Booming Italian let
loose in Somerset
Super-rare 750cc twin on the road
Reader’s lifelong passion
for Enfield’s sweet 250
FEBRUARY 2018 | modified triumph 650 | team obsolete | enfield continental | matchless 45 | wasp motorcycles | vintage trikes | fit electronic ignition | sunbeam project | issue #457
20 pages of
B r i t a i n ’ s b i g g e s t - s e l l i n g c l a s s i c b i k e m a g a z i n e
Beautiful TT replica hides cunning
upgrades for our modern world
Britain’s forgotten 1000cc twin
160mph Trident outfit ¤ Salon Moto Legende
Vintage trikes tear up Brooklands
Swiