ones, so this isn't a
figment of someone's imagination. The recommendation is to replace that little RLS4 in the endcover
of your series 12 before it lets you down. They are cheap, readily available at bearing shops and easy
to get at for replacement. And while you've got the endcover off, pull first gear off the mainshaft, get
your Maglite and take a real good look at the gears, particularly the load bearing side of the teeth. At
this age, there must be many chatty gears still doing service inside the trusted series 12 gearboxes of
our Velos. I've had 3 apart in the last year and I was hard pressed to make up one "good" set of gears
out of the three of them, such was the state of the hardening, particularly on first second and 3rd gear
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layshaft and the double sliding gear. Not surprisingly the gears with the most teeth seem to survive
longest! Has anyone else out there had a series 12 main shaft end cover bearing collapse?
#558 I too have a stack of #12 gearbox end covers that are cracked around the mainshaft bearing
area. Two of them I know are the result of gearbox blowups. And the good ones mostly have loose fits
in the bearing bore. I'll bet if you walk up to any Velo and yank in and out on the countershaft sprocket
you will find many with end float due to a loose mainshaft bearing bore. On my VMT I have eliminated
the circlip and use a sleeve that is held in by the end cap to hold the bearing in tight. Haven't had a
bearing itself go bad. All in all a good gearbox though and easily serviced. Count me in on one of the
new castings
#559 VMT 457 had a sleeve behind the inspection cover to locate the mainshaft bearing (in lieu of the
circlip) when we bought it in 1975. Rebuilt it with new bearings in 1982, ignored the onset of tooth wear
and got another 20 years out of it. Oil changes only and made sure water was kept out (using a
distributor cap rubber on the clutch cable entry - a must). When rebuilding as a 5 speed this year, I
noticed that the bore of the bearing housing was threaded, same as iron engine gearbox endcovers. So
I had a threaded sleeve nut made up, like the pre-war gearboxes, and now have positive control of end
float. Sometimes, winding back the clock can be an improvement!
L #562 During pull-down for rebuild of my 68 Venom Clubman I discovered that the gear change
internal assembly of two yokes (GC56), connecting link (GC58) plus clevises was missing in my
gearbox, replaced by a short length of twisted strip steel riveted at each end. I assumed this was a
temporary bodge fitted by some previous owner, until I ordered all the bits and pieces from a supplier
and received - a short length of twisted steel with rivet holes at each end! Did Velo decide, after years
of the complex assembly, that a steel strip was just as good? Should I chase the 'real thing' according
to the parts book, or refit its simpler alternative?
#563 The piece of twisted steel works fine and there is no real need to replace it in normal use. If you
want to reduce play in the linkage though I would suggest that you obtain a pair of 1/4" "Rose" joints,
one with a male thread and one with a female thread, and an appropriate locknut. Screw these together
and adjust to the same length and orientation as the ends of the piece of twisted steel. It may be
necessary to shorten the threaded end on one or both parts in order to get the required length. Lock the
assembly together with the locknut and a drop of loctite if you want to be doubly certain of things
staying together and use a couple of button head Allen screws and nylok nuts to replace the original
rivets and Bob's your uncle. If you're using a rearset linkage you can replace the external clevis
#564 The length of twisted steel with pins inserted can easily be replaces by 'rose' joints (or Heim
joints), as I've done on my VMT. The twisted steel is fine for a while, but eventually the pins wear out
their holes and sloppy gear changes result; a shame on such a nice gearbox. A retrograde step from
those early robust linkages, just as John Jennings found with the earlier end covers! Imagine finding a
length of twisted steel in there, surely a bodge!
L #574 In the following for gear shaft nut please read sleeve gear nut. I've two clutch spring
holding assemblies, #1 is a one piece unit, max depth 5/8", with four sets of four spring holding holes,
with springs presumably 3/4" long when new. #2 is a two piece unit max depth 7/8" with a separate
spring holder containing 16 equidistant holes. No springs. When I ordered a set of clutch springs for a
7-plate clutch from VSL they turned up at 1 1/8" long. I've only one gear shaft nut which is 7/16" long. I
can get the nut on to set #1 and the clutch works in this mode; but to try to get it on to set #2 I'd need
to be Britain's Strongest Man. Is there a gear shaft nut with a longer thread, or have I been sent the
wrong length of new springs, or what? Both sets would seen to fit behind the gearbox sprocket with
sufficient clearance. Why is a 21t gearbox sprocket as indicated in the Spare Parts Catalogue (SL 94/1)
not listed in any of the current main suppliers catalogues(it is listed under Viper bits);has it been found
to be unsuitable? Finally, the gearbox nut locking piece. When countersunk mine has the thickness of
a fag paper, so what does the little 1/8whit csk screw into?
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L #650 Please tell me the parts number of the gear box end cover ball bearing for prefix 5.
#651 I am not familiar with all of the various gearbox serial numbers and their potential
similarities/differences. I can tell you that this bearing in my '50 MAC is a FAG LS5. Readily available,
at least here in the States.
L #681 Could you please suggest any remedies for an oil leak from the kick-start ratchet box, it
appears to be coming from the shaft. Is there any way of fixing it apart from buying a new box?
#682 Try here www.velocetteowners.com/qanda/gb008.htm
#683 I used a 19-27-4 single lip seal obtained from Bearing Services Ltd., fitted into a 4 mm deep
recess carefully bored in the outer face of the kickstart housing. The shaft was carefully deburred and
its diameter cleaned (if it's pitted or damaged the seal will not last long) and eased through the seal lip
so as not to damage it with the flat for the cotter pin. The lever was fitted as normal, being careful that it
didn't slide back through the seal during assembly, and the whole assembly then fitted back into the
end cover as per the manual, but with a thin smear of Three-Bond silicon sealant on the mating face to
seal it. This part of my machine has been totally oil tight ever since.
#685 There are people who will do an exchange or conversion with an O ring seal fitted to stop the oil
loss. Colin East on 01522-810029 does, I'm sure there are others too
#686 Some years ago, I tried to cure such oil leaks and followed the advise found in FT Hints and Tips.
So I get the housing machined to fit an O-ring. This proved to be an improvement for a while, but
seepage came back, although less than before, as 0-rings are not designed to cope with repeated
rotations, and they wear. Especially if there is some wear in the assembly. I'm now considering to fit an
oil seal instead.
#694 A quick remedy to ameliorate the oil weep from the kickstart housing without recourse to
machining it, is to epoxy-resin a thin oil seal 1x3/4x1/8 imperial obtainable from a good bearing stockist
for maybe £2.00,to the outside of the housing cover over the kickstart shaft. This may sound a bit of a
bodge but it does work without interfering with the kickstarter engagement.
L #1086 Have some of you experienced another way to secure the sleeve gear bearing retaining
nut than butchering the g/b shell, each time at the same places, which I hate to do ? Is Loctite safe
enough ?
#1088 I've a very worn thread on my gearbox plus a worn sleeve gear bearing nut on my Venom I've
used Loctite but a retainer not a threadlock type. With normal threadlock I've had a problem, but with a
high strength retainer I've experienced no problems, though I must admit my threads are very worn. I
might also add I've had no difficulty in unscrewing the nut after I've used the retainer.
L #1969 After my 500 racer jumped out of 3rd gear several times at the last race meeting, I have
the gearbox apart. (And the road venom's gearbox for comparison) It runs a tt top gear and std 1st
gear. 1) The tt top gear with the sleeve-gear dogs looking very sorry. Does anyone out there have one
available ? 2) Any opinions on using a std sleeve gear plus tt 1st gear ?
#1974 You can use any sets of gears from a heavyweight box provided the total sum of the mating
gears on the main shaft and lay shaft add up to 44. There was an interesting article published by Bruce
McNair in Fishtail some years ago, which thoroughly analyzed combinations of using Prefix 12, 12R
and 14 ratios. Unfortunately I cannot tell you which edition of Fishtail it was published in. If you get
desperate I will scan the article and send it to you. You can therefore play with gears to ensure that the
engine stays within its power band for any particular combinations of gears. John Jennings from
Australia also developed a spreadsheet that calculates RPM and speed in gears. If you want I'll check
with John to see if he minds me sharing the spreadsheet.
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L #2218 I have a gearbox which is literally in pieces. I have the KSS spares list to identify parts
and the owners manual but need more info to assemble the parts. Is there an exploded view of a
gearbox to help with assembling the selectors and gears. Any advice appreciated.
#2222 The assembly of the MkII gearbox is largely similar to the VM prefix 11,12 or 14 boxes. You
should also have a look at the Venom service manual - still no pictures though! I can't think of an
exploded view. Anyone else help?
#2224 Thank you I have the Red Book and Bruce Mainwaring published book.
#2223 I had the same situation with my gearbox for the KSS, a couple of bags of rusty things and a
gearbox housing !! I searched all over the place to find a proper assembly drawing for the box, and
although not perfect, came across the following............ "service series No 11" from the magazine
'MotorCycling" dated 11th June 1953. It's entitled "Gearbox restoration routine for the MK11 348cc
overhead camshaft KSS and KTS Velocette" It gives a pretty good exploded view of the box, I found it
useful in conjunction with the KSS service manual. There are two other parts to that service series, one
from April 30th 1953 covering the restoration routine on the engine, and the other from July 16th 1953
covering the restoration of the cycleparts. All the articles cover mostly what is already in the service
manuals but include other small tips and those very useful exploded drawings. All these can be had
through the Classic Motorcycle as photocopies for a couple of quid or eight.
L #2376 I have a series 12 gearbox end cover with damage to the mainshaft bearing support. I
need to build up with weld and then machine the bearing housing. Can anyone give advice on the
appropriate weld material or method to build up the damaged area please.
#2378 A more expensive but permanent solution is available from long time Velo fettler Don Chesson,
here in Western Australia. Don has cast up 3 or 4 series 12 end covers with the area around the crappy
little 250 sized mainshaft bearing beefed up to take a slightly larger ball bearing - not as big as those
used in the pre-war heavyweight gearboxes but a better thing just the same. Phone him on + 61 8
95731286 if you want to discuss price and mailing costs with him. We are GMT + 8hrs, just so you don't
phone in the middle of the night.
#2381 Here's a little caveat while working on your gearbox: A friend who shall remain nameless had a
loose locking ring at the back of his gearbox, the 'punch' method having failed to secure it properly (and
who would be surprised after a 50% horsepower increase!). He logically decided to Loctite it in place,
problem solved. During our 'British Singles Run' the other weekend, (and yes that was my squish head
Venom clubman two-up, passing two Gold Stars on a fast run -thanks Dave Smith), said fellow noticed
gearbox oil exiting the 'box at the clutch side, and he can tell this as he has a belt drive primary.
Another primary strip down, and lo, the excess Loctite had pooled and blocked that little drain hole at
the bottom of the bearing assembly; it seems to be there for a reason! What's worse, when he tried to
remove the locking ring, he found that the red Loctite is the type that really doesn't want to come loose!
One buggered ring. That's lesson number two, or is it three?
#2384 Probably teaching my Grandmother to suck eggs here, but a great way of removing Locktite
secured bearings and threads is to play a gas torch over the area. Long before you do the metalwork
any damage - the Locktite will let go. Parts should be separated while still hot.
L #2612 I am in the middle of restoring my Venom back to a standard footrest and handlebar
arrangement from the Clubman guise it sported previously (rear set footrests and swept back exhaust).
I fitted the new (standard) foot rests last night, and was surprised to note that the folded kick start
position seems to interfere with the right leg. Now I know there are two types of kickstart crank (my
understanding that the clubman/thruxton crank was different), but I am unsure of which one I have, and
whether a different crank would provide additional leg clearance. How can I identify the crank that I
have? Would another crank provide a worthwhile difference to leg clearance?
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#2613 There are three types of kick-start cranks fitted to spring framed Velos: BK12/5 fitted to prefix
MACs with prefix 11 gearboxes BK12/6 fitted with spring foot piece retaining blade BK12/7 fitted with
spring plunger foot piece retainer If you used rear sets previously your kick-start is either BK12/3 or one
of the others that has been suitably modified.
#2614 If you used rear sets previously, your kick-start is either BK12/5 or one of the others that has
been suitably modified.
#2617 Allow me to offer an alternate answer for the part number impaired: I have S/A MAC, Venom,
and VMT in the garage. There are three different S/A kickstart cranks, as follows: Early S/A MACs with
the narrow gearbox (prefix 11) used a crank with approximately 1-1/2" of offset. You definitely don't
want this one. Venoms, VMTs and later MACs with prefix 12 boxes used one with only about 3/4" of
offset. There are two styles of these, the later one has a ball and spring detent and allows the pedal to
rotate inward, away from the ankle. The older style has a flat spring and the pedal points straight
forward. This style was used (up) on some later Clubman and VMT models, but some judicious grinding
will allow the pedal to rotate inward. This modification has greatly reduced the kickstart ratchet noises
when Zuma shifts 2MAC.
#2618 My kickstart is the one with the flat spring. Since I have just had the thing chromed and bought
new shiny stainless bolts and spring, the "judicious grinding" option looks like the approach to take. I
was blown away with the news that the spring type rotates inward. I checked all of my velo books and
not one shows the pedal rotated into an inward facing position. I never realized. Mine is a 1963 model,
which according to the records was built as a VM.
L #2833 The gearbox in a racer I've been working on tends to miss the upshift from 2nd to 3rd.
It’s a Thruxton engine in a 60s springframe with standard gearbox with the close ratio set installed. I've
stripped the box to bits several times, but have not found the cause. The rider is an experienced one,
so I place the blame on the box, not the rider. It doesn't happen on every attempt, but with sufficient
frequency to be a problem. The only thing not standard inside the box is the linkage, having been
changed to a short rod with heim joints, in place of the pressed steel plate that normally transfers the
movement. The shift forks are straight, and the shafts are shimmed to minimum end play. I did try
deepening the 3rd gear slot in the shift plate, with no change. Any suggestions as to why this is
happening, or any suggestions on where else to look would be appreciated.
#2834 I have the same problem on my Thruxton. It has been suggested to me by another club member
that the problem is due to wear in the Striking Pawl ( doesn’t rotate the camplate far enough for the
indexing pawl to drop into the third gear notch). As I'm pretty busy workwise, I have learned to live with
it and take a couple of stabs at getting 3rd gear if necessary. Usually however I can get the gear by
giving the lever a good sharp prod. I think this gives the camplate enough momentum to rotate far
enough. I can see why this wouldn’t work on a racer though.
#2841 I think that you will find that whoever suggested the pawl not engaging properly it spot on, this is
one of the most common causes.
#2844 I experienced similar problems, and several comments offered by Mr. Ed Gilkison were
conceptually reasonable. More to the point, implementing his suggestions resulted in a gearbox that
now shifts accurately and reliably. The first issue relates to the internal actuating lever itself (apologies:
I don't have my parts book in front of me, so my exact nomenclature is probably off), and in specific, it's
figure-8 shaped hole. The extents of this hole limit the travel by virtue of coming up hard against the pin
on which the cam plate and indexing hub pivot. With all of the gear shafts and dogs removed, I could
observe when actuating the foot shift lever that the cam did not fully rotate to the next indent position. It
is important when doing this to put a load on the cam plate, since you will otherwise observe the
misleading result that the cam plate rotates further when there is no load placed on it (I just applied
pressure with the palm of my hand). By slightly grinding the extrema of the figure-8 shaped hole, I was
able to get the cam to fully rotate to the next index position when under load. This required enlarging
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the hole by about 0.040", noting that different amounts were required in both the upshift and downshift
directions. Grinding away more than necessary is clearly contraindicated. In doing any of this, it is first
important to carefully inspect all of the external linkage elements for wear or play, and insuring among
other things that the foot shift lever does not bind against the exhaust pipe (or anything else). Ed also
noted that polishing the edge of the cam plate itself helps quite a bit, a notion that apparently was
brought to his attention by Graham Rhodes. In my case, this definitely helped. I also noticed that the
point on the indexing pawl was worn considerably, and the spring seemed a little weak. In this case, it
was easy to simply replace them. The actuator pawl and indexing hub were also worn, and I replaced
them as well. In terms of the former, both the teeth and the pivot hole were worn, which was clearly
obvious when comparing them with the replacement. All of these features conspire such that the cam
plate does not fully rotate as desired. In the end, I now have a gearbox that works exceptionally well,
and unquestionably shifts more smoothly than before. Parenthetically, I found it slightly humorous to
read in my original owners manual that none of the parts comprising the actuating system have ever
been observed to wear or need replacement. This was certainly not true in my case.
#2850 Missed Gears ! I had loads of problems with my racers last year - I ended up getting a 5 speed
cluster for one of them - which did not turn out easy to get going properly, but eventually provides a
delightful set of ratios. It turns out that the quaife cluster has _much_ tighter tolerances than the velo
clusters ... and that most of our gearboxes are running with a very sloppy fit for many of the parts, but
still shifting ok. This is, of course, in line with the standard velo factory policy of rejecting as few parts
as possible ! The moral of the story is that your gearbox does wear quite considerably, but you will not
notice it at first, but when you do, and you fix the first problem you find, you will also find that a number
of other parts are worn - like the shafts, which bend when you use the power ! (even a racing viper can
do this !) So, if you upgrade to a quaife cluster, be prepared to replace few remaining velo parts too !
L #3074 Being fed up with the brown burnt oil stain on the downpipe I intend to fit an 'O' ring in the
kick-start ratchet housing. I know we've covered this thread before, but I'm at a loss to find the
responses. I know some of have already done this mod and that a standard 'O' ring is available. Can
anyone point me in the right direction for the 'O' ring and dimensions of the groove to be machined in
the housing? Secondly I'm in the process of tidying up the Velo' and carrying out those little bits of
maintenance before the summer season. As part of this I'd like to tidy up the oil lines and petrol feed
pipes. Does anyone know where I can get some nicely made up steel braided pipes for a Venom or
where I can get the appropriate fittings from somewhere so that I can do the job myself ?(UK, West
Midlands area)
#3079 HMP Grease in the kickstart housing stops the leak and is cheaper. Mine has lasted 18 months
so far.
#3088 Forget 'O' Rings; for them to work they need to be retained and that involves fine machining of
grooves etc. Instead, fit a proper Oil Seal as described by Tom Ross in FT234. He gives a National No.
240735 for the seal and maybe this means something to a bearing supplier. Personally, I use an LE
Primary Shaft Oil Seal (Veloce Part No. LE431) and machine the Kickstart Housing about 0.020"dia.
undersize as the seal is rubber coated on its outer diameter. If you have difficulty pressing the greased
seal in after removing all burrs then turn off another 0.005"dia. and try again. The 21mm ID of the seal
is a correct fit for the Kickstart Shaft. This would be a good opportunity for you to join the LE Velo Club
(What! you don't have an LE? How many would you like?) and enjoy their truly delightful "On The
Level" magazine which averages more technical articles than most club journals. Failing that, the
number marked on their LE431 is: W11907915R21/29. Basically, the seal is 29mmOD x 21mmID x
5mm thick. For your braided hoses try: "AutoHose", 7b Bagnall Road, Milton, Stoke-on-Trent, ST2 7AY
Tel: 01782-542486; though you will have to make up the copper/brass unions at each end yourself.
#3091 I used a 19-27-4 single lip seal obtained from Bearing Services Ltd., fitted into a 4 mm deep
recess carefully bored in the outer face of the kickstart housing. The shaft was carefully deburred and
its diameter cleaned (if it's pitted or damaged the seal will not last long) and eased through the seal lip
so as not to damage it with the flat for the cotter pin. The lever was fitted as normal, being careful that it
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didn't slide back through the seal during assembly, and the whole assembly then fitted back into the
end cover as per the manual, but with a thin smear of Three-Bond silicon sealant on the mating face to
seal it. This part of my machine has been totally oil tight ever since.
L #3080 I have a swingarm MAC and she seems to lose a lot of oil into the primary cases, what
can I do to go some way to slowing this down or even preventing it happening, can I use grease
instead of oil, when the oil level has been renewed she changes gear like a dream and the oil will then
flow quite antisocially to the point of altering the gear change reliability I will then have 5 or 6 neutrals
and difficulty engaging gear the oil loss is excessive and needs to be resolved, any ideas?
#3082 You have a problem. The main seal between the gearbox and the primary chaincase is the two
shims either side of the sleeve gear bearing. If these have slipped or not been put in you will loose a lot
of oil. Also, have a look at the state of the sleeve gear bush, this may be worn oversize on the bore.
However, you are not likely to loose so much that way. Take the primary drive off and have a good look
at the gearbox casing while you're there in case of any other holes, cracks etc. Grease is not
recommended. The oil should stay inside the box for a long time with usual checks for level.
L #4027 A query for the technically wise out there. For the past 2 seasons the lightweight gearbox
in my '39 MAC racer has produced a constant stream of bronze in the oil whenever drained. The
source was from 3 places: First gear mainshaft bush - caused by the gear wanting to move inwards and
thus wearing away the end of the bush on the raised portion of the mainshaft. Cured by changing for
another first gear (assume the gear was not cut true or the bush in the original not bored parallel);
Second gear layshaft; Third gear layshaft. Both of these constantly run towards each other wearing
large amounts off the face of their bushes in the process (like 12 thou in 2 race meetings when last
checked). Have changed double sliding gear twice (thinking that if it isn't cut true maybe it could cause
some lateral force in the mating gears below) and rebushed these gears with careful parallel boring of
bushes twice. But still it persists. In desperation I have dealt with the symptoms by installing a 20 thou
thick hardened shim between third gear and the raised portion of the layshaft (as a trial), with a similar
amount taken off the face of the bush to maintain correct gear location and end float (about 5 thou).
Thinking like Frank, I figure that all this wear takes place when the particular gear is freewheeling on
the layshaft. Yet third gear is the most frequently used at our home track, so most of the time it is under
drive load and there is no differential movement between it and the layshaft. But it sure does itself
some harm for the two short periods when I grab top gear. By the way, mainshaft is new and true and
layshaft is not bent . Anyone else had this problem?
#4029 A word of warning - EP oils should NEVER be used in a Velo gearbox. As you say, the sulphur
content of these oils attacks the bronze bushes and will eventually lead to seizure. Most likely the first
thing you will notice will be a difficulty in selecting gears, and inspection will show the first gear bushes
to have seized on to their shaft. Straight or multigrade engine oils are what was recommended by the
factory and these work well. You could also try one of the modern racing 2-stroke gearbox oils which
should be suitable for use in boxes with bronze components and in wet clutches, although this isn't an
issue with pre-unit motorcycle boxes.
#4034 Your problem is that the EP Hypoid Gear oil that you use is chemically eating the bronze
material used for the bushings. Use SAE 50 and that will stop. I always use a bit of molybdenum
disulfide powder in the gear oil to inhibit wear. This problem affects both my Velo and Royal Enfield
gearset bushings, but not the B50 or Commando bushes. I've always assumed that there were different
confections of bronze used by different makers. I first ran into a similar problem in about 1984 when I
attempted to cure a leaking crankshaft seal in my Guzzi by addition of a Casite (Hastings) product sold
to dry up weeping seals. Lost the gudgeon pin bushings in about 150 miles, replaced the rods, changed
the oil, and lost the second set in another 150 miles, apparently from the residual chemicals . I then
installed bushings for a VW rabbit which did not dissolve. Once warned by this experience, I took notice
when my Velo and RE boxes showed the lovely golden glint in the oil when using the hypoid
concoction, and reverted to my SAE 50/Moly mix for no more trouble.
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#4035 I've heard horror stories about using EP oil, but what does the EP stand for? If you can tell me,
then I'll check my supply of oils to make sure that I don't use it. Is it called something else in America?
So what good is a gear oil that eats bronze? Why is this stuff made? I can't think of an application that
has lubricated gears, and doesn't have any bronze or brass too.
#4036 EP = Extreme Pressure. Developed for gearboxes where the tooth shape increases the
pressure but runs more silent. It was often branded as Hypoid.
#4037 In USA gear oils are GL rated. GL-4 is non EP, GL-5 is EP. Norton Commandos call for EP in
the gearbox as do some others with yellow metal. I buy GL-4 by the gallon and use it in everything just
to be safe. It stinks just as bad as GL-5 so it must be good.
#4038 I did some searching on Google, and found out about EP oils. EP stands for Extreme Pressure.
Some gear oils have EP additives, some have a little, some have a lot, some have none. The oils to
avoid are designated API GL5 and API GL4. The GL3, GL2 and GL1 have decreasing amounts of EP
additives, and will not harm brass, bronze and other yellow metals. Classification --API Designation
Like motor oils, there is an American Petroleum Institute (API) designation for gear oils. Unlike the "S"
category for motor oils, the gear oil categories do not necessarily supersede one other. For example,
API SL motor oil can be used in all prior gasoline "S" classifications. The API designations for gear oil
are API GL-1, GL-2, GL-3, GL-4 and GL-5, where the "GL" stands for "gear lubricant" and the number
indicates the level of extreme pressure (EP) additives in the formulation. Extreme pressure additives
give gear oils their infamous smell and protect the gears from sliding wear. GL-1 gear oils do not
contain EP additives. GL-5 gear oils (recommended for hypoid gears in most axles) contain the highest
level of EP additives. It is important to follow the manufacturer's recommendations for the API
designation, because, depending on the application, too high of a treatment of these additives might
hasten component wear. In other words, more additives are not necessarily better when considering
gear oils. One must select the proper level of additives to maximize component life. A case in point is a
manual transmission with bronze or brass synchronizers. Higher concentration of EP additives in
manual transmission oils might cause the softer "yellow" metals (copper, brass and bronze) to wear out
more quickly. API GL-4 contains approximately half the additive treat rate of GL-5. API GL-3 contains
approximately half the additives of a GL-4. So which is better -- GL-1 or GL-5? Again, the answer is
neither or both. One must always select the recommended API designation for each specific
application. A gear oil product meeting API GL-5 SAE 80W-90 is commonly recommended for both
manual gearboxes and conventional differentials in cars pick up trucks and sport utility vehicles (SUVs).
This fluid provides the full protection of an SAE 90 under high temperatures and hard driving
conditions, while still providing the fast flow characteristics of SAE 80W when the unit is cold. Likewise
API GL-5 fluids may also be recommended for use in industrial gear units. However, a typical GL-5 will
contain approximately twice the amount of Extreme Pressure (EP) additive as that of an API GL-4 gear
oil. When an API GL-5 fluid is used in an API GL-4 application, the additional EP additive may have a
negative reaction with the yellow metal components (brass, bronze, etc.) used in some transmissions.
The EP additive can contribute to chemical corrosion, etching or excess wear of yellow metals over
time, which may shorten the life of the transmission components. Always be sure that the correct fluid
with the proper API service designation is chosen for the application. Another common gear oil used is
a product meeting API GL-4 SAE 80W-90 which also provides the viscosity of an SAE 90 under hard
driving conditions while providing the low temperature flow characteristics of SAE 80W that are
necessary during cold weather start-ups. EP and antiwear additives are added to minimize metal
to-metal contact wear, but at approximately half the amount used in API GL-5 products. Likewise, an
API GL-4 product is commonly designed for both transmissions and differentials found in certain
models manufactured by Audi, Hyundai, Nissan, Porsche, Suzuki, Toyota, Volkswagen and others.
Always remember to double-check that the proper fluid has been chosen for the application. Although
not as common as other gear oils, some products are formulated to meet the API GL-3 classifications
and have limited applications. Currently the most common application is in certain late model jeep
vehicles. This fluid is available at your local Jeep dealer's parts department. API GL-1 SAE 80W-90 is a
non-EP, straight mineral oil. It contains no active extreme pressure additives that may contribute to
chemical corrosion, etching or wear of yellow metals such as brass or bronze. API GL-1 is specifically
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designed for use in manual transmissions, transfer cases and final drives in on-highway trucks and
off-highway equipment which require an SAE 8OW-90, non-EP, API GL-1, straight mineral gear
lubricant.
#4039 Now that you've been through all that, back to the Velocette application! The manufacturer's
recommendation for Velocette singles is to use exactly the same oil you use in the engine, whether it
be a straight 40 grade or 20/50 multigrade engine oil, the exception being if you chose to use Mobil oils
when they recommended their Monolube GX90 product which was presumably a 90 grade non-hypoid
gear oil. The distinctive smell of EP oils of most grades is attributable to the sulphur content of the EP
additive which is as you say, present in all grades but GL-1. It is this EP additive which does the
damage - if it is present at all it will still do the damage, it will just take a bit longer if there is less
additive. The only answer is to avoid EP Hypoid oils like the plague!
#4040 Thanks for the feedback, group. I let this one run for a while because the funny thing was I didn't
say what oil I was using in the initial post. Following investigation and a phone call to Shell, I'm satisfied
that even their hi-tech synthetic gear oil is the most likely culprit (GL-5 - ouch!)
#4042 A number of people had recommended that I put Mobile 1 synthetic gear lube in the tranny. I
pulled up the specifications on the web, and it states that it does in fact meet GL5 standards. Would the
potentially detrimental additives being discussed also be likely to be present in synthetic gear lube?
The same specification sheet says nothing specific about any additives, potential problems with certain
metals, etc.
#4043 I too have seen reports that 'modern' GL5 is yellow metal safe. Is the risk worth the reward? As
others here have stated, Velo boxes have lasted this long on motor oil and rain water.
#4044 I, too, put synthetic 80/90w gear oil in my Venom this summer, and my main bearings failed...
Actually, I looked carefully at this oil before using it, as its fairly well known (but not enough, clearly!)
here in the States that 'hypoid' gear oils eat bronze. There was no 'hypoid' on the label, but I'll check for
GL-5.
#4045 I called Mobile 1 Technical Support. They confirmed that their synthetic gear lubricants do, in
fact, contain the higher levels of EP additives that were previously mentioned. They further agreed that
these additives can be harmful to certain yellow metals, and stated that this product would probably not
be a good choice for this reason.
#4046 It may (or may not) be of interest to recall that Ralph Seymour always used R40 in his
gearboxes. It is of course well known that castor oils are far superior to all this synthetic stuff!
#4077 The effect of EP additives on bronzes may vary according to the type of bronze. I assume that
Velo gearbox bushes are phosphor bronze. Many car synchromesh gearboxes used something called
"aluminium bronze" for the synchro rings (or baulk rings, blocker rings if you prefer) with few problems
but not all manufactures specified EP80 for the 'box. Ford always specified EP Gear Oil (from about
1954 anyway) and even blanked off the gearbox drain plug to stop misinformed garages from draining it
and refilling with straight 50 grade.
#4079 It is the Zinc that is attacked and the more Zinc the worse it gets. Gunmetal (LG2) has 5% Zinc
(LG4 and Admiralty NES 830 have 2%). Phosphor bronze has the smallest amount of Zinc. Aluminium
bronze is a hard erosion resisting metal and not "normally" suitable for bearings, it resists Seawater
attack. It is sometimes used for Wormwheels under great load. In short the less Zinc the better but then
we get into the area of Tribology and have to decide whether we want the bearing to wear or the shaft.
L # 4847 Hi I have just purchased a 1960 Mac, the engine and frame are correct to the buff log
book. The bike is in good condition but the gearbox has a prefix of 14 (MSS type) as this is the last year
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of production of the MAC, would anybody be able to advice if this is the original gearbox.
# 4850 Yes, its the original type for an alloy MAC of that date.
# 4865 My MAC was purchsed with the 14 box. The bike is not original but is built from all the correct
parts. What engine and final drive sprockets were specified when the 14 box was used? Mine are 21
teeth for both.
# 4866 Your sprockets (21 T) are correct. Don't forget that the rear chain is 1/2 x 5/16".
L # 5289 On steel rear sets are the two threaded bars through the stand and swinging arm the
same length? and what are the lengths if different?
# 5615 Can some one point me in the direction of dimensions for the top rod and the tube on john tickle
steel rear sets? I have the top rod but it looks like it has been messed with and the tube is a home
made affair which doesn't do the job very well.
# 5617 The top rod is in fact a 10" long, 1/2" diameter steel bar, turned down to 5/16" and threaded
5/16"BSF for 1/2" at both ends. The LHS is turned down for 3/4" and threads into the triangular Dural
plate (I'd recommend Helicoiling the plate if not already done), with a 13/16" diameter x 1/2" long alloy
spacer behind the plate. The other end is turned down for 1.125" and again has a similar spacer behind
the plate. The plate is then secured on the outside with a 5/16"BSF nut with a plain and shakeproof
washer behind. When set up correctly the spacers should not actually touch the inner bore of the
suspension trunnion, but should be sitting centrally inside its ends. It sounds like a previous owner has
used a rod and tube modification to replace a damaged bar.
# 5890 When fitting steel rear sets is the same brake rod used ? I cant seem to get mine to fit any
which way.
# 5891 As I remember, you do use the original rod, although I made a stainless replacement for mine!
But you need to put a double bend in it to get round the obstructions!
L # 5631 Hi Guys, I find that I am having great trouble using the rear set gearchange lever on the
vmt.I am sure that I am not the first rider to have a problem. I find that in order to select gears,
especially changing down, I have to take my foot off the footrest to do so, surely this cant be right,
twisting my foot hard inboard I can just about change up.My vmt has the large bore pipe fitted, I dont
want to fit the small bore pipe if I can avoid it. Wearing a pair of ankle supported riding boots makes the
whole thing impossible, have any of you got any dodges to get round the problem? I am new to Velos
and this is spoiling my enjoyment of a superb machine.
# 5632 The problem is leverage. I was able to improve my VMT by drilling a new hole in the lever that
is mounted on the gearbox shifting shaft. The new hole is located at the middle point between the
square shaft and the original rod link, then the lever is shortened to get rid of the excess. This has the
effect of making a shift with half of the pedal travel originally required. It also allows the rod link to be
made shorter such that the pedal can be carried closer to the pipe in it's center position. If you don't
want to upset the original appearance of the linkage, you can, instead, shorten the lever on the front
end of the cross shaft inside the G/B cover to half length and achieve the same result.
# 5633 The real problem is that the rear set gear lever is tucked in to miss the kickstart. It all gets
complicated as it then must stop before hitting the exhaust! Depending on your boot size, you will have
to get used to some ankle agility when changing down. It's just a knack and will become second nature.
# 5643 I had the same problems you describe. Just couldn`t get my foot under the lever to hoist it up. I
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made a partial improvement by moving the gearpedal outwards by fitting a spacer 1/2" thick on a
specially made footrest support shaft. I cut up a kickstart crank and made a greater offset one to clear
the now moved over gearchange lever. I also extended the gearlever bit where the rubber goes on so
to nearly touch the kickstart crank. All this gives a little more space to get the foot under the
gearchange lever but is still a pain to use. Lifting the gear lever up is better but I still have to lift my foot
off the footrest to push it down. There is no just pivotting the foot under and over as it ought to be. I
even cut away the lower part of the pedal rubber until the metal part almost touches the exhaust pipe
(smaller dia one) to get maximum benefit. I think we have to admit it is not the best design in the world
but a cobble of parts to achieve a solution which is really not very satisfactory. Just a thought though, if
we went to electric start we could throw away the kickstart crank and have all the room in the world to
play with. Or is the solution to throw away the riding boots and wear modern GP racer type trainers.
# 5644 I assume that the discussion to date refers to the adjustable rod type of linkage. I changed
mine for the "simple" reversed gear lever and found that things are significantly easier. It still takes a bit
of getting used to but, wearing full length size 11 Gold top boots, I can change up and down without
taking my foot off the rest - something I could never manage with the rod type of gear pedal.
# 5646 We believe that the is a reverse cam plate available.
# 5675 http://www.croesus-consultants.co.uk/v-tec/Images/Cam-plate.JPG
# 5655 I would agree that the change difficulty is exacerbated by the big bore pipe. With the original
set up I found that the adjustment of the linkage had to be absolutely spot on. Lengthening the rod
meant that the pedal would strike the linkage rod on downward changes. In bad cases this would bend
the rod slightly making subsequent upward changes spongy, particularly if a spell of town driving had
led to a warm clutch. Shortening the rod adjustment meant that the pedal bottomed out on the big bore
pipe before the next gear upwards was properly engaged. Any new pipe fitted had burn marks from
boot soles within a few miles. As to big bore pipes; in the Seventies a close friend had a Thruxton
identical to mine in every respect bar engine number and his having a smaller bore pipe. We spent
considerable time in each others company cutting our high speed teeth on Scottish roads. His bike was
very slightly but perceptibly faster in everything other than chin on the tank full chat in top - not
something I have ever been able to admit until today.
# 5656 I too had problems with rear sets, big boots, not enough room between levers etc. There are
three sets Veloce fitted,1)wavy gear lever with steel brake lever & steel mounting plates. 2)the Tickle
type, chrome tubular gear pedal with remote linkage. 3)the late Clubman/Thruxton type, cast alloy
levers, alloy mounting plates & remote linkage. 2&3 need to be improved by fitting Rose joints to the
linkage [if you have the later "twisted strip"linkage inside the gearbox, replace that with Rose joints
also].The Tickle gear lever always seems to have a lot of slop in the pivot& depending on the amount of
wear it can be difficult to bush the tube. Type 1,works for me ,But ,I have put a 1.250"set in the gear
lever & a 1.375"set in the kickstart. Yes you will have to move your foot about to change gear, if you
shorten the throw of any lever it will make the change heavier, perhaps its best to accept the fact that
we are dealing with an old design of gearbox, made before some of us got used to twinkle toe gear
shifting
# 5658 The results of changing the leverage are three: 1-By reducing the length of the vertical lever
attached to the square shift spindle (or internally, the front lever on the big cross bar) by half, the
motion of the shifter pedal is reduced by half. 2-In the above case, the pressure required to make the
shift will double. If your clutch is properly set up with NO DRAG, the doubled pressure required is of no
consequence, as all other makes use such leverage with no problem. All that you are doing when
making a shift is sliding a few gears along their shafts. Check it out with the engine off and you'll see
that the effort is minimal, however a dragging clutch will make the shifting awkward, heavily loading and
wearing all of the components of the shift mechanism. 3-A properly set up and delightfully light and
positive shift with no awkward articulation of the right ankle. With a properly set up gearbox and clutch,
the Velo 'old design' is among the sweetest of all bikes, with a solid and smooth positive feel.
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L # 5657 Last night I changed the gearbox oil in my Venom for the first time (the bike only has
400 miles from new). When I first commissioned the bike last year (it had never been run when I bought
it), I used Castrol GTX 20w-50 in the gearbox. However, when I drained the gearbox oil yesterday I can
see the telltale bronze sparkles in the oil. Is this normal for a new gearbox breaking in, or should I be
concerned. Could there be something in Castrol GTX that is attacking the bearings?
# 5659 Use straight 50W with a dollop of molybdenum disulfide powder (dry lubricant) and you'll avoid
the chemical attack on your bushings as well as wear on your gear teeth.
# 5660 Is there something in the multi viscosity oil that attacks the bearings? I thought the only thing
we had to avoid was EP gear oil. For the Moly, Guzzi dealers sell a liquid Moly additive for the rear
bevel drive. Think that would be safe for the Velo?
# 5662 Something in the EP lube does chemically attack the bronze used in the Velo and RE boxes
that I've used. The Commando and B50 boxes seem to be immune to this attack. Perhaps a different
chemistry of bronze used? I've read that sulfur used in the EP is the culprit, but who really knows? The
evidence of golden oil in your new gearbox could be the GTX oil used or wearing in of the bushings and
the way to find out is to use the 50W. If the oil stays clear, then you know. If the oil turns golden, then
you know that it's mechanical wear. As to the liquid Moly additive, I have no experience. Bronze is
funny stuff. Some years ago, I added a treatment from the Casite Co. claimed to seal up oil seal leaks,
to my engine oil. Within about 400 miles, the bronze small end bushes had completely disappeared
from my Guzzi conrods. After changing the rods and the oil, I again lost the small end bushes,
apparently from the chemical remaining after the oil change. This time I replaced the small end bushes
in the conrods with bushes made for a VW Rabbit, and those performed normally.
# 5663 It's correct that EP lube should not be used under any circumstances in a Velo box due to the
sulphur content and its effect on the bronze bushes, but GTX is one of the recommended lubricants
and in my experience has never had a detrimental effect. And I certainly have never seen the gold
paste when using this over many years (unlike the time as an inexperienced youth when I used EP for
a while which caused the machine to grind to a halt within a few weeks suffering from a seized first
gear bush and box full of gold!). I'm inclined to steer clear of additives - once again you can never be
sure exactly what they contain - and I would advise against using straight 50. The gearbox will never
get to the same running temperature as the engine and the thicker oil will cause some additional drag
because of this, especially if the ambient temperature is low. Might be all right in the Sahara at the
height of summer but not at "normal" climates. I'd suggest that the problem here might be slightly tight
clearances in the new box - a careful strip and inspection of the parts should confirm this and show
which parts are wearing. A little fettling and clean out of the box, reassemble with new GTX and run for
another 500 miles, change the oil again and see if you still have the same gold mine. I'd lay bets that
the seam will have run out!.
# 5664 I use 50wt oil in my MAC gearbox and seem to suffer from a fair bit of moisture in there. Are
you suggesting that I can resolve this problem by using GTX?
# 5665 If you use the Velo in all weathers water in the gearbox is a fact of life. It runs down the clutch
cable and into the top of the box through the cable stop tower. The best solution I've found to reduce
this is to fit a suitable rubber boot on the cable to prevent the ingress of water. Of course, since the box
doesn't get up to engine running temps then the water is even less likely to evaporate. This is unlikely
to be a result of using 50W oil. The point is that especially at low ambient temperatures the 50W oil will
be almost as thick as grease with the equivalent amount of viscous drag. Until it gets up to operating
temperature (in an engine this can be as much as 135/C but this will never be achieved in a pre-unit
gearbox), it will also be too thick to reach the parts it was intended to. Use 20/50 like the book says!
# 5666 Moly in the gearbox can cause problems, oil from the gearbox can migrate to the chaincase and
the clutch does not like it, you may meet many that use it with no problems but is it worth the risk? The
clutch is adequate but not a lot in reserve a bit of moly may be all that is needed for the dreaded slip. I
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and my friend use Castrol GTX many with huge miles on their bikes with no problems. regards.
# 5716 My local Halfords who used to stock Duckhams has stopped selling it and it doesn`t seem to
be available now. Can 20/50 still be obtained or am I seeing the remnants of UK supply at auto
jumbles? Also GTX is no longer 20/50, more like 10 or 15/50. Is this what is being used?
# 5670 I dunno about 'viscous drag' being a factor in a gearbox. I can easily pour 50W from a bottle on
a pretty cold day. if you're concerned, there's always 40W, 30W, or even 20W, which is effectively the
viscosity offered by the 20-50 GTX when cool. My personal theory is that the most important job
performed by the G/B oil is to prevent the gear teeth from scrubbing as they slide in and out of mesh
during rotation, and for that purpose I think that the thicker oil offers lubricant and a 'cushion' between
the teeth. We've all seen the brinnelling suffered by gear teeth as they lose their hard surface and it
seems to me that anything we can do to reduce this damage is a plus. Therefore the 50W and moly
powder. As to the oil failing to reach the parts it was intended to reach, I've disassembled quite a
number of boxes and have never found one without oil everywhere unless run empty.
# 5671 On a VOC club run to the Castrol Research facility, it was explained (as most people probably
already know) that ordinary mineral 20/50 multigrade is 20 grade oil with additives that make it act like
50 grade when hot. Unfortunately the additives gradually lose their effect so if left in it the oil will
eventually end up as 20/20. Roller big-ends have a detrimental effect on multigrade, but 1,000 mile oil
changes minimize this effect, so that it can effectively be ignored (Duckhams 20/50 was recommended)
and this disadvantage was vastly outweighed by the multigrades superior ability to combat cold start
and cold running wear, especially on OHC engines. However what was explained that gears crush the
multigrade in double quick time and was not recommended, 40 or 50 grade is the stuff to put in the
gearbox. I have used 20/50 in the engine of my Mk 11 Cammy and 40 grade in the gearbox since 1974
without dismantling anything, it goes like the clappers, 500cc Rudges pull aside, and it is still quiet as a
mouse.
# 5676 The fact that you're see seeing 'sparkles' of bronze suggest it's mechanical wear. Chemical
attack would give a much more finely divided dull bronze colour without obvious particles. GTX should
be OK for chemical attack - it's the Hypoy series which is to be avoided. Since the box is new I'd just
refill and drain a couple of times - I suspect all rough edges will soon be worn off and all will be fine . Of
course if there's something badly mechanically wrong - eg shafts pulled hard against the edge of a
bush through inadequate clearances - you'll have to strip the box and sort it out regards.
# 5677 I frequently get cloudy oil when I change the gearbox oil (which I do much more regularly
because of this problem) despite having a rubber boot on the cable. Maybe I need to look a little closer
and see if there are other points of ingress. Which book says use GTX in the gearbox? I was sure that I
was supposed to use 50wt (although this might have been before multigrades were available). I do use
multigrade in the engine.
# 5682 My recommendation comes straight from the Red Book. Could be a late issue I suppose.
Someone else suggested one of the non-hypoid gear oils that are available nowadays and I should
think that these actually might be quite a good choice. They're usually marketed to the racing
community as light or medium gear oils and are formulated for use in (generally) two stroke racing
gearboxes with wet clutches. These are rated at around 75W90 and are available from people like
Silkolene, Morris, Motul, etc. Pete C.
# 5683 It may take a bit of searching, but most locales have a specialized lubricant supplier to meet
industry's needs. API specification GL-1 gear oil contained anti corrosive agents that were designed for
brass and bronze bushed gear boxes, and is eminently qualified and recommended for boxes as used
on the Velo and numerous other bikes Over time, API (American Petroleum Institute) has changed the
specifications for gear oils as the designs and uses of gear boxes has advanced. The current
specification GL-5 is not a good choice. Gear oil is almost always a better choice for power
transmissions than motor oil. www.api.org has a host of documents on line for those seeking greater
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information. As to viscosity, gear oil with 90 wt rating is ostensibly the same as motor oil in the 40 and
50 wt range. The following URL may help clear up some myths or misconceptions, or may simply add
to the confusion. Your call. www.repairfaq.org/filipg/AUTO/F_oil_facts.html#OILFACTS_003
# 5687 On the subject of red book recommendations, after last year's forum query about bronze in
gearbox oil I corresponded with local technical guru Norm Trigg and advised him: "On the subject of
gearbox oil recommendations my red book (publication no. 434/12R) definitely lists Castrol GTX for
gearbox. In other brands it's a mixture of straight grades and multi grades - eg BP Energol SAE40,
Duckhams Q20/50, Mobil GX90, Filtrate Plus 20/50. In all cases except Mobil the recommendation is
the same as engine 'summer' so for us Aussies the message was to pour the same stuff in the oil tank
and the gearbox." And then Norm (who used to work for Shell, but not as an oil technologist - he's an
electrical engineer) replied: "John, Interesting that your red book lists the oils you mentioned. A 484/5R
of Nov '62 gives all monograde oils of sae 40 except that in the case of Mobil, Mobiloil B.B. or Mobilube
GX90 is recommended, the latter being a gear oil. I can't believe the factory would have recommended
multigrade for the gearbox and wonder if a mistake occurred. I agree with you, straight 50 should be
used, or an equivalent gear oil, but certainly not an EP gear oil." Obviously opinions vary. My current
thoughts are heavy monograde or a non-damaging gear oil is required to minimize the wear on gear
teeth. The bronze bushes and ball races appear to survive nicely as long as there is enough oil to
splash around and wet the shafts and internals. And a distributor cap boot over the clutch cable entry is
a must to prevent water entering and turning your lube into milk.
# 5674 Both Mobil and Amsoil, and perhaps others, make Synthetic 80W90 Gear Lubes that are
"Yellow Metal Friendly" in that they don't contain any ingredients that will dissolve bronze or brass
bushings. Since these lubes are expressly designed for gears one can presume they will do a better
long-term job than engine oil in protecting the components
L # 6007 Hello All, Anybody out there using the Quaife 5 speed gear cluster in a road going
Venom? I have had a look at it, but would like to hear from someone who has fitted one and is using it.
# 6009 I have had a Quaife 5-speed in my VMT for several years and it is superb. With the 4-speed it
was difficult in city traffic because of the high 1st gear and I did not want to lose the top speed by
changing gearing. The 5-speed makes it usable in town and still gives the good top speed.
# 6010 For information, 5 and 6 speed boxes are being manufactured by Graham Dyson at Nova
Motors whose work I can commend highly. Graham is the man responsible for manufacturing most of
the close ratio racing boxes for the modern Supersport racers amongst his wide range of products, and
was half of the Barton company who produced the Phoenix machine raced by Geoff Barry until his
untimely death in the late 70s. Details of the boxes, ratios, prices, etc. can be found at
www.novaracing.co.uk/velocette.htm - It would appear that the 5 speed box can be used with or without
a kickstart but the 6 speed is for bump or electric start use only!
L # VOCNA 361 Putting the VMT back together for the rally and trying to get all the bits back
that I robbed over the last year. Before I carve yet another kick start housing out for an o-ring, didn't
someone come up with an external seal of some sort?
# VOCNA 362 There is a lip seal which can be fitted in a recess machined on the outside. I don't have
the number handy right now, but Ed has some here. It's what we've been fitting recently – it's a bit
easier than machining an O-ring groove, and seems to work at least as well.
# VOCNA 363 I have a single lip seal on my Venom, was made by National. I had the box laying
around in my office for years, but of course I can't find it right now. My local bearing shop had it, all I
did was give them dimensions. You still have to machine a recess for it in the kickstart housing. It
works pretty well. Found a neat part last week - a 2' length of ignition wire, copper core, with 90
degree spark plug caps on each end. It includes two coil caps that are a perfect fit for the clutch cable
entrance as well as the K1F. They are thick and new and won't split like the manual advance boot so
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many of us use. Drag Specialties, P/N DS-241901, "SPLUG WIRE COP 2LD BLK 90," $8 at my local
outlaw HD shop. The BigMAC should fire up today, first time since Kamloops, wish me luck.
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E.3. Final Drive, Chains and Cases -
L #20 The only thing I want to do now on the MAC, aside from regular proper maintenance is to
find a relatively decent cure for the primary case leakage, which is pretty massive, even after a new
seal was put on. May resort to black silicon sealer.
#25 Most pin type p/chaincases distort finally, so you'll hit this problem with second-hand cases. I
wonder if belt primary drive might not be the solution, for Velo singles in general.
#28 I've been let down on the side of the road on a Velo have been primary chains, and both times it
was my fault. The second was trying to run an open case using spray chain lube, when I lost the oil
drain plug on a long ride. Au revoir to chain and clutch chainwheel both
#31 I was pondering that very thought recently, but though I have seen belt drive units for several of
the more popular parallel twins, nothing for anything so esoteric as a Velo single..
#34 There are two manufactures of belt drives for Velocettes one is by a guy called John Watson
telephone +44 (0)1768 898599, the other is Kevin Thurston telephone +44(0)1525 404699 – both I
have seen, but not used and look well engineered.
#71 I recently fitted a belt drive cum clutch kit onto my Venom. As the space inside the primary case is
very crammed, a bit of machining of the pulleys was required to get the required clearances. But
otherwise the kit was of unusual high tech quality and fitted straight forward and the back up help from
the manufacture was more than excellent. Clutch action is better and sharper, and neutral can be
found at standstill too. But do not expect a complete dry primary case. I recognized oil still collecting in
it as the crankcase blows always a bit into the p.c.c. and also some oil from the sleeve gear bush
dribbles in it. I fitted the belt kit because I got tired of cleaning the rear wheel and the garage floor after
a fast blast. I assume the Mac case and clutch is similar to the Venom, but Mr. Watson will know upon
these details.
#133 I've been in touch with Dave Smith of Dave Smith Classic Motorcycles, in Illinois, and he handles
the John Watson belt primary drive system. He is going to get back to me on my MAC, regarding
pricing, because there is little call for this system on the MAC, mostly the Venom, and I would need a
different ratio compared to the Venom, of course. Supposedly a good quality unit with no major
obstacles to installation besides replacing the clutch plates as the new basket will have friction material
as produced, so new plates would help guarantee proper function
#135 A word on belt primary drives. As we all know, the mainshaft breathes some oil into the primary
chaincase. But neither the belt primary drive, nor the dynamo/alternator belt drive really appreciate oil.
The primary chaincase also stops oil from getting at the generator drive. This should be borne in mind.
#137 Most of these primary belt kits come with a complete new clutch. A Velo clutch will work dry, or
wet, but not both ways in alternance.. From experience, the best pressed-metal primary chaincases
don't keep oil well enough, Velocette or other. The same chain, inside a good, oil tight alloy chaincase
gives no great problems. Years ago, I met somebody who had cast up an inner Velo primary chaincase
out of alloy, but retained the pressed steel outer. I meant to follow this up, but for some reason didn't.
#139 Glad you brought this up. I have wondered how the generator/alternator v-belt is kept from
slipping with the engine breathing oil mist into the primary case. The belt primary drive I am thinking of
is of the notched tooth variety, and some oil shouldn't affect it too much, especially as these new
plastic/metal core belts don't stretch basically, keeping potential slippage to an absolute minimum.
#140 I guess the cast alloy back half of the primary would keep it somewhat more leak proof holding
normal warpage over time to a minimum. Was this a pin or band type case? You see, this is one of the
things I love about owning this dear old MAC. While I can appreciate wanting to keep these fine
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machines absolutely pristine, it is most enjoyable to figure out practical ways to improve on a good
basic design from an earlier time, while keeping the overall feel and "character". I plan on coming to the
Spring Opener of the VOCNA, and plan to ride the several hundred miles there, alone if needs be, but
with another member if possible. More enjoyable and perhaps handy in case of an oopage of some
sort. I expect my MAC to behave in an exemplary manner, i.e. to get me there, enjoy the rally, and get
me within 1 mile of home before tossing something out the exhaust. I did find out recently what drippy
mess it makes to overfill the Primary case with a less then perfect felt wiper seal in place over the
clutch. 2 ½ ozs. of oil just didn't seem enough, but, there you go.
#143 I'm still on primary chains, but I've noticed basically three schools of thought on primary belts.
Original chaincase, with the newer narrow belt, which presumably means the mainshaft breather oil
wanders about inside the chaincase unless there are some holes somewhere behind. A home-made
belt cover, where it is hard to know just what is going on, or nothing at all. We raced a Venom with no
primary chaincase, just some foam strapped to the frame under the ESA to keep oil off the track. It was
a while ago and I don't remember clearly, but the quantities of oil coming out were not massive, and we
didn't have a generator drive. Could be it isn't a big problem. I had a Venom Club, and from time to
time, possibly connected with bore wear and engine speed, it spat out considerable quantities of oil via
the engine/oil tank breather. A friend, more thorough than I, believed on his similar Club it was the oil
frothing too much and thought he'd pinned it down to a certain make of oil- we're talking of 25 years
ago. The only result was I checked engine oil, as a reflex, every time I stopped. The alloy rear half of
primary chaincase was a pin type. He'd beefed up the flange on the inner but did say that for a sand
casting, his inner was pretty thin. With a bit of imagination, it would be possible to fit the outer half of
the primary chaincase only with a belt drive, which would trap the mainshaft breather oil, and look more
"classic". 25 years or so ago, somebody in California I think made a complete alloy primary chaincase
but it was noticeable to say the least. Mechanically, probably a lot better
#147 25 years or so ago, somebody in California I think made a complete alloy primary chaincase but
it was noticeable to say the least. Mechanically, probably a lot better. Bruce FYI The patterns to said
item were in my possession up to a few years ago. I was unable to find a foundry to complete a set
(and was unwilling to try myself a la John Britten) so they went back to Olav Hassel. They were
originally made by Bob Strode of Washington State for a Venom Special road racer and included an
outboard swingarm trunnion support as part of the casting. The trunnion was an inch longer to fit the
case. Another friend had the finished bike until recently. I think Olav had one set made, but his latest
creations (a Metisse and a racing rigid MAC) had modified original items. Between the casting and
machine work it became a lot of effort to reduce the minor oil loss from the pressed steel case. Never
rode the Strode bike, so I can't offer an opinion re handling. ps Translation, please, Mr. McNair - by "pin
fixing" do you mean screw-type
#148 Yes, pin type is the same as screw type cases. Don't know why, but, there it is.
#149 I'm interested in the idea of a primary belt drive as most of my time is spent trying to keep the oil
in the chaincase or at least off the garage floor. One thing that has always worried me even in the
standard chaincase with the small amount of oil in it, is the lubrication of the clutch ball race assembly.
Having just replaced one it is not the cheapest item in the clutch
#150 Yes, lubrication is marginal as designed. The result of Britain's use of roundabouts instead of stop
lights? Many owners change the ball bearings for straight rollers; one can file the cage to suit. This has
been successful for many. The increased contact area seems to compensate for the rollers skidding.
For a more direct solution, I found a tip in an old FT that specified an oil slot, cut horizontally in the
"thrust cup" (C29/26) just above the ball race. I used an abrasive cutoff wheel in a Dremel tool. The slot
is about 1/16" wide by ½" long, cut from the clutch side, and slopes down toward the bearing when
viewed in cross section. This has improved oiling so that I am still using the original ball race, now with
30K miles on it. Thanks to Joe Keys. If/when I change to belt drive on the Venom I will probably change
to rollers (and keep the slot). The oil from the crankshaft breather should be enough in the original
primary case to reach the bearing. And of course I "never" sit at a stop with the clutch in...or follow
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stop-and-go traffic up Pikes Peak...
#151 I was actually referring to the large clutch ballrace assembly C26AS that is an interference fit in
the chainwheel assembly although the same problem would also exist for the clutch thrust bearing if
there was no oil in the chaincase, as you point out. I have converted my clutch thrust bearing assembly
to rollers also.
#161 I raced on short circuits from 1990-95 with an alloy chainguard over the chain using only chain
lube, the clutch release bearing having been assembled with grease and I didn't have any problems
only renewing the grease occasionally. In 1997 I started racing in the Isle of Man and reckon I do
about 700 miles during practice and race week. I use a belt drive that John Watson and I developed,
which runs dry. I lightly oil the chainwheel bearing, but just used grease on the release bearing and
have not suffered any problems. Try a belt drive, it's so simple and John even makes one that can run
within the primary chaincase with or without oil. I also used a shielded sleeve gear bearing to keep the
oil inside the gearbox and the front pulley on the crank has a "garter" seal to keep the oil in the engine
#168 I just fitted a Watson belt drive kit onto my Venom Clubman. I use it within the original primary
chaincase. The reason for fitting it was not a clutch problem, it was only the habit of oil spreading on
the left side of the bike and accumulating in the flanged alloy rear rim after prolonged high speed
outings. I got bored of cleaning the bike from oil. Now I expected no oil loss as none is in the case. But
bad news. The engine breathes out enough oil, that the case slowly fills up with oil again which finds
its way out of the case after a certain milage. Question : How can a garter seal be fitted into the drive
side crank case ? It seems there is not enough meat in the case to give a good seating. I have a "top
hat" steel insert in the drive side case plus a parallel roller bearing conversion. The breather hole in the
crankshaft is filled with Araldite. The engine cases are converted to the VMT type breather system. As I
see it, the seal must run on the boss of the (machined) gearbox sprocket, on which the pulley is bolted
on. Is this a very thin seal ? Would the oil not breath also between sprocket and shaft ? Would
scavenging be improved if that restricting "filter plug" is replaced by a normal plug ?
#176 This reply addresses several emails I received about the belt drive, garter seal and shielded
gearbox bearing and engine breathers. The belt in his road going conversion is unaffected by oil.
There is no number for the shielded bearing as it's a modified original sleeve gear bearing, although
there is another on long term trial in a road going Velo. Unfortunately they are likely to be pricey,
around £85 last quote. But I have recently been given the names of two companies who may also be
able to make such a bearing at a more reasonable price. Cost likely to be dictated by demand. I may
also show them a chain wheel bearing and get it costed. The garter seal mod is not too difficult to
achieve, but I think is dependant on certain factors:- the "shoulder/boss" on the inside of the front
sprocket/pulley where it abuts the main bearing inner race needs to be sufficiently wide for the seal to
run on it, mine is approx 200thou and poses no problem. I think that depth was achieved by machining
the inner sprocket face to clear the reinforced "Walker" crankcase. The shoulder needs machining to be
perfectly concentric and smooth so it doesn't tear the seal lip. I then measured the thickness of the alloy
where the crank sticks through the case. My crankcase was about 9mm thick, and as it isn't load
bearing where the seal fits could stand to be reduced to accept the seal. I then bought a seal which
was 4mm x 35mm (diameter of the sprocket shoulder) x 42mm. The seal is a NAK VR - 4 x 35 x 42.
The drive side crankcase was then machined from the outer edge to a depth of 4mm to accept the seal,
which can then be replaced without having to split the cases. This mod should also be possible on
cases which have been "top hatted." In answer to Johann Patek's question about replacing the filter
plug, I believe Veloce used a standard gearbox filler plug instead of the filter plug in later engines,
whether for cheapness or any particular reason I'm afraid I don't know. I think the answer to an oil tight
engine is sufficient/effective breathers in the crankcases. From the various engines I've seen it doesn't
have to be fitted under the mag, better in an accessible place like the top of the crankcase over the
"map of Africa" But it does need the internal drilling through the crankcase between the flywheels and
timing gears as on Thruxtons and later Venoms. I have also blocked off the hole in the crankshaft and
the fit of the sprocket on the main shaft doesn't seem to matter as the engine is no longer excessively
pressurized, at least not below the piston crown.!
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L #239 Has anyone tried to use a 525 O-ring chain on the final drive of a S/A Velo? It is only
about .020" wider overall than a standard 530, and the 18% reduction in roller width should be more
than offset by the modern chain's resistance to stretch. I'm getting 20 - 30,000 miles from the O-ring
chains on my more modern bikes. The ones on the Venom don't last but 6 - 8,000, and the sprockets
wear accordingly. This is not a good idea for a racer, as the o-ring chains suck up a bit more power, but
for a tourer it seems more reasonable.
#240 Decided to get a new final chain for my '56 MAC, getting ready for the Spring Opener. Is 428 size
the proper size to use on this sweet old thing? Have heard a lot being discussed on chains, and
overload has set in.
#241 You will have to skim the sprockets down to 5/16" width to use 525 chain, otherwise there should
be no problem. Most modern racers use 520 chain regardless of capacity, I've been looking after a
160BHP Yamaha R7 now in its 4th season's racing which runs 520 'O' ring chain and never had one
break yet, touch wood! The chain size is still imperial, given in eighths of an inch, hence 530 is
equivalent to 5/8" x 3/8" i.e. the 5xx is for 5/8" and the x30 denotes 3/8". 525 is therefore 5/8" x 2.5/8"
(or 5/16") and 520 is 5/8" x 2/8" (or 1/4"). There are exceptions such as 532 and 632 chains available
which were fitted as OE to such machines as the Kawasaki ZX10 and Suzuki Hayabusa, but the xx2
here refers to roller diameter which is larger than the standard designation for these chains and will not
fit normal sprockets. The main thing to watch on a Velo is clearance behind the chain which is tight
especially to the primary chaincase and will not permit use of an 'O' ring 530 chain due to the wider
overall width of the chain. I would advise use of a 520 'O' ring chain and skimming 1/8" off the back side
of both gearbox and rear sprockets if you go down this route, you should have no problems with stretch
if the correct adjustment is applied
#242 See my posted reply re 'O' ring chains for info on chain sizing. 428 is one of the strange ones
which doesn't fall quite right in the general rule, but is equivalent to ½" x 5/16". I've been using a DID
primary chain on my Venom which is sold as an endless primary chain for speedway bikes and is
exactly right for the Velo.
#246 Big-bore race bikes are not a good example of my o-ring proposal, they can change chains and
sprockets every race if needed. They use the 520 size to reduce drag. Street riders need longevity, or
they change for the "pose" factor. A 33% reduction in bearing surface between chain and sprockets
seems like an awful lot. Chains are relatively cheap and available to me, rear drum/sprockets are not.
Plus I am basically lazy and prefer riding to wrenching any day. Guess I'll have to find out for myself -
but I think I'll thin the gearbox sprocket from the backside only. Also, one should use 428H instead of
plain 428, it's stronger, lasts longer, and fits fine in the primary or on MAC final drives. The H means
reinforced (thicker) side plates. . lengths to suit Japanese bikes. I do this and get two primary chains,
it works out cheaper. The joining link has to be 428H as a 428 will not fit due to the H chain been
slightly thicker.
#249 Re chains. On all my British bikes I have owned the past few years, Velo's and Goldies I have
always used on the primary drive DID 428H. The H denotes heavy duty. 428 is equivalent to Reynolds
part no 110046 and 530 is equivalent to 110056. I tried using a heavy duty 530 on my Thruxton and
found it very lightly touched the outer primary chain. If you go to a bike shop you can buy 428H in long
lengths to suit Japanese bikes. I do this and get two primary chains, it works out cheaper. The joining
link has to be 428H as a 428 will not fit due to the H chain been slightly thicker.
#251 My reference to race bikes was intended to demonstrate that the smaller width of chain was not
likely to reduce the strength or ability to transmit power, and yes, I agree that race bikes can change
chains every race if budget or sponsorship permits. On the other hand, underfunded teams such as
the one I support have to make things last as long as possible and we would expect to use no more
than a couple of chains in a season of short circuit events, although I would always fit a new chain
before a TT race (different riders/team/bikes/environment). Gearing is changed for different circuits,
but mostly only the rear sprocket and then we generally use a range of only three or four teeth for all
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the circuits in the UK. The front sprocket is the usual (very) hard steel type, but the rear is Dural, and
we are still using the same set of sprockets we started with in '99. The machine has done 3 full
seasons of British Superbikes and is currently leading the MRO National Powerbike championship so
is fairly hard worked. We use Regina 520 ORS, and I'm very careful about adjustment - make it too
tight and neither your chains nor your sprockets will last long. A bit of extra slack might mean it slaps
on the swing-arm occasionally but shouldn't do any other harm. If it's too tight it not only affects chain
wear but also increases stress on gearbox bearings and upsets suspension function. Given the
amount of oil that finds its way on to the chain from leaky primary chain cases on Velos I have my
doubts as to whether there would be any gains in running 'O' ring. The additional drag is unimportant
when you have 160BHP but is a significant performance loss when you only have 40 horses. 'O' rings
are great on modern machines which don't leak oil and the chain would get little lubrication otherwise,
but I find the standard Regina "Professional" grade 530 RS non 'O' ring chain to work well and have
seen little deterioration in 3000 miles so far on my Venom. I would also add that changing the chain
before wear reaches a point that the sprockets begin to suffer will extend the life of these expensive
items quite considerably. You're right about the 428H, Regina's stuff has 2.0mm thick side plates as
opposed to 1.8mm on their standard chain. As far as joining links are concerned you should ONLY use
links made by your chain's manufacturer for that specific chain, there are so many differences
between chains that only the right thing will do!.
#253 I agree with Pete C's comments about chains, I use a 520 on sprockets thinned down on the
inside and even with an alloy rear sprocket (the hub's machined to take Vincent sprockets), they don't
need adjusting even during practice and racing at the Manx Grand Prix. But where does he get 40
horses out of a road going Velo? Surely he doesn't believe the figures in the red book, next he'll be
quoting 100 mph for a standard Venom! Anyone want to peck at the corn I've scattered?
#252 I run a 530 O-ring. I moved the countershaft sprocket out about .050 so it clears the primary
cover. Obviously this mis-aligns it to the rear sprocket but it has not been a problem (put a straight
edge across your sprockets sometime, I bet you'll be surprised how far out they are). I make my own
front sprockets out of worn out Velo sprockets by turning off the teeth and welding on a new outside
from any donor sprocket, this gives the .050 offset. I tried shimming out the sprockets once but it
doesn't help the already fragile drive dogs. Regarding horsepower loss, I got answers ranging from nil
to 10 hp. Regina chain told me there is some power loss when the chain is cold but when it heats up
it's insignificant. Somebody once did a dyno test, sure wish I could find it. Many small displacement
dirt bikes use them.
#255 To the racers: Racing experience, while impressive, has nothing to do with the question. Longterm
durability is the issue, not strength. If I have to throw a new chain at it every few thousand miles,
what has been gained? Been there, done that. If you believe the chain manufacturer's literature, a
properly lubricated o-ring chain has no more drag than a standard one. Even 400cc commuter bikes
come with them. The o-rings serve to keep grit and dirt out as well as keeping lubricant in. When
someone reports 20,000 - 30,000 miles on a standard 530 drive chain, I'll buy one like it!
L #284 In getting the '56 MAC ready for the Spring Opener, I replaced the felt seal that is
positioned over the clutch inside the outer primary case half. Making sure the seal was as even and as
far down in its positioning ring as it would go, I had applied Seal-All adhesive to its positioning ring.
After the adhesive had dried, I soaked the seal in oil over night, but I noticed the seal was not softened
up much, and was pretty firm to begin with. I put all back together, cursing the rubber seal/metal
retaining ring set-up, but finally got it right. Upon operating the clutch lever after this, I saw that the
primary case "bulged" noticeably when the clutch was disengaged, lever pulled all the way in.
Obviously the felt seal was interacting with the clutch, reducing free movement. I decided to carefully
run the bike a bit just to see, and except for there being almost immediate take-up of the clutch in low
gear from a standstill, shifting up and down while running seemed normal, no graunching or hard
changes. So, can anyone tell me if this is normal when initially running a new felt seal, and will some
running in reduce contact or? Thanks
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#285 felt seal case-bulging is normal with a new one, at least they've always done it on mine for the
first few months. I've also opened my primary case at times to find a lot of wool fibers in there. Maybe it
quiets the chain!
#286 The felt seal thing; when heated up from hard riding, the clutch would drag when I went from
neutral to low gear, once to the point of stalling. I now am wondering if this is a direct effect of the seal
contacting the clutch combined with some swollen friction plate material, or if the clutch alone would
create this situation. I adjusted the clutch as close to perfect as I could, which is pretty good, so it
probably isn't a matter of adjustment being off. But if it is like a number of other older bikes I've had,
mostly dry clutch, the plates will swell after hard usage
L #793 I have a copy of the BMS Velocette Singles Service Series book which covers the
Venom. With the inner primary chaincase removed they refer to the bolt head at the top/front of the
engine plates. It says if you want a leaky chaincase (is there a choice) fit a standard bolt at this
location. This one must have a thin shallow head to provide essential clearance. If this is true does
anyone know where to get one or do I just need to grind a bit off mine!
#798 If it were me I'd just grind it off (but then again I'm not a purist). I've got various electrical "bits" off
mine at the moment, so have a good view of the bolt. Its head is about 7/32" thick giving about 1/16"
clearance to the inner chaincase.
#810 Had a quick look at the book. It shows the offending bolt but if you look closer it is being used /
shown with the optional additional stiffening plate so I suppose that if you use one of those you need to
thin the bolt head down.
L #1041 Opening the primary case, I saw the following problem I never experienced : The primary
chain has seized links, some rollers are broken. The chainwheel is out of alignment, outside 2.5 or 3
mm. There is no sensible end play on the sleeve gear. I'm puzzled as there is no provision to shim
neither the drive pinion nor the clutch or the sleeve gear. Where could this trouble could come from,
and how to cure it ?
#1045 if everything in your clutch was fitted the right way, my suggestion is that the big threaded ring
that secures the main bearing loose and the whole clutch moved away from the gearbox because of the
force you put on it when operating the clutch. If the bearing sits relatively tight in the housing, you won't
feel any play. Anyway, if this is the case you should have encountered some clutch drag. Maybe you
adjusted it and some time later it occurred again and so on...
L #1383 Does anybody know from what year GTP's used a 3/8' pitch chain from the ½'' used on
earlier models. Also are there any differences in the chain cases?
#1384 The spares book says 3/8 used from gearbox number 6 - 1150, which is early 1936. The spares
catalogue says there is only one chaincase.
L #1825 My Velo owners guide goes into great detail on how to set the rear chain slack after
making a "special tool" and removing one shock assembly. What is the proper slack on a 66 Thruxton
with the bike sitting on the centre stand?
#1826 The amount of slack will depend to some extent on the size of gearbox sprocket, so the simplest
way to find out is to undo the bottom mounts of both suspension units and pull them back out of the
way. Then adjust the chain so that when the swinging arm is moved through its arc, the chain has
about ½ to 1 inch of free play at its tightest point. Refit the suspension units and measure the free play.
This is the amount you should set to in future when setting on the centre stand without removing the
units. To some there might appear to be excessive slack in the chain now, but I can assure you that if
the adjustment is not set in this way not only will your chain and sprocket life be shortened dramatically,
but the suspension will not operate correctly either since its movement will be restricted by an over tight
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chain. A slightly loose chain will do less damage than a tight one!
#1842 ...get someone to sit on the bike until the suspension units are at the requisite 11.5 inches.
L #1833 I have recently purchased one of the VOC "improved" chain case spacers with the rubber
0 rings. However it is a much bigger diameter than the original spacer. It will actually fit over the original
spacer with room to spare. Do different Velo models have different sized chain spacers? or is it
designed to be this way?
#1841To my knowledge, there is only one size spacer on Velo primary chaincases. The diameter is not
important but the length is. The two O rings seal the oil in. Remember that inside the spacer, there's
another spacer that goes over the 5/16 bolt to clamp the chaincase washer to the crankcase.
L #2192 Two questions: 1) Is it actually possible to seal the chaincase so it doesn't leak?
2) My original manual describes all lubricants and schedules in detail, but makes no mention of the
chaincase or primary chain. Does this imply that it is adequately oiled by virtue of the crankcase vent?
#2193 I have a 1961 Venom - I keep oil in the chaincase and it doesn't leak at all . Various Velo
handbooks all indicate that the primary chaincase should have oil in it: The Book of the Velocette by
Leslie Heathcote, 1941 says " the primary chain is enclosed in an oil bath chain case... replenishment
through the inspection plug hole in the front of the case. About a quarter of a pint is generally sufficient,
although excessive oiling will not cause the clutch to slip" !! The 1966 edition ( by Ferrers Leigh) also
says that a quarter- pint of oil is required A Velo handbook of uncertain age ( no cover or front pages -
my guess is 1950's) says that the chaincase should be refilled with one eighth of a pint of SAE 50 oil.
My 1953 Burgess "red book" is a bit confusing on the chaincase matter - on the one hand it says that
"The idea persists in the minds of some Velocette riders that too much oil in the (primary chain) case
will cause clutch slip. This is quite wrong, provided that the chaincase has always bee kept properly
supplied with oil and th clutch is properly adjusted" But the same red book also says " The primary
chaincases on Velocettes are not strictly of the 'oil bath' type, but provide sufficient protection from dust
and dirt to ensure that they are kept in good order. It is quite sufficient to squirt a little engine oil over
the chain, whilst at the same time moving it round slowly by means of the kick-starter to spread the oil
all along the chain" I guess that if you squirt the oil in often enough and the case doesn't leak(!!) you
could easily maintain about a quarter of a pint of oil in it. Take your pick - all seem to agree that there
should be oil in there, none of them give any tips on making sure it doesn't run out!
#2194 1/8" of a pint (Imperial) 70cc of SAE 20/30 Castrol GTX is in the Haynes manual. My chain-case
is the screw type with the cork joint.
#2195 Rod Burris in "Velocette" makes reference to 71cc of oil but also comments on the chaincase's
notoriety for leaking oil - irrespective of type/sealing system!
#2199 I stuck the cork gasket to the inside chaincase with silicone sealant and then lightly smeared
grease on the other side of the gasket. Then applied an 1/8th bead of silicone to the outer chaincase
and assembled it. That way the silicone forms a seal which can be dismantled and is still oil tight.
L #2774 I am assembling a MkII KSS engine and gearbox from bits, into a Viper frame. I have
modified the engine plates for the gearbox and the shell is in position. I am dry assembling the clutch
and primary drive to see what's missing and check alignment to the rear wheel sprocket. On the spares
book for a Venom/Viper there are shown various shims M245-M245/4 to go between the sprocket boss
and the main bearing . There are none similar I can find in my KSS spares list. The clearance between
the sprocket face and the bearing housing on the crankcase is .028 measured with feeler gauges. Are
they necessary and if so are they to ensure alignment of the clutch centre and the engine sprocket.
#2779 The shims are available to align the chain if required. I have never used any on a Velo and
doubt that you will have to. However they are there if you find the build-up of tolerances means you
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need them.
#2781 Call me a Doubting Thomas, if you will, - but you have the 'original' Viper gearbox SHELL (?) in
the frame & have modified the plates (?), but have you in fact checked the gearbox end plate assy. in
situ, against the KSS magneto chain case ? Unless miracles have occurred in the past 40 years, this
engine just does not fit, unless (1) you are using the earlier series rigid frame gearbox, or (2) you are
prepared to go without most if not all of the primary chain adjustment ? I have heard & seen it all in this
department, but I still stand by my original decision back in the 60's to cut the 2 bottom frame tubes &
lengthen them by some 3/4 inch to get enough room to allow it to fit & give you primary chain
adjustment. Result, original engine/gearbox plates match holes in Mk. 2 c/case, admitted with a slight
forward tilt of the engine that has never worried me. All the projected bits go into place no problem,
including the generator, which is pretty close to the front down tube, but works OK, all you have to do is
make up 2 new front engine plates, & modify the original primary chaincase, (details if you want them ) .
I cannot be sure, but I am prepared to claim that I was the first Velo freak to do this back in the 60's,
USING THE LATER SERIES BOX ! Sure, Ivan Rhodes,(bless his soul) had done it with his lovely Mk.
V111 engined special, around the same time, & others had followed suit with the Mk.2 KSS engine &
the earlier 'box. Cutting the frame tubes & inserting a couple of properly prepared (lathe) fillers, then
reassembling the plot with new front plates, then reaching for the arc welder, is no real drama at all I
can assure you ! My frame did in fact spring apart the required distance when I ran the hack saw
through the tubes ! I am in constant email touch with an 85 year old Velo rider/ enthusiast in the UK,
who is a retired bank manager & has little if any mechanical ability (& who isn't into the Velo information
stream). He has over the years acquired 2 such 'Specials' , one apparently with no primary chain
adjustment, with the service quirk of constant replacement of chains, & the other having problems of
the same order, but he has now had for some time a magnificent special built by someone who really
knew his stuff, & I suspect extended the bottom frame tubes the same as I did all those years ago ! I
know of one 'conversion' which I have never actually seen, where the offending portion at the front of
the gearbox cover, plus a quantity of the front nut/bush of the cross shaft was just removed ! - possibly
a part of the KSS mag. chaincase as well ! Would be interested to know if you do in fact have a
'miracle' on your hands ?
#2782 There is one alternative you have not considered, using a prefix 11 box. With this gearbox the
right hand side can move behind the timing case, only for the left hand side to foul the swinging arm,
however you can remove about an eighth from the left hand nut / bush which gives you about 7/16 th
clearance in total. Tight, but it just about works on my KSS special. Fitting GTP close ratio sleeve gear
and corresponding fourth gear gives you Venom ratios. As this gear cluster can support the power
outputs of both David Holmes and Nigel Lines racers the MKII engine puts relatively little stress on it.
Of course you are stuck with the seven plate clutch.
#2783 I have checked and I have room to move the gearbox within the limits of the slots so that forward
it does not touch the mag and back to almost the frame downtube. The gearchange approaches the
downtube. The limit on back movement is the slot in the chaincase back for the small shouldered
screws. I have not tried a chain on yet. I could with this mod move the gearbox further forward if I
lengthen to adjuster slots. I have not put the gearchange levers etc on so cannot say that all is well yet
but it looks it. This is due to my particular choice of method, sounds like a bit of luck also! I used the
original series 5 box. I did not want to move the footrest brackets back as I was not keen to try the
recommended unbraze and slide option. I do not have the heating equipment or much experience of
brazing or welding. This also leaves the option to put a Viper engine and gearbox in. I found the holes
on the Viper plates just aligned with the two lugs on the rear downtube of the frame and the upper
crankcase hole. I bought another pair of plates at an autojumble. Chris Wiggins gave me a tracing of
the rigid KSS/MSS gearbox plate and I traced on that the Viper plate with the 3 holes corresponding.
This showed that the gearbox was too low. I had the gearbox pivot hole, the forward gearbox slot and
the hole at the lower crankcase/footrest lug bolt filled and a piece welded in at the bottom for the
gearbox pivot. The Viper plate has a bigger hole forward for the Viper gearbox and is not closed at the
rear. I drilled and filed a new forward gearbox slot and gearbox pivot hole. The rear slot with the
adjuster corresponds. I replaced the through bolt between the footrest lugs with 3 items. 1 a piece of
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the end of the original 3/8 bolt shortened and threaded 1/4BSF to go into the timing side plate. I use a
nut on the outer end now in place of the bolt head. 2 a 1/4 BSF Allen bolt between the plates through a
sleeve (made by drilling out a piece of a 3/8 engine bolt) in the engine and 3 another Allen bolt through
the threaded end of a 3/8 bolt in the lug(CS head to miss the back of the chaincase). The holes in the
engine plates are close but the head of the timing side Allen bolt clears the cut down 3/8 bolt. I will have
to mod the spacer tube to go around the Allen head. The Allen bolts are stronger than turned bolts or
screws being cold forged and I happened to have a few from way back. The only slight reservation I
have is whether this combination will allow the bottom tubes to flex. The KSS power is less than a Viper
or Venom but there will be road stresses. Now the gearbox is in place I see that the plates are out by a
small amount at the frame. I can force the bolts in, probably because the plates are open here and will
flex, so I may file the little out of holes in the plates. I know it sounds a bit convoluted but part of this
bike obsession is solving problems. Thanks to all for the help to date. I am sure to come back and will
report back when I have succeeded.
L #3147 I've been assembling the proverbial basket case MAC, and understand that a spacer
tube is required between the two halves of the chaincase to prevent them from being squished. Is that
spacer all there is, or might there be another piece somewhere of which I'm not aware? There is a
listing in the parts book for another spacer, but no sign of it in the drawings. Any and all help
appreciated--a really good explanation of the spacers and their fitting is what I require.
#3148 Yup, Two spacers, the first to space out the cases themselves is a piece of tube which locates
around the flanges of the holes in the cases, the second is a sleeve which fits over the fixing bolt,
between the big washer and the crankcase boss.
L #3337 I'm confused by the reference to a felt seal used on the outside primary cover. I'm aware
of a cork gasket behind the inner between the gearbox, and the other around the pin joint, but where
does the felt fit? Is there any reference in the parts book? Mine is a '46 MAC, built from a basket of bits,
and I can see no remnants of felt on any of the chaincases I have--would this felt fit around the lip
provided by the clutch inspection cap? By the way, any idea how thick the cork gasket should be?
#3340 The felt seal fits inside the outer primary chaincase adjacent to the outer clutch plate which it
seals against. A soft rubber (neoprene?) lip seal instead of the felt. Over the summer a friend lent me
his '54 MAC and had problems with a dragging clutch (even after going through the adjustment
procedure). When you pulled the clutch in you could see the outer primary chaincase flexing. I
purchased a new felt ring and 'shaved' it down a little and this seemed to resolve the problem. I'm not
sure what the part number is for a MAC felt ring (if there is any difference) but, the MSS / Venom part nr
is F309. If you can get your hands on a MSS / Venom Parts book the felt ring is shown on the inside of
the outer primary cover. I assume that your chaincase has been changed at sometime for the later 'pin'
/ 'bolt up' type rather than the band type. I've just popped into the garage and measured up a spare
cork gasket (the one that fits between the two chaincase halves) and they're about 3mm (1/8") thick.
Both felt and cork seals are readily available here in the UK but, I'm sure you should be able to get
some a bit nearer to home.
L #3869 I'd welcome recommendations on a make of chain to use for the primary chain on my
1956 Venom restoration. And to complete the chain, does it need a riveted link or will a normal spring
link be OK?
#3870 Regina do a standard primary chain for speedway bikes which is endless and ideal for the job -
but it does mean you have to fit the clutch/engine sprocket/chain assembly as a unit which can be a bit
of a fiddle! Available through any Regina chain or Pirelli/Metzeler tyre stockist in the UK.
#3871 I buy chain in bulk 10 foot lengths from bearing and industrial supply shops. It is much lower cost
than Reynolds or other "motorcycle" chains you'll find at your local brit-iron parts supplier. Typically it is
the brand US Tzuabki, or another brand name. I've heard that the chains with a brand name tend to last
longer than the generic ones. Still, these chains do stretch a bit. I can't say if they last as long as
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Reynolds, since I never have spent the money to try Reynolds chains. A 10 foot chain is enough for 2-3
primaries, or 1-2 final drive chains. The cost is typically about $20-30US, including one master link. I
buy from McMaster Carr, MSC, or Grainger in the US. You'll need to get a chain breaker tool for about
$15US to push out the pin to get the right length. Additional master links are around $1-2US each.
Here's a tip: safety wire you master link (spring like). I saw some race bikes doing it years ago, and I
have done it ever since. It is hard to describe how to do it, but you can probably figure it out. I can send
a photo if you like.
#3875 I have always used Reynold here in UK since 1955 without complaint. Always used split links on
primary and rear. On our low output machinery when doing say 12000 miles a year a rear would last
say 2 years and a primary four. This with good maintenance like thorough cleaning and boiling the rear
in a mix of tallow and graphite grease. Thank god for spray cans now.
#3874 I can't recall ever buying a chain of any description in my whole life that didn't come from an
industrial supplier, - as I see it from my entire working life in the engineering world, that is where the
best chain is available ! True, there are special applications, & prices over the counter, but it is a simple
matter (in honest terms), that what you pay for is what you gets ! In recent years I have bought all my
chain from a good friend who has a company that ' builds' all sorts of chains, (some of them huge)
using mostly plates, rollers, pins etc, that come from Japan in bulk, he swears that he uses only the
best quality materials available, & like my own experience, has no problem with the quality of chains
that are available other than 'Reynolds' etc. I of course spent most of my earlier life refusing to use
anything other than a British made chain, but common sense dictates that modern technology is
capable of producing high quality products in any (really) developed industrial country. Of course, even
the most expensive (non 'O' ring) chain will destroy itself in a short period of time if it is plain neglected,
under lubricated, &/or over stressed, - most Velo owners reading this will probably have had the
experience, at some point in their riding life. These days for the first time in my life , after many years of
shaft drives, I am being propelled by a modern O ring chain, & almost wear my eyes out checking it for
lubrication , for which I use the remains of a 4 gallon drum of industrial black 'Moly' grease, applied with
a handy wooden twig ! despite what you may think, this doesn't fly off all over the place as some of the
expensive chain lubes do, & it seems to stay where it is supposed to for a surprisingly long time.
#4809 I just bought a Reynolds chain and the familiar "Made in England" was missing on the links.
Does this mean they are now made elsewhere? I just wondered what brand of chain would be
recommended by the more experienced riders. I know the slim profile works better with the Triumphs.
Also on the box Reynolds insists that all production bikes should have the riveted link. I have never
fitted this type but now im a little concerned.
#4810 I should imagine that such commodities as chains are made all over the world - wherever labor's
cheapest. As for the riveted link - they're probably right, but the only failure I ever had of the familiar
split link was on holiday in the IoMan - fortunately a friend had a spare in his pocket and I was out of
action for just 10 minutes! I always have a spare tucked about me now whenever I take the Thruxton
out...
L #4202 Hello Has anyone worked out a way of determining the correct amount of chain slack in
the final drive chain without pre-loading the rear springs? In other words when the machine is off the
centre stand ( I don't have one) and the spring units adjusted to the mid point in the upper curved slots.
(I am just lazy - but also believe there must more than one way to do a job). The red book suggests
making a special jig with holes at 11 ½ inch centres and compressing the rear springs so that the holes
fit the bolts at both ends of the spring units so they are partly compressed.
#4203 I just sit on the bike and make sure it does not go too tight. You don't get this problem with a
rigid frame!
#4205 Don't get this problem with a rigid frame! Chain slack in the final drive chain without pre-loading
the rear springs? In other words when the machine is off the centre stand ( I don't have one) and the
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spring units adjusted to the mid point in the upper curved slots. (I am just lazy - but also believe there
must more than one way to do a job). The red book suggests making a special jig with holes at 11 ½
inch centres and compressing the rear springs so that the holes fit the bolts at both ends of the spring
units so they are partly compressed. Better still, I used to get my Mum to sit on the bike while I adjusted
the chain ;-)
#4223 What you are looking for is an additional amount of up/down slack to allow in the chain when the
Final Drive Shaft, Swinging Arm Pivot and Rear Wheel Spindle are not in the same line. Theoretically, it
should be possible to calculate a figure but it would vary with machine weight (full tank of petrol?
panniers fitted? clog irons in your toolbox), the degree of clappedness of your Woodheads' springs and
even the position of the spindle in the fork. There is no substitute for loading the rear suspension then
rolling the bike along until you find the tightest point. It would appear that all sprockets are slightly
eccentric and chains wear irregularly. Try using an old tie-down strap between the R/H fork and the
frame "arcuate slot" to pull the suspension down.
#4224 Set it up correctly at about 11 ½" remove the weight and measure the chain movement.
#4229 The book published by BMS based on Geoff Dodkin info and pictures says 11/4-11/2 inch at
centre of chain run with bike on stand and rear wheel clear of floor. Seems to agree with the 19
between centres method.
L #4794 How can I tell if my Venom primary chain is worn? Is it to do with the length compared to
a new one, or when gearbox adjustment reaches maximum? Can anyone tell me the length of a new
chain?
#4795 Take the slack out of the chain runs and then try to pull the chain off the back of the clutch
sprocket. If it comes away more than a little it's shot! Alternatively, lay the chain out straight and see
what slack there is between one direction - closed up - and the other - out tight. There should be less
than 2% wear. More than that and its time for a new one. Don't bother with the side play type test, that
just shows if the sprockets were out of line and have thus caused wear on the links sideways.
L # 4821 Here's my twopennyworth to the chain debate, for many years I used Renolds timing
chains when overhauling Jaguar XK engines. As the price went up the quality seemed to go down,the
chains stretched requiring constant adjustment, so I switched to Sedis chains. I have been using Sedis
chains for over fifteen years in standard and competition engines with no problems whatsoever and
would have no hesitation in using one on my Velo' or any other bike. They are French though! With
regard to tyres for a Viper, I fitted Avon AM20 & AM18 on my Venom and am very pleased with them.
# 4822 just my experiences with joining links I had one lose the spring (horse shoe) part of it on my
bandit, this was on a new chain and sprocket kit lucky it held, i also lost one on my bonnie whilst doing
60mph on tha a40 at northolt which jammed the chain between the sprocket and swing arm locking up
the wheel 'till the chain snapped again and freed the wheel and i managed to stay upright luckily!!. if
you can, get a japanese chain with a proper soft link, not sure if velo sizes are made i assume they are
as i got one for the bonnie ok safe riding.
# 4827 I have usd spring links for many years and have never had one come off, work loose or
whatever. This includes racing when I was younger. I always use DID chain which is far superior to the
"Reynolds" available today. I believe its been made in France since the early 80's For primary chain
use use 428H, make sure its H as that denotes heavy duty. This size is sutitable for both Venom or
Viper. On the rear use 530 on the Venom. Its equivilant to 5/8..3/8 Reynolds. I would suspect that any
quality Japanese chain would be better than the stretchy Reynolds that seems available today. Fit the
spring link the correct way and you will have no problems.
# 4830 I'll second that! Modern Japanese or Italian chains are far superior to Reynolds who are no
longer major players in the field. From Japan choose EK, RK, DID or pretty well anything with "Made in
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Japan" on the box, or Regina from Italy. Regina actually sell a standard endless chain for speedway
primary drives which just happens to be exactly the item required for Velo primaries too! As far as split
links are concerned I would advise using an endless chain or rivet link in the primary, but have no
problem using a split link in the final drive chain so long as it is fitted correctly with the closed end
pointing towards the direction of travel of the chain.
L # 4849 Does anyone know if a modern O-ring or X-ring 520 chain will fit on a Venom? --Shane
1970 Venom Clubman
# 4852 No, but a 530 chain will. 520 is equivalent to 5/8 x 1/4 in old money - completely the wrong
size unless you're prepared to skim 1/8" off the back side of both sprockets! Only problem with fitting
any "O" ring chain to a Velo is that it will probably foul the primary chaincase due to the extra width of
the chain. I've found that a modern 530 heavy duty non "O" ring chain runs very close and will rub the
paint off the case. I can live with that, but I think an "O" ring chain will be just too wide to fit - unless that
is, you're prepared to do the mod suggested above!
# 4857 Re the query about O ring chains. I was going to fit the narrow 520 or X ring chain by
narrowing the sprockets. That was until I felt the weight of a heavy duty O ring chain. I have also found
that a heavy duty 530 chain willl take the paint off the outer primary chain case:
#4860 My neighbour's Kawasaki GPZ550 puts out a lot more power than most road going Velos and
is fitted with a standard 520 chain and sprockets and the wear rate on that is satisfactory. To help
reduce overall weight I use a 520 chain on my Venom racer and reduced the sprocket width on the
inside to provide extra clearance for the belt drive. Again wear rate is acceptable. This is a simple mod
but leaving it standard is even simpler and the wear rate is non-existent.
# 4894 The Regina ref number is 126 SP3, which is available as 10m lengths or as boxed endless
chains of 62, 64, 66, 68 or 70 link lengths. I believe the 500 Velo needs a 68 link primary. RRP around
£25. Should be available from any main dealer who stocks Pirelli or Metzeler tyres in the UK.
L # 6120 I am out looking for a replacement drive chain (#530) 100 links No one seems to have
the light duty narrow type. There is not enough clearance on the drive sproket (1937 MSS) for the
regular and HD type chain. The question is this... Who makes the kind of drive chain that will work?
# 6125 I've used a standard 530 Regina chain on my Venom for a number of years. It runs close to the
primary case, close enough to have worn the paint off at the rear of the case, but that's all. Don't see
why your MSS should be any different. The Regina designation is 136 RS I believe. They also do a
perfect endless chain for primaries, sold as Speedway primary chain, designation 126 SP3, in lengths
of 62, 64, 66, 68,and 70 links. I think the 68 link length is correct for the Venom and perhaps for the
MSS too.
# 6128 Dave, I use chain from the industrial and bearing supply shops. It is typically $20US for 10 feet,
includes a master link. Try MSC, Grainger, McMaster Carr, or other similar shop. The brand name is
usually US Tzubaki. By coincidence, Ed Gilkison was just telling me yesterday that if a thick primary
cover gasket is used, the final drive chain will rub the outer primary cover. He suggested using a thick
gasket, and fitting a mainshaft from a swingarm bike. They were about 1/8" longer on the drive end,
identical dimensions inside of the box. That will space the drive sprocket outboard, giving clearance for
the primary cover.
# 6130 Don't use industrial chain on a motorcycle. It's not rated for the speeds that a bike drive chain
runs at and is likely to cause some damage when it either sheds rollers or breaks. Use a proper
motorcycle chain from a reliable source. You get what you pay for and the reason industrial chain is so
cheap is that you are buying a lower grade of chain. .
# 6138 The US Tzubaki chain is a great product. I've been using it for going on 10 years, with no
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problems.
# 6142 I'm not knocking Tsubaki chain - they make a good quality product intended for motorcycles.
But that's the difference. Like most chain manufacturers they make chain for a range of applications.
Motorcycle chains are made to withstand high loads and speeds, industrial chains usually transmit
either high or low loads, but at very much lower speeds than are experienced on a bike and so the
construction and materials can be quite different. They are tailored for the relevant application. Some
manufacturers even specify non standard dimensions to ensure that only the correct specification of
chain can be used for a particular application, Suzuki for example used to specify a 532 chain (which
had larger diameter rollers than 530 although the width and pitch were the same) on some of their
range of big capacity machines. The cynical might suggest that this was a ploy to sell more expensive
spare parts to the unsuspecting public, but at least it ensured that chain of the correct spec was fitted to
their high performance machines - an important safety consideration I believe. Bike chains are not
normally stocked by industrial chain stockists, although they may obtain some for you if you ask, and
you may even get a better price than from a bike shop, but do be careful. Tsubaki have a fairly good
web site www.ustsubaki.com/ where you can view the specifications and dimensions of their chains. I
would suggest that their QR product is probably the most suitable for Velos.
L # 6276 does anybody know how to get the band type primary chaincase oil tight!. Even Bob
Burgess Velocette service manager for many years in his books admits it`s a pain in the butt. Velo seal
is W shape and even with silicon will not stay oil tight for long, the other problem is there is no way of
checking how much oil is left in the case, because of the bar that runs just below the filler hole. the only
thing you can do is drain out what’s left and top up to 70cc and refill it. 1/8 of a pint is not a lot of oil to
lubricate the 1/2" primary chain which leads a hot hard life in the chaincase. AJS Machless use a T
shape seal has anybody tried one on a Velocette if so was it any improvement?
# 6278 Simple answer on the band type primary cases is to take the neoprene seal and clean it, place
in a bucket of HOT water. Check that the faces on the cases mate up nicely. Assemble the chaincase,
leaving the central bolt looseish. Dry the seal up and fit in position - as it is hot it will be pliable. Fit the
band over the top - don't dislodge the seal - and carefully screw the band up. Then tighten the centre
bolt. Job done. As regards oil; don't worry about it! Add a shot as often as you think about it. It will be
lost from the final drive sprocket hole anyway - and the odd sundry leak. The recommended capacity is
so small as to be daft anyway. Using the above method it is possible to achieve a nice & fairly oil tight
chaincase, always providing all the bits are in nice order.
# 6279 I've posted part of an article from an old Fishtail that was written by then-Technical Secretary
Geoff Steele. He discusses the entire case, with some handy observations including an alternate
source for outer bands. It's in the Files section, in my Tech Tips folder. As usual, these suggestions are
used at your own risk!
# 6280 To check the level, kick engine over 2 or 3 times on the valve lifter, and look at top run of chain
thro' filler hole. If the chain is not dripping, add a bit of oil and repeat till it does. Main secret to getting
the band to seal is to make sure that both grooves in the neoprene are clear of debri, and warm it in a
bowl of hot water. fit over cases and pull the ends together firmly. If there is any overlap, trim the length
till the ends just butt up. Nip up centre bolt to hold it in place while you fiddle the band into place. I have
never managed to get a chaincase oil tight, but have found the band type better in this respect than bolt
up ones.
# 6285 A while back I decided that (until I had time to strip the whole case off again for careful
re-assembly agin leaks) I'd leave it empty & give the primary a squirt of top quality chain-lube each ride.
For the first ride or two she stayed beautifully dry .. . . but then started dripping AGAIN . .. . .
presumably from oil venting in from the holes in the left case near the mainbearing . .. . . I guess this
MIGHT be one reason to plumb the vent into the oil tank instead of venting it up/over/down ~ the oil
venting out would at least stay on board instead of being a net loss, not that it matters much either way
I suppose .
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# 6310 If you own a Velocette, or any other motorcycle of venerable age, you have to accept the
undeniable fact that there will be times when your beloved machine, instead of distributing surplus oil to
the 4 winds, will show a smear on the outside somewhere, & unfortunately if you are stationary instead
of riding & enjoying it, -- it will shame you visibly at times unless you are prepared to park on loose dirt,
or carry some sort of collapsible drip tray, or a roll of modern 'magic' house tissue. On the other hand it
is possible to eliminate some of the traveling vent holes, but in the end it will do little more than
concentrate the black mark in one spot. Normal fettling, ( & washing & riding) pretty much ensures that
surplus gearbox oil & water will finish up in the primary chain case as noted, & there isn't much that can
easily be done to prevent a healthy engine from breathing into the same place ! & it all ensures an
overfull case in my experience. Although I have never had cause to consider it, it seems to me that a
simple 'overfull' drain from the chaincase with the associated length of neoprene drain hose ( that many
modern wonders use !) would allow surplus liquid to either be dropped on to terra firma while riding, - or
into the drip tray that I assume we all use to keep our garage floor pristine. This would at least prevent
the build up of liquid to the point where it dribbles from the drive shaft openings, & if you fit a drain plug
to the chaincase as previously mentioned, you can at least ensure that anything in the chaincase is
mostly oil at the correct (?) level !!! On the other hand maybe a couple of tips on curing leaks elsewhere
?? On my Mk. 2 KSS machines, I have adapted the front of the inner chaincase fitting, to take an 'O'
ring that snaps oiltight over the driveside crankcase bearing housing boss, so this eliminates the dribble
of oil at this point. I first did this on my 'Special' where as a result of my bottom frame tube lengthening
operation, ( approx 3/4 inch) the optimum engine/gearbox drive centres increased by about half that
amount, & surprisingly there is enough room around the standard engine drive sprocket, ( assuming no
chain disintegration !), to allow the drive shaft hole to be moved this distance. The removal ( &
destruction) of the original tinplate bits, required that a new one was machined from solid stock, & it
became obvious that the original oil containment at this point could be greatly improved by the addition
of an 'O' ring. The result, -- no more leaks here ! This mod. should (?) apply to the M series as well.
Another annoying spot is that spacer tube between the 2 cases, -- but this is an easy one ! -- forget
about all the sealants & junk, & simply do a neat cut in a piece of stock radiator hose, to make a rubber
tube that is a little longer than the steel spacer tube, & fits over it. Bear in mind that I have been using
this trick since the days of canvas reinforced natural rubber hose, -- & yes, - I know that the oil will
attack it & soften & swell it all up, -- but this only makes the seal better ! In these days of neoprene, it
will be necessary to make sure that the ends of the tube are accurately cut square, or smoothed square
on the linisher belt, or the judicious use of the grindstone, (not really a good idea !) What ever, -
properly done, this is simple to fit & results in the elimination of another annoying smear of oil. As for
the rest of the leaks, -- you are on your own fellows !!
# 6312 These ideas are very useful and practical but for those with access to the UK VOC spares
scheme they do a very neat alloy spacer with o rings in each end. This gives a good oil seal and still
separates the two chain case halves correctly. I once saw a Velo racer with a "nappy" to catch the oil
drips. Not as bad as it sounds as it was a neatly made sheet metal plate, similar to the military/trails
bash plates seen on other bikes but with an absorbent foam layer to catch/hold any drips! Never tried
myself .I think I would rather be shamed by oil drips than admit to being a forty five year old who still
uses nappies!
L # VOCNA 122 A friend of mine bought a 1936 KSS at the Vegas auction. I went over tonight
and we got it fired up, made sure it had oil pressure to the cam, etc. After it ran for a minute a large
puddle formed under the primary. No problem I said, the primary has filled from sitting, just have to
drain it off. We couldn't find a drain plig anywhere! Did they not have them back then? It has the
normal fill hole with spring clip. You guys ad drain plugs?
# VOCNA 123 Obviously a KSS needs no drain plug, as it all comes out on the ground anyway! I'm not
sure if I still have a KSS primary laying around, but adding a drain and level plug is always a good idea,
as is silcone sealant!
# VOCNA 124 The KSS does not come with a drain plug. It is not really worth the effort to fit one
because there is no seal and provision for one around the clutch. Run the bike for a few miles and it will
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disgorge itself down to the near empty level and all the bits aft of the countershaft sprocket will be
liberally coated in oil. In my experience the big problem with KSS s is that they eat primary chains. In
conversing with other KSS owners this is a common trait. If you want to do anything to the KSS the first
thing I would do is try to get a seal between the clutch and chaincase. If you achieve that then you will
likely have to put in a drain plug. I plan on putting a belt drive on mine this year and eliminate that oily
mess completely.
# VOCNA 126 Alternatively, one could use a suitable high temp lube on the various bits in the
clutch/shock absorber assy and simply run chain lube in the chain case to keep the mess down. Since
the engine breaths out of the nearside main bearing there will always be some mist coming out whether
you are running a belt or devise a clutch seal.
# VOCNA 127 I don't recommend using only chain-lube on an enclosed primary. I tried this with my
Thruxton a few years ago, and it won me the Crock award when the chain siezed up and took the
chainwheel with it. I had lubed the chain every 50 miles, or whenever I stopped, but it wasn't enough,
obviously. Conversely, on my open primary bikes, a little chain lube once in a while seems most
sufficient, so it must be the heat inside the case which is the issue.
L # VOCNA 389 Any thoughts on the V-ring seal (looks like maybe CR-400954) as a replacement
for the felt clutch seal? I tried one years ago and it split but I may have had the spacing wrong.
Anyone using one?
# VOCNA 390 I tried the v-type seal that the club spares scheme offers, and it ripped to pieces in a
few miles - they refunded my money with no questions asked so I bet I was not the first to have this
happen. There is little to no clearance between the outer clutch and the inside of the primary cover
when the clutch lever is pulled in. I understand the clearance varies among bikes and mine is one that
has virtually zero. An oil soaked felt ring works OK as the outer clutch plate can rub on it, however, the
lip on the lipped V-seal covers the outer ring that holds the felt seal and acts to cut through it. I would
be interested in hearing others experience with this.
# VOCNA 391 I've tried various methods of sealing the gap between the outer clutch plate and the
outer primary case. The results have ranged from fair to bad. One common factor for success is the
face of the clutch plate must be smooth, very smooth. The variation in gap from bike to bike
complicates the problem. The best seal I made and with the least resistance to clutch movement was a
ring of thin wall neoprene tubing epoxied to the felt retainer. I placed the tubing butt joint at the bottom
to drain the oil. Once the epoxy cured I made a circumferential cut with an Exacto knife around the
periphery of the tubing.
# VOCNA 399 I tried the tubing trick once but bodged the razor cut after waiting all night for the epoxy
to dry. Did you make the cut using the outer flange in the cover as a guide? I tried making the cut
freehand at the high point (center) of the tubing. Maybe I'll try cutting the tubing first.... Never thought
about the V-seal getting cut by the cover but I'll bet that's what happened to mine as well. I even went
so far once as to fit a lip seal to a thin plate glued to the outside of the primary cover that sealed on the
countershaft sprocket. Oil tight but has to come off to adjust the primary chain or clutch, bit of extra
bother.
# VOCNA 400 The problem with rubber seals relates to the fact that they aren't concentric with the
clutch, the lateral wiping action rips them up rather quickly. Felt seals can do the same. There was a
tip about a homemade leather lip seal in an old FT, have heard positive comments about this one.
# VOCNA 402 The guy who has been fitting lip seals (CR-400950) for quite a while is Matt Chapin.
However, these seal are too thick, and I understand that before fitting he reduces the thickness of the
solid part by about half (not sure how!). Several folk will have his seals installed It is very important that
the outer clutch plate be absolutely smooth and polished. This also helps with the eccentricity problem.
The leather seal described in FT could be the best alternative. Roger Slater used one of these when he
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was racing Velos way back, and reports that it worked well.
# VOCNA 414 The tubing I used was 3/8" O.D. with and very thin wall, about 1/32" as I recall. After
epoxying I used a 1/4" lathe tool bit as a guide and walked the exacto knife around the periphery. It
worked rather well and was still in the bike after several thousand miles when I sold it to a guy in
Missouri. I talk to him occasionally . He has not mentioned any issues with the seal. I had surface
ground the outer face of the clutch plate. I got the tubing from McMaster-Carr. I tried to find some Viton
tubing, but no luck. I have wondered if milling machine way wiper strip stock could be bent in a circle
and adapted.
L # VOCNA 392 I ran into a glitch with the KSS assembly (fancy that!). I installed the outer
primary cover tonight, and when I put on the rear chain found that there was no clearance between the
chain and the chaincase - in other words the chain jams against the chaincase and the sprocket will not
turn. I cannot get the chain on properly, so it is hard to tell how much it needs to move, but probably
1/8" would be ample. Possible explanations that I discounted: 1. The lower flange of the outer
chaincase was a bit bent when I got the bike and I straightened it out somewhat - but I did not go near
the area where the chain is fouling, so I do not think this is it. 2. I used the cork gasket that came with
the gasket set between the inner chaincase and the gearbox - it was pretty thin, but if the new ones are
a bit thinker than the original it could be pushing the whole chaincase assembly outboard a bit. I could
take it out and put a well greased paper gasket in. 3. The sprocket I have I think is for a Venom, and
Ed said these will fit if you turn a small chamfer onto the outer edge of the inner boss where it goes into
the mainshaft - it must fit inside the nut that holds the clutch on. When I first offered it up it fouled the
clutch nut just as Ed said, and I put a bevel on it and it now fits all the way on as it should. However I
also tried the original sprocket and it actually provides marginally less clearance for the chain - so this
isn't it either. Is there any variation in the thickness of the primary case gaskets? I have 6 or so and a
visual inspection suggests mine are all the same thickness, but perhaps those for the early bikes were
thinner?. I could shim the sprocket out a bit, but this seems a bit dodgy and should not be necessary.
Anyone have any ideas??
# VOCNA 393 I'm no KSS expert but here's a few general observations: Is your main shaft all the
way out to the left? If the bearing on the other side has shifted that will move the shaft in. My KTT
main shaft is a bit shorter than later swing arm shafts. Probably irrelevant but goes to show there are
different length main shafts. I shimmed a sprocket out when I first started using 0-ring chains. Still
have the shims if you want them but I wouldn't recommend it. The sprocket failed at the dogs from not
being fully engaged in the main shaft. What I do now is cut the teeth off a worn sprocket with good
dogs and cut the center out of a generic sprocket and weld the two together with enough offset for the
chain to clear. You could do this if you can't come up with a better answer.
# VOCNA 394 I wondered about the mainshaft - I think I will pull the gearbox cover off and have a look,
but I think it's location is set by the bearing and nut on the right side and I do not think it can move to
the left, but I will check. If I cannot find an obvious solution, I may shim the sprocket just to get it on the
rally and address it properly later. Let's see what the rest of the gurus say first!
# VOCNA 395 By coincidence, Ed G. and I have been talking about this issue in the last few weeks.
How thick is your gasket between the inner and outer chaincases? If it is 1/4" then use one that is 1/8".
Using the thick gasket and the main shaft from a Rigid Velo will cause the chain to foul the outside of
the outer chaincase. Ed has told me that the later mainshafts are longer, but just the portion that
engages the final drive sprocket. He recommended that I use the later mainshaft, and a nice thick 1/4"
gasket, to get a better seal on the chaincase. Mine has always leaked, and I had asked him for advice.
He is sending me a long mainshaft to try out. Maybe you can get one too. Swapping the mainshaft is
surprisingly simple, if the clutch is already off the bike..
# VOCNA 396 Take the bike out behind the garage and shoot it! I've tried the shim under the sprocket.
But, the main shaft nut kept working loose. I ran into the same problem today on a Clubman
restoration. I placed the chain case on a drill press table with an old chain wheel on the inside and
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placed a ring on the center then pressed the center down to give clearance. Maybe that will work for
you.
# VOCNA 397 Being Canadian, I don't have a gun, but I may just try that trick with the drill press. I
like the idea of the longer mainshaft and may give Ed a call today about that. I have not measured the
thickness of my gaskets, but there is no way they are 1/4" thick, but I will check. Best solution I receive
by 6PM when I get home from work is the one I am going for - anybody else??
# VOCNA 403 Venom mainshafts are a little longer at the drive side end, and will fit in a KSS/MSS
gearbox with no problems. The sprocket will be spaced out accordingly. The extra length is to
accommodate the thicker clutch (extra plates) used on Venoms etc. The chaincase gaskets are either
1/8" thick or 1/16" thick. There's none ¼" thick.
# VOCNA 398 The main shaft location is set by the bearing but the bearings are often loose in the
bore (at least on the later boxes). If you do end up shimming the sprocket you have to make the shim
in the shape of the dogs, a simple washer won't do it, too small OD and the sprocket will flop around
and come loose. Now it may be possible to fit a shim on the other side between the main shaft and
bearing to move it over, have to take a look at the main shaft and see but off the top I don't see why
that wouldn't work as long as there is still enough unthreaded shaft engaging the bearing.
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F. Running Gear
F.1. Steering Head, Forks and Shocks -
L #134 I have a 1960 Venom road test that states the top speed is 95mph with 65mph lights. But
with the sidecar on this makes very little difference to us. Can anyone explain why the forks can be
removed with ease but are quite illegitimate to put back to obtain the correct pressure on the shrouds
to prevent them rattling. Or has anyone learnt the secret.
#136 There is probably some approved method to stop rattles. The hairy method a few of us use is to
run the bike, down a very quiet road with a few bumps but not too many, with the lower pinch bolts out.
Don't brake heavily, it could be interesting. Stop from time to time to see if that's done the trick, and
when it has, put the pinch bolts back. This is slightly suicidal and I refuse any legal liability, but it
generally works when bouncing up and down has failed
#138 By the way have you remembered to offset the forks springs to the nearside and include the
rubber washers between the shrouds and springs?.
#144 I start by putting the bottom yoke in the vice. I clean any paint off the inside of the inside of the
fork yoke and grease it. I then put a wedge in the slots of the lower fork yoke, and check the top spring
claw, F262, will fit easily. I leave the wedge during assembly. My tools include my version of LET 796,
and another device which I can't identify on the shelf, for holding the damper while screwing the bottom
nut.
L #229 This is a pretty specific request for info; does anyone know if there is a replacement
taper-roller steering head bearing for KTT's mk 1 and 8? I just pulled the forks from my mk 8 and the
cups are, understandably at 64 years, a little dimpled. As I'm also ready to put my mk 1 back together,
I thought it a good idea to change this out as well. Anyone have any experience here?
#230 There was an article in UK Fishtail 298 on using taper rollers in a MKII KSS that maybe of use
#232 May I suggest taking the original bearing races to your local bearing supplier. Try Yellow pages. If
you get the ID right and the OD can be cylindrically ground to fit. Might be worth a shot
L #278 I am ashamed to ask to the member, it’ a non-Velo thing. But I am interesting to know
what kind of none original Tele fork fit on the Velo swing arm frame? and how do they fit ? How
handling effected? I am thinking the machine for novice racing purpose as well as road ( 250cc). I
would prefer pre-63 folk and English one. ( timing cover said "MADE IN ENGLAND" is it?),no
alternation to the frame ( in case I will replace it back later) and more widely available than Velo fork
with rebound damping. once I heard that Roadholder would fit, but I realized there were several type of
Roadholders. I gave it up because not knowing what I was looking for.
#279 You could try a set of Metal Profile forks. These were British, available for many years without any
major changes and were commonly used as an aftermarket upgrade by racers of the period. You might
find some by scouring the autojumbles or spares advertisements.
L #294 I've two sets of suspension units, both incomplete, both slightly different. The most
salvageable have annular spring supports fixed(?) to the damper unit: the other set has an indent
approx halfway up the damper, presumably for collets. Anybody recognize this description? If so
please where can identification/spares be obtained?
#296 Woodhead Monroes measure 6.5 cm OD and have an annular ring at the bottom.
L #300 Does any one know what pressure I should pump the air forks up to on my '48 MAC I
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have been told it is virtually impossible to obtain seals for them here in U.K is this true.
#301Do not over pressure it. Just a few strokes of the hand pump until the forks are nearly fully
extended. Then with your weight on the saddle, release some air out of the Kilner valve until the edge
of the shroud coincides with a small dimple, or perhaps a little before if you want a bit more ground
clearance. The dimple was originally painted with a red dot.
L #359 My newly acquired Venom is less than stable at the back end, especially with a pillion and
there is smear of oil on the left shock absorber. The shocks are the early Woodhead-Monroe type and
I would like to retain the appearance. There is a web site for a place in the USA that will rebuild these
shocks using new parts and retaining the appearance but I don't want to send them that far, not least
because I'm enjoying riding the bike and don't want it laid up for both weeks of the British summer!
Hagon have Girling pattern shocks for Venoms available but they have no parts that are compatible
with the "long fat shroud" look of the W-Ms. Is there anywhere in the UK that can repair or replace W-
M shocks for Velos? Or should I bin them and fit Hagons? (The bike is mainly for riding and isn't totally
original anyway - VR cases etc.)
#363 You could try contacting Martin in the attached Q & A
www.velocetteowners.com/qanda/su001.htm
#416 I've solved my immediate problem with the original leaky dampers by buying a new pair of shocks
from NJB - www.njbshocks.co.uk (reasonable at £78 + post). The bottom eyes of my original shocks
had 2 tapered rubber bushes, the NJB shocks come within a parallel bush and shim washers to line
them up. They have transformed the ride and are highly recommended - they look identical to Girlings.
Now I've got my old shocks off I can see that the dampers are way past simply refilling. The tube has
rusted where the bike was stood for years and the seal has gone. The options seem to be somehow
hard chrome the damper and replace the seal or get new damper units for the old covers. I don't think
I'll bother as I'm happy with the bike as it is now but I can't see how drilling/refilling alone can be
satisfactory..
#487 My 1948 MAC has Dowty air filled forks fitted, working fine till last weekend run of 110 miles, they
now lose pressure completely over 4 day period, anyone else had this problem and is it curable? I
have refilled each leg with clean oil and hope this may help, what grade oil is best straight 20 grade
recommended originally.
#524 I hope changing oil has rectified your Dowty. I had a pair that I was going to fit to my 1948 MAC. I
dragged them around three house moves in twenty years, leaking oil continuously! I looked to fit new
seals but these are now virtually impossible to get hold of. Carol who does all the UK Velo auto jumbles
had some seals for Dowty, but I don’t know if she has any left. The last number I had for Carol Kear
was 01242 239432. Another alternative is that Sammy Miller does/did spring conversion kits for Dowty
www.sammymiller.co.uk if you get desperate..
#528 Thanks for reply the oil change has made things worse, forks lose pressure in 10 hour period
now, are they likely to "collapse" suddenly whilst being ridden? Could you let me know how to contact
Carol to see if she has any seals, cheers Dave..
#684 I have managed to find a source of Dowty Fork Seals at a much lower price than other suppliers
charge, that is if you can find a supplier, I can get them through the hydraulics company I work for.
L #658 I dismantled the (girder) forks the other day - an interesting exercise! - but I can't seem to
free the bottom of the spring from the forks, anybody know if it's screwed/clamped on or is it just being
held on by rust? Forks are marked "The Webb" if that helps!
#664 The bottom of the spring is screwed onto a flattened thread: tap it a few times, lubricate it and
then unscrew.....they can be tight.
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L #879 Here's a question for the group... where can I get tapered tube for heavyweight Webb's to
replace my damaged ones. And how were they made originally, was it in one complete tube from the
top lug down or two? (i.e. four tubes per set or eight tubes per set).
#882 I believe that Percival and Webb of Dudley West Midlands are still going strong. I think they still
make girder forks and do overhauls and repairs. I think they are a offshoot of autocycle which is run
by Chris Williams.
#889 Try Ray Daniels 144 Station Road Stechford Birmingham B33 8BT Phone 0121 789 8900
L #1033 my 500 velo has a set of ajs or matchless front forks, which I think are the same, I just
wondered why? can any body tell me if there is any benefit to them.
#1034 You don't give a description of them, but later model Matchless forks were both compression
and rebound damped with a rebound spring that kept them from "topping out". The Thruxton and
Scrambler Velos had rebound damping, but for off road the Matchless forks were a better bet. Norton
(I'm in trouble now) put the Matchless forks on their P-11 desert racer instead of their Roadholders.
L #1076 One of my VM's gives a very slight 'fluttering' sensation from the front end on fast
sweeping bends. It is worse with flat bars, with clip-ons and weight further forward it is not so bad, but
still there. What could be causing it? Frame and forks are straight, s/arm is fine, r/shocks are new, tires
are good TT100's. S/head + wheel bearings are fine. Yokes are straight and forks straight in them. I
thought of these possibles: 1. Tyre pressures wrong 2. Im not going fast enough (quite possible) 3.
unequal damping from front forks - i.e. no oil in one (I’ve not checked this properly, but one is leaking)
4. front wheel unbalanced (full width hub using TLS) (not checked yet) 5. front wheel out of true (not
checked yet, but using alloy rims so not impossible) Screwing the steering damper down a bit further/or
backing it off has little or no effect (on the flutter). Any advice welcome.
#1077 had the same problem on a high mileage bike a few years ago. Eventually I found I could make
the problem go away by putting a slight drag on the front brake while heeled over in a corner.
Disassembly of the forks revealed nothing "wrong" but I finally discovered that the bottom fork tube
bushing had worn the slider out to where holding the slider in a vise the top of the fork tube could move
back and forth over a quarter inch. New sliders fixed it. Hope this helps.
#1085 For what it's worth, here's my experience with Velo handling issues; Regarding the head waggle
at lower speeds; I'd definitely check the fork bushings. Slack or shagged head bearings can give a
similar feeling, but usually only at slow speeds. Unequal fork oil levels give more of a rocking motion up
front; setting your shocks to slightly different places on the 'arc' does the same at the rear, as will slack
or shagged swingarm bushes and completely worn out shocks. Combining all of the above makes the
whole plot feel seaborne, but the bike won't throw you even when completely worn out in the chassis, it
just takes more bottle to ride quickly - at least this is my experience. (This applies to swingarm models;
if you ask me, the rigid MSS/KSS mk2 shouldn't be trusted at the limit, the geometry doesn't 'sing' as do
earlier KTT/KSS models) All Velos will weave a little at over 100 mph; not dangerous or scary, just one
of those Velo traits we come to love. Except the mkVIII for some reason; it feels very true at high
speeds, which is odd given the geometry of the swingarm models is basically the same. Could girders
be more stable at high speeds? My rigid KTT mkIV weaves just like a Thruxton at over the 'ton', but at
that point it's the least of your worries! Brakes please! In light of all this, check your forks! Velos feel so
much more secure when all is shipshape. And I can't recommend Work Performance rear shocks
highly enough; I've had them on my VMT for 5 years and now I only notice the front fork's
inadequacies.
L #1096 Simple perhaps, but so that I don't waste time & money ,what is the modern equivalent
please ,of the oils recommended for the front forks in the Service Manual.
#1097 I like Silkolene SAE 20 fork oil. It's sold at most motorcycle shops.
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L #1342 As part of my complete Winter strip/rebuild I took the front forks to bits on my 1960
Venom, not that there was any problem it was just that all the parts were being resprayed so it seemed
a good opportunity. I replaced the pistons and the bushes in the fork damper tubes and also the front
fork tube bush and the fork slider tube bush and the oil seal. The fork tube/stanchions were straight and
did not appear to be particularly worn. I have just put the fork legs back into the steering column
assembly and the fork cross member and tightened everything up. With the bike on the centre stand if I
grasp the front wheel between my legs I can move the handlebars a couple of inches. I removed one
fork from the bike, removed the spring dust cover and also the headlamp cowl bracket. I refitted the fork
leg without the wheel. Although I could twist the slider tube against the spring there did not appear to
be play in any direction. I refitted the spring cover etc and refitted the fork leg. Without the wheel I could
twist the slider tube but there was no obvious movement. However once I put the wheel in I was still
able to twist the handlebars whilst gripping the wheel. I realize I must be missing the obvious but frankly
I do not know what it is.
#1363 Install the front fender brackets-all three of them making sure they're straight-and snug the bolts
fairly well. Check for your "twisting" action now. It should be significantly less. With the front fender
mounted the whole assembly should twist very little. Be sure the fork pinch bolts on the lower steering
head are tight, too.
#1366 I think you are spot on in your suggestions. I think there were two problems. One - I hadn't
appreciated how important the mudguard brackets were to the rigidity of the front forks and secondly
having cleaned the rust from the fork stanchions so that I could get the sleeve tubes off to remove the
springs, how important it was to get the bolts really tight on the lower steering head. Although I thought
mine were tight with the rust free stanchion it was allowing the sleeve tube to move when I tried to twist
it.
L #1374 Can anybody tell me / point me in the direction of a drawing / write up of how girder forks
are supposed to be assembled? The spindles / plates in mine (Webb) seemed to have an odd
combination of threaded / not threaded which did not make them easy to get apart! Also, what
material(s) are the spindles / bushes supposed to be made of?
#1376 The answer re girder fork assembly is rather long and depends on whether you have the right
bits to start with! The spindles should be a decent steel EN16T (not silver steel or mild steel) The
bushes are a bronze, not specific really but not too soft. The spindles are screwed into the link on one
side and the opposite end is unthreaded and shouldered. This allows the spindle to be screwed into the
link to adjust the length and hence end play. Between the link and the yoke or girder blade there is a
knurled hardened steel washer. This must be adjusted to allow one washer to revolve with no side play.
There is a lock nut outside of all the links. The threaded end is a lock nut which sets the spindle length
fast once the adjustment has been made. The other (on the smaller end) stops the link from falling off!
Follow the above and you can get forks which are a delight to ride with and the handling can be nicer
than tele forks (on the right surface)
#1377 How do I make a puller to get the bushes out (what's left of them - I strongly suspect the ones in
the bottom link are totally worn away?
#1378 Richard, look at expanding type pullers made for pulling bearings from blind holes. Kukko,
Hazet, and Heyco, all three well known German automotive tool makers, build very nice examples. In
the USA, MAC Tools make several nice examples.
#1379 Tap a thread in the bushes, screw in a bolt and tap them out with a drift from the opposite end.
#1380 The new bushes should be pushed in and bored in line. As you will probably not be able to get
that done you will need an in line reamer or at least a reamer with a pilot to ensure that the finished
bores are in line with each other. There is one other method. This requires a lathe. The reamer is held
in the chuck and the fork member held with a centre in the tail stock. The reamer passes through one
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ush and then reverse the fork member and ream the other bush. As the lathe has been used the
bores should be in line. Whichever method you use you will require some expertise and tooling.
#1381 I am thinking to buy the reamers. But I do not know how to use them. Big question of Hand
reamer makes hole really parallel? Reason is that someone previous owner reamed first gear bush
but did not do parallel. As sequence first gear on layshaft lost the almost one side of tooth. It can be
very expensive. My mistake was I bought the bushes, not having the reamer or any tool but used wet
and dry very carefully. At the end my engineers square said it not parallel!! So now I wasted £10 for
bushes. My next step was phone some velo related shops today. They are all busy and not really
interested in such one small job(I do not blame them.) My next step will be buy reamer( I do not know
which I should get adjustable, taper or so on and it seems to be more type from previous mails) I still bit
afraid of waste further £10 bushes and cost of reamer. I have micrometer ,engineer square and patient
to work on. If I get the reamer it will be all fine? how to use them?(is it fit on the tap holder?)
#1382 Hand reamers are among the most difficult cutting tools for a machinist to master. Accuracy can
be improved if the reamer can be held in a chuck and the part to be reamed is held in a lathe chuck,
machine vise, or on a flat table. Reamers are easily damaged if dropped, turned backwards, forced, or
harshly used. Adjustable reamers are best when one must ream numerous holes that vary by a few
thousandths and want only one reamer. Good quality reamers are expensive and one could expect to
pay $40.00 US dollars and up for a good quality hand expansion reamer for ½" holes. Spiral reamers
are easiest to use and easily produce straight holes with out chatter. Reamers in most all cases must
be flooded with cutting oil to work best. There are cheap adjustable steel blade reamers that sell for
$10.00 US dollars and up, but are not easily used by hand and will chatter and give a poor finish in
most cases. Only freshly sharpened reamers or new reamers should be used for brass bushes.
L #1652 Haynes velo manual says.."occasionally difficulty is encountered when attempting to
reposition the fully assembled fork legs in the steering head yokes. If the lower, split yoke cannot be
spread sufficiently to ease the passage of the stanchion before the clamp bolt is replaced, a rope
tourniquet can be used to good effect". Is there any other way than using a 10lb hammer and chisel to
widen the split yoke in order to get the split collar in place? Wouldn’t the tourniquet just compress the
springs?.....anyway funny the red book doesn’t help in this.....Any environmentally friendly suggestions?
#1653 Re: the bottom fork yokes. The right way (I think) is to use a tapered wedge with a hammer - not
10 lb its rather overkill - and ease the split clamp on the yoke just enough to allow the separate
stanchion clamp to slip into place; align the spring location to angle the fork slider & fork spring
correctly then remove the wedge and clamp up with the bolt. If this is done sympathetically its an easy
job, otherwise......
#1655 Well I tried to prise the lower yoke and managed to open the gap but it seems the yoke hole is
now slightly elongated and it is harder to get the split collar in. Do you wedge the yoke open while its on
the bike? I took it off and tried still no joy Have you ever tried the tourniquet? Have you ever tried to fit
the collar first by knocking it in the yoke? Now I wonder how I ever got it off. Are there any other tricks?
#1663 I also struggled with my forks recently, I managed to get the collar to fit most of the way into the
yoke when I cleaned the rust etc off both. I persuaded it to fit all the way by pushing the bike forward
and pulling the brake on as hard as possible. Another way is to lift the front end of the bike and drop it
rapidly. Harsh but does help as long as someone is holding the bike.
#1664 Thanks I was beginning to think there was no hope on this one. I even dreamed about the
darned thing. Only problem is im at the beginning stages of rebuilding the bike so only the bare frame
to work with. I guess if I heated it up and maybe froze the collar that might help, but then id lose the
paint.
#1753 When I overhauled my forks I cleaned all the surfaces with fine wet dry to as shiny a finish as I
could get and put a light oil covering and that made the sleeves at the top of the springs go into the
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yokes ok I also used the rope Spanish windlass trick and a few thumps with a heavy hide ended
hammer to overcome the stick friction if you know what I mean. I also use the bumping technique to
ensure the forks were bottomed and the spindle aligned before tightening the forks bolts as per the red
book.
L #1731 I have reassembled the forks on a venom and topped them up with oil. There is a slight
oil leak past the large retaining nut which secures the damper assembly inside the bottom of the fork
leg. The BMS service series book says this is common and can be fixed by removing the nut with the
weight on the bike to keep the damper in position after draining the oil. They degrease the thread etc
and use 3M super weather strip adhesive, or a sealer used on Vauxhall Viva's (that dates it). Does
anyone know of a more modern sealant that I can find easily?
#1733 Bath silicon works a treat. I also make up top hat washers to accurately locate the 3/8 bsf thread
in the much larger hole.
L #1838 I have a Venom 57 which is currently fitted with Girling units of type TT Gas Shock.
These might be fine for racing, but is uncomfortable in regular road use. I am looking for a set of units
with a softer setting ideal for one-up on road. I know of a few alternatives: Hagon, NJB. Are there more
alternatives, and which is the one to choose ? Nice if someone with experience from testing several
alternatives could give me a recommendation. Any thoughts about ideal spring rating front and rear?.
#1839 I would recommend that you use the standard spring rating for Velocette shocks and simply set
the top mount in the forward part of the mounting arc if you want a softer setting, or the rearward part if
you want a harder ride or are carrying a pillion. This is the reason for the Velo spring frame design and
is superior to other manufacturers' designs up to and including the present day. This is because 99% of
other machines which have any form of adjustment on the suspension system use spring preload
adjustment to compensate for carrying heavier loads. This method does not change the spring rate
(which is what you really want) but basically alters the ride height by changing the amount of load
required to start compressing the spring(s). Ideally your machine should be set up so that sitting under
its own weight there should be a small amount of sag (about 8-10mm at the rear and 20-25mm at the
front). This can be done on the rear on Velos with Girling, Hagon or Koni shocks by adjusting the
preload ramp cam to give the required amount of sag. When you then adjust the position of the top
mount in its arc, the resultant change in leverage ratio changes the effective spring rate without having
to change the spring, which would be the only way to achieve the same result on any machine with
fixed suspension mounts. If you have damping adjustment on your units (a luxury not afforded to most
Velo owners although some Koni units do have some internal adjustment) you should not make the
mistake of winding on too much damping. The trick is to have just enough to keep the machine under
control - too much rebound will cause the units not to recover quickly enough after hitting a bump and
wind itself down over a series of bumps in quick succession with the effect that the ride will feel hard
due to the system working on a harder part of the spring and in some cases the machine might develop
a weave due to the resultant change in geometry. Too much compression will transmit shocks straight
through to the frame and will give the feeling of riding a road drill!
#1840 Many of us here in the US have had Works Performance shocks on our VM and VMT's for
years; the owner, Gilles Vaillancourt, is a Velo enthusiast, and has made what some consider the
perfect Velo shock. I think John Ray described them best, 'you just don't notice them when you're
riding' - high praise when you think how often you 'notice' your worn out Girlings! They have modern
internal specs, and I think he offers 'deception' shocks which have long covers like early Woodhead
units, but I've always used the open spring type which look appropriate on my VMT (yes, my '60
Clubman uses nos Woodheads, which are rapidly becoming noticeable).
L #1916 Are the original Velo clip-ons longer in bar length than generics available today; are they
different in any other way?
#1924 I don't think that the current ones will be any different in length , but watch out on the fork leg
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diameter . I bought a pair of clip ons from Grove which were supposedly 'Thruxton type ' but were not
correct . the Velo clip on bars butt onto the tube which clamps onto the fork leg . the ones I obtained
were secured in front of the fork leg clamp . I kept them until I found a pair of second hand ones at an
Autojumble .
#1917 What is the exact bolt up configuration for the loops most forward bolt on both sides?
#1925 These bolt into the fixing point inside the 'arcuate ' section of the frame . 5/16 bolts with
spacers to ensure they clear the shock absorber tops on adjustment . The offside mount is also the
mounting for the VMT oil tank.
L #2170 As part of the continuing re-build I took the rear damper units off the 1963 Venom, and
discovered there is about 12 thou of side play on the swing arm trunnions. Otherwise they feel fine.
Now I have owned the machine since 1970 and the previous owner since 1967, and since neither he
nor I ever touched them, it maybe they havent been moved since they came out of the factory. So the
question is what should I do. I could 1. just tighten the thing up (need to be creative re the tool required)
2. take it apart and put new felt washers in (is this still the state of the art?) 3. just forget it If I move
anything I am worried about getting the whole thing lined up properly without the mystical, special
alignment tool Input anyone?
#2171 It depends if you are purely talking about end play or if there is play in the bushes. If end play,
set bike up on centre stand with rear wheel on the ground and slacken one trunnion clamp and tap the
swinging arm with a rubber hammer or similar to take up play. The relationship between the two
swinging arms will remain the same. If there is play in the bushes these and a new trunnion if
necessary can be obtained from Grove Classic Motorcycles (great service). I undertook this work over
the winter on my Viper, and it was not as difficult as the service manual makes out. Use a local
precision engineering firm to ream out the bushes to size once fitted into the frame The finished
sizes/clearance can be found on the Velo Ownere Club Web Site under technical info. Setting the
swinging arms up in parallel needed a little bit of ingenuity and a metre spirit level. The swinging arms
were clamped together using long threaded rod and a 2 large brass plumbers nuts of a diameter wide
enough to clear the trunnion and 2 suitably sized steel washers.
#2187 There should be NO endplay on the swinging arm assembly. Two special washers are pulled
together using a length of studding through the "pin".
L #2661 I have fitted new bushes top and bottom to my 1961 venom and reading the technical
info came across this which refers to the top bush:- "Original bushes were slightly shorter with a
machined grove to allow the oil to seep back to the fork leg. Only suitable for the 1.250 dia.
stanchions." My bushes do not have this return groove will this be a problem?
#2685 Don't worry, most of us are using non grooved bushes
L #2826 According to the various books I have all I need to do is slide the fork slider tube
assembly smartly along the tube to jar the seal and bush free. Does anyone have a trick or alternative
method? For further information if this helps. The forks tube is rusted and must be replaced. Judging by
that much of the other parts are due for replacement.
#2830 That's exactly how to do it! Clamp the slider by the spindle boss in a set of soft jaws to protect it,
screw out the spring from its location and remove it, then use the stanchion as a slide hammer to
remove the top bush and seal - easy!.
L #3133 I am currently re-building a 1970 Venom Clubman, the shock absorbers are well past
their best. Could anyone recommend a replacement? I have heard that NJBs are quite good? Any
advice would be gratefully received..
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#3137 Last summer I had to replace my rear shock and have been quite happy with a pair of Hagon
Shocks.
#3140 Heard suggestions that Hagon aren't good long-term, but don't know exactly what long-term
means.
#3150 I fitted NJB's last year, because the Girlings failed MOT on damping, but only a few miles and
seem OK.
#3151 Heard our Australian friends reproduce the Konis, under a name which is more or less "Koni"
backwards.
#3152 They sell all the KP they produce under the name "Castlemain"
L #3597 Vibration on my '66 Thruxton has broken the central stay on the front mud guard. The
break is thru the 5/16" bolt hole, where the stay is clamped between the slider and the triangular plate.
My first inclination is to fabricate a steel gusset and weld the damaged stay. I'd suspect I'm not alone in
this malady. Is there a "recommended" repair to reduce the likelihood of this stay promptly breaking
again?
#3601 I've had to make this repair a number of times, and the best repair that I've found is to cut the
stay on both sides of the wheel about 1 1/2" above the broken bolt hole and make up a lower portion
from 1/8" plate about 1 1/4" wide and long enough to reach an inch above the cut off stay, then drill new
mounting holes in the new plate. The vertical centerline of the new mounting plate will then be well
behind the centerline of the original stay, so I notch the new plate to match the cut end of the stay, butt
weld the joint and bevel cut the remaining square corner off of the new lower plate. After painting, the
mod is noticeable to only the discriminating eye and the stay will not break again. I tend to use a lot of
revs when I ride so have had a number of these breakages over the years and have decided that the
cause is due to the requirement that the engine balance is biased to a front to back shaking which
makes a pendulum out of ancillaries such as the fenders (mudguards), oil tanks, etc., leading to bracket
cracking. The centre front stay is weakest at the top bolt hole, so that's where it breaks. If you watch the
rear extension of the rear mudguard (fender) of your Thruxton, you'll see cracks developing near the
rear mounting holes which will soon lead to the back portion of the fender together with rear light and
number plate dropping into the road. I was able to make a repair to mine, using a portion of a larger
section BSA fender of heavier material and slightly larger radius. I trimmed it to fit inside the VMT
fender and welded it in place, bridging the break by about 6" each direction. After careful smoothing of
the welded joints and repainting, people only saw it after I pointed it out and it did not break again.
#3602 That centre stay isn't really a mudguard stay. It helps keep the two fork bottom sliders in the act.
L #3864 Can anyone recommend a suitable material for the damper on Webb Girder forks.
#3865 There are readily available discs for M20 BSA's and the friction discs used on Harley WLA (and
similar models) rocker clutch pedals may be adaptable
#3868 For years I have used friction material tossed out by the clutch service mobs, It appears that in a
lot of cases a ring of material of a suitable size is cut from flat sheet, this leaves a whole lot of scrap
circles up to about 4 inches in diameter. It comes in various thicknesses, but the thinnest, while being
thicker than what was used originally can be adapted to do the job. I even 'Araldite' slabs together to
make up new friction drive cones for one of my ride on mowers . There are several different compounds
used. Try visiting a clutch repair specialist shop, & ask the shop foreman. All my steering & fork
dampers have this material installed.
L #3881 I am the proud owner of an MAC which is close to the same age as me, thanks to a
generous Christmas present from my wife. The MAC was first registered in January 1947, so it must
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have been produced around the same time as me in August 1946. Like me, the MAC looks well worn,
but unlike me it should be amenable to refurbishment. If I held the front brake on and pushed the
handlebars back and for the fork spring looked unmoved, but the top spindles moved in their links. I
have now removed the girders and comparing the parts to a 1939 Spare Part List I appear to have
lightweight girders with the thicker bottom links, married to a 'Heavy Type' steering column. This leaves
me with three 7/16 spindles and one 3/8 at the top of the girders. I raided the Club's spare parts store
and found all the necessary new bushes and the three larger diameter spindles. I also purchased a 3/8
diameter stainless steel rod of the correct length, threaded at both ends at last week's Kempton Park
autojumble. The threads were advertised as 26 t.p.i. and match the threads on the other spindles. This
leaves me with at least three problems with which I would appreciate your help. What is the best way to
repair the threaded top link. Perhaps I could use helicoils, but I can't find any advertised at 26 tpi is
there an equivalent thread designation, e.g. BSF etc.? With the answer to this question I can get a
matching tap and extend the thread on my ss rod. I would also appreciate advice on how best to
remove the existing bushes; will I need to resort to a hacksaw blade? Any other related 'watch its' or
pearls of wisdom would also be appreciated.
#3882 While I have no personal experience in what I'm about to write, I've read extensively and the
following comments are derived from that written information: In the old Fishtails, it was stated
repeatedly that stainless steel has very poor shear strength and that the use of stainless in fork
spindles may lead to failure. You may want to visualize the result of shearing of that SS spindle that
you got at Kempton. There are different grades of stainless and the more easily machined (threaded)
grades are also the weakest.
#3883 Im not sure I follow but if you have a "bad" hole that is 26 tpi you can certainly rebore it to the
next larger size and retap Have a machinist turn a "knocker" to the appropriate od and id and press or
knock the old bushings out, Its very simple to make and can be of any material even aluminum.
#3885 1) Helicoils, try www.uni-thread.com/helicoil1.html 2) Removing bushes. Using a larger tap cut a
thread in the bush, screw in a bolt and drift the bush out from the other end. 3) Don't use the stainless
you bought for the spindles. The recommended material is EN16 steel. 4) You should "line ream" the
bush, not ream the bush from each side separately.
#3886 If I can add a few thoughts. The steel to use is EN16, another material to avoid is silver steel.
Taps & dies are available from Tracy Tools, Dartmouth. A steel bush oversized screwed into the links
and silver soldered or brazed in place will allow you to re-thread to the required size. As Dai said, a line
reamer or one with a pilot is essential. You can however do the job with a lathe and suitable tailstock
centre. Hold the reamer in the chuck. If the bushes are out of line you will have wasted a lot of effort!
#3890 Girder fork links, I don't know if my method is the best, but it's certainly the simplest in my mind. I
wouldn't know how many sets of links that I have refurbished, - or how many new sets that I have
made, however, I just drill the old threads out cleanly, then fill up the hole with bronze gas welding &
retap. There is more to this sometimes, especially in the case of early Velocette two strokes, old plain
bolts sometimes having been used in drilled out links, in place of the original spindles! - if all the links
are in bad shape, (bent, twisted, offset, plain & threaded holes elongated), & of the same dimensions, it
is better to start, (after straightening!) with a link with the ruined smaller plain holes, - & just redrill these
& tap to the required size, to make a link with the larger diameter 26 TPI threads. This process is
repeated with the other plain hole link if needed, & you finish up with a couple of links with stuffed
threaded holes both ends, these are the ones that you fill with bronze & redrill to the original small size.
This may sound a bit confusing , but it's quite simple. Silver soldering a 'slug' of mild steel into these
holes is also a good way, as I prefer to do the drilling & the tapping of the new thread AFTER the hole
has been filled, rather than making up fiddly threaded inserts, the thread of which isn't improved by the
heat of silver soldering into place. There is also the problem in cases of bad linkage damage of making
sure that the new holes in the links are in fact of the same distance centres. The GS rebuild, (& many
others), has a complete set of links rebuilt by this method, & NOS spindles. One perk of using the
original links, rather than making new ones, is that you retain the makers stamp on the side of the links
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if you are lucky ! As to the spindles, - obviously a No No to use silver steel or stainless. As it happens I
have a large quantity of high quality (probably original British spares) NOS spindles, ex the stock of our
old Velocette exponent Frank Mussett, I am lucky in that I can just go to the shelf & select a new set, -
but certain sizes & lengths are now depleted, & I have resorted to shortening existing (longer) stock to
do the job. I don't know if I have the size(s) needed, or if postage is viable, but given the size needed, I
can check what I have left. I also have many NOS 'exotic' spindles of the 20's & 30's that I cannot
identify, possibly Rudge etc. maybe of use to some enthusiast.
L #3908 Anyone know what taper-roller bearings are suitable for the head- races of a 1946 rigid
MAC, or failing that a source of good cup & cones as there are some very poor ones floating around at
present. My MOV has tapers, but were fitted by the previous owner, so apart from removing them I
cannot identify them.
#3910 You can use the same ones as for a Venom/MSS etc, but the o/d is slightly different so they
have to be wrapped in suitable shimstock for a tight fit. The lower inner or the stem needs modifying
slightly also. Taper rollers or cups and cones are available from your friendly Lakebay Velo dealer!
www.veloed.tripod.com
#3913 Not quite a simple as that, because the base of Venom (etc.) cups are basically square,
whereas the rigid models are "cupped" on the outside as well as the inside.
#3914 That's true, but they can be packed out and fitted nonetheless.
#3915 Unless the Venom taper races are very much shallower, then the outer ring of the races will
have to be ground into a curved shape to fit the frame, so together with the Venom races being a
smaller diameter there is a lot of work that needs to be done to make these fit. I think I shall have to
dismantle my MOV and see how it was done.
L #4113 can anybody tell me what sort of oil to put in the struts of my 65 viper thanks
#4114 I'm using 10w/40 at the recommendation of Ed Gilkison. He also recommends 120cc per leg
check out http://velogb.tripod.com/page14.html
#4115 I had a look at that link and it may have given me a lead on why my primary chain eats my chain
case. thanks again
#4117 I, and many other Velo users I know use Silkoline 20W fork oil as it's designed as a fork
damping oil www.silkolene.com
L #4133 Why the scratch on double-damped Velo forks? I've ridden single-damped Venoms hard,
and the yabbada yabbada of the front end over less than perfect roads did nothing to inspire
confidence! I've put later style front ends on all my tele fork Velos since then. Now, girder forks can
tend to make one's wrists ache and teeth chatter, so all hydraulic forks seem like luxury by comparison,
even if heavier.
#4134 If you have the girder fork's dampers up too stiff you will have a rough ride. Let the forks 'float'
and the difference is amazing. This will not affect the roadholding either. By comparison, the double
damped forks are too stiff on compression and transfer road shocks far more. (at least on our roads!)
#4137 Having restored the dd-forks on my Venom I found the stopper plates for the damper piston
rings to be a very tight fit in the damper cylinder. During compression the oil has to pass through this
clearance and then through the gap (axial clearance) between the piston ring and the stopper plate. In
order to get a more defined flow area (resistance) I reduced the diameter of the stopper plate by about
1 mm. This should transfer the flow resistance to the axial gap alone. The gap was then adjusted to
0.25 mm (by guessing). The result is a somewhat softer compression damping but surely not ideal.
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Rebound damping also feels insufficient. Has anybody experience of tuning the velocette double
dampers (compression/rebound damping? What are the spring rate rates in front?
#4139 I had a Velo fork tube in one hand the other day and a damper out of a '70's Moto Guzzi in the
other. With a bit of trimming the Guzzi damper looked like it might fit, though Guzzi dampers are not
known for being all that good. They do make after-market dampers for the Guzzis, so with a bit of
research and effort one could have gas charged, adjustable, modern dampers in a Velo fork. That said,
the stock dd forks with 10w oil work fine for me. I will take note of Ingebrigt's observations next time I
have some apart.
L #4136 Greetings all, I need to replace a worn out set of gaiters on my '66 VMT. Knowing the
upper spring seat must be "twisted" on the stanchion to ensure the spring is clamped in the spring seat,
is there a way to install new gaiters without completely stripping the mudguard, stays etc. from the
bike?
#4138 The easiest way to fit gaiters is to remove wheel & guard, drop off the sliders and providing you
have short tubular shrouds fit the gaiters & all the rest. Without short tubes to hold the gaiters you will
have to strip the stanchions off too. Have fun - its really not that bad!
#4141 Surely he must have short tubes if he is replacing the gaiters. If it had the long shroud tubes he
wouldn't be able to fit the gaiters in the first place. Totally agree with you regarding the replacement
method. When refitting the top bush, I found it useful to use the old two piece split clamp headlamp
bracket(beloved of all old café racers) as a slide hammer to knock in the bush. Don' forget the oil seal
before fitting the bush.
L #4145 While we are on the subject of front forks I will ask a question again just in case
someone out there has the answer and missed my question last time around. What is the centre to
centre distance between the front fork tubes? I have measured various top and bottom yokes and they
are all different centres so I am looking to find a set which will make the fork tubes parallel. Hope to get
a distance this time
#4148 You could undo the top stanchion nuts, undo the damper rods ( retain with string for reassembly)
slacken off the bottom fork yoke bolts and draw the stanchions right out downwards... probably have to
undo the brake cable.
#4150 I'm not sure how I'd be able to reassemble and rotate the upper spring holders 15 to 20 degrees
to lock the springs tightly in place. Am I missing something in the reassembly phase? I can not think of
any way to do this task except remove the mud guard and stays, orient the sliders to the side and
reassemble. I'd hoped to save a few steps and avoid the potential damage to the paint work.
#4151 Exactly; you cannot locate the spring carriers with the fork legs complete below!
#4170 Sorry to disappoint you but the distance that you are looking for is a variable; it's one of the
reasons for the front wheel spindle having that shifty little bush which is clamped in the L/H fork slider.
No doubt there is a Charles Udall drawing that shows this dimension but I would be interested to know
what the +/- tolerance is. I have fork yokes that have been bored so far off centre that the forging has
been built up with braze in order to keep the appearance of concentricity - by the original manufacturer!
The yokes were bored as a pair and must be kept as such. If your yokes are out of parallel and there is
no evidence of impact damage then it is possible that they are not an original "matched pair". The
forgings are soft as butter and it doesn't take much to knock them out of alignment. By the same token,
they can be easily re-aligned but you need to find the right bloke to do it.
L #4406 So after spending a year or so rebuilding the venom and riding it around for 700 miles or
so I managed to fall off it a couple of weeks ago. Looking at the bike the damage seems pretty
cosmetic although there are a couple of points I need a little advise on. 1. The gear change level got
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ent. This is aluminum and I think it can be straightened. My question is should I use heat, and how
much? 2. I cant be sure on this because I cant lift the bike onto its center stand yet, but the front wheel
alignment does not look right. Is there a way of checking this apart from eyeballing it? If something is
bent does anyone have any advice re straightening the forks?
#4407 . I'd straighten the shift lever cold. Just take it off, clamp in a vise with protected jaws, and bend
it straight. I've straightened a lot of forks as follows: Disassemble the legs and place a stanchion on a
pair of alloy blocks that you have made from a chunk of metal about 2 ½" square by 1" thick, bored to
slightly larger diameter than the stanchion and cut in half so that you have a pair of vee blocks with
round cradles. Then place a third block on the bent area to receive the ram of a hydraulic press, and
press it straight. I use a dial gauge on a holder to find the high spot, mark it with felt pen, then press.
The stanchion will have pretty good memory, so you'll have to press it past straight and it'll spring back.
Take it slow, checking regularly, and you'll be able to get it within .002"-005" of straight if it hasn't been
kinked. When I'm trying to get the last bit of bend out of it, I mount the gauge right beside the ram of the
press, take note of the gauge reading, and increase the deflection .002" per attempt until it is the best
that I can get. Then I mount the lower triple clamp in the vise with the steering stem horizontal between
the jaws, and clamp the stanchions in place. I use the MK I eyeball to verify that the stanchions are
parallel in the horizontal plane and then slide the top triple clamp on to verify that the stanchions are
parallel in all planes. If not, I bend the lower triple clamp cold, using the clamped in stanchions as
levers until it's all parallel. Reassemble, and Bob's yer uncle!
#4410 A quick and easy way to check if the forks stanchions are bent is to simply undo the large top
nut and pull up the damper rod a little. If it is not coming up the centre of the stanchion, the fork leg is
bent. The damper rod is seldom bent, revolving it will soon show it is.
L # 4881 My first post to this group after owning a prerestored (500 miles) Venom circa 1957 in
Greece for 1 year and now the restoration deficience are coming to light, although I adore the bike. I
am currently fitting the breather modification as described here and helped by parts and advice from
Nick Payton. This I hope will give me half a chance to keep a proportion of the oil recirculating in the
engine. The main reason for this mail is despite the previous owner replacing virtually every part in the
front forks I can grab the front wheel between my knees and turn the bars 1/8 of a turn in both
directions. I've checked all yoke pinch bolts and top nuts, so the problem appears to be in the fork bush
to tube fit in the lower fork tubes. What are my options to correct this? Is this a normal wear point, a
friend described the resultant handling as good tank slapper. ( yes, mudguard and stays are all fitted
and tight thanks.)
# 4889 I read about this difference in diams but am not sure what it applies to. The list below is what
the previous owner fitted to the forks (supplied by Mike at Grove Classic) so I assumed all would be
compatible and the only error or wear could be the original bottom leg where the bushes are fitted.
Front Fork Top Bush 2 LE215 Front Fork Bottom Bush 2 LE216 Fork Slider Tube Oil Seal 2 LE335/2
Front Fork Tube 2 F246 After I have reassembled the engine with breather mods, I will pull the forks
apart and see what's what.
# 4893 Fork stanchions changed from 1.240 to 1.250. Not sure when but when I refurbished the forks
on my Viper chassis circa 1963 it had the 1.24 fork legs and they were corroded so I had to fit the
modern ones. The bushes from Grove are machined to fit the lower leg and fitted in my case. You can
only tell by measuring and if you have the 1.250 the problem may be the way in which the mods were
made. Are you sure the legs are not turning in the yoke? If you change to the 1.25 legs you have to
ream the holes in the lower yoke and in the upper yoke of the steering. The lower is easy as it is a
through hole. I borrowed a 1.250 reamer. I put the lower yoke in a vice and lightly put pressure on the
clamp bolt ears with a clamp, then rotate the reamer by hand and remove some metal, then try legs
and if tight increase pressure. Go slowly because if you go too far the clamp bolts will not take up the
clearance and that may be your problem. This way keeps the bores parallel. I use a thin wedge when
reassembling to increase clearance l. The upper are more difficult being blind. I used the reamer till it
bottomed and then lapped the tube in with fine grinding paste. Double damping. According to the
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eprint from Geof Steele the clues are a screw driver slot in the protruding stud at the bottom of the
slider, although some owners have added this to ease assembly, and two small holes in the damper in
place of one larger. See the reprint of technical notes pages 30-31.
# 4899 My apologies to all for an error in my last. I remember now that I reamed the fork sleeves not
the lower yoke. It was still important to go easy because Grove did not have any in stock.
#4902 You mentioned changing the bushes and stanchions but did you unsolder and change the
lower fork tubes? they could be worn. Made a lot of difference when I fitted new ones.
L # 5038 I need to make some girder fork spindles. Can anyone tell me what grade of stainless
is equivalent to EN16? Or should that be EN16T?
# 5039 Stainless steel is hard to get in high tensile grades - despite what the suppliers tell you. I
strongly suggest using the current equivalent of EN16T. The ends were painted black originally anyway
so why go for stainless?
# 5042 You are of course right that most are painted black. I'll find some EN16T. Probably cheaper
than stainless anyway.
# 5040 It is said (seemingly with good reason) that Stainless Steels are not a suitable material for fork
spindles. Where do you live ? I have a large quantity of NOS spindles ex. Frank Mussett's old shop in
Melbourne. These are not just Velocette, but all sorts of strange items, some I have been told are
Rudge, some have strange 'washer' sections. Left & Right hand threads! If anyone is interested, I may
be able to help. My Velocette items are pretty depleted, but I won't be needing any more now, but over
the years it has been great to just go to the sorted 'pigeon holes' & pull out a full new set !
L # 5078 Does anybody know where to get A314/3 stainless long type damper covers? The last
ones I bought from Ken Gardener but Mike Fotherby hasn`t any.
# 5079 Andy Molnar ? www.manx.co.uk/
# 5080 If I recall correctly, someone advertised he was making them and other stainless stuff in
Fishtail a while ago. Can't remember his name but Richardson rings a bell. Have a look at the front and
back for the trade adverts and also in "Going Spare .
L # 5130 Anybody know the spanner size for the later type steering head locknut - F270/2 (
steering damper type) ?
# 5133 Mine is 1.2" across the flats which I think equates to an 11/16" Whitworth spanner size. In the
absence of one of these I've used a Snap-on 32mm flank drive single hex deep socket to good effect.
Even though it's a bit oversize it works well but you could do equally well with a good adjustable since
the nut should only ever be used to adjust the steering head and should never need to have large
torques applied.
L # 5822 Should my 1965 Thruxton have butt-welded bars or the lay-on type ? It was purchased
as a box of bits and I am trying to make it a authentic as possible.
# 5825 Butt welded - the 'lay-on' type was fitted in 1970.
L # 5917 My '54 MAC is getting closer to completion and after filling the front forks with SAE20 I
have had happy memories of the 1970's (last time it was on the road) flooding back. Apply the front
brake and the number plate smacked into the headlamp. I don't have the front numberplate anymore
but the forks are still in need of some help. More oil or a higher grade 30, 40 or fill with grease?
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# 5918 Try fitting a new set of springs. It's very likely the old ones have just got overtired! Filling with oil
of a higher viscosity will only increase the damping which will tend to have the opposite effect than that
which you require in that it will slow down the rebound after hitting a bump, making the amount of
available travel for the next bump rather less. On a rippled road surface this is a real problem, not so
much on a billiard table motorway or race track surface.
L # 5935 On the steering head is there some kind of cup affair which bolts on to stud.fk239 to
stop my bars clattering my tank on full lock, I vaguely remember someone pointing it out it but it isn’t
shown in the book,
# 5936 I believe what you're referring to is the cup that is mounted onto the stud of the steering stop
when a Sidecar is mounted to the machine. The OD of this cup is about 30 mm and it severely restricts
the lock-to-lock movement of the bars for solo riding. This same part I believe was also used on race
bikes of the period for obvious reasons. I had this same problem on a newly-restored 1960 Venom
where one fork tube barely kissed the right side of the tank, and I machined up a stainless steel cup of
the same basic design but of a much smaller OD than the Sidecar Cup so I still have reasonable fork
movement. I have one of these Sidecar Cups and if you need accurate dimensions I'll be glad to
measure it.
L # 5938 Can sombody explain to me why the fork legs on a venom clubman 1963 is not listed in
the spares list. I have had an e-mail reply from a company with a price to re hard chrome my fork legs
for the sum of £195 a pair. This appears to be a bit steep. New fork legs are available for about £80.00
a pair. Are these correct for a venom clubman?.
#5940 Be careful when having Velo fork legs rechromed. It is imperative that the forks are ground
concentric to the bottom diameter where the bush is fitted otherwise you will find that the sliders will
jam. Many rechromers do not realize this and use a centreless grinding procedure which is fine for
forks of a constant diameter, but definitely not for the twin or triple diameter design used on Velocettes.
# 5952 The chrome legs Grove et al sell will be fine, the legs I have seen are chromed over their full
length. Veloce produced fork legs with two different diameters, but as you should change the fork
bushes this should have no affect on the fitting. I would even recommend fitting chromed fork legs to
reduce internal corrosion even where fork shrouds are used, as there is only a relatively small
difference in price.
L # 6155 I`ve recently obtained a 1936 MAC fitted with th double damped forks (dd). This being
my first girder fork machine I seek advice on the following: if I hold on the front brake there is
considerable movement in the lower links. I assume that the bushes are worn or? Riding the bike is not
too nice as the forks feel unstable, a wiggle on the bars causes a reaction in excess to the force
applied. If i`m looking at an overhaul of the forks (expected) what advice is offered, i seem to recall
reading about special reamers in fishtail. I am a capable engineer equipped with a lathe, drill, press,
surface tables etc
# 6158 I have a sneaky little method of dealing with BADLY worn forks, -- that is those that have
bearing holes that are hopelessly elongated. I seem to remember that I detailed it in the restoration of
the GS Velo, so it will be back there in the records of the last year. Rebushing can be done in the case
of reasonable wear, but the system that I have described is basically one of filling the bearing holes
completely with bronze welding, which is difficult & wasteful, -- however it can easily be done with a
minimum of bronze filler, by the use of bored dummy slave spindles, -- but there is a bit more to it than
that ! Hit me if you cannot access my email on the GS subject. On the other hand, if the wear isn't too
bad, -- & assuming that the forks do not have bushes fitted, & your machinery has the capacity, just set
up the worn parts & bore to take bushings. Final reaming is the problem, but high quality adjustable
reamers can be fitted with extension mandrels. Somehow over the years, I have always managed to
bring even the worst condition forks back to as new, it's just a matter of perseverance. If the wear
problems extend to the links, I have a tried & proven method of refurbishing them, by filling the worn
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holes with bronze weld & re- drilling & tapping them, If you think things out, - you only have to reverse
the links & bore & tap out the original small end of the link- then fill the threaded end, - & make that the
end with the small plain hole. I have even drilled the links out, silver soldered a slug of mild steel back
into the holes & redrilled etc. Simple links can be made from scratch from flat bar steel, or cut to shape
with modern techniques , - even if they are made with bosses, just use thicker material, do all the
drilling & tapping, & then run the new link blanks on to a spindle held firmly in the lathe chuck, &
machine off surplus material to form the bosses, & take the links down to the required thickness. (A bit
like 'flycutting' in reverse !) The above applies to 'Webb' type forks, forks with left & right hand threads
are best converted to the Webb system in my opinion. I have a quantity of quality NOS spindles, so that
makes the whole job considerably easier.
L # 6334 Need to replace the head bearings on my 1939 MAC (Rigid frame, Webb forks). Can't
seem to find needle roller bearings anywhere, am I to resort to the cups, cones and balls? Anyone
know if/where I can get needle-roller bearings that will fit? The VOC spares bearings are for the
swing-arm version and have a smaller OD.
# 6335 I presume you mean taper roller bearings - needle rollers would be most unsuitable! I'd suggest
you take your old cup and cone ball assembly to a good bearing supplier such as BSL and see what
they have available in taper rollers that will match or at least come close. If you can get something
which has the correct OD and ID and a similar thickness then you're quids in. If the correct OD and too
small on ID, the ID can be ground out to size by a good engineering shop. You'll find that most
proprietary update kits are made this way using a pair of standard bearings with the lower one ground
out to fit the larger diameter of the bottom end of the steering stem..
# 6345 I too am in the process of trying to fit tapered roller bearings into a 1937 rigid MAC frame. The
cups were removed from the frame using the ring of weld method, rendering them unfit for further use.
There is quite a large radius on the cup outer and a corresponding radius of what appears to be bronze
on the steering head aperture. I'm reluctant to remove this as it will weaken the frame, but a
considerable amount must therefore be removed from any proprietary bearing that will be used in place
of the original setup. OD and ID appear to be minor problems, but I'm unable to measure the height of
the original cup and cone assembly. I'm guessing it to be much less than any standard roller bearing
available, adding further concern to what started out as a simple conversion.
# 6348 Tom, What you say is true, but in practice it doesn't seem to matter. We've fitted the taper
rollers in several bikes, a couple of them being raced, and there seems to be no problems. The cup and
shim were Loctited in place, after pressing
# 6341 For taper roller conversion, you need SKF Cone 07100 and Cup 07204. The outside diameter
of the cup is 2.047" but the steering head socket is 2.050", so you'll have to wrap a 1½ thou shim
around the outside of the cup before pressing it in.
L # VOCNA 376 Does anyone out there have any good recommendations on fork oil for
double-action Velo forks? Weight, amount, brand?
# VOCNA 378 120cc per leg according to Dai's great website www.croesus-consultants.co.uk/v-tec/
I've heard that 20W works well.
# VOCNA 379 4 fluid ounces (US) (120cc) of 10W-40 in each leg. SAE 10W-40 is about the same
viscosity as SAE 20 at normal outside temperature, bur does not vary significantly with temperatures
likely to be experienced in the forks. SAE 20 will thin out if works hard and heats up, thereby reducing
damping. This is fine for single damped forks too
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F.2. Brakes Wheels and Tires -
L #44 Bob Jolly makes replica mk VIII magnesium hubs/brake plates/shoes (yes these are mag
too), in Australia, they cost about $800 us/ea, depending on exchange rate.
L #21 I found that a set of tires, Avon Speedmaster ribbed front, Roadrunner rear, lasted 3
thousand miles, period. .
L #83 Does anyone know the correct tyre pressures for Dunlop TT 100's when fitted to a Venom?
#90 Avon Roadrunner AM20 90/90H19 front @ 22 psi, Avon Super Venom AM18 100/90V19 rear @
24/26 psi. An added benefit, they even make the bike look faster!!!
#653 1960 Venom clubman, I am using Dunlop K81 (TT 100) tyres front and rear. What are the
suggested tyre pressures?
#84 Modern tyre pressures need higher pressures than those figures published in 60's and 70's. I have
a table of pressures for tyres which I hope to publish on the technical site soon. However if my memory
serves me well, TT100's are 3.60 X 19 front, 4.10 X 19 rear. That gives pressures of 26 tpi front, 28 tpi
rear for a machine and rider of 580 pounds. This was confirmed by a leading UK supplier of tyres who
independently recommended 24 and 28 respectively. By the way I run Avon Venoms and Super
Venoms on my Venom at 22psi front 26 psi rear, and they handle perfectly.
L #172 I have recently acquired a Venom Clubman which has a very slightly buckled Front wheel
rim. In addition, the front brake is grabbing and sending a vibration through the forks which feels like
the wheel brake drum has become slightly oval. Please could anyone advise the best course of
action? Is it possible to skim the drake drum, and to straighten a slightly bent rim, or do I need new
components. Also if anyone has any contacts who have experience of such work, I would be very
grateful to receive your feedback. Finally, I am considering at the same time upgrading the front brake
to a twin leading shoe one. Again, any help in sourcing one would be useful.
#173 Is the rim actually dented or merely out of true? A bit of careful and patient spoke tuning will
correct the latter. If it is dented, it must be disassembled and straightened. Don't let some sharp talk
you out of it, as Dunlop alloy rims are very desirable items. Personally, I have had little luck skimming
Velo drums when not spoked to a rim. If you can find a lathe that will accept a complete wheel, it is
worth a try. True the rim first.
#174 Before you buy a TLS, make sure the drum is round and the linings well matched. Give the
original brake a fair trial. I changed my Venom over to a Dodkin/Velo TLS in 1988. It has never been
much more powerful than the original, and is utterly useless when backing down a ramp! Perhaps the
racers find it more fade resistant, but don't assume that it will let you do stoppies.
#175 Grove Classics sell the iron half of the front hub for a Venom/Viper approx £150, if you need to
replace it.
L #226 I have a Borrani WM2/1.85-19/36/Record RM-01-4354 Rim laced to a Venom full width
hub. Does anybody know if a replacement is available that matches or nearly matches this Borrani
#227 I am assuming you have a flanged Borrani aluminum rim. Currently I have three Velos that sport
alloy rims including Dunlops Akronts, UK made ali rims and have had Borranis in the past. Borranis are
recognized by those in the know as being the best. Even if you find a second hand Borrani you need to
ensure that the dimple pattern, spoke hole angle and diameters are suitable for lacing to a Velo hub.
Currently in the UK to my knowledge there are two replacement flanged alloy rims available. Unless
you look at them closely they look similar to Borranis or Dunlops. However they are not as well finished,
so if you buy one check in the area of the weld for the quality of finished. Secondly one of these rims
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has very crude looking dimples, so take care. Further details on the rims can be found via the link
below. www.central-wheel.co.uk/cwc/rims.html
L #463 For my 1952 MAC rigid documentation say front and rear tyre both 3.25 x 19. My front tyre
is Metzeler Perfect ME 11 - 3.25 x 19. My rear tyre is Avon Roadrunner 90/90 H 19 - 3.60 H 19. I was
informed that it could be difficult to get the rear tyre homologated in Germany. Is there any information
/ documentation available about my rear tyre size being eligible?.
#471 From the German representation of Avon Tyres I got confirmation that the "old" tyre size
3.00/3.25 corresponds with the actual specification 3.60 (or 90/90 in Metric). So they have sent a
certificate to me saying that the tyre 3.60-19 is the right application for a Velocette MAC.
L #547 I was wondering what would be some appropriate tires for my Venom. I'm looking for
something a little more modern than what was originally used.
#548 You can't get any better than a good set of TT 100's they were good enough for the TT they will
give you everything you want with the venom.
#549 I'm a Dunlop fan for the moderns, but on the Velos there is nothing better than Avons,
Speedmaster II front and Roadrunner Universal on the back. They are made in the old molds but of
modern compounds. They wear out very quickly (

type) The front rim is 21" WM1 36 holes The rear is 21" WM1 40 holes Which brake rod are you
referring to? - the rear is .25" with a BSF thread; the front isn't (I'll have to check if that's the one you're
after.) The rear brake drum has 1" linings for the KTT, as far as the width of the hub overall goes I'll
have to do a sketch.
L #1081 I have just laced a pair of alloy rims for my Clubman and am having a lot of trouble
getting rid of the few last high spots as I try to true them. Are alloy rims inherently more difficult to true?
How near enough is near enough in terms of run out? I'm somewhere between 1 - 2 mm, but compared
with the results I've had with steel rims they still look a bit wobbly to me.
#1082 In my experience (I have built a number of wheels, but not the VM one referred to) it is generally
more difficult to get alloy rims absolutely true - and the Dunlops are worse than the modern Akronts
GENERALLY, although I have had at least one Akront that had to be sent back as it really was too bad.
(I have never worked with Borranis). For road going machines I'd suggest a RADIAL run out of about
2-3mm but no more is fine, so I would be happy with the 1-2mm you mention. It is usually very difficult
to completely get rid of the 'kick' where the rim is welded (i.e. rim is joined to make the circle). I'd guess
racers would want to achieve something a bit better than this, but that should be fine for the road. So
yes - I'd expect better results with steel rims but not to worry too much with what you’ve achieved with
the alloy ones.
L #1338 Hi I have bought the rear brake drum(worn tooth) the reason ,I was told I could fit the
detachable sprocket. I am told the instruction of how to do this and it is seems to be reasonable as cost
of drum was £5.00. new was £60.00. the problem is I do not have the lathe and welder. my school lathe
is too small do anyone know who I ask to do this ? I am sure that who knows Velo know exactly where
sprocket have to be( I am bit confused because drum was from Venom but I want to put the small ½"
chain.)
#1340 , Re. 're-toothing' your rear brake drum/sprocket try John Hemming at 01547 530 759. He did
mine & it's a good concentric job. More than fifty quid though.
L #1294 I am rebuilding a very original '57 Venom and would like to fit modern - but original
looking tyres to preserve the period appearance. Could any of you advise me on a suitable choice and
supplier (in the UK)?
#1302 Avons are a very good choice, they are period ,were fitted original, are still made in the UK I
think and the rubber doesn’t crack like the Dunlops. Ribbed front.
#1303 See the following post on the VOC site www.velocetteowners.com/qanda/ty001.htm I will also
add that you could equally well fit an Avon Roadrunner rear and ribbed Speedmaster front. If you are
seriously riding your Venom, my advice would be to stay away from the block treaded Avon MkII SM
Regards.
L #1640 Can anyone offer any advice with this first-time wheel removal problem? I took the rear
wheel out yesterday to fit a new tube. My bike is a 1951 MAC and I noticed (when removing the wheel)
that the speedo drive outer housing had been turning with the wheel, leaving a very tight bend in the
cable immediately after the connection collar. With the wheel out of the bike, the speedo drive unit
pulled off and I checked it over. It seemed OK and the inner part was free to turn and was well-greased
with clean grease. There was a spacer which I guess pinches up the outer part when the wheel spindle
is tightened up, leaving the inner gear free to rotate, driven by two lugs. There were no bearings or
anything like that inside. When I put the wheel back in I was careful to make sure that the Speedo drive
was correctly installed and that the outer part wasn't free to turn with the wheel. After a trial run, I see
that's done it again, and the cable is being forced into an even more acute angle this time. Can anyone
give me any advice on how to solve the problem?
#1642 There Should be a spacer known as a clamping sleeve on the inside of the speedo drive. This
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locates on the extension of the bearing spacer tube and its inner end butts up against the RH wheel
bearing. The speedo drive is clamped between the outer end of the sleeve and the distance piece
whose other end sits against the inside face of the swinging arm. When the spindle is tightened up the
whole thing should be solid and the speedo drive will not turn. It's not unusual for the clamping sleeve
to have dropped out and been lost when the wheel has been removed at some time but I should warn
you that the machine should most definitely NOT be ridden without it! There is one other possible
cause - that a FRONT wheel spindle has been used in the rear. This is longer than the rear spindle and
will bottom out in the stub axle before it clamps the plot together!
#1643 Thanks a lot you've confirmed something there. The speedo assembly did indeed fall off and a
piece dropped out, which is obviously the clamping sleeve you mention and I'm pleased to say that I
worked out what it must be and fitted it again when I replaced the wheel. You've also confirmed by
assumption that the whole assembly is held in place just by pressure. So maybe I (and the previous
owner) just didn't do it up tight enough. (probably unlikely.) I certainly couldn't move the outer speedo
drive by hand after I'd tightened up the spindle. I'll check the tightness of the spindle again and then
compare the lengths of the front and rear spindles.
L #1910 I'm rebuilding what was an incomplete '57 Viper. Is there a washer/ spacer between the
single leading brake plate and the RH fork tube? If so what thickness should it be? It looks like it needs
a spacer of about 2,5 mm. But I not sure and can't find anything in the books about the subject.
#1912 There should be no spacer between the brake plate and the fork lug. The wheel spindle (W21/6)
is inserted from the LH side, through the split sleeve distance piece (W64/2) and dust cover assembly
(MAS73), through the bearing spacer tube (W62/2)(inside the wheel hub), through the brake plate
distance piece (W52/3)(which normally stays firmly corroded in place in the brake plate itself), through
the RH fork lug and is secured with a thick washer (KS51/2)(about 1/8" thick) and the wheel nut
(W65/2) on the outside of the fork lug. Tighten the wheel nut first with the brake lever pulled in, then
with the pinch bolt on the LH fork lug loose, bounce the forks up and down a couple of times to
centralize the assembly, then finally tighten the pinch bolt.
L #1963 I am rebuilding the wheels on my viper, but am still undecided on chrome or aluminium
wheel rims. What are the advantages and disadvantages.
#1965 Ally looks pretty, is slightly lighter and won't rust. Steel is better in virtually every other respect.
#1971 also you should consider stainless steel, the boys at srm do that stuff and it is not much more
than British chrome.
#1977 An early Borrani rim on a MAC front hub saves 3 pounds, 13 vs. 16 without brake or axle. The
flanges trap oil and the alloy is harder to keep polished. Great for a Clubman, overkill for a tourer.
#1992 Strength, durability, repairability, resistance to buckling or damage from tyre levers, even
electrolytic corrosion from non alloy nipples although I am guessing now. It really is just my opinion,
and it depends whether you want to use the bike as regular transport or show it. I would have gone for
Borranis every time when I was 19, and TT100 and KR70 if I could have afforded them, but now I would
keep to steel for practical reasons. The concept of unspring weight which is often dredged up when
making a case for alloys has been proved to be bunkum if my information is correct, so it really is
mainly a question of aesthetics, unless you want out and out performance and are prepared to take a
little more time on maintenance.
L #4918 I have a wheel which appears to have been laced with an incorrect rim. The spokes are
not lined up as they should be. The rim is a Dunlop which I was going to have rechromed until I realized
that it wasn’t correct. How do I recognize what the rim is. Are they stamped with an ID Ref. so it can be
seen what the rim is? I need the correct ID Ref. for a rim for a cotton reel rear.
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#4919 No such thing as an ID for wheel rims as you describe. The difference is in the drilling. This
varies for spoke angles. I would recommend that a tame wheel builder would identify the drillings
wanted, then have the rim re-plated.
L #1987 I am looking to have my wheels rebuilt, stainless rims, spokes, and nipples. dose anyone
know a good shop here in the usa that can do that? most of the places that I have found online are in
the uk and they are hard to connect with.
#1988 Buchanan's www.buchananspokes.com/ don't list stainless rims on their web page, but when I
spoke with them several years ago they were not adverse to using customer supplied rims.
#1989 North East Wheel Building (John Smith) Ridgewood The Boundry Shinney Row Co. Durham
0191 385 4266
#2005 Ed Gilkison's. www.velogb.tripod. com
L #2212 Hi All, Does anyone have any recommendations regarding tyres for my clubmans
Venom? At present I have a 3.25/19 ribbed on the front and a 4.10/19 studded on the rear, according to
my Velo manual the rear should be a maximum of 3.50. Are there any modern compounds available in
the correct sizes?.
#2213 have Avon Venoms rear100/90/V19 and front 90/90H18 The bike had these on when it came to
me. . I was thinking more along the line of touring style tires as I shall not be racing it! Perhaps Avon
Speedmaster front and Avon SM2 rear (or Dunlop K70) Any comments from you more experienced
riders would also help.
#2215 The 4.10 section is fine for the rear of a VR or VM - it’s a replacement effectively for the 3.50.
#2219 See Q&A section of Velo Owners Club Site. I fitted the Roadrunner AM 20 Front and Super
Venom AM18 Rear as recommended there to my 56 Venom (Clubmanised) Best tyres I've ever had on
a Brit Bike.
#2227 For goodness sake leave the tyres on. In my experience all red blooded Velo riders can't help
but indulge in a bit of scratching when out touring, when road and weather conditions are right. When
you're sliding down the road watching your pride and joy grind away its extremities you'll regret not
having the best 19" road tyres money can buy. And at the moment the widespread consensus is that
the Avon AM18 / AM20 combination is the best for our Velos. I've had them on VMT457 for the past
couple of years and they really are very good. When I put my '69 Clubman on the road for the first time
last April, the pristine looking (but 20 years standing) tyres were hung high in the roof of the shed as
museum pieces and new Pirelli MT65's were fitted. These are also quite suitable for Velo use. There's
no way I would ride a bike of any make equipped with aged tyres on the road, whether riding with
purpose (which all Velos should be!) or just pottering.
L #2267 My venom has tire security bolts installed (to stop the tire slipping around the rim). Dave
Smith (Dave Smith Classic Motorcycles) tells me that Velocette never installed these on
venom/thruxtons/etc What the forum's views on the need for these. I am planning to install the new
Avon tires as recommended on this message board. The bike has dunlop steel rims.
#2268 Cant imagine any Velo needing them. Power delivery is not that brutal
#2269 Security bolts are not needed on any Velo unless its used for trials with low tyre pressures. They
are truly not of any benefit!
#2270 My experience with my '49 MAC (in '49 - '55!) was that I needed security bolts with chromed
wheels but the painted rims held. Not originally fitted - I had to drill a hole. These would have been
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Dunlop 3.50 x 19" (rear) Admittedly, this was mostly on corrugated, pot-holed gravel roads, and I used
to shove her along a bit.. Would modern tyres be any different? The roads certainly are.
#2271 As rubber has improved, it seems to grip the rims well in - in addition to the road! I have raced
with chrome wheels and alloy and never had any need to use security bolts. Different with a more
powerful machine perhaps but even a Manx was OK.
#2398 I had a rapid deflation on the freeway years ago, which required the use of three lanes to
prevent falling, due to the tyre beads falling into the center well of the rim. Since that time, I have
installed two rimlocks (balanced) on everything I ride. This summer, during the first morning of the US
Club rally, one of the members had a rapid deflation which put him in and out of the hospital due to lack
of rimlocks for the week of the rally. I saw him at an event a couple of months later, and his bike
sported rimlocks. Obviously, this won't happen to everyone, but why take the risk?
L #2325 Hello list. Who do you like for wheel rim replacement and rebuilding? (48MAC) I don't
mind buying rims from the UK but I hate to send the wheels that far for rebuilding. Anyone here in the
US?
#2326 Buchanan in California is supposedly among the best here in the States:
www.buchananspokes.com/
#2356 I believe that Ed Gilkenson's business, Velocette Repair Service, in Lakebay, Washington does
wheel building. I've dealt with him for years and he is one straight-up guy.
L #2912 My Viper (1955)is in need of a new wheel rim so thinking of fitting a twin leader brake
instead of the original, is it a simple matter of just swapping drums or do I need to do any mods to the
fork leg? Also can twin leader drums still be obtained new if so from where? Finally is it a worthwhile
conversion on a bike to be used just for touring?
#2913 Mike at Grove Classics( 01582 )873066 has remanufactured the Thruxton type TLS which is a
straight swap!!
#2914 If your Viper has a full width hub you need only to change the backing plate assembly. I did this
on my '67 Venom, thought the TLS would help coming down our big mountain passes, two-up. To tell
the truth, the original well-bedded SLS was its equal. It also works when backing up - unlike the TLS.
The soft linings on the TLS didn't last very long, either. But the TLS sure looks sexy!
#2915 Same drum, different backing plate. I've had both types and I think that the VM/VR brake is
adequate for everything except high performance use. If yours doesn't work well it may be time for new
linings and careful setup. These drums are not able to withstand kludgey lacing and will pull oval by
over-tightening of the spokes, giving a pulsing feel to the lever. This can be corrected by a minimal
turning of the drum in a fully trued wheel and oversized or shimmed linings to match.
#2916 If I remember correctly you may also have to change to the Thruxton front fender stays of which
the right hand one is slightly cranked to clear the top cam arm. I concur with the fact that the TLS brake
only works when you are going forwards, making hill starts on steep inclines a case of juggling feet! But
I found the brake to be quite a bit better than the single leader if fitted with racing quality linings (I
originally used Ferodo AM4 material although this is no longer available - a brake lining specialist
should be able to advise a modern equivalent), machined to size to match the drum and correctly
assembled and adjusted.
#2919 As an alternative to new a stay you can simply use a ½ inch spacer
#2923 Grove Classic have them in their stock list - £299.00 + VAT + Postage I agree with Tom Ross, a
correctly set up sls with good linings is as good as the 2ls and I've raced on both. And the sls is better
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in reverse. What else could you spend that £360 on for the bike?
#2929 You could try "floating" the brake shoes.
#2934 Don't forget that pre-unit Triumph rear shoes fit the Velo rear brake perfectly, and are already
"floating". The cheap, bonded import ones on the back of my Venom worked very well with no
bedding-in, and lasted 25k miles. The drum and sprocket were both done by then, but the shoes were
not (quite) worn out.
L #3042 Just got off the phone to the very helpful folks at the Avon tire company office in
Washington state as I was unable to find a new replacement tire for my 1970 Velo Thruxton. Both front
and rear rims are 19" WM2. This presents no problems in the front as a 90/90 AM 20 Roadrunner is
available, however nothing for the back, without changing to a WM3 19" or WM3 18" rim. Don't really
want to switch rims on this bike, although I certainly will to keep riding it. Just wondering if anyone else
had come up against this problem and how they resolved it?
#3043 Some time ago the famous Geoff Dodkin recommended the following tires for my Thruxton, to
which I stuck with best results till today: Front : Avon 90/90 H 19 Roadrunner F2 (a ribbed racing
compound) Rear : Avon 4.10 H 19 Roadrunner Universal (use only road compound !) Although the front
is a soft racing compound it lasts on the road for appr. 6000 miles. As much as the rear, if you choose
road rubber. Once I tried even the rear in racing compound, but this got me only 1000 miles out of it.
You will be amazed how handling will be improved with the above tire combination.
#3044 I see two possibilities and while I was on the phone ordering a set for a '49 Ajay, I checked stock
on both possibilities. Both possibilities in stock!! Tires were ordered from my fav tyre supplier, South
West Moto Tires, 1-877-805-8473. With new Metzler tubes, freight free, cost was $186. Ordered AM 20
front "Road Runner" 325-19 TL, fits 2.15 - 3.00 rims AM 18 rear "SuperVenom" 100/90-19 TL, fits 2.15 -
3.00 rims currently used on my '66 Thruxton running Dunlop WM2 alloy rims, and in stock Speedmaster
Rib, 3.50 - 19 TT fits 1.85 - 2.50 rims SM MK II, 400-19 TT, fits 2.15 - 3.00 rims.
L #4537 Can anyone help with the setting up of a new twin leading shoe assembly I purchased
from Grove Classic and which is currently performing at about 10% of the efficiency of the single
leading shoe standard set up I have just removed ! The brake is very spongy and lacks feel and bite
and is currently not safe for the road.
#4539 Quoting straight from the "Red Book" Re-Setting the Brake Shoes. The brake shoes are set
when the brake is assembled at the factory, but renewal of the brake shoes will necessitate re-setting.
To do this, remove the split pin and withdraw the clevis pin from the yoke end at the top of the adjuster
rod. Operate the front brake handlebar lever which will bring one brake shoe in firm contact with the
drum and retain the pressure on the lever by securing it to the handlebars by the use of a strong rubber
band or other means. Slacken off the two lock nuts on the adjuster rod and apply firm pressure to the
top cam operating lever which will bring the second brake shoe in contact with the drum: Hold the cam
lever in this position and turn the adjuster rod to a position where the clevis pin can be inserted through
the cam lever and yoke end of the adjuster rod. Then re-fit the clevis split pin, tighten up the lock nuts
on the adjuster rod and release the pressure on the handlebar lever. Finally, check the brake control
cable and carry out any adjustment which may be necessary.
#4540 In a recent magazine article it was suggested that if you really want a 2LS to work at its optimum
performance it is essential that both brake arms on the back-plate are parallel, otherwise one shoe will
get more effort from the handlebar lever than the other one. Do this first then let the shoes bed in. It
may take a little time, but when you think about it the end result will be the best brake. If you have had
the drum skimmed you may need oversize linings.
#4541 First make sure that the outside diameter of the mounted brake shoes is close to the inside
diameter of the drum. When you apply the brake, the angle of the lever to the cable should be slightly
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less than 90 degrees. This should correctly adjust the first (lower) shoe cam. Then the link to the
second (upper) shoe cam should be adjusted such that both shoes will meet the drum at the same
time. Then ride the bike a little, remove the backing plate, and inspect the wear pattern on each shoe
for drum contact. If you don't have full contact, the arc of the shoe does not match the arc of the drum
and must be corrected to achieve that condition. The drums are weak and can be distorted by careless
tightening of the spokes. The common repair for this is to 'turn' the drum which produces a larger drum
ID, which then requires thicker lining turned to fit.
L #4818 Currently, the chrome rims from my '39 Mk2 KTS are both WM3s, with 36 spokes at the
front and 40 at the rear. The state of the rims means that they both need replacing. My wheel
(re)builder suggested I rebuilt the front with WM2 (1/4" narrower apparently) to take a narrower tyre.
The spec' in Ivan Rhode's "Technical Excellence Exemplified" suggests the tyres should be 3.25 x 19"
(front) and 3.50 x 19" (rear). Should I have the front rebuilt with WM2 or stick with WM3? What was the
original size and what would handle best? Should I be fitting 3.25 x 19" (front) and 3.50 x 19" (rear)?
(the tyres were already removed when I took over the bike so I don't know what it last ran with)
#4820 3.25 front tyre should be on a WM2 rim 3.50 rear tyre on a WM3 rim these old British bikes
usually had this combination so your wheel builder sounds OK to me.
#4823 I believe the difference between the mkII KSS and KTS was the difference in wheel sizes, the
KSS was 21"/20" versus the 19" on the KTS. This is not news I'm sure. I did want to point out that over
the years your machine may have had modifications. My point is that the correct wheel/tyre
combination should fit nicely with the mudgaurds. Machines that have had the wheels converted to
smaller sizes generally don't look right visually with too much of a gap between the tyre and mudgaurd.
#4826 I have original Veloce sales brochures from 1938 and 1939. In both years the following rim
widths are noted by Veloce: KTS WM3-19; KSS WM1-21 front, WM2-20 rear.
#4824 Some memory in the back of my head of something that I read long ago tells me that the KTS
came supplied with the unlikely WM 3 X 19" rims both ends. I can't quote the citation, but I remember it
as being authoritative.
#4825 Regards the KTS tire/rim query; I would stick with WM2 front and rear, as a WM3 rim is really for
4" plus tire sizes, and isn't standard on a prewar bike anyway unless it was a real hauler, like an Enfield
KX or something American (which used small truck tires prewar, it would seem; there must have been
no corners here at the time). I've owned a few Broughs, and they all had WM2/19". Plus, in terms of
handling, you'll probably find the bike is more responsive the narrower the tires you put on, but more
comfortable the wider the tires, which is my general rule for early machines. So, as an example, my '28
Sunbeam has 21"/2.75" front and 20"/3.00" rear wheels, and my mk1 KTT has 21/3.00" on both wheels,
and each handles like a surgeon's knife. They will even go between the Bott's dots on a road warning
grid without a bump (do you have them in England?). These bikes are used for high performance bend
swinging. As a contrast, I use 19"/3.25 and /4" on my Venom, as it's used for more long rallies. I have
used 3.50" on the rear, which really made it corner more quickly, but was generally more nervous
feeling. I would recommend 3.25-50" for the front, and 3.50/4.00" for the rear of your KTS.
L # 4818 Currently, the chrome rims from my '39 Mk2 KTS are both WM3s, with 36 spokes at the
front and 40 at the rear. The state of the rims means that they both need replacing. My wheel
(re)builder suggested I rebuilt the front with WM2 (1/4" narrower apparently) to take a narrower tyre.
The spec' in Ivan Rhode's "Technical Excellence Exemplified" suggests the tyres should be 3.25 x 19"
(front) and 3.50 x 19" (rear). Q's: Should I have the front rebuilt with WM2 or stick with WM3? What was
the original size and what would handle best? Should I be fitting 3.25 x 19" (front) and 3.50 x 19"
(rear)? (the tyres were already removed when I took over the bike so I don't know what it last ran with)
Many thanks for any advice.
# 4820 3.25 front tyre should be on a WM2 rim 3.50 rear tyre on a WM3 rim these old British bikes
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usually had this combination so your wheel builder sounds OK to me.
# 4823 I believe the difference between the mkII KSS and KTS was the difference in wheel sizes, the
KSS was 21"/20" versus the 19" on the KTS. This is not news I'm sure. I did want to point out that over
the years your machine may have had modifications. My point is that the correct wheel/tyre
combination should fit nicely with the mudgaurds. Machines that have had the wheels converted to
smaller sizes generally don't look right visually with too much of a gap between the tyre and mudgaurd.
# 4824 Some memory in the back of my head of something that I read long ago tells me that the KTS
came supplied with the unlikely WM 3 X 19" rims both ends. I can't quote the citation, but I remember it
as being authoritative.
# 4825 Regards the KTS tire/rim query; I would stick with WM2 front and rear, as a WM3 rim is really
for 4" plus tire sizes, and isn't standard on a prewar bike anyway unless it was a real hauler, like an
Enfield KX or something American (which used small truck tires prewar, it would seem; there must have
been no corners here at the time). I've owned a few Broughs, and they all had WM2/19". Plus, in terms
of handling, you'll probably find the bike is more responsive the narrower the tires you put on, but more
comfortable the wider the tires, which is my general rule for early machines. So, as an example, my '28
Sunbeam has 21"/2.75" front and 20"/3.00" rear wheels, and my mk1 KTT has 21/3.00" on both wheels,
and each handles like a surgeon's knife. They will even go between the Bott's dots on a road warning
grid without a bump (do you have them in England?). These bikes are used for high performance bend
swinging. As a contrast, I use 19"/3.25 and /4" on my Venom, as it's used for more long rallies. I have
used 3.50" on the rear, which really made it corner more quickly, but was generally more nervous
feeling. I would recommend 3.25-50" for the front, and 3.50/4.00" for the rear of your KTS.
L # 5123 I've not had any luck in finding Akront rims suitable for the Velo although one does
routinely find them for other bikes. The most readily available rims seem to be the EXCEL valenced
alloy as handled by SRM in the UK and I'm sure these are superior to any other similar rims and will
probably go this way if I can't locate any Dunlops. My Venom presently has original Dunlop steel rims
fitted but I've always loved the valenced alloys.
# 5124 George, Try www.akront.com/ or www.buchananspokes.com/Akront_shld.htm Their S or MS
series (depending on whose web site you look at) valanced alloy rim is the one I used and is a very
good substitute for the period Dunlop or Borrani valanced rims. In the UK they are available from the
Central Wheel Company www.central-wheel.co.uk I gather from their site that the tooling has been
taken over by a company called Morad who, like Akront themselves, are based in Spain. I've not been
able to find a good reference to Excel rims or SRM, but gather that Excels are quite a bit more
expensive than Akronts. Personally I consider that the Akronts are well up to the job, look right, and
there is no reason to go shelling out the extra for the Excel alternative.
L # 6147 I bought a 1938 KSS today and have spent the last couple of hours making lists of
what to do (I'm sure you all understand the feeling). The bike itself was restored about 10 years ago,
doesn't seem to have done many miles since then but has been stored in not very good conditions for
the last 7 or so years. Some good pointers - the petrol tank had been filled with oil to stop rust, the oil
tank is full to the brim with clean oil. I've resisted the temptation to turn the engine over and will do the
sensible things about oil circulation etc before trying to start it. I'll let you know how it goes. The main
point of this post is about tyres. The ones on it look OK but I'm a bit nervous of trusting them on the
basis of their age. I would probably replace the tubes anyway but what about the tyres? There have
been a few posts about the lack of availability of 3.00x21 front and 3.25x20 rear tyres. Anybody got up
to date information about a UK supplier?
# 6148 Tires are now available at Lambrook's in the UK. I got a pair about 6 weeks ago.
L # 6177 I'm restoring my Viper '67, and trying to remove the right hand bearing of the rear
wheel. The owners handbook of Haynes, page 114 mentions that the bearing retaining ring has a right
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hand thread. My brother who owns a MSS tells me that his workshop manual mentions a lefthand
thread! Because some force is required for removing my ring and I want to avoid to demolish this ring
or inner thread, I would like to know what is right? Do I have a left- or right-hand thread?
# 6178 I have just checked a wheel from my Thruxton. The bearing retaining ring unscrews by turning
it CLOCKWISE .
# 6180 Haynes strikes again...that's a left handed thread. Nice photos, but not 100% accurate. The
Red Book, or "Service Manual" as published by Veloce Limited, is indispensable. You can order a copy
from most dealers. Or ask your brother to make a copy, if it lists the Viper model on the cover.
L # 6203 Anyone got any tips on how to remove the rear wheel bearings ?
# 6205 The outer bearing races can be a bit tough to get out. Sometimes you can knock them out, by
hitting a drift passing through the hub center from the opposite side. If they are tight in the hub, run a
few beads of weld onto the race surface. As the weld cools, it shrinks, and pulls the bearing race
smaller. Then it will fall out of the hub. Careful with the weld though. Stick welding will throw weld
spatter all over your hub. TIG or MIG are cleaner to use.
# 6204 You cant do much better than read the instruction book.
L # 6202 1) I have a 350 rigid MAC from around 1940, question is would the wheel rims be
chrome or would they be black? 2) I have girder/webb forks so the speedo would be on the front hub.
BUT my bike also has a speedo drive on the rear hub. If I use the front speedo drive then can I remove
the rear speedo drive, if so, do I need a spacer or are the rear hubs different for speedo and nonspeedo?
e.g. Were the hubs different widths?
# 6208 My 1954 MAC originally had shiny chrome on the outsides with dull chrome in the middle. Also
had black spokes. But 1940 versions would probably have been different. Wartime lack of shiny stuff?
# 6209 I know the KSS had chrome rims in 1939 with black painted spokes. I have a photograph that
suggests that they may have a dull chromed - but I can't be sure. (Note the difference between bright
chrome and dull chrome was determined by the whether or not the nickel plate, used before final
chroming, was manually polished or not. The nickel plate used today has brighteners which avoids the
need to perform this polishing step) The 1937 KSS model has the black centers with bright chrome
edges. Some people say there was also a gold line as well but I see no evidence of this on my very
original 1937 My 1937 KSS is the similar to yours having a rear speedo drive. Up until Dowety(?) front
forks, all were delivered with front wheel speedo drive. I have a letter from Ivan Rhodes which states
the conversion to rear drive was an after-market conversion and that he has seen a number of bikes so
converted. I have not taken mine apart yet to see how it is different from the drawings in the service
manual. Mine has rear speedo drive and what looks like a standard spacer. I cannot confirm this but
the gear ratio between from and rear drive may be different. This will affect the indicated speed.
However, I am also told that the speedometer internal gearing can be changed to suit. Mine does not
have the original speedo. It's 80mph Smiths speedo was probably fitted sometime in the 50's (only
shows 800 miles). Perhaps the front to rear conversion happened when the original speedo failed? I
would be interested to know the dimensions of the rear hub on a 1936-40 rigid frame machine to verify
the originally of the rear hub on my KSS._
# 6210 I just had a look at my 1936 brochure and it lists chrome rims as an extra
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G. The Frame
G.1. Frame, Bodywork, Paint and Polish -
L #302 Finding it hard from archive photos to tell which alloy surfaces should be polished and
which left 'rough' on my '68 Clubman 500 rebuild. Timing chest cover is obvious but what about brake
plates and surfaces on other side of hubs? Gearbox cover on kickstart side? etc.
#304 Regarding which areas to polish on a Velo restore: timing cover valve inspection cover gearbox
outer cover brake plates hub backs Some people do a lot more, like crankcases and gearbox cases,
and some Velos came with unpolished timing covers and gearbox covers (the Specials, with
fiberglass engine covers), which sometimes show up on other bikes. Engine/gearbox cases were very
clean as cast, but not polished
#306 My '68 VMT came from the factory with fully polished engine and gearbox cases. It is totally
unrestored (some might say neglected) and the only remaining polished area was found behind the
primary case! The first (and only previous) owner was definitely not the polishing type, more of a
"working machine" sort. OTOH, my Veeline was completely "as cast". It had f/g covers that hid
everything up to the bottom of the fuel and oil tanks. The difference is very obvious, the castings are
quite rough. I polished the timing cover on the Veeline myself, not a Simichrome job, needed my
buffing wheels and plenty of compound. Still not sure if it was a good idea. I have read that the factory
left the engine and gearbox unpolished on Specials and Veelines to save the labor. Plus it cools better.
But most Velos came with polished cases. Not like a mirror, just bright. I applaud any attempt to resist
"overpolishing" your Velo, too many are overdone.
#307 I have owned both my Venom and MSS since 1973, they too were unrestored. Polished areas
were consistent on each set of castings covering the following Timing cover T/S crank case around
timing cover periphery, front edge of pump housing, front edge of filter bolt housing, front right hand
side of T/S crank case D/S crank case barrel flange, front and bottom of face of crankcase Gearbox
cover and sleeve gear cover Top inch or so of the shell where the serial number is, right the way
around to the concave front side of the shell. Front and rear break plate Front full width hub on the near
side 3 hole disc only on the rear FW hub I was also told by an ex Velo dealer.
#1036 I am always envious when I see Velocettes with polished timing covers and gearbox end
covers. My timing cover is smooth but their gearbox is a very rough casting. Has anyone any useful
advice on how to improve the gearbox appearance. I am not necessarily after a mirror finish but at
least an improvement on what it currently is.
#1037 It basically requires lots of elbow grease but have a look at www.englishcustompolishing.com it
has a wealth of info on the subject
L #352 For the colour schema Velocette had their own identification which gave the original
polychromatic Silver Grey of the 150 the no. 1. For to get this colour I recommend to contact L.E. VELO
SPARES Bullers End 43, Bradford Lane Walsall WS1 3LU.
#447 I have a Le Velocette mk1 I am trying to identify the greyish colour, that they are painted. Does
anyone know the exact colour and where I can get it
#452 According to Roy Bacon's book "Velocette Flat Twins" the colour schema for the Mk1 from 1949-
50 is: Main frame pressing, top and bottom fork crown, front mudguard, front fork legs, front fork lower
shrouds and saddle bracket in silver grey. Polished alloy leg shields and wheel rims, chrome plated
fork stanchions and headlamp rim, dull chrome plated exhaust pipes. Black headlamp shell,
handlebars, headstock, radiator surround, rear engine pressing, rear fork footboards, cylinders, sump,
hubs, generator, silencer box, number plates, battery strap, stand, rear brake pedal and pannier
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frames. Also saddle top and pillion black and black footboard rubbers..
#468 Some of the MAC / MSS type single width hubs seem to come in a kind of metallic green'ish
colour. Does anyone know :- a ) what the color was ( is now ) b ) was it specific to some models c )
what models ( was it the Green bikes only ).
#469 Vipers were made in a colour called Willow Green between 1956 and 1960 – not sure of the
equivalent colour today.
L #655 Velocette MAC 1951 Today I began the process of neutralizing the rust in my tank and
applying a sealer. The first stage was to pour in a de-greasing agent and slosh it around. Then I had to
wash out the tank with clean water to remove all trace of the sudsy stuff. When I'd finished I noticed
that all the water has made the "velocette" tank-transfers wrinkle and start to lift. As it was a sudsy
water solution which caused the problem, I'm assuming that they were the slide-on type transfer and
I've got a couple of questions if anyone could advise me on how to go about replacing them when the
job's finished:- Any tips on the best way to remove the old transfer remains? The VOC parts list
includes " A132 - Tank Transfer (modern)" Is this the right one, and if so, is it a slide-on type? I was
thinking of applying the slide-on type transfer and then giving the whole tank a coat of spray laquer.
Does this sound like a good idea? I'd be grateful for any pointers.
#657 I have got the same problem the Velocette tank transfer has wrinkled its been like it since I have
the bike so have no idea what caused it, the rest of the tank is perfect, The problem is how to remove it
without damaging the enamel? I have two water slide transfer to replace them, I am told if you use a
drop of washing up liquid in the water, it reduces the surface tension so they can be positioned easily
without wrinkling, and gently pad dry with a tissue then leave for 24 hrs, before trying to use any sort of
fixing spay, I certainly would not try lacquering the whole tank, as any Paint sprayer, will tell you need
to remove all the silicones from the surface which is very difficult to do, without damaging the enamel.
I am not sure of the best way to fix the transfers, onto a polish surface so they are permanent. Are
there any experts out there to tell us the secret.?
#661 I've got an old Velo manual - unfortunately it's lost its front cover so I don't know the precise title
or year but it has the following section on "fixing transfers": "Transfers are printed on duplex paper and
the two sheets must be separated before transferring. Divide them by rubbing a corner of the transfer.
Apply a very thin and even coat of adhesive varnish to the face of the transfer and keep as close as
possible to the lines of the design. Allow the varnish to set until very tacky and then place in position.
Press down evenly and firmly and drive out all air bubbles by rubbing with a soft cloth rolled into a ball,
commence in the centre of the design and work out to the edges. Then with a damp - not wet - sponge
or washleather press down again taking care not to move the transfer. When you are absolutely certain
that every part of the transfer is in contact with the surface apply water freely with a wet sponge. When
the support/backing paper is well soaked lift it up starting at a corner and peel and/or slide off. Press
the transfer down again. Sponge with clean water to remove all traces of material on the surface of the
transfer - this is very important as unless properly done the transfer will crack on drying. To remove all
traces of adhesive varnish around the edges of the design use a wet sponge to which has been added
a drop of paraffin, quickly wipe off with a damp washleather. When the transfer is dry - about 24 hours -
varnish to add lustre. It must not be varnished directly it is transferred."
#663 My 1952 red book manual for the MAC. chapter on transfer, is more or less the same as
Professor Lunt, quoted. except it says use the old fashioned goldsize, instead of varnish. but that was
50 years ago. The A132 tank transfer (modern) is now the replacement supplied from Veloce spares
ltd, which suggests it will be the modern water slide type, not the old duplex type transfer, So the water
slide type should be applied as I said in my earlier mailing. It is the way to spray fixed it after? to stand
up to the all that spit & polish that we lavish on our pride & joys these days, I would make sure it is not
a cellulose base spray.
#666 I cannot say I have fully mastered applying transfers even after rebuilding a few bikes, but here's
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my experience. Varnish transfers - when you get them right they are the best, but they are not easy to
apply. I have an oil tank with all the letters attached but if you look closely it looks like "alphabetti
spaghetti" . Follow the instructions posted by George. I have used Polyurethane varnish successfully,
but you must get the tackiness just right. Buy a spare transfer and try applying one on a can first!
Waterslide are easy to use but they can appear translucent rather than transparent. There is no need to
use washing up liquid as they float off easily, in fact it may cause problems with subsequent lacquer
adhesion. For both types of transfers I always rub the tank down carefully with something like 1000 to
1500 grade wet and dry to remove any high spots. Rub two pieces of wet and dry against each other
first to make it even finer. After doing this you can polish back with T cut if you want. You can lacquer
over the transfers, I have used two pack with no problems, but I suggest you buy a spare transfer to
see if there is any reactions first.
#1014 Martin Arscott sells self adhesive transfers at £5 a pair. Tel +(0)1442 862966 or mail
marscott@t... I have used both varnish and waterslide transfers. Varnish are very difficult to apply, and
waterslide leaves a slightly white finish. For your tank I would recommend two pack
www.austinseven.mcmail.com/paint.htm successfully as you can repolish it. I have painted four Velo
tanks with two pack, I recommend a clear lacquer over both the paint, transfers and lines - sorry I don't
have the correct paint codes
L #825 One of the previous postings suggests Car Plan Vauxhall Antique Gold as a good match
for petrol tank lining colour. It seems to be unavailable, at least round where I live. Any others
suggestions welcome.
#831 You might want to contact one of the specialist painters such as www.precision-mcpaintwork.co.uk
who do gold lining on petrol tanks and have the original templates. They are extremely
helpful and answer EMails.
#835 I use 0.25 inch gold tape from car accessory shops, applied before the two pack lacquer - I think it
looks excellent. You need to use a hairdryer to soften the tape to make it bend round corners. It's not
an easy job
L #997 I have heard the term 2 pack paint but here in Canada it is not a term we use. I assume it
means paint and hardner but really I don't know. Could anyone help me to understand this term and to
perhaps lead me to find the correct blue and silver colour for the 67 VMT. Paint codes useful in North
American would be good. Also what recommendations do you have for the type of paint to use, and
lastly what is the best method to deal with the tank transfers. It seems the 40 VMT's that came to
Canada were delivered with this colour scheme.
L #999 I've spent a while this evening trying to remove the closing/fastening screw from the
toolbox lid so I can deal with a bit of rust. I thought at first that the washer at the base of the thread
might be a circlip, it doesn't seem to be. Then I thought that the knurled portion might be screwed onto
the threaded portion, it isn't (unless it is extremely tight). The parts list/exploded drawing I have calls it
an assembly so isn't any help. I really can't see how it is assembled.
#1000 The knob assembly comprises 5 items, and is assembled in the lid. There is the knurled knob,
the stud, two plain washers and a double coil spring washer. The latter three are placed on the reduced
diameter outer end of the stud, one plain inside the lid and the other washers outside the lid, and the
knob is either screwed on, or pressed on, and locked. It is not intended to come apart!
L #1098 Greetings, I'm seeking a colour code or year/make/model info on an automobile for the
proper colour for a 1967 Thruxton. Can anyone on this group help me identify the colour?
#1100 I've already got the silver parts done, but need to complete the blue. I really amazed at how
difficult it has been to locate a colour code or even year/make/automobile model information to get the
colour right. I've been working on this task on and off for about two years. The closest I've come is the
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colour was called Oxford blue when used on Rover autos some time in the late fifties / early sixties.
Pursuing this thru Land Rover disclosed a current Oxford blue, but is has a fair degree of pearl added,
and I suspect the formulation for Oxford blue has changed to a more modern appearance. Another
colleague told me that the 1964 Triumph auto used the same blue, and/or British Leyland used the
colour in the mid sixties. I located a PPG brand paint supplier who had an online paint code selector
and found two possible candidates under British Motors for 64-67 as BU-45 Midnight Blue, or Bu-29
Alaskan Blue. The Triumph is #13126 Royal Blue. Alas, since I'm looking at a paint sample that was
scanned into a computer on their end and viewing the scan on my monitor, I'm not sure what colour I'm
really looking at. I'd sure like to "crack this code"!!
#1101 I think you should find that Grove Classic M/C's (UK 01582 873066) or R.F. Seymour Ltd (UK
01844 212277) can help. There were some original colour swatches around - I think either or both of
these Companies will have some (Goodman Engineering also, although not sure if they are still in
business)
#1103 I checked with a fellow VOC member who has built two or three Thruxtons, he states the colour
is Ford "Anchor Blue" www.fordanglia.com/paint.htm for the frame and originally Ford "Silver Fox"
which changed later to "Sirocco Silver". You need to use the 65 -68 colour swatch. Apparently it was
Reg Orpin who created the original colours and he uses off the shelf Ford colours. He also said that BL
"Oxford Blue" was not the colour. BTW, Seymour's cannot confirm what colour the tank and frame is.
While I cannon vouch for the accuracy of the information I hope this helps.
#1106 I have a bike with the original blue still on the parts. I had it scanned but it didn’t come up with a
clear reading as the surface of the paint was scuffed and not clear. The painter took the piece and
matched it by experimenting with a few mixes It was a ppg brand of paint. What I ended up with was a
sample and I cant fault the match. He came up with this code: DCCNCP CONCEPT MIXED
PAINT.....DU508 URETHANE HARD-PT AND DT87001 REDUCER. It definitely is an oxford blue that
with the eye you cannot find a difference. He suggested the urethane as it is a one coat finish that is
superior to other finishes. I was wondering if there was a match to this so that we would all be on the
right track. I also would like to know if you are going to do the blue, silver ,and black just as the original.
I asked the painter just for a nice Mercedes silver and it came back tinged slightly taupe. Also what did
you do for the transfers and the gold do you have a clear over them
#1107 I've used PPG as my paint supplier for many years and DCC is certainly my paint system of
choice. When used with the DU508 hardener it makes a great durable finish. It has been my
experience in the past, that whenever I had a custom color mixed, the PPG supplier gave me the
formula as a gummed label that was stuck on the lid. Did you by chance get the formulation and if so,
can you relay it to me? The info David Gibbison so kindly, and greatly appreciated, relayed to me
turned into a dead end for me at two PPG paint suppliers. Neither could identify the Ford Anglia
"Anchor Blue" code BJ. I must remain persistent. It is one of my best traits!!
#1109 Have just remembered - I got some help from Ray Thurston in the UK some years back on VMT
colours also my notes say 'Rover Night Watch Blue' and 'Ford Silver Fox Metallic' I have since sold that
VMT - but I do recall this gave quite a good match to the original (very thin) finish I have on the
unrestored VMT I’ve kept.
#1112 I got a lead from a colleague here in Washington state, Ed Gilkison, suggested I contact John
G., who emailed me several codes he found most acceptable when he restored his Velo. To quote
John" Dick, I actually found the original can of paint that I bought in 1980. It is a Sherwin Williams
"DARK BLUE #904 Mercedes Benz. The other can I have which is a newer match is R-M Mercedes
Code 904/Midnight Blue 7577. The silver I used was Honda Accord(car) Blade Silver. You want silver
with a flat fine metal flake not too metallic. You be the judge.
L #1102 Should my 1948 MAC have chrome or painted wheel rims?
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#1104 My 1947 Mac had chrome wheels (rigid, Dowtys, iron) Looking at a photograph of her now
(sigh!)
L #1134 Just finishing assembling VM1959. Came to refit petrol tank and am a bit confused about
the purpose of the petrol tank strap (A276/2). It obviously fits between the 2 studs under the tank but
I'm not quite sure why. It almost comes up against the frame front downtube but doesn't seem to
perform any function apart from joining together the two sides of the tank, which doesn't really seem
necessary. Am I missing something obvious?
#1135 Ian Indeed you may be missing something quite important. The tank strap stops the two sides of
the tank flexing. If they do then the tank will surely split at the rear and petrol will issue forth. This only
happens when the bike is ridden of course! Veloce normally had a very good reason for such details!
L #1699 Can any of you Venom historical buffs give me an idea of what the true original shape of
the '57 Venom dual seat should be? Having just powder coated the seat pan , I am about to have it
re-covered and want to replicate the original profile, but when I look the archive pictures on the VOC
site, I notice that no two seem to be the same. Some seem almost dead straight, whereas mine has a
deep "pan" under the pilot, and all seem to have uniform deep cushioning, whereas mine tapers to no
more than 2" at the front. Some have two curved stitch-lines on the side, others only one. The old
cover, carefully removed, appears to be original, but I have a sneaking suspicion that a previous owner
may have trimmed down (up) the seat-pan flange. Any advice - or directions to a definitive picture
would be gratefully received. On the same subject, can anybody recommend (from experience) a good
upholsterer in the south of England?
#1700 I think the flat seat came in 1958. The closest pic I have is a 56, but I don’t think there were any
changes for '57. The shot of the '56 I have is of a Viper, from side on unfortunately, but it does appear
the seat narrows markedly at the nose, where it mounts to the frame. There is a slight 'curve' toward
the frame rails at the front, but a gap is clearly visible - it is certainly not a flat seat. The seat is flat-ish
for the pillion, then follows the mudguard to the centre of the arcuate slot, then curves upwards to its
nose (hence the gap to the frame rails). There are two separate 'curved' stitches, the first starts in the
centre of the seat (on the top) and curves forward such that if one extrapolated the curve it would more
or less follow the rear line of the oil tank. The second appears to start at the rear of the seat and curve
forward to a point virtually at the maximum radius of the rear mudguard. I will try and scan it in for you if
the general consensus is that it is the right one. Phew - a picture paints a thousand words - how true
that is !
#1701 Just found the self same picture I described earlier in Steve Wilsons British Motor Cycles Vol 6,
p 225. Wilsons text appears to confirm no changes for '57, flat seat in '58. But I'd bet there are one or
two of this group who will know for sure.
#1702 Don’t mess about, send your seat to Leightons in Birmingham. they will do a top class job at a
reasonable cost. you just don’t get better www.rk-leighton.co.uk/ I can vouch for the quality of their
work.
#1710 When I recently re-upholstered my '57 Venom seat. I salvaged the cover and made a new foam
inner piece. I tried several means of fixing the cover to the metal seat base. I eventually used Velcro
strip to fasten the seat cover. This worked well. I acquired some continuous, 25mm wide Velcro tape
which had double sided tape on both faces. This went all around in the inside edge of the seat shell.
This stuck well to the recently painted inside face of the seat shell, The other piece of Velcro had to be
Evo-Sticked to the cloth side of the PVC seat cover. The hardest job was tailoring the foam block to the
right shape. I did not have a pattern to work to. I used a high density reconstituted block foam which
was faced with a 10mm thick flexible foam to ensure any lumpiness of the reconstituted foam would not
show through. I used a combination of tools (saw, bread knife, surform, etc) to sculpture the block foam
to the right shape- the seat shell has a lump in it for the mudguard and the pillion part is a little higher
than the front part. It took quite a time of trial and error to get it right. I did not glue the block foam to the
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seat shell and this will help if I need to re-do it soon. I do not think it will move. It looks good. Perhaps
next time I will get it done professionally.
#1714 To sculpt foam when upholstering seats etc. use an electric carving knife. Borrow one from wife
or available at car boot sale near you for around £2.00 PS. Buy two if you can cos they tend to fall off
the workbench and smash or be stood upon when wrestling with seat covers!
L #2019 When refitting the petrol tank today I sheared one of the studs which are used to fasten
the stiffening bar across the front of the tank. In my defense, when I look at it, it has been sheared
sometime in the past and a new stud brazed onto the part still in the tank. It’s the brazing which has
failed today. Is the stud brazed into the tank or is it screwed into a threaded boss which is brazed into
the tank? In other words can I screw out what's left of the stud, make another and screw it in? If the
stud itself is brazed in the tank my current thoughts are to (very carefully) drill into it and tap it say 3mm
(it’s a 1/4 BSF stud) then make a stepped stud, threaded 3mm at one end and 6mm at the other and
screw it into the 3mm tapped hole with Loctite. The stiffening bar could then be fitted as normal. I want
to avoid brazing if possible.
#2023 Firstly, I assume you are talking about the 3½ gal tank with round badges and knee grips. The
stud for the strap is threaded ¼" BSF, but has a 3/8" dia boss to locate the strap, and a larger flange
above that. It is (or was originally) welded (not brazed) to the tank. It is not a separate, plain stud
screwed into anything! I'd recommend cutting the old stub off completely, and turning up a new piece to
be welded in its place. Welding is better than brazing, as brazing can cause local hardening and
subsequent cracking of the sheet metal.
#2024. The Velo tank is the one with badges and the studs look exactly as described, so it looks like
welding a new one on is the answer. Tomorrow or Thursday will be the first chance I get so if anyone
has any other suggestions before then, I'd be grateful.
#2025 Easier than welding, but not as permanent, if you make the new stud with a large area base
(tank end), maybe you could solder it in position, or even 'glue' it with Araldite.
L #2113 So I have partially dismantled the Venom that's been in hibernation for 25 years, and its
going quite well everything looks good, except for minor scratching to the piston (bore is ok). 25 year
old engine oil actually looked pretty good, which is more than can be said for the chaincase oil which I'd
rather not talk about. The questions I have are related to how to finish the bits and pieces I note in
many books there are references to "matt chrome plating" to be used instead of the original cadmium
plating on part such as kick start. What exactly is "matt chrome" and how does the plating process
differ from the regular polished chrome finish. The other question is painting cycle parts like primary
covers, oil tank and headlight cowl. I was thinking of powder coat, but now I am having second
thoughts. Which parts should be enameled/cellulose and which pieces powder coated? Any
recommendations? Anybody know of a good powder coat shop in the Bay area?
#2114 Many items were dull/matt/satin chrome in the first place and not cad plated. eg Kick start, steel
gear levers, brake levers, rear brake spindle steady plate, steel rearset brake pedal etc. etc. The
difference lies in preparation of the material. After polishing or other prep and before plating the part is
gently sand blasted. The chrome is not polished after plating. The details will doubtless vary depending
on your plater, but that's how it was explained, and done, for me. Painting should be just that. Veloce
dipped their bits in a production facility paint machine. That’s why the original finish is so smooth and
thin. Stove enamel can be applied to give the same (ish) finish. Often its too thickly applied. Same with
powder coat which is after all a plastic skin spread over the part. My opinion is that it all depends on
your requirements. Powder coat for a well used machine eg trials Stove for a tough good finish. Do it
your self for the right effect. This can be sprayed acrylic even brushed if you're really good at it. We
have a paint shop near me that sprays; not stove. The finish is excellent. This will not be as tough as
stove though. I would avoid powder coating as the parts look as if they are dipped in or made from
treacle - that's just my personal preference !
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#2115 I have tried to achieve a "Dull Chrome" finish. I have tried the bead blasting and then plating but
it does not look right. The closest I can get is "Satin Chrome" where the component is rough polished or
brushed - but it's still not right. I have access to the original factory specification for VM/VR if anyone
really wants to know what the finish on a particular component was. Regarding painting, I have tried the
following and here's my experience for what it's worth: Cellulose - easily applied cheap, you can cut it
back to polish it, but it chips badly; Two pack - great finish, you can polish, it will chip, but not too badly;
Powder coating - cheap, does not chip but scratches badly and you cannot polish the scratches out.
However it is ideal for centre stands, side stands and rear cotton reel hubs. Do not use it on iron front
hubs as it burns if you brake hard! Ask the coater to phosphate the component before coating, for
added rust protection; Stove enamel - my only experience of this is a bent MSS front mudguard with
original enamel on it. Even beating the enamel with a hammer had little effect on it. Finally I have seen
black powder coating used as a base coat for two pack black.
#2131 Decided to put my 2 bits worth in, I have been involved in enamelling surfaces for close to 70
years, had a panel shop around the time from cellulose to 'Dulon' etc. when it came to restoring
motorcycles, I soon discovered a few shortcomings, in conventional finishes, as many people have, but
after consideration & noting how well original finishes had survived on old British bikes, common sense
found me getting a small specialist (?) stove enameller to do a couple of Velo cotton reels, (hubs) for
me, & an excellent job he did too, & I happily laced up my wheels & admired the result. Unfortunately at
a later date I used kerosine to clean up oil deposit & the paint just went sticky & the resultant work
involved saw me deciding to do my own stove enamelling, & I have done so ever since ! Number one
lesson, if you stove enamel, make sure that it's baked properly! I use an old convection heating type
clothes dryer, with the circulating fan removed, & the electric element restrung in a box around 5 times
the original size, this has to be done to prevent circulation of fine dust by the fan, & the larger element
box is necessary to prevent sagging of the element when it becomes red hot. Also throw away the
wooden 'hanger' bars, & replace with steel rods. The outside of the cabinet is clad with insulating 'bats'
& outer thin gal. steel sheet. If you want to enamel a modern frame, there is a good chance that it won't
fit in a clothes drying cabinet, so you will have to construct something bigger ! Stove enamel is cheap in
the long run, & you use far less of it, & it's so much easier to use once you get the hang of it. I spray in
the open air, picking a good wind free day, but a light breeze is helpful in getting rid of the over spray. I
thin the paint well down & spray with lowest pressure possible, just 'drifting' the paint on, this is possible
with stove enamel. One of the reasons that I spray in the open is for the good natural light, black can
easily lead you into missing spots. I always give a couple of coats to frames upside down, before
turning right side up & finishing all over. The paint will tack dry quickly in the sunshine, & can be well
checked before going into the oven. My oven will not take the temperature up to what is recommended,
but just over boiling water temp in fact say 120-130, but I bake for longer, possibly half hour or more
after the temp. gets to max. & then allow temp to drop again. A wonderful advantage is that the enamel
never dries up in the gun, & in fact I have left it for months on end ! The best part is that once the parts
have been fully prepared, it's just spray & into the oven, & start assembling the bits as soon as the
parts are cool enough to handle ! I have one confession to make, I do the Henry Ford bit, - any colour,
as long as it's black ! any colour work is done in 'Dulon' or what ever it's called these days . Once you
have used stove, you will never go back ! & a comment on powdercoat. if moisture happens to get in
through a bad spot or a chipped area & it's not noticed a horrible disaster follows, maybe the process
has been improved in this respect, but I have seen slabs of powder coat come off after moisture has
somehow penetrated the surface. (possibly over baking ?)
L #2126 Folks, I need to repaint the fuel tank on my Thruxton. How do I go about removing the
chrome filler cap assembly? It is not obvious to my eyes. All help appreciated.
#2127 The cap is held on by a pin, approximately 5/32 diameter, that doubles as the hinge pin. The
ends are lightly peened over. I used a pin punch and drifted the pin out without difficulty. Try drifting
one way or the other and you will readily see which direction is easiest. 30 second task. Upon
assembly, I used a drop of Loctite 242 on one end of the pin and did not attempt to peen the end. No
problem in thousands of miles. Put a smear of thick grease on the blued steel spring that holds the cap
in the up position so the cap will not bind on the fresh painted filler neck.
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#2181 If you use a roll pin in place of the original plain pin (if indeed this is how your cap was originally
fitted) then there is no need for any further security. In fact if you purchase a new cap the chances are
that it will come packaged with a roll pin. This may need to be slightly squeezed at one end to aid
insertion but can then be tapped into place with a small hammer and punch and removed in the same
way. There is no need to peen over the ends after insertion.
L #2153 Any suggestions on cleaning a fuel tank? I just bought a bike that hasn't run in two+
years. The tank still has some old smelly fuel in it as well as surface rust inside. I'd thought about
ditching the old fuel first (2-3 quarts), flushing thoroughly with soap and water, rinsing with carburator
cleaner, followed by phosphoric acid to kill any residual rust, and then rinsing again with soap and
water, flushing with water and blow drying.
#2156 Be carefull. I would allow the tank to dry in little more than sunlight. Metel is porous and residue
petrol gas will continue to evaporate for a long time after even the best of cleaning. Explosive vapour
can collect until what we offshore workers call "The lower explosive limit" is reached and then ignited by
a heater in a blow drier or a static spark at the tip of an air line. I did my tank by water flushing and
shaking gravel in it, then flushing again. I then used a propriety two part sealer that formed a glass fibre
skin inside.
#2159 I've had excellent results using a two-part treatment sold by Yamaha, it is an enchant (probably
phosphoric acid) followed by a neutralizer. It leaves a clean steel surface that resists rust. The part
number for the Yamaha Fuel Tank Rust Remover is ACC-FUELT-CD- KT. It works on British steel as
well as Japanese. If the tank is not leaking or severely rusted I would stay away from coatings.
Exposure to modern alcohol-laden fuels can deteriorate them.
#2160 I'm with Tom on this one; tank sealers are only a stopgap until you get the thing welded up
properly. The alcohol in modern fuels seems to make the layer of plastic brittle eventually and they
come off in big flakes, blocking the fuel flow. It may be that companies have adjusted for this now in
their products, but still, get the thing fixed properly if its leaking. And if its not, I've used a phosphoric
acid etch to remove rust inside a tank, and it worked quite well. Careful where it spills though, as my
concrete garage floor has a reminder where my Brough tank sat, and leaked, with the acid wash. It did
such a good job cleaning my tank out that I discovered that one under-tank mounting stud went straight
into the petrol, held only by a little chewing gum, or old epoxy, or possibly even soap.
#2322 A month or so ago I posted a question regarding fuel tank cleaning. I had a solid tank that had
sat since 1972. The fuel, to say the least was nasty and the interior was rusty. I tried a variety of
chemicals, mineral spirits, ospho (phosphoric acid), acetone, and soap and water to clean it. I was
successful getting rid of the fuel and fuel smell but the rust remained so I got some rocks and dumped
them in the tank with some soap and water thinking I could shake the tank and knock the rust off -- HA!
Physically impossible so I set the problem aside and thought. The solution? Our clothes dryer. I got
some more rocks, soap, and water. Plugged the holes and wrapped the tank in plastic trash bags. I
then wrapped the tank in blankets and stuffed it in the dryer with pillows, etc. to keep it from moving. I
set the dryer on Air Dry so there would be no heat and sat back and waited. My wife thought I had lost
my mind. After an hour I pulled it out and found one half of the interior looking absolutely new while the
other half was still rusty. It seems when the rocks fall they miss half the tank's interior. I turned the tank
180 degrees so as to rotate it the opposite direction and jammed it in for another hour followed by
turning it 90 degrees and then another 180 degrees. After four hours the interior of the tank is nearly
perfect and the wife had her dryer back. She still thinks me mad and is probably right. Oh, a six pack of
beer also helps.
L #2382 For a triangular type tool box, is there some sort of trick to removing the knob. It doesn’t
seem to want to unscrew. I was planning to do remove it before sending the tool box off to be painted.
#2390 John, assuming the cover has been removed from the box, notice a small circlip in on the inside
of the cover has been snapped into a groove on the knob's shank. Remove the circlip.
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L #2564 I am still building my mac (no 2) and even though she isn’t well advanced the time has
come round to start thinking about mudguards, the original guards where worse than u/s so I am
looking for a pair of originals, is their anyone out there that can help or advise on alternatives, (without
going down the fibre glass route)as I am starting to get a bit concerned, and I want the bike to look as
original as possible.
#2570 As far as I know fender (guard blanks) are still available ex Armours UK , while these blanks are
not exactly to the Velo pattern, I have used them several times over the years, making up the chain
'valance' for the rear section, & the tailpiece joint. For the earlier models at least, you need to buy 2
fronts, & 1 rear blank, the second front is necessary to make up the tailpiece on the rear, & get the full
length of guard. For Oz restorers there are 2 sources of new blanks here, one in Victoria & 1 in South
Aust., names supplied on request. Re Mark's inquiry other tinware, I still have some stocks of rear
chainguards for all models, & early 'D' toolboxes & No/Plate brackets etc.
#2571 I would give Renovation Spares a call on 01527 543796. They do a lot of pattern mudguards in
steel plus a lot of blanks. They might well have exactly what you are looking for. If not, and you can find
or borrow an original, they will make you a replica.
L #2653 I'm after a 'smallish' fly screen to fit onto the Venom (something similar to a Manx Norton
screen, but to accommodate the headlamp as well). Can anyone recommend one that will fit a Venom
with minimal alteration. The headlamp on my machine does not have the 'cowl' arrangement, but is
fixed via brackets off the fork stanchions.
#2655 A fly screen can be easily made out of clear (or tinted) thin plexiglass available at hardware
stores or the Big Box home repair conglomerates. A 2sq. ft. piece should be good for 3 or 4 of 'em and
if you get thin enough plex you can make the first cuts with sheet metal shears. The curve to fit over the
headlight may need smoothing with a Dremel and a flat grinding disk. Without the headlight cowl it will
be easy to make a couple of brackets that come off the headlight mount bolts. With the right bend they
can give the screen a nice aerodynamic curve. One inch strap stock will work nicely.
#2658 Brian, for just the screen try www.meadspeed.com
L #2697 I have a Craven carrier and some Craven panniers to fit to my Viper, carrier fitted ok but
how do the panniers fit to the carrier? I assume some sort of fitting kit is used, has any one any
experience with the Craven equipment?
#2698 All of the Craven equipment I've ever seen, and the set of mid 60's Golden Arrows use the same
type of mounts. The panniers have a three point mounting arrangement. On the back side,
approximately 2 inches below the top surface, are two cylindrical rubber blocks approximately 3/4 inch
in diameter, 1 inch long with a 1/4 inch hole in the axis of the cylinder. The cylinder is held to the
pannier with a sheet metal band. The axis of the holes in the rubber blocks is in the vertical plane.
These blocks are the "hangers" for the panniers. On the pannier FRAME, are two "L" shaped "hooks"
which engage the rubber blocks. One lifts the pannier to the frames and "hangs" the panniers on the L
shaped hooks. On the back side of the pannier at the bottom, is a sheet metal bracket with the "female"
portion of a Dzus fastener. If you are not familiar with this fastener, you should search the net and find
a picture as they are clever and rather difficult to describe. The pannier frame has the "Male" portion of
the Dzus fastener mounted in a sheet metal bracket. As Craven equipment was all made to be
universal, after about 100 hours of screwing around and getting the 200 plus pieces that made up the
mounts and panniers all aligned and mounted snuggly, the pannier was secured at the top by the two
hooks and at the bottom by the Dzus fastener. To remove the pannier, you twisted the Dzus fastener
1/4 turn, pulled the pannier away from the Dzus fastener and lifted the pannier skyward to pull it off the
L shaped hooks.
L #2709 How does one get the push/pull petrol taps to stop leaking? Got new corks to fit, do I fit
them dry, soaked in oil, or boiled in water after assembly? All methods have been suggested but which
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works.
#2710 When I installed mine I soaked them in petrol after assembly, they only leak now if the bike has
sat for a while, but they stop fairly quickly after opening.
#2711 The best idea would be to fit a better tap; not a sliding type at all. The sliding type are always a
pain in the arse.
#2716 I gave up on the old taps years ago for day to day use ! Most of my Velos have them still, in fact
I have a big jar full of dozens of the old tap's component parts, so that if it becomes necessary, I can
conjure up any of the various assemblies. But ! if you want a trouble free petrol tap, swallow your
pride & find one of the earlier rice water 'gates' fitted to trail bikes & such. They are equipped with a
small bowl filter with an 'O' ring seal, & can easily be adapted to the petrol tank outlet, & of course, you
have a reserve position as well ! I have had one on my KSS 'Special' since about 1970. While the
'loose' fitting nut is undoubtedly metric, I found that it screwed right on to the 1953 MAC tank fitting, but
I seem to recall that I may have had to use a small brass ferrule in between - maybe I was lucky ! The
worst that can happen is that you may have to sort out an adapter fitting, one thing for sure, I have
never had a leaking petrol tap since
#2717 If you are insistent on using the old style taps there is a solution I found that worked for me.
There is a grease that is used on aviation fuel valves that in insoluble in petrol A smear of this in the
valve and on the cork did the trick.
#2722 Dow Corning High Vacuum silicon grease is also insoluble in petrol and works well. It's readily
available.
#2723 cork-neoprene works for me.
L #2821 After stripping down to bare metal I am at the point where I need to decide on Powder
Coating or Stove Enamelling for my current project. Any input/advice/experience would be helpful in the
decision making process. After many discussions I am erring towards Stove - and if anyone can
recommend a decent supplier, ideally somewhere in the Greater Midlands UK, that would help too.
#2846 I would go with Powder Coating ( cos I can't paint worth a dam ) but...If you have problems
finding Stove Enameling talk to some of the specialist Bicycle ( pedal type ) builders they do some
great Stoving. Ellis Briggs in Otley ( ? ) used to do a great job but not sure about the Colonials.
#2823 Well I'm here for the stove enameling !, I tried stove enameling around 1937 for the first time,
when I worked for a Co. who painted 'Wayne' petrol pump panels, the home set up was done with a
lung powered insect spray, & the baking was done by hanging the parts in a 44 gallon drum with an
ancient electric 'Beehive' heater in the bottom of the drum. It was a grand success ! Move on to the 60's
& I was into restoring Velos, & when it came time to paint I decided to try again, but this time with
slightly better equipment. Having had a panel shop for some 8 years at one point, I had an air
compressor , paint guns & all the gear I needed, but was sick of the work & cost associated with
preparation to ensure a good finish. The fact is that most, if not all, the old motorcycle factories used
stoving on their frames & cycle parts at one point, so why not restore them that way. Advantages, I
don't use prime coats on frames or cycle parts, just get the metal smooth & clean & get a few good
coats on, & into the oven. But tanks & guards & sometimes tool boxes & things get a prime coat of Auto
3D which can be baked & rubbed down, I don't bake at the full recommended Temp. My oven goes up
a bit over boiling water temp. & I leave the parts in a bit longer, you can use a filler, I use panel beate's
'bog' but it must not be any real thickness, & you have to keep the baking temp down even lower. You
can have some bad experiences using fillers ! The paint never hardens in the spray gun, you can hang
it on a hook half empty, & come back weeks later & start painting straight off again, although I usually
spray things like brake pedals & stands on an old pot of paint, not that there is anything wrong with the
paint, but if there is the odd spit or blob from the nozzle it doesn't show. This uses up the pot, & then I
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mix a fresh pot of paint after giving the pot a bit of a swill with thinners, & spraying that through, you can
then get on with a frame or mudguards. The only time I give the gun a full clean, is when I start on a
fresh gallon of paint, which is quite often months or even more than a year ! I can hear the howls of the
purists now ! The fact is, stoving enamel is very easy to use, & is very forgiving ! The big plus is, that
after time in the oven, in my case an old converted vertical convection clothes dryer, the parts can be
taken out, & as soon as cool enough to handle, you can start assembling things. Any dryer has to have
the fan removed, otherwise everything is covered in dust particles & I have insulated my dryer with
insulating 'batts' & a second outer sheet metal skin. If the dryer has open strung elements, removing
the fan allows the heat to concentrate, & the elements will sag & touch, so the element box has to be
enlarged, with the length of the sides at least doubled, with a few necessary alterations. There is of
course more, but as far as I am concerned, auto enamels are for the birds, & I have never even
considered messing about with 2 PAK. & I have seen some disasters with powder coat further down the
track. From one who has been doing it regularly for 40 years, & will be painting the GS wheel hubs
,rims & spokes tomorrow ! - just a light coat to make sure that all is covered, then assembly of the
spokes, true the wheel, then several good light final coats.
L #2827 I'd like to refinish the chipped and aged paint on a cast iron engine barrel. I'd considered
the old fashioned way, but I understand HMS Mayflower no longer has a spring sailing from Plymouth,
in the new world, home to England. What more modern methods are available in the colonies?
#2843 I had mine bead blasted and stove enameled 2 years ago and all it takes is a quick wipe to
remove the oil and it looks as good as new. It was suggested that it might not allow it to cool properly
but I have had no problems.
#2852 I sandblasted and used an aerosol of heat resisting paint on the KSS. I stuffed paper into the
bore each end as a precaution when blasting. Can't say how good it is as engine not run yet. It is
Sperex VHT and claims to protect up to 700C. Instruction say cure at 121C for 15 min then at 315C for
1 hour . I cooked in the fan oven at 150 for an hour and reckon any further curing can be in service.
The finish is a matt black which should help heat transfer. The product is sold by Simoniz in UK and is
a trademark of PJH brands of USA. Mike
#2855 What hasn't been mentioned so far is that when Veloce started using cast iron barrels (initially
on the VR/VM Clubmans) they, rather sneakily, painted them silver. Was it to disguise the fact that the
barrels were no longer "Alfin" - who knows? Anyway, my 1959 VM has always had a silver painted
barrel so when the time came for a rebore I used that Sperex VHT aerosol stuff but in silver.
Surprisingly it reached right to the roots of the finning. Not having a low-bake oven I "baked" it whilst
running in. Then I got carried away and sprayed the blue/rust exhaust pipes on my Harris "Matchless"
G80. These glow red hot when the engine is running at a fast tickover if the bike is not moving. Only the
two inches nearest the exhaust port has peeled in over 3 months winter use.
L #2849 Among other pieces I was about to send off my forks to the painter/powder coater. I
didn't know about temperatures used in powder coating, or for that matter, in stoving: so, apart from
scraping off some of the expensively applied coat after getting them back, what's the answer please?
#2851 Powder coating temps will weaken or melt the solder on forks. Otherwise it is fine to use
elsewhere and I have found that the quality of finish has dramatically improved over the years.
#2853 Powder coating is also a good way to keep it looking good and shiny as well as being tough. I
did mine, but of course you must block the holes with tin can lids and a long bolt. Don’t worry about
threads as they tap out very nicely. Powder coating is efficient as it goes in to all the little places and
the part can be installed straight-away.
L #2856 The full width hubs on my 65 viper were painted black {dulux} and the front hub has 6 no.
1 inch go faster holes drilled. I know the drum has to be painted but what about the rest? do I paint like
the drum or do I polish like the engine any ideas or suggestion greatly received
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#2857 Paint the iron brake drum section and clean/polish the alloy bit - just like Veloce did! The iron bit
was a thin aluminum type paint; no thick stoving please.
#2891 I asked Ian Barnard (he of the "Best in Show" VM at Stanford Hall) about full-width front hubs
and his reply was: "I understand that Velocette originally electroplated the drum (so say Seymour's)??
Mortimers (Blunham, Beds.) have a paint called Astra Silver that is the closest I could get, I did try 2
others that were crap. I think it is stove enamel. Thin silver aluminum paint will peel off in less than a
year. The choice is yours, it ain't exactly in a place that is easy to re-do and I'd rather have something a
bit thicker if it stays on!" Now, if Veloce plated the iron part of the hub it would almost certainly have
been with cadmium. Here in the UK cadmium plating is only permitted for museum display use,
apparently. Unpolished cad plating is best matched to vapour blasted unpolished alloy. The problem is
keeping it looking as good as it does when first assembled. Recognizing that the alloy would require the
occasional buff with Autosol, or whatever, Ian chose the pre-polished route - hence the choice of the
Astra Silver enamel. We do not know if this is a Vauxhall colour or not. Mortimer's number is
01767-640551.
#2892 We understand that the Brake-side of the full-width hub was Cadmium plated. Cadmium is a
poison and is now frowned on. Dull chrome is the next best. Just ensure the plater "masks" the brake
face and bearing housings.
#2895 I have checked the original factory specifications - it wasn't plated, the finish was described as
"aluminum enamel". A clue if not the total answer.
#2906 Could I lacquer my ally hubs to protect the finish after having them bead blasted or suggestions
on other options
#2943 I have had them bead blasted already and a couple of people have suggested having them twin
packed ally colour ?? I have polished the brake plates to a nice shiny finish but I don’t know what the
hubs looked like when they were new as im way to young!!!! so any more advice gratefully accepted
#2945 I assume you have the composite full width hubs. The left hand side aluminum, the right hand
side brake drum cast iron. If so the left hand side is polished, leaving the radial ribbed area as cast. The
right hand side is silver enamel or twin pack.
#2946 Polish the outside of the alloy (left) half, paint the iron (right) side with a flat (matte) silver.
Assemble the two halves, and paint the entire ribbed center again. This hides the fact that they are
dissimilar metals. Twin pack is good, it sticks better. But I have used plain brushing enamel with good
results. A rust-resistant primer is a good idea on the iron. Apply very thin coats. If you don't stir the
enamel and decant some of the solvent off, it will look more like as-cast alloy.
#2953 Dull chrome makes them look alike.
#2947 You can leave the rear (all alloy) hub as-is. It will soon be covered in oil anyway! The one on my
Venom was never polished. But you can polish the thin alloy cover that goes over the wheel nuts.
L #2902 can someone tell me what finish should be on the oil pipes up to the rocker box as mine
have been polished down to the copper is it just silver paint?
#2904 Bright chrome.
#2905 I've had several unmolested engines, all of which had the feed pipe plated with cadmium and the
drain pipe to the pushrod tube plated with bright chrome.
#2908 The rocker feed, ball valves feed and return elbows are all described in the factory specifications
as being "dull chrome" I have unsuccessfully searched for a plater that can "dull chrome" for many
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years.
#2910 I think that you are right about the feed pipe, as mine are not discolored as I would expect
cadmium to be, but the drain pipes are definitely bright chrome on all my engines, which are US
imports.
#2917 I might be inclined to disagree here. On my machine the rocker box drain pipe is bright chrome,
but the feed pipe is satin chrome. I believe this is the original finish. The machine is a Venom which
was first registered in '62 but left the factory in '60.
L #3497 Anybody know the thread size for the screws, that attach the round velo tank badge to
petrol tank?
#3537 According to my measurements it is 5BA.
L #3708 Has anybody purchased a seat from R.K.Leighton, I need a new one for my MAC (1955).
I saw one sold on Ebay for £123.00 recently and from the photo's it was difficult to tell the actual quality.
Leightons have quoted £106.00 inc vat for one including the shipping. which by comparison seems
quite reasonable. I’d just like some idea of the quality.
#3710 I have a Leightons seat on my 1954 MAC (although I decided not to go for the split level
version). Quality is good. They are well made. Mine has been on there three years now and still looks
good. The brackets did need a little adjustment though.
#3720 You say you didn't go with the split level seat on your MAC, which one did you use, as for the
brackets do they come with the seat when supplied by Leightons. The ones on my MAC are a home
made affair and are not good....being 6` 1`` a split level seat is not good as I seem to be half on the
tank and half off it not good when braking.
#3712 I have bought from them on several occasions and always had good service. They used to make
the seats for Veloce originally.
#3721 Presuming we're talking about RS frames, there are three sets of seat fixations. First is 3.5
gallon tank on 3.5 gallon frame, second is 3.5 gallon tank on a 4.25 gallon frame (about 1960) and third
was 4.25 gallon tank on 4.25 gallon frame. The rear fitting stays about the same, but the front one
changes position.
#3722 Mine is the 3.5 gallon tank on the 3.5 gallon frame the front lug is above the down tube. It’s a
standard 1955 spinger MAC....I'm not fully versed in the velo jargon so not Sure what a RS frame is
forgive my ignorance.
#3723 RS frames are the rear sprung push rod engined items. i.e. MAC, MSS, VR, VM, VMT but not
KTT.
#4416 I noted a subscriber asking about new Velo seats some time ago. I'm not aware of whether he
found what he was looking for, but I recently ordered a new seat cover from R.K.Leighton, Birmingham
0121 333 3130 www.rk-leighton.co.uk and have been delighted with the very high quality and perfect
fit. The firm also supplies new Velo seats complete.
L #3887 Is there a way to remove the tool box knob/spring/washer//male threads from the tool box
cover? Also, the cover has been chrome plated....did some bikes come that way or is this a 'custom'
addition?
#3888 The stud is a tight press fit in the chromed knob. It is normally supplied already assembled to
the toolbox lid and is not meant to be dissembled, but it is possible with care and a suitable press. I
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don't think any models left the factory with chromium plated tool boxes, but they may well have been
supplied like that through USA dealers, who will have had them plated locally. It could of course be an
owner modification.
#3891 It is not generally known that the washer that prevents the knob from falling out of the lid, did in
fact originally have a threaded internal diameter that matches the thread on the screw, or did have
once !!! original assembly was easy, the washer was just screwed on, until it fell on to the 'waisted'
diameter of the screw against the knob, when a sharp tap on the end of the screw easily burred the
start/end of the thread on the washer, (or screw), it was then virtually impossible for the threaded
washer to accidentally pick up the start of the thread & unscrew & fall off when the box was opened . I
realize that all this happened long ago, & I have come across knobs with a small hole drilled through
the screw & a split pin inserted, as well as other cute mods. The fact is that it took many miles of the
washer rattling around on the waisted screw, before it finally wore the hole in the washer large enough
so that the washer fell off the thread at a time when the box was opened. I have made dozens of 'D'
boxes, exactly to the original design & use this method still. In your case, the chrome lid is of course a
'happy' mod. & the knob can be removed by the careful use of a hand held 4 inch grinder , but a simpler
way where damage to paint etc. isn't a problem, is the judicious use of an oxy cutting torch to easily
slice the side off the washer & enables it to be removed, then a new washer, (I use a rather thicker one
) can be threaded & used when you are ready to reassemble, after what one would assume to be the
removal (?) of the chrome, & a new paint job !
#3893 I appreciate the detail. This knob has a fancy flat spiral compression spring behind it that I think
did its job and prevented the assembly from vibration damage...or the box wasn't on a bike long -
#3911 There's no reason why you cannot do as suggested, but I think it is wrong about the original
washer being threaded. It is listed as a standard plain washer SL6/32. For initial assembly, this plain
washer is first placed on the plain end of the stud KA253, which is then inserted through the toolbox lid.
Then the Thackeray washer SL57/21 (we have them in stock, by the way) is slipped on the outside of
the lid, and finally the knob KA251 is pressed on.
#3894 I have to admit that I forgot about the spring washer, but it, like lots of other bits have gone
missing in a lot of cases over the years, & I don't include one in my 'boxes' (where would you buy one
anyway ?). The washer is in fact what is known as a 'thackray' (?) washer, quite common in early
Velo's, (& other bikes) as an anti- vibration device, the hand gear lever pivots was a common spot.
L #4356 Any suggestions about how to stop rear mudguard stays breaking on a Venom? The
RHS one has broken just behind the middle fixing (by the suspension). I've had this before and bought
new ones but this time I've brazed it together, repainted and refitted it. This time I've put rubber
washers on all the fixings. Any other ideas? (Other than revving less!)
#4357 Does the venom have tubular stays?, I broke one on my mac last year and fixed it by turning
down some tubing to an interference fit with the stay and putting the two pieces together, then tig
welding the break, then wrapping a piece of med gauge sheet metal around that and tiging up the seam
and ends, then sanding down and filling etc, then paint. the repair is barely noticeable ( small bulge in
the stay ) and has held up fine for several months. this is on a rigid frame mac.
#4358 Does your Venom have the centre stay fitted? i.e. the one over the top of the mudguard - part
number MAS60. Without this the whole plot will flex unduly causing premature fracture of the rear
stays.
#4359 I am surprised to note the breaking of the stay on a rigid MAC, the rigid framed models were not
prone to breakage in my experience. However noting the repair method used, - internal tubing, - outer
sleeve etc. Experience in my earlier years soon learned me that the moment you start welding broken
tubular stays, (& a lot of other things for that matter,) using any form of welding etc. the basic strength
of the parent metal is impaired to the point where eventually it may certainly break again close to the
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original break, usually at the point where the internal insert, or the outer sleeve, (whichever is the
furthest from the weld) ends. I have to add that this does not necessarily apply in the case of a well
done frame tube repair, simply because the frame is a normally rigid non flexing assy. whereas fender
stays do come in for a certain amount of fatigue strain. The rigid M series stays were pretty much bullet
proof, only breaking from accidental damage to the major assemblies, or bending & rebending
damaged areas over the years. I have made dozens of new stays to replace lost ones in basket cases,
& it isn't difficult to make new stays to replace the broken ones. Modern steel tubing is easy to obtain in
16 gauge wall which seems adequate, & any bending required of this tubing is easily accomplished
cold by pulling around a convenient curved surface, in fact in my younger days a lot of this forming was
done by simply pulling the tubing around my knee ! (maybe that contributed to their failure !) Do not use
heat for this type of small tubing ! Over the years I have turned up forming 'spools' for small Dia. tubing,
& these are just used in the bench vise, & the tubing pulled around by hand with a larger neat fitting
piece of straight tube over the part being pulled & kept in as close to the spool as possible, & being
moved away as bending progresses. The flattened ends are easily done, most Velo. 'flats' being just
that ! but if you want to do the professional looking rounded edge of the 'flat' This can be done by using
the back of the 'jaw' in an open ended spanner of 5/8th inch minimum width, although some years ago
when I progressed from a heavy duty bench vise to a hydraulic press, I took the trouble to make up a
simple die plates to press these ends on smaller tubes. These dies had nicely rounded edges on the
working surfaces, rather than the sharp edge of spanner jaws. While on the subject, I have a 100 % (?)
cure for the spring frame front guard mount breakages, & also for those rear guards with 'valances' that
fracture at the top as a result of those pesky tailpiece flutters at low RPM, (like sitting waiting for the
lights to change ).
#4373 The first thing obviously is to get some more strength into the bottom of the vertical stay, the 2
bolt holes in the original stay really pushing the boundaries. I have heard of a more substantial piece of
steel being welded to the bottom of the broken stay, but I always have serious doubts about welds in
those circumstances, so I use a piece of machine steel, key steel or similar, a little thicker & a little
wider, it doesn't take much, admitted it's a pig of a job to get the bend right, up at the top of the loop in
the heavier & tougher material, so that the pristine fender surface isn't damaged, but it can be done, I
spent a lot of time linishing the contour on the top surface to match the fender, although I have since
considered using this part of the old stay & locating 2 good welds just below the edge of the guard to
two new separate bits as described above. There is little if any stress at this point. The rebuild on my
bike took place after an idiot (on his way to church !) had driven through a stop sign & done a 'U' turn
across my bows ! so the original guard, & already broken & repaired stays were well beyond repair, (&
the 19 inch rim & spokes also !) The fork tubes & clamps straightened OK. I was already considering
going to a 21 inch tire up front, I was riding it solo in those days, so that's what I did, & with the idea of
lowering weight & stress on the vertical stay, I replaced the front guard with a sportier looking narrower
steel item from ' Wassell' of the UK. - (are they still in business ?, if not Armours ?) I soon found that
there was a lack of real space at full fork compression, so the guard was put right down on to the tire.
At this point I decided that I may as well go all lightweight, so the lower rear stay was bent from 3/8 inch
OD 16 gauge tubing right around the rear of the fender, with 2 small lugs & two 1/4 inch bolts.
Attachment to the fork lug at the lower bolt, - I think I had to fiddle the tubing here to get enough 'meat'
to go around the bolt. The front stay is formed in one piece, from 3/8 x1/8th. flat secured to the inside
front of the guard by two 3/16 th. bolts. It is SMALL ! I had to forge the end of the flat a little, to get it out
to take a 1/4 inch HT bolt safely at the fork attachment. There are NO gussets anywhere ! The
unfortunate fact is that the entire forces of the guard trying to move back & forth is taken by the single
vertical stay, & the 2 bolts. The rear & top front stay, just going along for the ride taking no real radial
movement strain. If you have a Velo with the 'valanced' rear fender, it will almost certainly have
fractured the side valance pieces from 'tail piece shudder'. I started off by inserting wires in the edges,
& doing a 'perfect' repair job, but it soon broke again, so a bit of observation with the motor idling
showed that the problem was one of the valances flexing in & out sideways, - stop that & it should be
OK ! I never even repaired the fractured valances ! I bent up 2 short lengths of substantial section, ( 1
1/4 x 3/16th inch as I recall) flat steel that anchored on the inside of the top shocker bolt, & laid
perfectly flat down the outsides of the valances, this involves a bit of time & effort to get it perfect, but
once done, drill a 1/4 inch hole through the valance to correspond with a hole in the lower part of the
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strap, a LARGE diameter flat washer on the inside of the guard, & despite the fact that the split is still in
the valance, but almost impossible to see as the strap covers it on the outside & the large flat washer
on the inside. The fender has never shaken since, & nothing has ever broken.
#4360 No I don't have the centre stay MAS60 fitted. My rear mudguard assembly isn't like the one
shown in illustration H on Page 37 of my parts book. This illustration shows the centre stay but shows a
two piece mudguard with stays parts 56 and 57 which fasten at one end to the frame and the other to
the mudguard. My rear mudguard is one-piece with long curved stays which bolt at the front end to the
frame just in front of the suspension units and again at the rear of the suspension units before curving
down and attaching near the back of the mudguard. A difficult thing to describe but if you look at Steve
Bland's bike in members machines on the owners club site
www.velocetteowners.com/membersmachines/blandsteve/blandsteve.htm you'll see what my stays are
like.
#4361 You need MAS60. If not, the mudguard will bounce up & down and then - the stays break! In the
photos of Steve Bland's machine this bridging stay is hidden by the seat - its there though I'm sure.
L #4635 The front tank mounts on mine consist of a rubber bushing with a tube through that has a
thick-washer type end on the outside (all one piece). Is this correct? Does the rear frame rubber fit
between the u shaped area at the rear of the tank? Does it need to be trimmed?
#4636 The front tank mounts are the same for all 'RS' frames from '53-'71, a moulded rubber grommet
flanged on the inside to prevent the steel tank from making contact with the frame. The mounting bolt is
a shouldered 3/8 Whitworth which can be screwed into the female threads in the frame only until the
shoulder makes contact with the frame, so that it does not crush the rubber grommet. The bolts and
grommets are also the same for all RS frames. My VMT had a molded rubber block to support the rear
of the tank, which dropped onto and was supported by the block without any effort. If yours has the GP
carbie, you may want to have the back of the tank free so that you can raise it in order to tickle the float
chamber, pivoting it around the front mounting bolts.
#4637 The front mounts appear correct and the answer to the rear mount is yes it is correct and no it
doesn't need. Further to my reply, I should amend that to read that particular front mount is correct for
use with a fairing.
#4639 Who knows the part number of the U shape rear rubber block ? My VM has a Thruxton tank, but
I don't have the VMT spares list.
#4646 Regarding the tank front mounting, you will need to remove the fairing bush and fit the normal
shouldered bolt and washer as described by Frank in his reply. Otherwise use an ordinary bolt through
the fairing bush, but it will look much better with the shouldered bolt set up. Yes, I also glued the rear
rubber to the frame and the tank rubber may need shaving down slightly to fit within the saddle at the
rear of the tank. I have never seen a supplement showing the tank mount/fittings.
#4648 I have a parts list of Aug 1971 It gives the Petrol tank fixing bolt buffer FK151/4 for Venoms,
Vipers and variants etc 2 off and for the Mk2 Clubman and Thruxton Petrol tank rubber A353 one off.
When I had my 3 ½ gal tank modified for a KSS engine in RS frame the distance between the rear ears
increased, so to avoid stress on the tank I have fitted a rubber washer here.
L # 4966 I know this has been discussed before but what should I use to paint/spray the front
cast iron side of the front drum with? I would prefer to spray with an off the shelf aerosol if one can be
recommended.
# 5037 The process I have used on more than one bike including my Venom with the alloy/cast iron full
width front hub is to use aluminium paint as a primer. This adheres really well to both the alloy and iron
if thoroughly degreased. I then use silver Smooth Hamerite paint either as an aerosol spray or hand
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painted which I found equally good. This gives an excellent finish. If just silver paint is used it will
yellow. I have not found that Hammerite paint blisters, but maybe my front brake isn't as fearsome as
some demon riders out there !
L # 5077 Are there any compatibility problems associated with water transfers and modern
2-part poly razamataz paints?
# 5131 I've used both varnish and waterslides under two pack with no problems. However, I suggest
you test one on a piece of scrap material first.
L # 5104 I have just split a new petrol tap cork while trying to fit it, before I ruin anymore can
anybody give advice please?
# 5109 Try soaking the corks in boiling water before fitting.
# 5117 I tried everything to get my corks to seal i.e. boil in water, soak in petrol, soak in oil etc. etc.
nothing worked they always leaked so I fitted 2 1/4 turn Triumph taps.(bit of a debate on this site
approx 12 months ago on the subject)
# 5128 I have had exceptional luck with Dow Corning silicon grease. It is not soluble in petroleum
derivatives.
L # 5240 I am restoring a MDD (#12156), and now I am about to put things back together the
problem is which colour it should be. I have read a lot about the colour in all kind of books, one says it
should be khaki another say green or bronze shade brown. This is very confusing because I never saw
a original one, and what do they mean with khaki. Who can help me with this problem, I would like to
get it as original as possible.
# 5242 I owned a couple of WWII bikes until a couple of months ago, an M20 BSA, 16H Norton and a
Royal Enfield WD/CO. There is no specific colour for wartime bikes as the vast majority were painted a
dull Khaki green colour. Bikes in Africa were yellow and Some Northern European bikes were Earth
Brown. Usually all the available paint was mixed up and thrown over the bike, saddle, engine etc but I
wouldn't suggest you go that far. All the nuts bolts and handlebar controls were originally a dull
cadmium finish but ended up painted as well (no chrome anywhere), Only post war vehicles had any
sort of shiny finish. Bronze/green is a post war colour but it is quite acceptable as it is almost
impossible to get Khaki Green unless you can get it mixed.
# 5249 I have just finished putting together a BSA M20, and one of the military BSA experts suggested
I use Dark Olive Drab Matt paint, available from Jeep Parts UK, Phone 0870-240-4691 FAX
01948-840847. It seems to be a good match for the few original items I have and is pretty tough. It is
probably sprayable only.
# 5280 I have a MDD generator cover with original colour on the back. It is a lot lighter than olive drab
and also may be a satin sheen rather than a flat matt as on most military bikes!. If can get a colour
match I will let you know The rear mudguard you had from me was original and may have the correct
paint under the black!
L # 5338 Having just been quoted £400 plus(!) to have a 4.25 gallon tank cut open, blasted,
seriously patched and welded back together I wanted to know what my chances were of obtaining a
second hand one is decent condition? It is from a 1961 Venom Clubman (with the aluminium bands
and plastic badges) that was stored for far too long in my Dad's cellar..... If anyone knows where I might
find one that would be fantastic, otherwise I guess it's Fishtail, then VMCC then Old Bike Mart?
# 5341 If you do find one to buy it may cost you more than getting yours repaired. I think Mike at Grove
Classics may have some new ones.
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L # 5492 I am starting a Venom/Viper based project and have a 1960 frame (with the down tube
welded to the bottom cross member). What interests me is just how accurately aligned or straight
should I expect this frame to be. What has prompted this query is that I have been offering up a pair of
rear set footrest plates that have a 5.875" fixing hole spacing to match the nominal distance between
the centres of the swinging arm trunnion and the bottom centre stand mounting lugs. Having
deliberately not incorporated significant clearance for adjustment, the offside (right) plate fitted neatly
but the nearside (left) one did not line up. Measuring the actual distances between centres on the frame
showed 5.9" (right)and 6.0" (left). As a result I have attempted some basic alignment checks, with the
frame upside down using an machinists spirit level and plumb lines, that show for example that the
bottom rails when set level across adjacent to centrestand lugs are up to 1/16" out crossways adjacent
to the front down tube lug. There is no sign of accident damage on the frame so I am coming to the
view is this level of innaccuracy is probably typical i.e. within tolerance. Is this view correct? Your
thoughts and advice on this and how best to carry out checks would be appreciated.
# 5493 I suspect that frame building was not always as accurate as we might imagine. The front
engine plates on Mk VIII KTTs are drilled to suite each frame; they cannot be swapped over as the
bolts will not pass through. These frames are more of a blacksmith's job than might be expected.
# 5516 I'm sure you are right. Perhaps as long as the swinging arm trunnion bearing is perpendicular
to the headstock bearing, what happens in between, as long as it looks in line, is of no great concern.
L # 5536 can anyone send me info on the toolbox/rear stay fitting. I have a 1936 MAC with a
repro rear stay FK58/25AS supplied with no fixing studs for the mudguard or chainguard. The problem
is: I don`t have a toolbox (yet), I`ve established the position and made/welded on studs for the
mudguard, chainguard. The parts book shows a fourth stud on the toolbox side. Question any info on
location of this stud, is it for the toolbox, how long, what thread.
# 5545 All studs would originally have been 26 TPI, but question as to if you do in fact have the correct
repro. vertical stay. ? If you did , the toolbox mounting would be obvious , as the right hand side stay is
flattened, & 'kinked' forwards to give a vertical, forward facing flat area with 2 holes drilled in it, to which
the rear face of the toolbox mounts with two 1/4 inch bolts. ( I would venture to suggest that the stay is
incorrect ?) Toolbox mounts to the front underside seat stay tube with clamp. Also you mention welding
studs to the stay , - an original type stay would have all studs already welded into place, - 2 to take the
mudguard mounting strap, ( correct position & length is critical), & one for the rear chainguard mount. I
have one repro 'D' type toolbox left in stock, ( complete with all fittings),& have no plans to make any
more.
# 5548 The stay you refer to is the later type FK58/42AS which me previous MAC had. The bike I have
now is earlier according to the parts manual both descriptively and graphically does not have a
flattened section to accommodate the toolbox.
L # 5543 When replacing the split beading around the headlamp cowl (viper) I assume it should
be fixed in place with adhesive, if so what adhesive should I use.\
# 5544 No glue; the beading just clips on.
L # 5566 I know that this is a recurring theme - but can anybody recommend from experience, a
high quality electroplater anywhere in the UK that could do a nice job chroming a restored (but not
chromed) Venom Tank? I don't mind where I send it as long as the results are worth it.
#5567 Cleveland Chroming Co., Ltd (Middlesbrough) TEL 01 642 244 911
# 5574 Try Marque Restore, Unit 4 Shilton Industrial Estate Shilton, Coventry Tel 02 476 622 225. I
have just started using them after seeing the resoration work they did on a badly damaged Gold Star
Tank. The tank was badly dented by the clip on and now looks better than new. I am restoring a Honda
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500/4 for a customer and found it impossible to buy a new front chromed guard or even a used one
wilthout rot. I gave it to them with holes in palce where the water is trapped and got it back weeekend
again good as new, well better the chome looks thick and deep, far better thatn my present chrome
platers which are local to me. They are not the cheapest but I thoroughly recommend them.
L # 5606 '54 MSS, illustration H, part identification 31, part number KA303 "Rear mudguard
extension bolt" is the total explanation. Groves only lists it as "bolt" with a price of 2.25 Pounds each!
The thread is 1/4" BSF and I'm guessing the length to be 1/4". Is there something special about this bolt
that warrants such a high price?
# 5608 Ref rear mudguard bolt for the MSS. They were originally stainless and had a semi-domed
head. Stainless, because when you needed them undone it was usually for a puncture and we all know
that punctures only happen in the pouring rain, miles from anywhere and in total darkness. Therefore
you could tell by feel which bolts to undo to enable the rear section of the mudguard to hinge up and
knowing they would undo and not seize or shear.
L # 5614 I know there has been discussion in the past on how to reproduce the satin/pearl
original chrome finish that Velocette used. I have never seen a definitive answer so I posted the
question on finishing.com and this is the response I got. (See question 34723) This seems to make
sense and in order to reproduce the satin finish with today technology there needs to be a way to "dull
down" the nickel plate before applying the chrome. I was wondering if anyone has tried this? John
=============================================================
Modern chrome plating is bright and reflective because the underlying nickel is bright and reflective. In
1937 the processes for producing bright nickel were pretty much in infancy, so much nickel was plated
in the unbrightened condition, and then chrome plated, or it was buffed bright and then chrome plated.
I'm guessing here, but from what I know of the history of the British plating industry and British bikes, I
will hazard the guess that the original nickel plated was deposited in the dull or, at best, semi-bright
condition and then chrome plated, giving a "satin" finish. Plating for a smallish manufacturer like
Velocette was basically a cottage industry (they may have done their own), and was not very
sophisticated. What they lacked in reflective brightness they made up for in thickness so some of this
old plating has proven very durable. No plating is done by those seventy year old methods today, but a
plating shop which specializes in restoration plating can probably duplicate in appearance what you
have if you have at least one piece in good enough condition for them to see what needs to be done.
Look in Hemmings Motor News for such platers. Good luck restoring your Velo. As they say, we need
to save every one of them as there will never be any more.
#5616 I recently had to have my kick start lever replated after it sustained some road rash. I sanded out
the worst of the rash and presented it to one of our local platers, Queen City Platers in Mukilteo, WA.
They finished taking out the rash as well as shaping it, and rechromed it with satin chrome. It is good
enough that I don't believe most people will know it is not original. Frog
#5618 My front hub, brake side, is "dull" chromed by Cleveland Chroming as a substitute to Cadmium.
L #5699 I needs some help please. My VMT had a ding in the side of the tank that exactly
matched the backside of my thumb and twistgrip. I took some digital photos of the lining (aka
pinstriping) before I had the tank repainted, but had a booboo with the photos. Would someone who
has a VMT with original hall Green lining still intact please do me a favor. I'd like to get a measurement
of the width
of the lining, and a top and side photos of the tank to show the man who will do the relining. Those
who've had a tank repainted/lined, do you add some sort of paint or urethane over the lining and
decals?
# 5706 hello there, if you live in England, you could go to FD motorcycles near Stanford airport. they
relined my tank in gold and also painted Velocette on the tank. I gave Them a Thruxton tank that was
genuine factory paint and he recopied it faithfully. I think he will have templates of the lining and the
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position of the
# 5725 My tank painter here in Llincoln lined my tank in gold paint using the masking method. He
actually mixed the gold to match the tranfers I provided him with. One tip I would give is to make sure
the painter knows exactly what you want. I provided a dimensional drawing taken from the Thruxton in
the Museum and also photos and the BMS book as a guide. He decided to use a combination of all
three as his guide and the transfers had to be removed as they were wrongly positioned. It now looks
absolutely first class with its lacquered final coats. He said there were approximately 14 coats of paint
on it finally.
# 5720 I bought a beautifully manufactured pin-striping roller from Beugler, a Los Angeles based
company. It produces miles of perfect stripes (once you get the knack) and works well on petrol tanks
too. Take a look at www.beugler.com
# 5752 Actually, applying gold leaf is pretty simple for the DIY's out there. I use it all the time in my
work, but on much larger surfaces like building details and furniture. Directions as follows - Source your
gold leaf pack (buy what's called 'patent' gold leaf - its stuck to the paper backing instead of loose and
flying around...it should be about $40/pack - that's twenty 3" square sheets) at the local art supply store
or signwriters store or wherever, and buy a good quick-drying OIL-BASED gold size (don't use the latex
size as this never dries and your gold will rub off easily). Lay out your pinstripe line as mentioned in a
previous post, masking with pinstripe tape or other usefully bendy tape. It definitely helps if, like Hall
Green, you use a yellow paint undercoat on your pinstripe, as your leaf may have small cracks when
you apply it, and the undercoat helps this disappear. Make sure your yellow line is completely dry. Paint
on your gold size over the pinstripe, and let it dry to a hard tacky surface; you now have about an hour
to work with it, depending on the weather, so don't go have lunch! With the patent gold leaf, you simply
press the paper backing with the gold onto your tacky surface, and it will stick as long as that gold size
is on your tank. Follow your line around, using up your individual sheets of gold piece by piece; you'll
waste some, but that's inevitable, and is an interesting metaphor for life anyway. Fill in any gaps or
cracks with the smaller pieces of leftover gold on your sheets, which should be fairly obvious, and make
sure you press your gold carefully into the edges of the stripe where it meets the tape. You'll want to
burnish the gold when you're done - traditionally used is a highly polished little nubbin of onyx, but
anything very smooth will work. Be more gentle than you were when you fell in love with your wife. All
that's left now is to remove your masking tape, which should leave you a perfect surface. The 'old
school' method of protecting your gold is to va rnish a line over the top, a little fatter than the pinstripe.
It’s a better job to simply clearcoat the whole tank though, as the clearcoat tends to last a lot longer
than any varnish available today, especially when in contact with gasoline.
L # 5788 My Viper tank is for the moment free of leaks, with the help of some brazing and
pressure testing but, despite cleaning, there is an ongoing problem with rust particles - fine enough to
pass through the tap and carb filters and show up in the float chamber. The next stage, unless others
know better, is to use a tank sealer such as Petseal. I'm concerned, however, that this is a one way
process that may compromise any future repairs. In the OBM there is an advert for flexible aircraft tank
sealant that the suppliers claim is removable. Has anyone got experience of using this. Would
appreciate any advice on best approach to dealing with an internally rusty tank.
# 5789 Richard I used a cleaner/sealer sold at Yamaha dealers (previously recommended on this
board). It works really well and is not a coating. It somehow changes the metal surface so it does not
rust. I wouldn't consider anything else now, since to problem of dealing with a flaking sealer 10 or 15
years from now is going to be worse then the original rust
# 5798 I found the Yamaha tank rust remover sealer as recommended on this site some time ago, very
good. make sure when you order it, the kit consists of 2 x 500ml bottles one being the neutralizer also
make sure that you top the tank right up to the top with water so it treats the roof of the tank I have
heard bad reports about the epoxy type tank sealants that they are affected by unleaded petrol over a
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period of time
# 5799 Have contacted two main Yamaha dealers, both deny knowing anything about this stuff and
both mentioned Petseal!. Can someone please tell me its actual name and or direct me to the relevant
message numbers on our group site.
# 5806 The Yamaha part number was posted on the site but it was about 18 months ago but the search
engine on this new site only goes back a couple of months. I know that our local dealer could not find it
on their computer until I supplied the part number and then only the sealant arrived they then had to
chase up Yamaha UK for the neutralizer so I am afraid I can not help anymore
# 5796 Richard, I've had good results using POR-15 from The Complete Automobilist
www.completeautomobilist.co.uk/online/item529.htm Easy to apply and stays flexible unlike Petseal
which is brittle when set. Not sure if its removable though.
# 5802 Try Clive Repik, he advertises in Fishtail and has long experience of the aircraft tank sealer
that you mentioned. I have a similar problem with a Kawasaki GPZ250 tank (not mine, I hasten to add).
How can a tank rust so badly when left standing for 5 years but nearly full of petrol and with the filler
cap tightly closed? Advice from a Woburn Chapter member is to pour in a pound of sharp tin tacks with
a couple of pints of paraffin or diesel and dance the Samba for about 48 hours whilst holding the tank
above my head! Any tacks that won't submit to the eventual extraction process can simply stay in there
doing no harm. If even that fails, I shall resort to the caustic soda tank and electrolysis as per the "On
The LEVel" article of a few years ago; the process does not lift off the exterior paint finish as long as
there is no rust under it.
# 5810 . Following is my personal experience. No responsibility accepted. I use a handful or so of
washing soda in a plastic bucket and a 12 volt car battery charger and strips or bars of stainless steel
connected in parallel for the anode, disposed around the object to be treated, depending upon its size,
shape. Some people prefer mild steel or reo (concrete reinforcing rod) in preference to stainless, but I
find difficulty in achieving sufficient current - needs several amps. Particularly note the polarity. Do not
use to clean aluminum, copper, brass etc as they will be rapidly eroded away - only for iron & steel.
Paint is removed. The current can be regulated to within the battery charger's capacity by adjusting the
proximity of the anode and/or more or less washing soda. Current will usually increase as the
electrolyte warms up. Time required will vary from 1/2 hour upwards to days. Some people use caustic
soda (lye) but this is nasty stuff. Washing (or baking) soda is much safer. Hydrogen is produced -
ventilate, no ignition source.
# 5805 If you live in the US, the Eastwood Company, which sells professional body shop supplies,
sells a small gas tank ruster remover\sealer kit for about $39.00 and it works great. Look up their
telephone number on their web site www.eastwoodco.com/
# 5811 Have contacted my nearest Yamaha dealer again, who, with the part number you provided,
now recognizes this item as 'fuel tank conditioner'. Hopefully they will call me back to confirm when they
can get some.
# 5813 From personal experience I can report that the Yamaha kit will remove and prevent rust nicely.
I have tried sealants from two sources, one commonly available at bike shops and the other from an
aircraft parts supplier, and they WILL flake off and get into your filter(s) eventually. The latter sealant
was advertised as alcohol resistant. That said, the sealants are useful for fixing small leaks, which the
rust treatment will not help. The last time I bought the Yam kit it cost less than US$20.
# 5816 Richard I used this flexible aircraft fuel tank sealer a year ago and it worked as described. It
was simple to apply and the instructions stated it was also easy to remove if repairs were necessary in
the future. I bought it from a firm advertising in one of the classic bike mags by the name of "Merlin"
something or other.
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# 6011 Here is the part reference for the Yamaha fuel tank conditioner kit ACC-FUELT-CD-KT. After
first denying all knowledge of it, my nearest Yamaha dealer finally ordered it. On collection today all
they had obtained was the one bottle of fuel tank rust remover clearly showing this part number. I have
explained that it is a two part kit and of course the instructions on the one bottle make it clear that a
bottle of neutralizer is essential. Is there another part reference for the neutralizer or has the Yamaha
parts system failed. Of course it should be up to the dealer to sort this out but they seem to want their
hands holding and I need the rest of the kit.
# 6016 I went down to my local Yamaha dealer in search of the product in question. They actually had
it on the shelf. It is two separate bottles that are shrink wrapped together. The stuff works pretty well.
Just be sure to use them in the correct order as the bottles are the same size. I think it would be easy
to mistakenly mix the conditioner with water thinking it was the acid remover and vice versa.
# 6017 Having never had my hands on this product this is only an educated guess, but I think borne
out by what Greg says regarding the two bottles wrapped together. The part number would appear to
be an abbreviation of what it actually references, i.e. ACCessory-FUELTank-ConDitioner-KiT. I think
you've been short changed.
# 6019 I have the complete Yamaha Fuel Tank Reconditioning Kit - the "Fuel Tank Rust Remover" and
the "Rust Remover Neutralizer" - and the part number on both 16-ounce plastic bottles is the same:
ACC-FUEL-CD-KT. I bought both bottles about 4 years ago and the dealer had multiple bottles of each
product in stock at the time..
# 6018 You are right. Apparently on the basis of my request the local dealer ordered six kits. He says
they are all just bottles of rust remover - I did ask him to check whether some were neutralizer but
apparently they're not. He hopefully has accepted that his stock is 'not fit for purpose' and will make
some effort to sort this out.
# 6021 Thanks for your response. Have again today spoken to the Yamaha dealer who has now been
in touch with Yamaha UK. Hopefully it will now soon be sorted out. Perhaps of significant interest is that
it is apparently classed as a marine product rather than a motorcycle item. Perhaps the answer is to get
it from a Yamaha outboard motor dealer.
L # 5844 A friend is putting a Viper back together and would like to fit the 'narrower' style
mudguards rather than the deeper original style, does anyone know of a UK supplier?
# 5847 Mike at Grove Classics has both mild steel and stainless steel versions of front and rear guards
available. He is waiting for the front stainless ones to be polished but has mild steel ones in stock.
# 5848 Try Armours at Bournemouth, www.armoursltd.co.uk tel 01202 519 409. I got stainless guards
for my Venom and was pleased with them, realistic prices.
L # 5870 I am nearing completion of my 1970 venom clubman, and have been wondering if it is
a good idea to try and rubber mount the oil tank @ battery box. When I first bought the bike the top oil
tank bracket was fractured and showed previous signs of repair, as did the battery box any advice
would be much appreciated.
# 5873 It is a good idea, indeed Veloce did rubber mount the oil tanks on the 1970 Clubmans. I also
have a 1970 Velocette Clubman. It was supplied with the Thruxton oiltank with heatshield. It is set
further back as on the Thruxton and is rubber Mounted. They also fitted the tool box on the nearside,
They used the large Thruxton toolbox, mine has solid mountings and has not fractured yet. 1970 was
not a good year for Venoms, with the company in financial difficulty they used many previously rejected
bits just to get bikes finished. There did not seem to be any consistency in the parts fitted and you may
well have had the standard toolbox and oiltank fitted. I like the later ones and find they are up to the job.
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# 5882 I rubber mounted the tank on my Venom after a repair to fractured lower mount. There is info in
the compendium of articles given out last year with Fishtail. There are many alternatives, some
advocate shouldered bolts and rubber grommets in enlarged holes. I used rubber grommets and lock
nuts on the fixing bolts, a bit of a fiddle to reach the nuts in behind the engine plate but if you do not
have access to a lathe to make the bolts an alternative. Another is to drill holes in the bolt heads and
wire them together when you think there is enough compression of the grommets. I tried this on the
KSS/Viper.
L # 6159 Just started the preservation (as opposed to restoration) of my recently acquired 1937
KSS I extracted what was once oil from the oil tank (it was so disgusting I almost threw up) and
discovered a rusted hole in the bottom. Its pretty much in the middle of the flat bit. Apart from this the
tank's is in a very good condition with original factory applied stove enamel and a still visible oil level
transfer. If at all possible I would like to retain the paint and finish. What I was thinking was to soldering
a brass plate underneath and then the coat the inside with epoxy. I don't have any brazing or welding
gear.
# 6160 If you solder or braze the plate, you'll never be able do a proper weld later, as the lead or
bronze will impregnate the steel. Just use epoxy. There's no pressure in the tank, so epoxy should hold
just fine.
# 6161 On second thoughts, a TIG welded repair on the bottom would be possible without spoiling too
much paint - that should give a permanent repair and that is what you really need.
# 6162 If you want to keep the finish as it is, you won't get the steel clean enough to solder a repair
strongly enough. Try an epoxy or fibreglass repair - but clean very well first; oil under the repair will
cause it to de-laminate. Also, whichever repair you use keep a very careful watch on it in use. As the oil
heats the tank it could easily begin to come away - and that might be oh so inconvenient!
# 6163 Hi, what about a nut and bolt with two steel and fibre washers (as large as possible)?
L # 6171 I used Eastwood Rust Dissolver for the first time last night on the oil tank. This is pretty
remarkable stuff. I had a gallon, so I just dunked the oil tank in a bucket and left it overnight. All rusted
areas are now clean bright metal. Where the paint it was solidly attached, it untouched and is now nice
and clean.
# 6172 My fuel tank is in pretty good nick, as things go, but does have a couple of patches of rust
inside. This eastwood rust dissolver, would that be okay to put into a tank and shake around for a few
days and then drain out and start using the tank again straight away? or does it need some extra
treatment afterwards?
# 6173 The only issue with this is the piece that you are going to de-rust needs to be continually wet
(needs to be immersed). In the instructions it says you can set up a pump and continuous spray but I
haven't tried that. My oil tank was immersed for about 15 hours. As soon as it is removed then it is
potentially subject to surface rust (if wet) and needs to be sealed For fuel tank you are better off to use
the two part Yamaha "conditioner" which was discussed on this board a month or so ago. The first part
cleans/neutralizes and the second part seals.
292

G.2. Cables, Controls and Instruments -
L #39 The Scitsu electronic tacho www.scitsu.co.uk/
L #737 Velo. VM6333E had been abandoned in swampy Louisiana after the speedo cable had
done its magic on yanking the handlebars to full right lock - it didn't take a forensic scientist to figure
out the cause of its loss of favor with the original owner.
#739 I'm intrigued by this common reference to the speedo cable somehow becoming wrapped around
some other component. There's even a part in the VSL list which seems to be designed to prevent this
occurrence. I haven't run my being-rebuilt bike yet, but I can't visualize how this situation would arise.
Are we talking rear wheel drive, single sided hub or what? I'd be grateful if someone could describe in
simple terms the cause & the remedy of this problem,
#740 This can only occur on machines with QD rear hubs, and rear wheel driven speedo (which is just
about all of them unfortunately). The cable runs past the hub on the way to the speedo that is usually
mounted off centre on the handlebars, right? One day, one of the cap nuts from the QD hub works itself
loose, right. Some time later, just as you're peaking out in third gear exiting a sweeping right hand
bend, the nut decides to exit the sleeve in the hub, right? Instead of whizzing out and disappearing
without consequence, as the tube it resides in is in the top arc of its travel or the bottom arc of its travel,
instead it decides to poke its head out just as it passes the speedo cable, right? It jams and as the cap
nut attempts to coil the cable outer around the rear axle, there is an immense and unplanned tension in
the whole speedo cable, such force being transmitted right up to the point where the cable is anchored,
i.e. on the back of your offset handlebar mounted speedometer, right? Now simple high school physics
comes into play - turning moment = force x length of lever arm. Basically the whole plot takes an
unexpected turn to the left or right (depending on which side the speedo is mounted). Hence the sad
tales of these hapless riders, such as the former owner of the PD'O Endurance in Louisiana. The
solutions? A dab of loctite in each cap nut on assembly, and/or A push in plastic or rubber plug in the
open end of the 3 tubes in the rear hub, and/or Mount your speedo directly over the centreline of the
steering head (not very practical), and/or Leave your speedo cable and your brake levers at home and
attain some legendary cornering speeds!!
#742 Actually the problem only exists for full width hubs, the older "cotton reel" hubs don't trap the cap
nuts ("acorn nuts" here in the US) so they are not a problem.
#744 Re Speedo cable causing problems, I mounted a holding clamp matching that for the tacho cable
on the other side of the under tank strap. This I made tight on the cable and only tight enough on the
tank for the strap to perform its original function. Theory was that if the cable started to pull, the clamp
would twist and give a few seconds vital warning that something was not quite right. Obvious solution is
to never leave home without first checking your nuts.
L #959 I've got to the fitting of the speedo. It's a Smiths 3" Chronometric & looks in v. good order
apart from the alloy spigot which carries the thread for the speedo cable. This has been crossthreaded
at some stage and may not retain the cable nut(I haven't got a cable yet). Does anyone have
any good dodges to avoid an expensive solution, or at least know what thread is used on this item?
#982 I noticed some of the newer cables are a very tight fit so you might find they will work for you
when you try your new cable.
#984 An unholy but effective dodge is to hacksaw through the cable nut end, across the threaded
section, in an "X" fashion and fit a small hose clamp over this part. You then slip the cable nut over the
alloy spigot threads and tighten the hose clamp until it engages what's left of the threads. You then can
carefully run it up snug and finish tightening up the hose clamp to lock it in place. Properly placed, the
clamp screw will not even be visible.
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#1001 Every screw in your smiths speedometer and the gearbox on the back of a Shadow clock is
Metric.
#1002 You are correct in saying that the screws on the Smiths Chronometric instruments are metric,
and also that the two screws that hold the mechanism into the case are an unusual thread, but the size
you give is incorrect. These are in fact M5 x 0.75, not 4.8mm diameter. I have tried without success to
source these from every possible supplier, including the current owners of the Smiths rights -
Speedograph Richfield in Nottingham. Beware of ordering these screws from SR - they will supply plain
ordinary 2BA screws and charge an unbelievably extortionate price for the privilege of supplying the
wrong items! I can only report them as being one of the most unhelpful companies I have ever had the
misfortune to deal with! The good news for those who want to manufacture their own screws is that
taps and dies are listed as available on the Unithread web site www.uni-thread.com At £11.70 each for
taps and BGP14.00 for dies they are quite expensive, but that's the price you pay for oddities. The
correct thread for the cable connection is M12 x 1.0, not ½" BSC x 26 TPI, hence your sloppiness, .
Apparently this is because the original Smiths instrument company started life in Germany before
coming to the UK between the wars, so is not quite as British as most people believe!
#1004 You are correct in saying that the screws on the Smiths Chronometric instruments are metric,
and also that the two screws that hold the mechanism into the case are an unusual thread, but the size
you give is incorrect. These are in fact M5 x 0.75, not 4.8mm diameter. I have tried without success to
source these from every possible supplier. The good news for those who want to manufacture their own
screws is that taps and dies are listed as available on the Unithread web site (www.uni-thread.com). At
£11.70 each for taps and £14.00 for dies they are quite expensive, but that's the price you pay for
oddities. The correct thread for the cable connection is M12 x 1.0, not ½" BSC x 26 TPI, hence your
sloppiness.
#1012 , I have just checked with Johnson's the thread is M12 X 1.0 at the speedo end, on the rear drive
end it is ½ BSC X 26 tpi -endcab .
L # 5209 The cable on the valve lifter has snapped (bar end nipple pulled off). I ordered (and
received promptly) a couple of replacements from Grove. These have adjusters with a larger thread
O.D. than the failed cable and won't thread into the plate at the bottom of the push rod tunnel. Are there
two types of cable? The push rod tunnel base plate is original from manufacture. Any suggestions
please. As an aside trying to start the bike without the lifter makes you appreciate what a useful wee
gadget it is.
# 5210 Get a soldering iron and alter them yourself. I've rarely got a cable that fitted `out of the box'. Its
not hard to do and is a useful skill.
# 5220 Although this doesn't solve your problem, I recently fitted a valve lifter cable on my Thruxton
that is angled where it connects at the pushrod tunnel base so that the cable doesn't run up the side of
the cylinder, ie. it's angled away from the cylinder. It's a great improvement on the "straight" fitting. Got
it from Dave Smith Classic Motorcycles in the US.
# 5227 I may be reading the situation wrong,if I am please fogive me chaps,but I think there are some
members out there, who being new to the art of old bike fettling,perhaps, could do with a bit of
encouragement to get stuck in & make something & cable makeing is a good place to start, cheap too.If
you do not have access to a local old bike emporium, have a look at push bike shops, mountain bike
cable spares, inners outers etc, provide useful material for valve lifter & carb cables. Next time you see
a mountain bike in the street, have a good look at the calliper brakes, I bet you will see a use for some
bits on a Velo. Get your self an electric soldering iron [120w],some tinmans solder, some flux & a good
pair of 8"end cutters & have a go, with a little practice you will be amazed. Try to get hold of a copy of "
The Vintage Motorcyclists Workshop " by "Radco", may be out of print but worth the search. When you
have reached the state of enlightenment! on the small stuff, have a go at the clutch & front brake cable,
always seem to feel much sweeter when homemade.
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# 5228 Hi, Vehicle Wiring products Ltd. Tel: 0115 9305454 include control cable parts (and a range of
motorcycle items) in their catalogue
# 5231Tommy Johnson Cables do universal kits for brake, clutch etc. You can cut to size and solder on
one nipple and you have a cable that fits correctly. Usually about 5 or 6 quid for the kit. Usually seen at
the bigger autojumbles but also advertise in Old Bike Mart.
# 5232 Complete cables made to measure or all the components to do it yourself are available from
Venhill Nylocable in Dorking (+44 1306 885111), including stainless cable and nylon or teflon liners. But
remember if you're soldering nipples on stainless cable you do need special flux or stainless specific
cored solder. I got a sample pack of cored solder from a solder manufacturer whose name slips my
mind, but if anyone's interested I'll hunt it out. I would reckon there's enough in the pack to do me for
my own needs for the foreseeable future.
L # 5310 Does anyone know where to get an old type (flat) speedo gearbox for a Thruxton? I've
just restored one, took it out for the first time and did minus 27 miles and never got above 0 mph. So,
not difficult to conclude it drives the wrong way. I've tried Seymours, Grove, Nick Payton etc and all
they have is newer torpedo type with cable coming out the bottom. Do old types from other bikes fit, eg
BSAs, Matchlesses etc and drive in the correct direction (ie. clockwise, looking into the square hole)?
# 5312 Pop out the brass bushings, turn the drive shaft around and you're good to go.
# 5314 I have also recently taken to the road on a re-furbished Thruxton. It is fitted with a speedo drive
below the rear axle and has, I presume, had the internals reversed to rotate in the required direction. I
was told that Velocettes were the only bike with the speedo drive above the axle and that they are now
"completely unobtainable": don't know if that is true.
# 5316 Yesterday I removed the speedo drive from my recently purchased 1969 Indian Velo. They
have a speedo drive fitted on the opposite side of the rear wheel ie the Chain Side of the bike. This
drive is like most of the Velos with the drive cable on the top facing forward. I checked two things 1)
That it drives the cable clockwise to fit the normal speedo Yep its right. 2) The number on the inside of
the speedo drive - its BG 5331/247 2 to 1 ratio Later I checked the speedo drive numbers in Rod
Burris's book on page 113. I noticed that the Speedo Drive number on my Indian Velo was the same as
the 1967 to 1970 Velos My brain soon asked the question how could you fit the same speedo drive
onto the late later bikes. Rods email answers the question that my brain posed after finding the speedo
drives were the same as the later velos. As Dr Sumner Miller said " why is this so" Veloce reversed the
fitment of the speedo drive with the cable at the bottom on the Venoms and Thruxtons etc so it drives
the correct way ie. clockwise I think you will find that the helix gears are angled in the opposite direction
on the BG 5331/247 drives and are not just the standard gears turned round!!
# 5330 Having posted my message the other day, I tracked down an old type speedo gearbox with the
correct drive direction and with the cable coming out above the axle. Try Mark Garside at Saddleworth
Classics. I've mislaid his phone number, but his address is Saddleworth Classic Motorcycles, Knarr
Mill, Oldham Road, Delph, Oldham, OL3 5RQ. He had 2 and I've bought one.
# 5331 RE: “I noticed that the Speedo Drive number on my Indian Velo was the same as the 1967 to
1970 Velos. Veloce reversed the fitment of the speedo drive with the cable at the bottom on the
Venoms and Thruxtons etc so it drives the correct way ie. clockwise”. It would seem that your VMT at
number 1046C is likely to fall into this date span therefore the drive SHOULD be under the axle.
# 5320 When replacing the old flat type speedo drive gearbox, with the later rounded item, you also
have to change KS62/3 Rear Hub clamping sleeve & KS52/4Rear Wheel distance piece, also
KS61/2Rear hub retaining ring. Sorry I don’t know if the part numbers changed along with the
dimensions of these components.
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L # 5569 Hi all, has anybody got any ideas about how to stop the valve lifter cable melting on the
head?, is there an angled adjuster on the market?if yes where can one be purchased.thanks.
# 5570 I cut a vertical groove in the head fins above the adjuster so that I can feed the cable up behind
the oil return pipe. Makes a straight run and is out of the way.
# 5572 I wind about 12 to 15 tight turns of soft solder wire around the cable in the area where it
touches the fins. This works well and prevents heating of the cable as the heat is easily dispersed
through the solder wire. Looks neat too.
# 5575 Get a weak stainless spring whose inside diameter is a little larger than the outside diameter of
the cable, stretch it out lengthways so that the coils are pulled apart somewhat and feed it around the
cable, looks good, doesn't interfere with the cable run or its movement.
# 5588 Last night I just fitted a new valve lifter cable I obtained from Dave Smith Classic Motorcycles. It
has a 90 degree bend on top of the adjuster. I set it up to point away from the engine and miss the
exhaust. This seems to give a better run and hence a better action than the regular cable.
# 5573 Zip tie it to the tacho cable which should be clipped to the front tank cross stay bolt.If you dont
have a tacho fitted, disconnect the cable and have a good look at arranging the cable route around the
tank stay and clipping it out of harms way.If you dont have a tank stay, fit one or your tank will
# 5580 Be really posh and buy a stainless rear brake return spring from the club, beats solder,
machining fins and it works.
L # 5577 Anyone have a recommendation for someone who does reliable Tach and Speedo
refurbishment on Smiths as fitted to Velos? I had heard dennis Quinlin in Australia did good work, but
haven't seen anything on him in a few years. I'm in the NE US, but would like to get these original
instruments cleaned up and minor repairs made.
5583 There is a guy in england called Paul Beck. he is very good and his prices are very fair.
# 5587 Hi Mark, Quinlin has been "retired" for a few years, but last year when I spoke w/ him, he said
he could be "encouraged" to do a few. I've had excellent results from Nisonger in New York
www.nisonger.com/ They have been at this game for about 50 years. They work on both magnetic and
chronometric instruments.
# 5589 I have used Nisonger Instruments. Address is 570 Mamaroneck Avenue, Mamaroneck, NY
10543. Telephone is 914-381-1952. I haven't called them in a couple of years so check on the area
code as these seem to change regularly. I have dealt with them from the 1960's on all types of Smiths'
instruments with nary a problem.
# 5645 I've had Joel Levine in Atlanta do 4 or 5 instruments for me, including the two on my Venom.
Excellent work -- the clocks will come back mechanically sound, with new faces, and even the original
stick-on warning labels. I don't have his number handy, but he always advertizes in Walnecks.
L # 5624 I am getting ready for a major restoration of a 1964 Venom - it's in Clubman trim,
registered as a Venom Sports in the RF 60 logbook. In the box of bits that came with it is a mounting
bracket for twin "clocks" - it's a thin, 1/8th, alloy casting about 10 x 4 inches, with an alloy Velocette
badge riveted to the top section between the two "clock" holes. The clock holes each have a stiff rubber
circular sheet riveted on the back, the rubber has various cut -outs in it. Unfortunately the alloy casting
has fractured across one of the clock mountings. The bike currently has the speedo and tacho mounted
on separate alloy brackets secured to the fork top nuts. Question - is the broken casting I have a
standard item for a Clubman - I can't find it in any of the 3 spare parts lists that I have and I've been
unable to locate any pics that show details of the set up of the clocks on a Clubman. I'm assuming that I
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can get the casting welded / strengthened but would like to know just how authentic it is.
# 5625 George From your description you appear to have a period aftermarket item supplied by
Stephens (circa 1966). The originals were a bent steel item in the shape of a "C"that fixed to fork top
nut and fork yolk. The left hand and right hand fitment were mirror images of each other.
L # 5708 Hello What is the correct length of the outer and the inner front brake cable for a 1957
Venom. Current one has streched too much and a replacement just bought is too short.
# 5756 The inner is .075" diameter, 38.125" long, outer is 32.75" (this excludes the adjuster length).
L # 5792 I have a chronometric speedo that appears to be in good condition...looking through
the light socket I can't see any corrosion and the face, numbers, and needle are like new. When I
hooked up a speedometer cable and gave it a finger twist the pointer went up to 20 mph and only
returned to 10 mph. I believe the internals need lubrication but can't figure how to get to them. How
does one remove the bezel?
# 5793 The bezel unscrews with a normal RH thread. If you take a couple of screwdrivers, you can
then pry the needle off the shaft vertically. It prolly does need lube, but will not return to zero unless the
cable is rotated in a 'slow down' manner, as the 'clockwork' innards have to be retuned to zero speed
for the needle to return.
# 5794 Yup, playing with the cable I made it return to zero. I thought the bezel screwed on/off but I
can't give it enough oomph with my hands to move. I put some penetrating oil around the junction and
I'll try it again tomorrow..
# 5797 You may well get the bezel off with a strap wrench, I use a leather belt. Hands just can't grip in
the right direction. Careful with the internal lubrication, ask an instrument man for advice & don't oil it.
L # 5840 My 1954 MAC speedo gearbox appears to be falling apart. There should be 4 very
small screws holding it together and I notice that there are only 2 left and the threads on those are not
doing their job any longer. Anyone got any idea where I might find a replacement?
# 5861 Replacements are hard to come by. If you do find second hand ones they tend to be worn past
being usable. If it's only the set screws are the problem, replace them with some longer 8BA set screws
with Loctited nuts on the end. It's a little Frankensteinesque but it works. You can get 8BA nuts and set
screws from model engineer shops.
# 5863 After close examination it appears that it is only the screws that are causing the problem. I'm off
to the big city of Hereford in the morning and there is quite a large model shop there, I'll give them a try.
Funny really as I have a complete set of BA taps and dies - (somewhere). I have 2, 4 and 6 BA set
screws and they are too big. I'll let you know if I can source some.
# 5864 If it's not too non-u you could always try 2mm metric - cheap and freely available.
# 5871 Fixed OK. Model shop had 8BA set screws and nuts. The threads in the housing are knackered
so loctite will hopefully stop my nuts dropping off. Tried to get some 2mm set screws but they didn't
have any.
# 5872 I was wondering if anyone has tried "Permatex Stripped Thread Repair" The catalog is at
www.permatex.com P/N 81668. Looks like just the job for bodgers who find themselves in a desperate
situation.
# 5874 I used the permatex about 5 years ago on a Honda 350 project bike when I found the threads
in the frame stripped when mounting the footrest components. I knew it was a shortcut, but wanted to
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finish the project. It has held ever since. I'm not sure what would happen on a bike with more vibration.
L # 5853 Can anyone give me definitive answer regarding the original diameter of the clevis pins
on the gearchange and TLS front brake on a '67 Thruxton. I am fairly sure that the TLS brake is a later
Bloomfield rather than a Tickle. Also should the actuator/adjuster rods be 1/4" dia. or 5/16" dia. My
gearchange linkage uses 5/16" dia. pins and 1/4" dia. rod, the TLS brake uses 1/4" pins and 1/4" dia
rod, have they been "modified"?
# 5857 Checked the pins and rods on my 1970 VM clubman, They are both are 1/4" on the brake and
the gearchange. The rearsets fitted to mine are the later alloy ones, Brake is the later TLS Bloomfields.
The pins elongate the holes in the alloy linkage levers so they are often reamed out to the next size to
take out the slop. Better idea is to fit rose joints that clamp to the alloy rather than pivot in them.
L # 6045 I have bought a new speedo cable for my Viper, on inspection the inner cable is dry
and appears free of lubricant. Is this correct, or should it be lubricated and if so with what?
# 6047 Plenty on nice light grease. We use LM.
# 6052 you should use a high melting point grease, never use oil
# 6054 Withdraw inner from casing, lightly smear inner with HMP grease & enter inner into casing.
Wipe excess grease from the last 12"(300mm)of inner wire to prevent contamination of speedo head.
By using a good HMP grease you will avoid the problem of the liquid oily component in the grease
separating out & working its way up to the speedo head & damaging it. Please note that some cables
as supplied these days have an inner wire a little too long where it enters the speedo head, this puts an
end load on the mech of the head leading to rapid wear and big bills, check before tightening up the
knurled nut. RCP.
# 6069 The cable should suit the speedo. A chronometeric speedo head needs a different cable to the
later types. Check with a specialist. David Woods of Chichester repairs speedos and is very
knowledgeable. Tel/Fax 01243542521.
# 6059 Not sure how black graphite grease would be considered in this application, but having had
most of a 4 gallon bucket of this stuff around for 30 odd years, it gets used in my shop for this sort of
thing all the time . Anywhere there is a need for lubrication of things that slide or rub, --including the
speedo drive unit, - Velocette or otherwise, I have a small handy container of this stuff within easy
reach ! It gets smeared on the inside of the rear chain, & between the concave washers of the clutch
thrust, & many other places that I cannot remember. (but not into ball & roller bearings of course !).
L # 6070 Gents: The speedo drive on my Venom has decided to call it a day. Does anyone know
how to disassemble one of these to see the condition of the worm and ring gears? On the housing, at
each end of the worm gear, there is a pressed in brass piece. How are these removed? Will they drop
out with heat? As always, thanks for any and all help.
# 6072 No heat required. Just drive the spindle, together with the blind bushing, out from the driving
end. The ring gear is retained by the pressed steel stepped washer, which is rivetted to the body
casting. On reassembly, I use short lengths of 1/16" welding rod for replacement rivets, and hammer
and blunt chisel to restake the end bushings. The casting is very soft and requires good support while
restaking in order to prevent warping and misalignment. Replacement internals can be scavenged from
other scrap gearboxes and should match your ruined parts. It's simplified by reading the drive ratio from
the steel retainer for the felt washer so that you replace with the correct bits. It will be either 1.25-1
(15-12) or 2-1 to match speedo heads marked 1000 or 1600.
L # 6164 I'm looking for a set of brake and clutch levers to suit the 7/8" dia clip-ons on my Velo
Clubman. They must be the ones where the magneto and choke controls are an integral part of the
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levers and preferably ball-end type. They were originally made either by Amal or Doherty. Does
anybody have a set for sale or know where I can get some please ?
# 6175 Armours in Bournemouth (tel: 01202 519409) have some British made "Combination Levers"
advertised on page 17 of their latest catalogue. The illustration show plain ends, but they could
probably mix and match ball ended.
# 6169 Surrey cycles has just relieved me of 78 quid for two combi levers, they are quite nice but a lot
of cash for what they are.l
# 6170 I have jsust phoned them and they confirm that they can supply the correct combination levers
at 39 Pounds each. Steve PS If you think the levers are expensive, take a look at their price for a GP
Carburettor !
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G.3. Exhaust Pipe and Silencer -
L #3613 Hello all, I have a 1960Venom with the alfin barrel and have just had pointed out to me
that I appear to have a Viper swept back pipe . The working outside diameter is 1.5" but the pipe has
an o.d of 1.75" where it joins the fishtail silencer and is 2.00" where it fits over the exhaust port stub. Is
this correct. If not, then where can I obtain the correct pipe(with sweepback). Is the small bore affecting
my low and midrange torque? Would this contribute to difficult starting?
#3615 I think Veloce reduced the diameter of their swept back exhaust pipes from 1.75 to 1.5 at some
point - I'm not sure exactly when - to improve mid range performance. It wouldn't affect starting at all.
#3616 Were there sweptback pipes and narrow bores in 1960? I can't remember. If you have rearsets,
you need the "higher" exhaust system.
#3617 My own take on this is that Veloce used Viper exhaust pipes for the Venom. About the norm!
The small bore pipe gives a power step which the large bore does not. I would use a large bore any
day, but if you happen to have a small one, use it!
#3618 I have found that the Viper head has a reduced diameter exhaust stub, about 1.5". Unless
someone has welded a larger section to the end of the pipe to go over the larger Venom exhaust stub,
what you have is therefore a Venom pipe. I had a small diameter sweptback on my Venom some years
ago. It went fine on it.
#3619 To clarify; the VR head stub is smaller than a VM. The small bore VM pipe is the same bend as
the VR but of course has a VM sized end fitting. Hence Veloce got two sorts of pipe bends at one go.
Only the stub fittings are different. There is a difference in performance between the small & large bore
pipe. The smaller one gives a bit more bottom end torque. However, overall the larger bore on a 500
lets it run out freer. Not of interest unless you use the twistgrip correctly!
L #4612 It seems you can never get a bike in absolutely original condition and hence the
restoration always involves discovering what was botched and how to rectify it properly. I have a late 67
VMT and I have a few questions about the exhaust. The front pipe is a later type with the pipe being a
smaller diameter it is affixed to the front footrest. I wanted to know the parts involved and the order of
assembly of this stud. Is it a square stud with a nut and washer on the inside, then an oil-line bracket,
then through the frame to a spacer, then the exhaust bracket then the washer and nut? If there is a
spacer how long is it and of what shape. Now to the rear silencer from the inside of the frame out is it
nut, washer, through frame to front footrest bracket, then silencer bracket, ( which if these two is first)
then rear footrest? If this is correct how much clearance should there be between the frame and the top
of the silencer. Mine is about the thickness of a piece of paper. And if it is not the correct order how do
you get the clearance needed for the silencer. I have another question about the older than pre- mid 67
silencer for the VMT, thats the one with the tube instead of the triangle bracket on the top of the fishtail.
What exactly does the rear footrest and stud look like that holds this silencer on?
#4613 I do not know the late 67, but I have a early 68. The front tube there is 2" in dia, and is mounted
to the frame in front of the footrest.
#4622 have this problem with every new exhaust pipe I get (I've had my VMT 30+ years) as they're all
slightly different. I turn up the spacer after measurement from a bit of ½" galvanized iron water pipe. It
gets so filthy down there from bits of road and oil that nobody'll ever know.... There's a tradeoff - too
short and the pipe fouls the engine , too long and it fouls the kickstart. But it's not thou accuracy
required. Or perhaps you're after concours?
#4631 I read with interest (and sympathy) the problems seemingly encountered with exhaust systems
generally, as I have had considerable trouble fitting up my 68 mk2 clubman system. Firstly the original
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fishtail was rotten and not being too impressed with the modern manufactured replacements available, I
sourced an original in good condition and had it fully refurbished including chroming. This was fairly
costly and few platers are keen to undertake this work as it tends to contaminate their baths, fortunately
I knew someone, etc, it was still cheaper than the new abortion. Secondly I had a stainless pipe
commisioned at JT tubes in Creekmoor (Poole Dorset), this again was forced upon me as off the shelf
ones were bloody awfull, the custom made one was not a perfect fit initially and I would advise anyone
going down this road to have it tacked, fitted on the bike and checked before final welding up. The
problem was exacerbated by the proximity of the kick start (cotter), gear change (linkage type rear sets)
and alignment- of the silencer (plus all fixing bracketry!)- as you all know. After optimising the geometry
to avoid all these elements and still keep as near as possible to the original, I ended up with an
excellent result, providing you like the bronzey look along the entire length of the pipe, which I do,
especially as you can clean off burnt oil and boot rubber easily (aggressively), run the motor and
restore the colour perfectly every time, A further complication was due to the replacement of the rear
suspension units with velo pattern JB's, these are longer, as are Hagons that I acquired at a jumble,
than the original Girlings by up to ½". This caused no end of trouble, as contact between the rear wheel
spindle nut and the silencer became a distinct possibility, necessitating setting the silencer further out
(1/8 - 1/4") by rotating the pipe on the cylinder stub, increasing the spacer thickness for the pipe
mounting bracket and fitting a spacing washer for the silencer mounting (pillion footrest mount), hay ho,
so it goes on, just as well I was intending to make new mounts in stainless (longer threads so that I can
use Nyloc's!!!)
L # 4961 Is it just my bad luck, I have tried five exhaust pipes, from various suppliers in the past
ten years, nothing fits. Problems so far include wrong size tube, bends wrong, crap plating & bracket
crafted by an ape with a hacksaw. I don’t want cheap, I am prepared to pay a fair price for a pipe that
fits. Anybody know where I can get a good MK1 clubman pipe in the U.K.?
# 4962 Yes; Martin Arscott imports excellent MkI Clubmans pipes in stainless from Australia. tel 01442
862966 good luck!
# 4963 Try Overlander, Warrnambool Aust. he specializes in stainless products. He supplied me with a
couple of plain bends recently, - because I can't be bothered bending pipes any more - one was for the
GS. His workmanship is first class, & I believe he exports to the UK. Overlanders address is :- Barrys
Road, Bushfield, Vic 3281 Phone no is (ozzie no.) :- 0355 62 6362 -- you will need to add on any other
numbers for international etc., or www.dropbears.com/o/overlander
# 4968 A word of warning - the small bore stainless swept back Clubman pipe I obtained from Martin
Arscott still needed the hole in the bracket to be reshaped and drilled to suit the individual machine, and
even then it succumbed to vibration in a very short time indeed. My solution was to have an additional
strengthening plate added at the back of the existing bracket, making a much more robust and almost
invisible repair which has lasted several years so far without further trouble. The more annoying
problem was that the pipe overall was constructed from much lighter gauge tubing than the originals,
including the sleeve that fits over the exhaust stub whose ID was oversize by 24 thou, requiring
shimming with a strip of 12 thou shim stock and had no slots to facilitate clamping. It may be that Martin
has found supplies from an alternative source now, I got the impression at the time he was using
someone more local than Oz, but the item I bought was certainly not a straight bolt on replacement for
the original and did need some further engineering to finish.
#4969 I can't speak for Martin Arscott, or anyone elses exhaust pipes, but don't forget our Velos were
not mass produced in millions, but were individually made and assembled. I recently 'borrowed' a pipe
and silencer from one of my velos to put on another. It took me about 2 hours to 'fettle' it to fit. I suspect
that a pipe that goes straight onto one Velo, with a perfectly happy purchaser, may be a right **** on
another, with an unhappy purchaser. Try swapping the wavey back mudguard stays with another Velo
and see if the mudguard is still in line with the bike. I did when one broke - I had to drill some more
holes in the mudguard. I suspect they were only drilled as the bikes were assembled. Remember, your
Velo is unique, no other one is quite like it. Expect to do a little fitting as no one could make a pipe that
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would go straight onto every Venom ever made.
# 4971 I bought a Clubman exhaust pipe for my Venom last year from Armourers, Bournmouth and it
fitted reasonably well without a lot of swearing and tweaking. As previouisly posted no two Velos are
the same and while one pipe will fit straight on to one the same pipe when trying to fit to another may
need a lot of persuading.
# 4972 Thanks for all the replies, Yes I was aware velos were hand built & selectively assembled, but
when you take into consideration the major fixed points IE exhaust stub on cylinder head, r/h footrest
lug and silencer/pillion footrest mounting lug, there cant be too much +/- involved. Problems
encountered so far include top swage ID + 0.030" bend fouls timing case ,bracket so far out of position
no amount of hole fettling will get a bolt anywhere near the footrest lug and at the same time the pipe
fouls the kickstarter housing/gearbox endcover .I will follow up a couple of leads & report back.
# 4976 Having just gone through the assembly of a 67 VMT I found out that there are 3 pipe types
and 2 silencer fixing types for the VMT from 1965 to 1970 (please correct me if there are more). The
tolerances that were engineered into these exhaust systems meant that the pipe did have about 3/16th
of an inch clearance at the timing chest, and didn't foul the kick starter. I have several pipes and
silencers. There seems to be absolutely no problem when you have the correct original pipe fitting onto
the correct model year. Problems will occur when you have mismatched reproduction parts. In fact it
seems all original parts do fit the models they were intended to in my experience, and this idea of hand
assembled, or hand made is a bit silly.
L # 5333 I'm baffled. The exhaust baffle came adrift but when I took the muffler (silencer) off
there were two pieces rattling around inside. One appears to be the normal baffle as illustrated in the
parts book. The other piece in there is approximately 3" long, cylindrical with the "D" shaped
punch-outs and split down the longitudinal axis. What is this extra piece? Can I ditch it?
# 5334 Sounds as if the baffle is in two parts (Broken). Should be one piece about 12" to 14" long.
# 5336 Your "extra piece" may have become detached from the silencer. If you look at where the two
halves of the fishtail are welded together, you will see on the underside a thickening of the weld where
your piece should be welded in. The longitudinal split is the giveaway. It's quite a common point of
failure because corrosive condensate collects at the bottom around the weld. Your silencer may not be
quite as silent now and you could experience some loss of mid-range torque. Some Velo owners are
unaware of this piece because theirs has been burnt/blown completely away. There is no way of
refitting it that I know of..
# 5337 It's either another part of the removable baffle or it's the end of the road for the fixed baffle,
which is welded into the bottom seam at manufacture. It is a larger diameter than the removable baffle
and has a domed end, and the D shaped slots. Problem is, it will fit neatly into the neck of the fishtail
and at high revs can kill engine performance - the harder you tug on the throttle wire, the greater the
exhaust throttling effect and the slower your Velo goes. Many people pull the remnants of the fixed
baffle out through the front (piece by piece in a brutal fashion using long nosed vice grips). Then they
slide the removable baffle back in and carry on with a noisier but still functional silencer. I have done
this once or twice but prefer to rebuild and rechrome - can be done by opening along the bottom seam,
folding out a bit, installing the new fixed baffle then closing up and re-welding the bottom seam, being
sure to capture the vertical leg of the new fixed baffle in the bottom seam as you weld.
# 5354 Fabricate it from sheet metal. You won't find it listed in the parts manual, that's for sure. It
shouldn't take too much trouble to make. Just hope that the original is still in sufficient detail to use as
the basis for designing/making a new one.
# 5355 2 things. First I agree that the wayward fixed baffle is unlikely to be the cause of hot starting
problems. It comes into play once you've got the bugger started. Last time it happened to me my mate
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Jiggo effected a temporary fix with a piece of fencing wire coiled like a mattress spring - he wound it
into one of the oulet holes in the fishtail until the round end beared against the cone of the loose fixed
baffle, then tied it off. Pretty ugly but it made sure that the neck of the fishtail couldn't be blocked no
matter what the throttle opening on VMT457. Second, Tony is right - the new fixed baffle you weld in is
best fabricated by a 76 year old retired plumber who makes tinware as a hobby, using the bits you
carefully extracted (then reassembled to make an identikit of the victim) as a pattern. I actually asked
him to hang it from the top so it wouldn't rust out in the next 100 years but he found this a bit hard and
mounted it from the bottom a la original. On second thoughts, perhaps it wasn't too hard for him - he
was just protecting me from the purists.
L # 5359 My VMT exhaust pipe/silencer joint has a gas leak, what is the best type of sealant to
use in this area?
# 5360 Silicone.
# 5362 Gun Gum in a tube Happy sticking!
# 5364 I use Loctite clear silocone on my Viper far less mess than gun gum and it lasts longer too.
# 5363 Gun Gum goes hard and falls out, silicone don’t. Applying silicone to ex,pipe and silencer
lubricates the assembly whilst you line it all up before bolting it into place.
# 5365 I use a white exhaust sealing paste in a tube, like the previous post says, it lubricates and aids
assembly, seals well in use but this type also helps removal, it powders up when you twist the joints
apart. I am not sure of the name, its in a white tube with a car manifold picture on it, it may well be Gun
Gum. It has the consistancy of tooth paste, seals when the exhaust gets hot. I found the original gun
gum in a tin was no good for assembling tube joints and was best used for filling gaps after assembly..
# 5383 The white stuff used to be called "Fire Gum" and is simply a mix of fine fireclay and water. I
believe Holts or CarPlan market it under another name now. However, the fit between silencer and pipe
really should not demand use of it and a smear of colloidal copper grease (on the pipe only) ought to be
sufficient. Check that your pipe reaches past the slots in your silencer - you've got no chance of
preventing leaks if it stops short..
# 5366 I've successfully used a Permatex high temperature silicone that contains colloidal copper to
allow stability at very high temperatures. The couple of times that I've removed the silencer from the
pipe it all came apart quite easily and the residue can be "rubbed" off with your fingers. Plus it doesn't
leak!
L # VOCNA 150 Do any of you chaps know of or have access to a good custom exhuast shop. I
want to repop the 1965 Thruxton exhaust pipe. I have a sample. I'd like 6 + or - pipes depending on
cost. I only need the pipe bent to the sample. I'll make the cylinder head spiggot connector and weld up
the assembly jigged on a engine frame mock up I use. I've tried the local shops and have found one
that can do it. However, they don't have the correct mandrels and will have to make the bends by a
combination of small bends. The result is the pipe will have ripples on the surface. If any of you know of
a shop that will work via mail order let me know. Also I'm looking for a pair of good Venom cam
followers for a customer project.
# VOCNA 151I Armours simply too unreliable in quality? There is a shop in Berkeley called Norman
Racing, they make incredible pipes for racing cars etc, but I think they use small bends too. I'll give
them a call and see what they are capable of.
# VOCNA 158 I had not cosidered Armours. If everything fails in the USA I'll give them a try. Exchange
rates and shipping costs may be a problem.
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# VOCNA 152 Norman racing is not set up to do pipe bending as such denis ectiverry is the welder guy
who deals with that sort of thing by welding preformed bits together to make what you want he may
know of a place to get the correct bend and I know that jimmy dewar at megacycle cams can weld up
and resurface venom spec followers as I had occasion to pay for the radius jig so he could do mine he
also has the jig for /8 cams mahalo jeff scott 1
# VOCNA 154 Are these going to be the early style larrge diameter pipe that sweeps up aft of the
gearbox? If so, are you also having the high-mount silencers made, the ones with the transverse tube
mounting? If so, are you also going to have the rear footrests made with the long stud? If so, put me in
for one of each!
# VOCNA 156 I plan to use the exhaust pipes to be able to offer a 1965 exhaust system and a large
diameter exhaust pipe for post 1965 Thruxton and MKII Clubman owners who want more top end
performance. I have been assembling Velo silencers in my shop for several years. I get the stampings
made off the original dies from Dave Holder. Simon Goodman showed me how to assemble them. I
currently have a silencer out for chrome plating with the transverse tube and frame relief on the back
side. I also plan to make the foot peg with the long stud out of 303 stainless steel. If you want a set of
parts, assuming I can get a proper pipe made, you may want to buy them bare and get the chrome
plating done at a local shop. Illinois hates chrome plating shops and has wiped them out in cities and
towns. All the shops remaining are in small towns or out in the country. The shop I use charges me
about $180 to do a silencer and $90 for a exhaust pipe.
# VOCNA 155 Phoenix Engineering here in Riverside makes custom headers with nice smooth bends
and have agreed to look at a sample. They were not too encouraging, normally they run bigger
batches. But if it's as relatively simple a job as it sounds they might help. They expressed concern
about multiple radii, but that may not be a problem on the VMT head pipe. I have both 1-1/2" straight
(not upswept at the footrest) and 1-3/8" examples in my garage. One or the other should suffice for a
quote. I can verify fit on my '68. Exactly what are you looking for?
# VOCNA 157 All that I am looking for is the exhaust pipe alone. I'll fabricate the pipe and attach the
cylinder head spiggot adaptor and frame lug mounting adapter. I'd prefer two pipes. Both the same
except on has an aprox. 5 degree kick up under the trans. kick start housing. If the kick up become a
problem I'll just get them straight and add the kick up in my shop. Your 1 1/2 " pipe should do for a
quote. The most difficult part in forming the pipe will be that the contour is 3 dimensional. As far as I
know most custom header are made up of a series of 2 dimensional segements welded together.
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H. Manuals & Spares
L #31 By the way, I am wanting to obtain the Haynes manual for the Velo Singles to add to my
growing library, but no luck.
#50 Yes, the Haynes is out of print. I have an original copy of the Service Manual for the 1953
SwingArm MAC which should probably cover 99% of the 1956 models main service needs. Also picked
up an original copy of the owners manual which is a LOT more in depth then the ones we get these
days.
#51 There are several sources for out of print Velo manuals. As Bruce mentioned, ebay is a good one
and Velo manuals crop surprisingly often. To skip all the browsing through Harley parts, I usually
shorten a search to 'velocette', or 'motorcycle manual'. There's also www.Bookfinder.com where I've
found literally hundreds of difficult to locate titles on motorcycles. If you log on, it's pretty selfexplanatory,
and there's none of the waiting as on ebay, but be careful, you may get hooked. Also,
there's ARTCO, that's www.autoliterature.co.uk
#57 I have both the Haynes manual and the Main-Smith one. I find the alternative pics the most useful
parts, as their tech stuff is mostly the same as in the red book.
L #43 The compendium of tech articles which Dai Gibbison referred to was put together by Tom
Ross.
L #54 I copied the list you provided through the VOC of all the technical reports from past
Fishtails. Is it possible to get copies of any of these, and if so, how?
#55 The only way you can get copies of these individual articles is through the VOC UK club librarian.
His details are in the back of Fishtail
L #323 The Red Book is essential. I only use the Haynes manual in conjunction with the Red
Book because of the photographs. The other manual I refer to frequently is the BMS Service Series
book. It has lots of useful tips.
#330 Okay, so I'm green .After all this is my first attempt;,but what is the Red Book & where is it
available?
#332 Generally, when people on this side of the pond speak of the Red Book they mean the Service
Manual published by the factory. The Burgess book is another good source of information, but the
emphasis is on the older (pre-'53) machines
#333 I've found that ebay is actually a good source of manuals, even if one went to an insane price
recently. I've bought manuals for just about everything there, or found connections to people who have
them; sometimes it just takes diligence. If you send an email to a vendor (those are the people with
300 plus beside their name!) asking them for something specific, you might get lucky. Currently the
price average for a 'red book' or Haynes manual is about $40us. Often these are advertised in the
Fishtail or VMCC newsletter, or even Old Bike Mart. Seek and ye shall find. Also, for those literate
souls with a computer, www.Bookfinder.com may be useful; just type in 'velocette' under the book title,
and you may be surprised at what you come up with.
#334 The “Red Book” refers to the original service manuals issued by Velocette for the MSS, Viper,
Venom and Thruxton models. They differed slightly over the years, the final ones being the best (and
the easiest to obtain) publication number F484/11R dated march 1971. The “Red Book” Paul refers to
written by Burgess covers M, K , GTP and LE is not as comprehensive as model specific books, but is
worth buying if you see one. For earlier Velos service manuals are brown, buff and pink! You can buy
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photocopy reprints of any of the service manuals from either the Velocette Owners Club or Bruce Main
Smith publications www.brucemainsmith.com Personally I prefer to buy original second hand copies,
which are often available from the booksellers at auto, jumbles, normally retailing at £ 12. When I next
go to an auto jumble I will provide details of the sellers. Finally, I believe that the Red Book is the best
and despite having built four Velos I always read the relevant section in the Red Book before starting
work on any job no matter how small.
#335 Thanks for your replies re. 'Red Book'.I've got the Service Manual - I just didn't understand the
terminology - the cover of my copy is white.
#486 Don Mitchell Tel: 0116 277 7669 has some original copies of the red book called "Service Manual
for Viper, Venom, MSS, Clubman, Scrambler Models and Thruxton supplement" Publication number
484/12R probably issued in about 1972. 124 pages. About £12. This is very similar to the photocopied
(larger size) reprint issued by Veloce Spares under part number VSL102 at £7.70.
[Editors Note: see also, www.mercianmanuals.co.uk, www.elk-promotions.co.uk ]
L #490 There is "VELOCETTE MOTOR CYCLES, a practical guide covering models from 1933"
by R. W. Burgess, edited by C. A. Pearson Ltd., my photocopy is from the 3rd edition from 1956.
Another "Red Book" in the same format is "The Book of the Velocette (Covers the LE and Valiant
"twins" and the Single-Cylinder models up to 1958)" written by Ferrers Leigh, edited by Sir Isaac
Pitman & Sons Ltd., mine is the 2nd edition from 1959.
L #553 3. does anybody know the ISBN No. for Ivan Rhodes book Technical Excellence
Exemplified I am told it is out of print now ?
#555 The ISBN is 0-85045-717-3. Yes, it is out of print. It frequently turns up on a search for
"velocette" on eBay
L #15 Got a few Velo bits from Grove Classic Motorcycles in England, pretty fast service.
#370 By the way, while Ken Gardner has retired and sold his business to Mike Fotherby (who appears
to be doing a great job) Ken has retained stocks of Velo two stroke parts mainly for his own
restorations, his number is 01608 684904. Please respect his retirement and only use him in
emergencies!.
#642 I have been trying to contact Goodman Engineering, Evesham, regarding their verification
service for several days - telephone is out of order and e-mails are returned "unknown address" - any
information about them please??
#643 Simon Goodman sold his business to Grove Classic Motorcycles about three months ago. Mike
Fotherby's number is 01582 873066.
L #32 I have been in touch with Ed Gilkison and Geoff Blanthorn, and Dave Smith of Dave Smith
Classic Motorcycles, and they are all good fellows to deal with, whether for available parts or good
advice
L #160 Sorry for the delay in getting back to you. Below you are the telephone numbers of UK
suppliers of reconditioned mags, I have not used them so I can make no recommendations. Some may
only provide exchanges. Dave Lindsley +44 (0) 1706 365838 FTW +44 (0) 114233 6269 Independent
ignition supplies +44 (0) 1237 475986 Dynamos only P Dunn +44 (0) 1782 856839
L #273 If you want to update with a practical solution for everyday use with a modern carbs I
would suggest contacting Allen at: Unit B9, Moorbridge Road, Bingham, Notts Tel 01949 836733 Fax
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01949 836734 they have Mikuni alternatives with suitable base setup and a good supply of spares
should they be needed.
L #279 Rebuilding the Lucas magneto? I have sent off the armature to Independent Ignition
Supply in Devon(?) They seem like competent folks, and their prices are quite fair. Sent my magneto to
him which he extensively overhauled. I was impressed with the service and how helpful he was. Mine
has been running perfectly for the last year. I would give him a call and discuss your concerns. His
number is below. Tel +44 (0)1706 365838
L #408 (suspension unit rubbers) If you can provide a pattern or drawing, Hill’s Rubber Company
in the UK should be able to make them for you or grind down the VSL ones. They are not normally very
expensive; telephone number is 44 (0) 1189 580535.
#409 I think this is a spare that is still available. Contact Seymours' (01 844 212 277) or other dealers.
L #472 Anybody know of a good machine shop (preferably around Glasgow / Edinburgh)? I have
got the engine in my U stripped, and now need to get a new bottom end bush made
#474 You could try Owen’s Velocette drawing office for original copies of the drawings of the bushes if
you want a machine shop to make them up. (Also remember to check the wear on the shaft)
www.owensvelos.co.uk
#475 have a look at the Scottish bit on the VOC web site. There are a couple of people listed there who
might be able to help you.
L #478 Paul of Grangemouth Ship Repair uses Smith Electrical (Don't worry about the name)
Contact Eddie Williamson Tel: 01 324 888 020.
L #485 Here are some useful suppliers for Velocettes - Control cables: Johnson's Cables Tel:
01844 237479 - Wheels Essex Wheels Tel: 01787 460230 - Speedos: Jim ??? Tel: 01604 861930 -
Tyres and tubes: John Lovick Tel: 01760 722886 - Number plates: P Mellor Tel: 01484 653559 -
Chrome plating: S B Products Tel: 01733 266138 - Brake relining: Terrac Engineering Tel: 01604
647655 - Magneto and dynamo repairs: Dave Lindsley Tel: 01706 365838 - Spares: Grove Classics:
Tel: 01582 873066 - Spares: Veloce Spares Ltd. Fax: 0116 275 2703 - Painting: Lewis and Templeton
Tel: 024 7660 4663 - Transfers: Robert Derrick Tel: 01454 260596 - Service manuals and other books:
Don Mitchell Tel: 0116 277 7669 - Sprockets: Sprockets Unlimited Tel: 01386 831341.
L #520 Martyn Bratby can be found at:- No1 The Coachouse Works Limepit Lane Huntington
Cannock Staffs WS12 4PA Tel 01543 572583 He does Velocette clutch plate inserts and replacement
clutch friction plates (also a vast array of springs and reconditions carburrettors).
L #728 Does anyone know of a good supplier of s/s tube offcuts in lengths suitable to make my
own tiddly mudguard stays-1/2" & 3/4" o/d ?
#730 Mail Order Metals in Nottingham Tel 0115 9748211 Fax 0115 9745469 Email steve@m... Web
site www.mailordermetals.co.uk can supply the S/S tube
L #796 The best source of the unique parts is the USA is Olav Hassell, he is most knowledgeable
and an avid scrounger / source of Scrambler parts.
#815 Olav, I've found him very knowledgeable and willing to 'work' at sourcing parts for you and he's in
virtually the only place where Scrambler spares can be found.
L #809 Re parts source in the USA; Ed Gilkison has quite a lot of stuff, but can be very slow in
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delivery. If he doesn't have it, often he will refer you to another who might.
L #830 Dave Smith is at 815 254 3998 He used to be the exclusive dealer for Goodman's here in
the US, and is a valuable resource for spares.
L #1725 As I arrived at work this morning noticed a missing nut on my horn - 1961 Venom, Altette
horn - does anyone know where I can get a replacement - slightly tapered domeheaded, chrome nuts
that are fitted round the peripheral chrome ring of the Altette.
#1727 From Taff the Horn - 01792 23 37 63
L #1782 Does anybody know if the route holders that clip onto the handle bars are still in
production, and if so where I could buy one.
#1783 Try www.oldbikeshop.com
L #1843 Can someone please help my poor failing brain - and remind me what the thread form is
re: the four little tappet cover screws on a VM/VR/VMT
#1844 3/16 Whit. Same as timing cover.
#1857 3/16 Whitworth can be replaced with 10-24 UNC, the minor mismatch is not a big deal on such a
small size. I found exact duplicates of these "cheesehead" screws in stainless that way. The same
thread is used on alloy MAC rocker cover. And thread replacement kits (Heli- coil) are available in
10-24 for that broken off screw.
#1902 hello there, could anyone please tell me what the thread forms are for the rockerbox bolts and
also the oil drainpipe bolts and also the carbs flange bolts.
#1904 Rocker box bolts and carbs flange studs are 5/16" BSF, the oil drainpipe and all other banjo
bolts are 1/8" BSP.
L #1966 Bell Engineering (Whitworth heli-coils, magneto & Dynamo repair) PO Box 4182,
Colesville, MD
(301) 622-5015
L #3428 Does anyone know where you can readily get Hylomar aerograde from?
#3434 Try, Hylomar Ltd, Cale Lane, Wigan, England, WN2 1JT. Tel: +44 (0) 1942 617000 Fax: +44 (0)
1942 617001. Medium is adequate for general shop use.
L #3937 Hello all, Anyone know if there is a dealer of pre-AMAL carbs bits in the UK? Specifically
I'm looking for a float for a B&B carbs. If not, maybe I'll have to try Founders Day.
#3938 Have you tried www.amalcarburettors.co.uk
#3939 I've found the website but it seems that they deal in AMAL parts (and I've seen the Surrey
Cycles caravan at autojumbles - they have a lot of AMAL parts). I'm looking for older carbs bits than
AMAL.
#3941 Have you tried Martyn Bratby? Although he mainly deals in pre-concentric Amals I know that he
sometimes has other bits and pieces (he sold an old B&B for a mate of mine) or he might know
someone. I haven't got his number at hand, but you may find it in an Old Bike Mart. Failing that I'm sure
someone in the group will have his number.
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#3958 My old float is a cylindrical float with an indentation top and bottom and a tube through the
middle top to bottom. Don't know if its common B&B design but the float chamber needle isn't attached
to the float but is attached to a mechanism in the float chamber top. The float rises on the fuel and
pushes a couple of bob weights upwards and the pivoting action causes the float chamber needle to
sink and restrict the fuel flow. Sound familiar? The indentation on the top (and bottom so the float can
be used either way up) is to allow the mechanism full travel. Anyway, if this sounds like one of your
floats I'd be very interested to hear from you.
L #4312 Does anyone know a source for tank knee pads:- 1956 MSS Scrambler? It’s the small
tank with the cut-outs for the fork upper stanchions.
#4315 Try Mike at Grove Classics (01582) 873066
L # 4963 Try Overlander, Warrnambool Aust. he specializes in stainless products. He supplied
me with a couple of plain bend exhaust pipes recently, - because I can't be bothered bending pipes
any more - one was for the GS. His workmanship is first class, & I believe he exports to the UK.
Overlanders address is :- Barrys Road, Bushfield, Vic 3281 Phone no is (ozzie no.) :- 0355 62 6362 -you
will need to add on any other numbers for international etc., or www.dropbears.com/o/overlander
L # 5000 In the UK in the 1970's Champion did a promotion of a free plug spanner with each set
of four plugs. The spanner was small and almost undoubtedly useless in most car applications, but
could be used to take the plug out of a Thruxton with tank and fairing in place. Sadly all three spanners
that I had, have gone over the years. Anyone got a suitable alternative that works?
# 5001 Try here: www.tool-up.co.uk/shop/diy/MELPS14.html I keep one of these in my pocket with a
boxed spare plug taped into the handle. Pete C.
# 5003 www.123bikes.co.uk/acatalog/index.html?http%3A//www.123bikes.co.uk/acata
log/TOOLS.html&CatalogBody Just scroll down, it’s an MT004 and I use an MT005. But I'm sure you
can buy them locally cheaper.
# 5004 Just shows how much mark-up some people put on when you mention motorcycles -
Tool-Up.co.uk list the MT004 and MT006 under their own part numbers of MELPS14 and MELPS21
and at £1.65 and £1.75 respectively compared to XS Parts (123bikes.co.uk) price of £4.41 each, which
they also charge for the fixed head MT005. Your choice - but is it worth looking further at that price?.
L # 5872 I was wondering if anyone has tried "Permatex Stripped Thread Repair" The catalog is
at www.permatex.com P/N 81668. Looks like just the job for bodgers who find themselves in a
desperate situation.
# 5874 I used the permatex about 5 years ago on a Honda 350 project bike when I found the threads
in the frame stripped when mounting the footrest components. I knew it was a shortcut, but wanted to
finish the project. It has held ever since. I'm not sure what would happen on a bike with more vibration.
L # 5898 I have found a source for new and rebuilt Velocette camshafts. Gary Robinson, on the
Isle of Wight, can supply these parts. He has been rebuilding Vincent and Velo cams for 30-40 years.
He can build new cams from scratch, using EN19 steel, or build up the lobes on a worn cam with
stellite and then grind it to the correct profile. He can supply cams with the following part numbers: K17
K17/2 K17/5 K17/8 K17/10 K17/11 M17/3 M17/7 M17/8 Here is his contact information: Gary Robinson
(calling from USA): 01144 1983 760 765 Cranmoore Ave Cranmoore Isle of Wight UK PO41OXS
# 5906 Gary has just done the cams and followers for my KSS. An excellent job.
# 5909 Interesting to hear that Gary will still restore worn cams. I read in MPH recently (sorry, my
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etter half is a member of The Other VOC) that he could no longer accommodate this work because
the specimens that were being sent to him were so knackered - all the good ones having been built into
Vincents.
#5912 Hi Also Merv Stratford of Rudge racing fame is producing camshafts. He has M17/8 on the
shelf. One advantage of Merv's cams are that they are already bushed and he grinds the taper for the
cam wheel half a thou over to accommodate any growth of the cam wheel hole. Merv also is in the
process of producing racing MAC cams M17/6 and also the KTT tell+44 (0)1844 238425
L # 5996 Can anybody recommend a company or someone to recon a competition mag for a
velo.
# 6008 Dave Lindsley does a good job. I have had a Lucas and a BTH overhauled by him. He also
does dynamos. He advertises in Old Bike Mart. 196 Pilsworth Rd Heywood Lancs OL103DY
01706365838
# 6055 Try, CMES (Bristol) Classic motorcycle electrical specialists including dynamo/magneto
reconditioning. Unit 6, Dean Court, Gt. Western Bus Park, Yate, Bristol, BS37 5NJ Tel: 44 (0)1454
323434 email: sean@bikemechanics.com while I haven't used them myself numerous people I have
spoke to rate them very highly.
L # 6233 I just found this web site. It is focused on cars but there are lots of interesting and hard
to get 1930-50 stuff here. Gas taps, pipe fittings, wiring, etc, and the prices look pretty good too.
www.vintagecarparts.co.uk
# 6238 We deal with Paul for our 1934 Morris and would recommend his services.
L # 6250 I think I have "cooked" my JG Voltage Regulator and need a replacement (I have seen
somewhere on the web figures for resistance on the connecting leads for these units but cannot find
them at present). I live in Cardiff, Wales, and the only address I have for a supplier is Dave Lindsley in
Lancs (from the VOC Q and A Section). I want to get a new one and fit it in time to get to Beaulieu on
Friday afternoon, any suggestions for closer suppliers to me?
# 6251 I replaced mine, a few years ago, with one supplied by Classic Motorcycle Electrical Services
(CMES) of Yate near Bristol, the only faults discovered were of my own making and the unit has
performed without fault. It's not a JG Unit, but his own make. Speak to Sean, I have found his service
very good in the past. I think the Tel. No. is 01454 323434 Unit 6, Dean Court, Great Western Business
Park, Yate, Bristol. BS37 5NJ
# 6252 Sean manufactures his own voltage regulators so not sure if he sells the JG item you want, he
still has the same Phone number and address but operates under the name of Hawker electrical, top
man very good friendly service.
# 6257 I gave Sean a ring early this am, he starts at 5:30am, and was on his doorstep by 11:30, he
overhauled the dynamo while I waited, changed the connections back from JG to standard to match up
with one of his regulators and tested the lot to ensure all ok. I took away my bits, new and old, and by
3:45pm was looking at a VMT with as good a charge as it ever had at 6 volts but at 12 volts as per the
JG unit.
L # 6281 Fibre unit gave up the ghost on Sunday. Please, where can we obtain a steel unit c/w
Auto advance and retard in the UK.
# 6283 John Hales - +44 (1509) 813507. He will take your ATD and refit it to one of his excellent steel
gears. Pete C.
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# 6287 Price Productions do an exchange system for these units.Not sure you can get them with a
steel gear. Contact Roy 01480473225. Address 14 Heron Court, St Neotts Cambs PE19 1TH. email;
priceproductions@bigfoot .com
L # VOCNA 32 I just found this fastener supplier who carries a good range of BSF/BSW/CEI
fasteners and tools (including helicoil/recoil kits for the BSF/BSW sizes). I found the section "learn
about British Threads" informative as it provides all the thread forms and tapping specs for all the weird
stuff BA, BSP, BSTP, etc. www.britishfasteners.com/
L # VOCNA 363 Found a neat part last week - a 2' length of ignition wire, copper core, with 90
degree spark plug caps on each end. It includes two coil caps that are a perfect fit for the clutch cable
entrance as well as the K1F. They are thick and new and won't split like the manual advance boot so
many of us use. Drag Specialties, P/N DS-241901, "SPLUG WIRE COP 2LD BLK 90," $8 at my local
outlaw HD shop.
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I. Miscellaneous
L #29 the Velo OC Thruxton Registrar would be glad for anybody to sent him the numbers of their
Thruxton, whether or not the owner is a VOC member. His name is Ray Thurston.
#910 Is there a list of the 1008 genuine thruxtons worldwide.
#920 Ray Thurston of the Woburn Centre keeps a Thruxton Register.
#1031 I have the VOCNA copy (thanks Dennis Q.) of invoices for Velocettes received by Lou Branch,
the US distributor, from 1950 to 1960. Any member with a machine from this source and time period is
welcome to ask for a copy, scramblers were particularly popular.
L # 169 Background: I have inherited a Velocette from my late Grandfather. It is a 249cc 2stroke,
dating from 1929, reg no EN 4251 (light two-fifty, or Model U, maybe looking at the pictures etc
on the velocette owners club website). Owned by my Grandfather since about 1938, and ridden
extensively around the Lake District between than and when it was last ridden (when it was involved in
an accident) in around 1953. I believe that it is essentially complete, although it obviously needs a full
restoration! The bike is currently in the Lakes, waiting for me to move it to Scotland so I can start the
(what will no doubt be long and protracted!) restoration! Question: I believe that the reg number was
registered with DVLA in the early 80's when they went computerized, so I am interested in becoming
the registered keeper, but we cannot find any documents amongst my Grandad's effects. I have got
the from the PO, but it has a space for chassis number, so anybody got any idea where I might find
this, to save me hours groveling round with an inspection lamp? I'd be interested in getting in contact
with anybody out there who has tackled the restoration, or keeps up, a similar machine, so I can
depress myself with the task ahead.
#355 The Model U I have inherited has now arrived at my house, and I have had a chance to examine
it in detail for the first time. AFAIK it was last used around 1953 when involved in an accident - but
some work has since been done by my Grandad - the tank for one has been taken off and cleaned. I
am trying to understand the controls it should have (getting ahead of myself? - I think so - the engine is
stuck (piston in bore) - I have filled the cylinder with diesel, just waiting for it to do its thing). The bike
has been modified in use (I'll post some photos when the film is developed), and is fitted with a twist
grip - is this original? What is the small thumb lever on the LH handlebar for - should this be
connected to the decompressor on the engine (and what is that for anyway?). The bike is also fitted
with a type FD Maglita - but the lighting function has been disconnected - a groove has been machined
into the flywheel to take a v-belt, and we found a battery support bolted onto the frame, so assume
that at some time it has been fitted with a dynamo. Has anybody got any info on the Maglita? Thanks
in advance.... My plan is to get the bike back up together for 2004 when it will be 75 years old, so this
will no doubt be the first of many pleas for info! Amazingly BOTH tyres hold air, and the rear - which
looks as if it was almost new when it was taken off the road - has obviously been kept in the dark as it
still looks serviceable - the bike will rarely - if ever - be ridden on the road (for one thing I don't have
the necessary full bike licence - yet!).
#358 There was even a super-sports variant, the USS, produced in 1929 only, which was good for
nearer 60mph. Mine was registered in July 1929 according to DVLA (fortunately the appropriate things
were done in the early 80's and I was able to get a new V5 without any trouble). What were the
differences for the USS? As regards the controls, I have seen them with both lever and twistgrip
throttles. Dismantled the twistgrip last night - it is indeed the internal scroll type. Not sure it is original
as it is fitted with a distinctly homemade looking shim on the bar. Reversed clutch and brake levers,
Front brake is set up on the right - is this normal or reversed? magneto lever on the left, Can see no
evidence of a cable entry to the Mag, but then most of it is covered with about 1/4" of oily dirt- which
has fortunately kept the worst of the rust at bay. I don't know that all the two-strokes had
decompressors (the early 20's models didn't), but if yours has one it's for stopping/slowing the
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machine, not for starting. Definitely got one above the LH exhaust port, but no cable connected. I hope
this helps, best of luck, Pd'O Yep, always keen to learn/understand more - I am a long way off worrying
about getting the controls right though!
#171 Richard While I don’t have a model U, I do have a GTP that is similar in a lot of ways - the next
generation so to speak. The issues I foresee MAY be the following. They are mainly limited to sourcing
parts that are beyond refurbishment. If the steering races are worn, these are impossible to get hold of.
Similarly cups and cones for the wheels are difficult. I also believe it has a three speed box and parts
for these are difficult to get hold of. The engine is simple as with the GTP just phosphor bronze bushes
for main bearings. Frame number should be found on the lug at the junction of the seat tube and top
rail on the off side of the bike. If not look around near the bottom of the down tube again on the off side.
L #422 Where is the number usually stamped on a head? I just want to make sure what I am
looking at is Venom and not MSS. Any other quick visible or measurable differences.
#426 The MSS and Venom head is identical apart from the inlet size. MSS inlet is 1 1/16 inch, Early
Venom is 1 1/8 inch, most Venoms are 1 3/16 inch. The early MSS also had 5/16 inch cylinder bolt
holes.
L #581 I bought a 1951 MAC recently, because my brother in law has a 1952 one. Now we notice
that his engine is about 2 inches "shorter" than mine. What I mean is - the push-rod tube is shorter, i.e.
no top section, and the cylinder is shorter to match, with much more of the rocker-cover visible than
on my engine. The engine runs fine, but I was wondering if this shorter engine is a standard one, as
we have never seen another and every picture we've looked at has the same size as my 1951. (Picture
of the "short" engine is in the "pictures" section under "Keith Brettell."
#585 My 1953 MAC is like yours, the rockerbox is right up under the tank and it has a two sections to
the pushrod tube but it is an alloy engine and the first of the swinging arm frame macs click on the
club Velocette site & history scroll down to 1913 & click the catalogue link scroll down to 1954 Click on
mac.
#586 also click on 1949 catalogue mac on velocette club site it’s a rigid frame one
#588 Just took a look at the short MAC. I've never seen one like that before. I was thinking that maybe
it might be a MAC/MOV hybrid as the MOV barrel was a bit shorter than the MAC but I can't see it
being 2 inches shorter. Maybe it’s a short-stroke special?
#591 The "short engined MAC" is mine, for anyone who's interested I've added a couple of close-up
Pics on the Photos section in the Keith Brettell Folder.
#618 Re Short MAC , In fishtail 184 Ivan Rhodes describes how in 1973 he acquired a box of bits
including an unusual short M type engine fitted to an RE frame , He re-built it into a 53 MAC frame in
1980 to be what the MOV might have become . He describes , engine number NOM 3184 , with short
6 fin barrel, NSU conrod , what appears to be a Viper head ,53 MAC gearbox, light flywheels ,17/6
racing cam . Maybe you have something similar inspired by the F/T piece.
L #453 Can I use Araldite "Rapid" to plug a leak in a petrol tank?
#455 Many years ago I used Araldite to repair seeping welds underneath a Gold Star petrol tank that
had being repaired and welded by a tank repair specialist and had no problems. I got the weeping area
hot with a fan heater so as the Araldite ran into the weeping area as well as on top of it. It worked for
me.
#457 As Araldite is epoxy, as far as I know, it is supposed to be petrol resistant
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#462 Thanks for your reply. I went ahead and used Araldite Rapid (a large blob, reinforced with a small
piece of cloth) before I'd read your message. Bottom line is... it worked! That's 3 days with no sign of a
recurrence of the leak. Speaking to a chemist I gather there's apparently no reason why Araldite
should dissolve in gasoline. I guess the only problem may be lack of adhesion of the resin to the metal
surfaces over time. Still - this was a cheap temporary repair that lasted a 250 mile ride on a sunny day
and longer. I left a polymerised "blob" of Araldite immersed in petrol in a jam jar overnight as a control
after effecting the repair and there's no sign of deterioration of the polymer. So - this was a "cheap fix".
Time will tell.
#470 I also used Araldite to repair a T90 cylinder head same place and also Araldited a TR6 clutch
together, we also use it where I work to repair steering units for the Challenger tank.
L #616 Can anyone tell me which numbers (engine, gearbox, frame) should match? My 1951
MAC has matching engine and gearbox numbers but they don't match the frame number.
#632 I have never known all the numbers to match, as Velocette built engines, frames etc and put them
into the stores for assembly later. The only way to confirm this is to check them on the original factory
records held by Ivan Rhodes.
#633 I can confirm that it is rare for any two numbers to match. The gearbox number would be stamped
with a prefix which I assume Tom is ignoring. Depending on the model there are generally a different
number of digits in engine, frame and gearbox numbers. Then there are various alphabetic prefixes and
suffixes. I would guesstimate that 50% of machines no longer sport the original set of numbers. I keep
a selective record of the machine details returned by VOC members, some 5000 plus machine entries
to date. Within the bounds of confidentiality, I will be happy to interrogate them on request.
#634 This is getting even more puzzling then, because my bike has engine number with the prefix
"MAC" and gearbox with the prefix "9-" both followed by the same 5-digit number. (The frame number
is different.)
L #715 I'm about to buy a 1958 Venom. I want to restore it to what it originally looked like (without
being obsessive about it). I'd like paint, transfers, mudguards, seat etc to be right but I'll use stainless
fasteners etc. Advice welcome on how to find out original spec as looking through various websites I
can find lots of 1958 Venoms which look quite different from each other. I'd also like advice on which
workshop manual(s) are best.
#716 Best thing to do is get all the manuals and info and decide which picture of a 58 you like best then
buy or build or adjust the bike to suit you. Parts can always be added or replaced. I think overall it is
good to buy the bike already running and fixed up as there is a lot of problems in a rebuild that are
frustrating. I have done this to a 59 and it turned out to be a great bike, but one I had done by someone
else was horrible. With the Velos you get a lot of flexibility as to what the bike "should look like".
#719 I would concur with the what everyone else says regarding rebuilding your Venom. Attached is a
link to 1958 road test of a Venom in Clubman trim, which you may want to use as a starting point.
www.netbikes.com.au/roadtests/venom.htm Even the official Velo catalogue for 1958 was incorrect
www.velocetteowners.com/photogallery/catalogues/58venom.htm as that year the tank had badges
rather than transfers. Contact Mortons Motorcycle Media who can provide you with photocopies of the
road test for that year www.croesus-consultants.co.uk/v-tec/articles.htm
#731 you might want to get a good record first of everything that this motor does or doesn’t do 10 miles
wouldn’t be enough to find that out, especially with a bike your not familiar with. I have done a few,
they’re easy to take apart not so easy to put back properly Detailed notes on the workings and the
dismantling always help including photos. Also what is the known history that may help too.
L #769 Would anyone happen to know the approximate weight of a MAC. (If anyone has specific
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data to hand, mine is a tele/rigid).
#773 according to MOTOR CYCLING, July 26, 1951, weight is 330 lb (dry weight?) for the rigid MAC
with Velo front fork.
#777 I just weighed ZUMAC, our 1950 iron rigid MAC w/teles. It's complete and running, but no toolkit
and has about a gallon of fuel in the tank. 150 front, 164 rear, so Walter's number is "wet". Oh, and
there's no pillion seat, you can see this bike in the Pics section.
L #1719 Here is an extract from the Owners Handbook you may find useful:
RUNNING IN A NEW ENGINE - A new machine must be driven with restraint, and must not be worked
hard until all working parts have settled down and are thoroughly free. The engine will not give its full
performance until this has been achieved and the process of causing it to settle down and free off is
termed running in." During this period hard pulling (" slogging at low speed on large throttle openings
must be avoided and no attempt must be made to drive at constant high speed. The throttle should
therefore be opened only a small amount, and changes to lower gears made in good time, so that the
engine may run lightly loaded. It is not advisable to drive at a set low maximum speed or to keep to a
regular speed, and provided that the speed increases on only a little throttle, as it will often do on
running downhill, there is no need to hold the machine back. After about one hundred miles use the
machine should be accelerated for short sharp bursts of speed. The speed and duration of these short
canters should be increased as the mileage increases and it will be found that the machine will usually
be run in after about a thousand miles.
STARTING THE ENGINE -Turn on the fuel, using for preference the right-hand side tap. Flood the
carburettor sparingly by depressing the " tickler " on the float chamber top or by leaning the machine at
a steep angle to the right for about ten seconds. Do not flood the carburetor excessively. To flood so
that fuel overflows from it is quite unnecessary and is wasteful. Do Not Flood at All When Restarting a
Hot Engine. Close the air lever three-quarters of its travel (leaving the air valve a quarter open) and set
the throttle so that the throttle valve is not more than I-in. open. Further opening will reduce the
depression on the pilot system and make the mixture too weak to give an easy start. Raise the exhaust
valve lifter lever on the handlebar and whilst holding it up depress the kickstart slowly. After a small
movement the ratchet will engage the ratchet gear on the layshaft and the crankshaft will be rotated on
further depression of the kickstart. Release the kickstart when it reaches the bottom and repeat the
movement several times quickly to draw combustible mixture into the cylinder and free the engine.
THE STARTING "DRILL"- After this, release the exhaust valve lever and' depress the kickstart slowly.
As the kickstart moves down resistance will be felt due to the compression of air and fuel vapour in the
cylinder. Upon feeling this raise the exhaust valve lifter and move the kickstart very slowly to the bottom
of its travel. This must be done slowly to avoid spinning the flywheels further than is needed and we
stress the point as being important. Bring back the kickstart to the top, and after engaging the ratchets
by making the first movement slowly, thrust it smartly downwards without this time touching the exhaust
valve lifter. It will be found that the crankshaft will turn several times and the engine should start. Keep
the hand off the twist grip when starting as the action of pushing down the kickstart tends to jerk the
hand and open the throttle involuntarily, causing weakening of the mixture and making starting difficult.
If the engine does not start at once, depress the kickstart again against compression, ease the piston
over compression slowly, using the exhaust valve lifter as already described, release the kickstart and
valve lifter and try again. Although as described this method of starting may seem lengthy and
complicated, a little practice will soon enable it to be performed automatically. Be sure never to kick
sharply before engaging the ratchets properly otherwise the crank may slip and cause damage to the
ratchet teeth. It will be noticed that as the kickstart crank moves downwards it moves across the face of
the disengaging ramp formed on the bearing housing, and the ratchet moves inwards under pressure
from the internal engaging spring. Careful and deliberate movements in conjunction with the correct
throttle opening will give better and quicker results than continued rapid kicking. Release the kickstart
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immediately the engine starts. The ratchets make a little noise just before disengaging when the engine
is running, and this has occasionally caused enquiry. It is quite normal and can be disregarded. After a
few moments' running, open the air valve gradually, otherwise the engine will begin to fire irregularly,
usually missing about every other beat (eight stroking) and black smoke will come from the exhaust.
After starting a new engine, or if the main oil feed pipe has been disturbed, the oil circulation must be
checked. All normal running is done with the air valve full open. Do not close it when re-starting a hot or
warm engine.
OBSTINACY IN STARTING.- During cold or damp weather the engine may fail to start because the
high tension cable is wet and dirty or the outside insulation of the sparking plug coated with mud. This
provides a path for the high tension current from the magneto to leak to earth and diminishes the
intensity of the spark at the plug points. Clean the affected parts with a dry rag. Excessive flooding of
the carburettor in a cold engine, normal flooding when hot, or leaving the machine leaning over to the
right with the fuel turned on, can all make the mixture too rich to fire readily and will prevent starting.
Rectify by opening the throttle and air controls fully and rotating the engine several times as quickly as
possible with the kick starter to clear the over-rich mixture from the cylinder. In an extreme case of
over-flooding the fuel should be turned off until after the engine has started. After clearing as
described, close the twist grip, and, leaving the, air control full open, make another attempt to start. If
unsuccessful, take out the sparking plug, and clean the internal insulation and firing points thoroughly.
They may be wet with unvaporized fuel. Check the point gap and if necessary reset to OW to .023' and
rotate the engine several times to clear the combustion chamber before replacing the plug. Provided
that the trouble is not of a more serious nature necessitating workshop attention the engine should
start.
MOVING OFF- Allow an engine which has been started from cold to run a few moments before running
it up to high speed. A fast idling speed is best, and will allow the oil time to reach all parts. It used to be
the rule to run an engine very slowly to warm it up, but nowadays it is considered better to drive off
without any lengthy preliminary warming up. Obviously a machine just started from cold should not be
opened up to high speed right away even if the engine has been run in.
L #2030 I am planning to resurrect my Venom, after approximately 25 years of sitting in various
garages I have owned. As becomes my advancing years I was planning to rebuild it in a more standard
Venom form than the clubman style it is currently in. The question is what to do about the engine and
gearbox. At first I was thinking of a professional rebuilt but it's pricy and also takes a long time. As an
alternative I was thinking of checking what the head and piston looks like and check out the state of the
big end. (All this was good when I stopped riding it) I was thinking I would check out the engine first
before moving on to the electrics, clutch esthetics etc. I am planning to have the mag rebuilt, and
clearly oil/fuel/carb/pipes etc need to be cleaned and/or replaced. I would like to avoid a bottom end
rebuild if possible. Is there anything I could do to flush the engine Are there specific problems that I
need to be aware of or things I should do before proceeding along this "incremental restoration" route?
#2033 It seems an "as necessary" approach could work here. Has it had oil in it all this time and will it
kick over? If so, then set the valves and check for compression. If that turns out well move to the
sparkplug {probably get a new one}, and if that's working go to the oil tank and change the filter, along
with new fluids all round. The carb will require a dunking in a can of carb cleaner and reassembly. The
fuel tank and lines would also need cleaning. At this point the thing could start. If it does the tyres and
chains should be looked at for serviceability. Battery, lights,cables, etc. Easy first ride - gearbox noises,
wheel bearings, steering head bearings... Check it out slowly and change fluids often. Maybe all this is
too much to hope for, but it'd be more fun to ride for a while than to just tear it apart and throw money at
it.
L #2234 I am beginning the restoration of my old bike and would appreciate people's advice on
various points. Please bear in mind that I am aiming for a working bike, am not intending to ever show
or sell the machine. I am not too troubled by the concept of originality as the bike was a bitsa when I
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obtained it in 1975 and was even less original when it was stolen from me in 1979. I have decided to
have most of the larger cycle parts powder coated by a local firm (RPA). I know that I cannot have the
fork sliders baked because of soft soldered lugs, are there any other parts that I should omit from this
treatment? The bottom half of the engine seems sound and I am tempted not to split the crankcases
before building the engine. If I do split, am I correct to assume that I will not have to worry about main
bearing pre-load as long as I don't alter anything? One rocker and pushrod is missing and the
remaining pushrod is bent. There is a slight 'lip' on the inlet valve. I think the bike was probably
over-revved at some point and suffered a dropped valve. The unfortunate person who briefly 'owned'
the bike rebored the cylinder. What are the actual sizes of the various over bored cylinders or am I
better taking the barrel to someone who has a stock of pistons and matching it up that way?
#2235 I wouldn't use powder coat on anything with a 'fit'. eg fork yokes, swinging arms. Nor on fuel & oil
tanks. Frame, possibly engine plates, chainguards, battery platform, brake pedal. As regards the
bottom end. How do you know what's fallen in there? Safest to strip & assemble properly. VM pistons
were available in +.020", .040",.060" as 20thou is .5mm you can measure the bore size easily, even
with a cheap ruler! Find out what size you have, find a reborer who will accurately measure the barrel
and then decide if its useable or if you need to bore again. A new barrel & piston may be available (not
sure) Be as thorough as you can and you will get a good machine that will last. Cut the corners and its
trouble all the way!
#2236 I cant overstress enough that you should send your bottom end of your motor away and have it
overhauled and modified. nick payton is the man for you, he used to work for geoff dodkin and his work
is first class. my mate was a bit like you, he had a venom that was off the road for years. he put it back
on the road and it ran well. 500 miles later the crank axle started to pull through and it took out the
crankcase bearing ring. the bottom end was parceled up and sent to nick payton who had a batch of
drive side crankcases made and he machined it to his existing timing side half. if you send off your
lower end before it does that, you will save the cost of a crankcase half. the crank axle is a part that
may never pull through although there are more cases as the motors progress with age. having a shock
absorber spring wound up on it 24/7 and for years on end usually does the trick, mr payton has the
flywheel machined and a tophat mainshaft fitted and pinned and after that it is good for the life of the
motor. another very sensible and worthwhile mod is having the later breather added, which is easy to
do when the motor is split. also having a one piece pushrod tube fitted is a very very good and sensible
mod, which does require crankcase machining but again easier with the crankcase apart. he can also
check out your oil pump and bushings on the timing gears. one other thing I would do is to check and
see if your cyl head has been rose cut around the cylhead studs to accept a o ring. if not, have it done
and also if you do decide to have a one piece pushrod tube fitted, you will have to have a machine job
done on the cyl head to accept an o ring. I hope you can use this info, and please heed my warning as
the crank axle does come out and I can send you photos to prove it.
#2237 The Velo Owners Club UK sell an Engine strip and rebuild video (and a gearbox one too I seem
to remember) - the example engine used is a Viper. You will pick up a lot of good tips from this, esp it
demystifies the bottom end worries - i.e. once you’ve seen it done by an expert you will see how
relatively straightforward it is. I'd concur with Peter - take it all the way down, check that bottom end
properly and rebuild it well - it will reward you in the long run. The VM engine is such a good motor
when its right. Personal choice but I wouldn’t use powder coating if starting from scratch (although my
VM frame is powder coated - previous owner - and is looking good still) - for the reasons Peter
suggests - and also it can cause problems if water gets under it (although I hope you are going to paint
that grotty oil tank with something !)
#2240 New (iron) barrels for VMT and VM are available from Mike Fotherby. Pistons - Mike was due a
batch of Hepolites last week - I’ve not checked yet to see if they’ve arrived. Im still looking into get a
small batch of forged pistons made by Arias, think cost might be prohibitive though. No sign of the
Omega ones still.
#2248 Seymours of Thame also carry spares, but the VOC scheme is a must really - as well as being a
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great Club, excellent magazine etc. Not sure who the barrels are made by - but they look pretty good
(ask Mike and he'll probably tell you) Let me know if you are interested in forged VM piston - I need to
get a minimum of 4 made before Arias will take on the work. But at such a small batch size it looks like
these will be £150+ when you add on the VAT and postage - ouch. the Hepolites are cast not forged,
and I believe will cost around £110 from Grove - but Grove will give you an exact figure of course.
#2252 I have just measured the barrel and it is bang on 86mm. It looks like it has been honed rather
than rebored or even just roughed up with emery. I had not done a huge mileage since a new barrel so
I am not really surprised. There is a bit of a ridge that has not cleaned up near the bottom of the barrel
and no wear ridge at the top. There is a tiny chip at the very top near the inlet valve position which
holds with my dropped valve theory. I have two of the rings and they both give a massive gap so
hopefully they wore rather than the barrel while I was using the bike. I can't wait to try a standard piston
now. To tell the truth, uncertainty about bore size has been a big procrastination factor so thank
goodness for the internet.
L #2350 This week I have collected my Mac that I bought a couple of weeks ago. Some of you will
remember my earlier posts. Today, I drove it for the first time. Very nice bike with surprisingly good
brakes (both half with hubs). I noticed some things that I want to change. 1) The seat is quite high. It
feels that I am sitting on top of the bike. The seat is original looking but it is a replica with a fibreglass
pan. There are also mountings for a saddle on he frame. Are there different seats available? 2) The
speedo is a bit slow. I know that it is not a fast bike!!! It is a 120mph chronometric type No. S467/123/N.
Is this correct? I think that it reads approx 20% to slow. 3) Are original type handlebars available? The
presently fitted bars are to far pulled back. That gives even more the feeling that I am sitting on top of
the bike.
#2351 My 54 MAC has an 85mph chronometric speedo. I'm reasonably sure that is standard fitment for
a MAC. There ain't many need a 120mph one. As for handlebars, I bought a pair that I liked at an
autojumble. There is a vast variety of 7/8" bars out there at a reasonable cost. Just find a set that you
like.
#2361 For a short period of time MACs were listed as being fitted with 120mph speeds (SC3308/00)
previously they were fitted with a 85 mph S433/1/L. However on latter speedos the key number is a four
figure number which follows the code if its anywhere near 1600 it should be OK. The speedo you have
is similar the speedo fitted to early Venoms the only difference being the last letter, so it should read
OK. The other thing to check is that you have the correct hub drive should read BG5303/10 or 11 (or
52283/6) - look on the little brass end cap for the number. Finally regarding handle bars, the problem
you experience are probably to do with the standard footrests. Having experienced, clip ons, ace bars,
standard bars, rearsets and standard footrests. In my opinion standard bars with rear sets are the most
comfortable for riding. The best bars I have found are Laverda Jota adjustable bars that I have fitted to
my Venom, you can adjust them wherever you need them to be. Often I adjust them before setting out,
depending if I am going on a fast ride or a potter. What other opinions are there on bars/footrest
combinations?
L #2548 Can anyone suggest someone who can straighten or repair a 1967 Velo 500 frame, here
in the states?
#2551 Contact the Frame Man at GT Enterprises in northern California. I've used his services on
several occasions and his work and labor rates are excellent www.snowcrest.net/gte/index.html
L #2941 Hi Just a few basic questions for my first assembly. 1) Is Wellseal a good gasket cement
for the crankcase halves? Or is there another recommendation? 2) There was a 30 thou spacer under
the barrel is it a good idea to put another 30 thou spacer to counter the poor gas we have or is it better
to adjust the timing to suit. Hear in Canada we have a rating of 89 for so called premium. 3) With
regard to this spacer should there be a paper gasket below and above it?.....if I have 2 spacers is that 3
gaskets? Is there another option rather than the messy appearing gaskets?
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#2951 When assembling my VMT 334, with 3 shims, I used Hylomar Aero Grade between each of the
three metal shims and zero paper gaskets. Hylomar was also used between crankcase halves. In
almost 7,000 miles last year, this bike has remained dry, save for an early weep at the upper two piece
push rod tube/head mating. This joint was remade with Three Bond gasket goo and has not weeped
since. I'd not add any additional spacers.
#2948 1 When I put my shiny black barrel and shiny polished head back on do I need new studs and
nuts(the four long ones).
#2949 No - if youre nuts are in good nick you don't need new ones
#2952 You can squeeze the nuts in a vice or tap them with a hammer. This will compress the Nylon
and give a better "second-hand" lock. As a matter of principle we always use new cylinder holding
down nuts. And always fit new O-Ring seals under the washers.
L #3167 Hi All, I have an interest in purchasing a basket case 1966 MSS. Can anyone tell me
what the differences would be from a Venom? Basically all that is there is an engine and frame. What
kind of wheels, g\box, fenders,tank etc would it have had?
#3168 There are a lot of differences between a 66 VM and MSS. Mainly in terms of hubs, (half width),
mudguards (what is a fender - around a fireplace?) black enameled steel with valances, mudguard
stays. The engine is nearly the same and it may have a lower compression ratio and M17/7 cam. Gear
ratios could be 14/ prefix or 12/ - depending on buyer's spec. None of the 'clubman' spec parts are
appropriate. I suggest you find a few photos and have a look.
#3169...also the MSS 1 1/16" port and carb.
#3170 Different cylinder head, piston, cams, carb, barrel length, for the motor (but by '66 more and
more bits were the same). Probably a wide ratio prefix 14 box and some different bits of tinware. Hubs
& brakes were the same as Venom by then. However basics are the same. Engine should be MSS
13xxx and frame RS 18xxx or 19xxx. You can build it pretty much as you like, depending how much
you want to spend. Don't forget that by that date, the MSS was the rarest of the singles- 48 MSS, 53
Viper, 157 Venom and 224 Thruxton, according to Ivan Rhodes' book, made in 1966. Not a lot. The
MSS is not a motorway bike, more a machine for the twisty back roads.
L #3318 Hello All, I'm fighting for months against an oil seepage on my 1957 Venom : starting
from cold, after 5 to 10 minutes, running or idling, oil begins to leak from the lower rear timing cover
screw, the one close to the oil pump. I try several remedies : surfacing the cover, mounting the screw
with various washers (copper, aluminium, Dowty), different gasket thickness, various sealing
compounds, loctited screw...It doesn't change anything. Some clues : the oil pump bore has been
sleeved; the paper gasket shows a good contact in this area between the case and cover; there is a
steel insert (not helicoil) in the tapped hole, loctited. I think oil leaks as soon as the oil fills the chest to
the level of this screw, but can't understand which way it takes. Has someone experience this already ?
Any idea will be very welcome.
#3319 Is the screw too long and not tightening up the cover? Is it the cover or the case? Tried fitting
another cover? Is there a hairline crack somewhere?
L #3505 Hi, is there a preferred method to place the engine back in the frame? Must the G\box
and engine be installed together? From which side is it better to work from?
#3509 I have found it best to install with the gearbox attached and from the nearside (primary). It is
awkward but possible to do with the engine fully assembled if you don't mind knocking chunks out of
the frame paintwork (bitter experience !). It goes in better and is a lot lighter without the head and barrel
assembled.
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L #4399 Greetings A couple of weeks back I bought a proverbial 'pig in a poke', a 1946 MAC
engine from the Kempton Park autojumble. All the major lumps look to be intact, but I will need to
helicoil a couple of threads in the crankcases. Can someone please tell me the correct thread form?
Just out of interest one of the cam lobes and its follower were worn to a frazzle. The oil passage from
the pump through the timing side crankcase, was blocked. By one means and another I cleared a
spring and a ball bearing out of this passage. This suggests the presence of an oil pressure valve, but
none of the oil circulation diagrams I have seen show such a valve. The other curiosity was that the
steel base plate to the oil pump was cracked; the pump itself looks OK.
#4400 The thread for the drain plug is 5/16" X 26 TPI in CEI form, The thread for the primary case
holding bolt and the dynamo clamp bolt is 5/16" X 22 TPI in Whitworth form, the thread for the upper
rear crankcase bolt and pushrod tower hold down is 1/4" X 20 TPI in Whitworth form. The "Oil Pressure
Valve" appears to be a bodge from a Demented Previous Owner as is the cracked oil pump plate which
is made of cast iron. These plates are often cracked by use of the four holding screws to pull the pump
into place in insufficiently warmed crankcase.
#4402 I may be mistaken but I think you will find the drain plug thread to be 1/8" BSP 28 tpi. The
threads in the timing cover and pump holding screws are 3/16" BSW. Exactly what threads are
stripped? As there are a number of other 5/16" and 3/8" W in the crankcase.
L #4482 My 1967 VMT had many nuts lock-wired together. They were all removed . Now it is time
to bolt everything back together again. Does anyone have any instructions or comments to share about
this subject?
#4483 Lockwiring is a possible indication that the machine may have been raced at some time, but not
necessarily so. Some owners may simply have preferred not to risk losing parts due to fasteners
loosening under vibration. Racing regulations decree that filler and drain plugs MUST be lockwired, but
any further wiring is at the competitor's discretion. The correct method of wiring is to wire against the
direction that the fastener will loosen, i.e. if two RH threaded nuts are wired together the wire should
follow a Z pattern from one nut to the other. If a single fastener is wired, use the same principle to wire
to a solid anchor. The cut ends of twisted lockwire are SHARP! - ALWAYS turn back the cut end of the
wire on itself - the scrutineer will not be best pleased if he lacerates his hands on your lockwire!
L #4565 Hi velo fans, new member signing in, can anyone tell me if all venom rear engine plates
including the additional stiffener are the same. I am interested to know as I have acquired a set which I
intend to use as a pattern in order to produce stainless replacements for my standard 1968 ones (mk2
clubman). Without pulling the engine out I cannot check/ compare the sets, which is currently
inconvenient (I hope to get a couple more rides in before a winter strip down). Alternatively are engine
plate drawings available, this could be handy as I need to produce a cad file so that plates can laser cut
ideally. Finally has anyone thoughts on whether stainless plates will be stiff enough in 5mm (standard
size??), especially as velo saw fit to add the stiffener?
#4568 I thought you would have had 10 answers on this already. I have a half dozen or so swing arm
MSS, VM, VMT frames and engines and all the engine plates are the same. Aluminum alloy plates
have been made (I have a set but never tried them) but can't vouch for their integrity or that of
stainless.
#4569 All steel alloys (including most that are "stainless") have very similar stiffness, but they do vary in
strength. These are different properties. Strength is important when one considers threaded holes.
Aluminum typically has about 40% of steel's stiffness, but I've seen it used successfully for the front
plates
#4570 The Venom/VR/MSS are the same, but Velocettes listed different plates for the later Thruxton.
Don't ask why, maybe it was a change from Cycle to BSF for the oil tank bolts. However, make sure
you have Venom plates, the swinging arm MAC plates look the same -but don't fit, I know as I got an
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odd one mixed in when I rebuilt my MSS. Confusion reigned for a few minutes when trying to fit it to the
engine.
#4571 VMT rear plates have the additional fixing holes for the cover plate over the top of gearbox,
otherwise just the same.
L #4579 Just a small thing, but as an apprentice motor mechanic years ago I was shown how to
bring copper up to red heat & quench to soften it. It is only in recent years that I have been told that the
quenching isn't necessary, - all the quenching does is clean the metal to a new brightness ! I have
checked this out & it seems to be correct ! but it does make one feel better to see the cleaned metal !
Another tip here, if you are working on an 'older' bike, & want to bend up a copper pipe with tight bends
& maybe a neat couple of 'coils' & don't have any of the (claimed) bending devices, or the expensive
low temperature alloy filler, just work out the length of pipe needed, soften it then press it straight (by
hand), on a flat surface, pinch off one end to seal it, flare the other end a bit to make it easier to fill the
pipe with molten lead. Run a torch up & down the pipe to make sure that it is filled. I use spanner
sockets to get the size needed for the bend or coil, just wind the pipe around the chosen socket till you
have it right, then out with the heating torch again & heat the pipe to run the lead out again. ( a bit of a
chore sometimes) It pays to rattle SMALL ball bearings up & down the pipe after you are sure it has
been emptied to remove any of the junk that lead is prone to leave behind, & then wash out with petrol
or similar . Note, lead is very soft, using solder etc. may run you into trouble on small bends. Very small
intricate bends can be made this way without hassle. On this subject, - don't try the above softening
method on brass of any description, the effect is to harden it & make it exceptionally brittle, but it can be
softened it would appear by heating it & allowing it to cool very slowly, such as immersing it in hot sand
& allowing to cool, I'll accept correction to this if I am wrong, I have never claimed to be a metallurgy
expert !
#4581 Hi All, Just adding my twopenny worth to this subject. The technical bit (ref. Engineering
Workshop Data - Caxton 1947). Annealing Copper Correct annealing temperature is from 200oC -
600oC according to level of impurities and level of cold work done to the metal. For most commercial
coppers 500oC is satisfactory. The mode of cooling, with copper, is immaterial; either water quenching
or air quenching is applicable but water quenching serves to remove dirt and scale. Annealing Brass
Ordinary copper-zinc are annealed by heating for about 15 to 20 minutes, at 600oC and allowed to cool
either in air or by water quenching. The practical bit (what it says in 'Model Boilers and Boilermaking' by
K N Harris 1972 and what I do) Nine times out of ten when you find instructions for annealing copper
and brass you will be told: " Heat it to redness and immediately plunge into cold water." The last part of
this injunction is completely superfluous, the only purpose it serves is to save time. Harris goes on
about air cooling to avoid distortion, but that's probably only relevant to complicated shapes not
motorcycle bits - I always water quench to clean the item and save time. To achieve the right
temperature with both copper and brass do not heat beyond just visible redness, visible in subdued
light, not in bright light or sunlight. For brass the 'heating for 15 to 20 minutes' is the stuff of dreams
(bad ones probably!) only for those with temperature controlled furnaces. It's more important not to
overheat brass and damage it's 'grain structure'. The practical form of heating is a gas flame - a
propane torch or for small items such as copper washers the kitchen hob is great (if you use it without
being caught!). 'Ordinary brass' (suitable for tubes) is typically 60% copper 40% zinc. In the annealed
condition both copper and 'ordinary brass' are noticeably soft and easy to bend at room temperature
(called cold working). After a modest amount of work they become noticeably harder to work (called
work hardening). It's important to stop bending or working the material as soon as work hardening is
detected. You then anneal the item and you can work the item some more. For complex items this
cycle has to be repeated many times
#4583 While I am well aware of the deterioration of brass alloys in seawater (& other mediums), & the
presence of steel, & the fact that it can lead to total destruction of the article, the culprit being
electrolytic action, I have often wondered how this sort of thing takes place over many years with sheet
brass items, I can only assume that it is a form of mild electrolysis taking place very slowly, by virtue of
the air &/or presence of other suitable elements of metal, & moisture in the atmosphere, this over a very
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long period of time ?? This is most apparent in some OLD brass articles, & while the original hardness
caused in say sheet brass , while it was being spun or worked, remains forever I guess, - unless
softening is attempted, & I am pretty sure that this would be disastrous on articles getting on to 100
years old ? This was most apparent recently when Mark Gibson presented me with an acetylene gas
generator as a repair 'challenge' This article was at least 90 years old I should think, & the water tank
part of it was full of the typical 'splits' in the metal that is apparent in old worked brass articles, -
especially something that has been work hardened by 'spinning'. In this case though, one side of the
tank pretty much fell apart in little bits of brass 'honeycomb' the moment I started to smooth the dents,
& the reason was certainly that the brass was nothing more than frail 'zinc removed' sheet, typical of
electrolysis damage. This plus other experience with old brass, leads me to accept that the electrolytic
process can destroy brass over the years, simply through the action of changing temperatures, - the
local presence of suitable metal, (stored in a steel container ?) & the action of moisture in the air ? this
of course only being apparent in very old articles. Maybe Richard can comment on this ? As for the
repair challenge, it was carried out successfully, but only after light gauge sheet copper (easily
available) was patched on the inside of the destroyed part of the tank after smoothing & cleaning, &
another 'patch' cut to bring the lost section back to the original contour, & the whole thing sweat
soldered back together, with clamps & such holding everything into place. Pic available if you are
interested)
#4584 You've got me delving back into the dim past with this. We are now entering the realm of theory
with a bit of guesswork. Like you I'm familiar with electrolytic corrosion. The problem you outline with
old sheet brass items is somewhat different. The reference is 'Engineering Metallurgy Part 1' by R A
Higgins 1964 - this has been a useful book over the years. The subject is 'Cold -working' brasses. The
most ductile brass is high purity 70% copper, 30% zinc. (Even small levels of impurity lead to a marked
loss in ductility). It's commonly referred to as 'Cartridge Brass' or 'Deep drawing' brass and this would
be ideal for making items such as acetylene generators. For info only, such brasses are rather sensitive
to annealing temperatures and it's easy to 'burn' the alloy. (This trade term should not be confused with
oxidation. It is used to signify overheating, the result of which is rapid grain growth that on subsequent
working/pressing shows up as an 'orange peel' effect on the material surface). The problem that I
suspect you have experienced however is due to the fact that hard-drawn brasses are subject to
'season cracking'. Higgins says 'In such brasses, any corrosion which takes place is usual
intercrystalline, so that cracks will ultimately arise, as internal stresses are relieved, by fracture at the
relatively weak grain boundaries. This effect can often be seen in old brass electric-light switch-covers,
particularly when they have been subjected to corrosion in a damp atmosphere. Season cracking can
be avoided by giving the component a low temperature, stress relief anneal at about 250oC., after
fabrication'. In addition, somewhere in the back of my mind, I'm aware that acetylene gas has some
pretty corrosive effects on certain metals but hopefully someone can remind us.
#4585 The process you refer to in brass is known as 'de-zincification' and commonly wrecks water taps
& valves in hard water areas. The zinc is removed by electrolytic action leaving holed brass which is
also weaker. In water installations it was the case that a sacrificial anode was provided. Better alloys
are the choice today - unless you happen to have cheap taps!
#4586 Thanks chaps, it seems that I was basically correct, & the fact remains that any brass, especially
that of high zinc content is prone to this problem in the presence of certain factors. A lot of years is
probably a big factor ! The fact is that we as 'ooman beens' can only experience these happenings over
a short space of time in the big picture, & very few of us have the opportunity to actually note what
really happens to metals of all kinds eventually. One would expect that in the case of brass, in the end
after long periods of time, all that would remain is some form of copper residue, as we have been
taught that copper is one of the things that never really gives up ! I had one experience with marine
propellers where extremely expensive props were hooked to 2 Rolls Royce marine engines & fitted to a
70 foot steel boat, which was built privately in a yard close to me, & I had mentioned to the builder that
he would need to buy & fit decent sacrificial zinc anodes to the back of the hull. He was Dutch & had
previously built timber boats, & intimated that if you fitted 'decent' props, as he had done, the zinc was
unnecessary ! The boat was launched into the sea, & some Summer cruising enjoyed, the boat lay in
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port through the Winter, only occasionally being used as a week end bar. The next Summer, the boat
had lost it's turn of speed, & soon could barely pull itself away from it's moorings & the Rolls engines
were racing. An underwater inspection revealed little more than the hubs of the props & 'nubs' of the
blades ! Nothing to do with Velo's ? but it appears that certain (if not all) EP oils can have the same
effect on Velo gear box bearings eventually. I have to admit that in ignorance of this fact, I have been
using EP 90 in all my gearboxes for years ! - so we live & learn
L # 5200 Gents: I'm in the process of restoring my 67 Clubman and would be interested in
advice anyone would have regarding motor and/or gearbox installation. I pulled the motor and gearbox
out as a single unit but now since the bike is in pieces my interest is to refit the engine and box without
dinging either the new paint or laboriously polished aluminium. With an old Sportster I'm building I laid
the engine on a blanket and more or less fitted the frame to the engine which worked quickly and
easily. Obviously the Sportster is unit construction but will a similar approach work with the Venom?
# 5204 Assemble engine and gearbox together with rear engine plates. Slip into position from RHS of
machine. Fit mounting bolts and front engine plates..
# 5207 It sounds so simple put like that, but never actually seems to be as simple when I actually do it!
I discovered another way whilst frantically working in the paddock at Cadwell Park one day when I had
to change the box after the sleeve gear locking ring "gave up." I now fit the engine into the front plates
and attach it to the frame. Then I fit the box in from the right, with only the offside plate attached, not
forgetting to put in the lower stud and the top two temporarily slipped in from the wrong side. Then
simply fit the nearside plate(s) and the job is done and all paint left intact.
# 5254 I can assure you that you will knock your paint about if you fit the engine and gearbox fully
assembled. There is little room to spare with the rocker cover barely clearing the top frame tube.
Suggest you build up only to crankcase level and you'll find the unit complete with gearbox easier to fit.
If you want just those extra inches for juggling, at least remove the rocker cover. Bubble wrap around
the lower and front frame tubes helps as does a scissor jack under the gearbox whilst you fit the
various bolts.
L # 6043 I have a unusual request for you UK Velo fellows. Would anybody out there happen to
have a good example of a 1957 UK tax disc that they would care to either sell - or colour scan for me? I
would like to photograph my newly restored Venom with a period disc.
# 6044 At a cost of £26 the Heritage motor museum in Gaydon near Warwick will send a replica tax
disc for any year www.heritage-motor-centre.co.uk/
L # 6217 I'm looking for a special spanner to fit the gland nuts on the vertical cam shaft tube on
the mkI KSS. The part number in the book is KA55. Does anybody know where I might find one of
these?
# 6225 Sold by the VOC spares scheme VSL364 GLAND NUT SPANNER For OHC vert shaft housing
nuts. L15.00
# 6219 Probably the quickest route is to make one - they are not particularly complicated. Colin East
made one for me, and may have made a few extra at the same time (01522-810029) but don't expect
anything in a hurry!
# 6220 I made one about 65 years ago & still have it, from memory I cut a blank by drilling a line of
holes around the outside, ( no oxy cutting gear in those days), then swung the blank in the lathe &
bored the hole to the vertical shaft diameter, plus a few thou. then cut away surplus metal. -- The rest
was done on the grinding machine & finished off with a file. I was stirred into action by the fact that Les
Diener had made one in the toolroom as a 'foreigner' with all the machinery available to him, & as was
our relationship in those days, -- I just had to have one also ! Do you know what it looks like ? It's about
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6 inches long overall. I would suggest making the action part much deeper from a piece of heavy wall
tube, -- such as a portion of a fork staunchion, & then weld a flat handle on to it. The original would
have been a forging, tidied up with a file I should think, -- can't say that I have ever seen an original ? I
have never really used the tool in anger since 'Silastic' arrived. I just use a couple of turns of graphite
impregnated string, & screw this down snug to form a mechanical seal, then back off the bottom nut &
smear a SMALL amount of Silastic around the circlip & tighten the nut down snugly. Then repeat at the
top joint. Nuts only need to be snug. DO NOT RETIGHTEN, after the Silastic has set !!! Any small
amount of surplus Silastic will remain in the small void between tube & bush housing, & I can assure
you that there will be no leakage, & no need for the original ongoing tightening of the gland nut. ( I well
remember this in the old days !) Of course I discard the paper gaskets between bush housing &
crankcase & the top joint to the cambox , by doing the mesh adjustment by machining minute amounts
from the bush housing flange or the bush facing, a bit traumatic the first time, but much easier than it
appears ! but on the other hand, -- once done properly, the meshing stays stable forever ! The sealing
of this joint is by an 'O' ring in a groove somewhat improperly located right in the corner of the housing
flange, -- the actual sealing being by the corner of the machined ( & quite often seriously damaged)
edge of the aluminium casting, into the 'O' ring trapped in the groove, -- but it works ! Mind you, it would
be possible to set up an 'O' ring in the bush body, but there isn't much room on the bottom c/case bevel
housing for a good 'O' ring seating surface.
# 6222 grove classics lists it for 8.50 pounds
# 6224 It's worth 8.50 pounds of my time to buy one instead of attempting to make a poor substitute.
I'm sure the homemade tools are excellent, but my version may be sub par.
L # 6239 I'm seeking a recommendation for raw material to turn several small end bushes for a
couple of engines. The original material was an aluminum based material. If possible, I'd like to stay
with the aluminum material. Can someone here recommend a material or two using either SAE or some
other widely recognized material identifier?
# 6241 R.R. 56 is the recommended material - not sure what the equivalent in today's ali is.
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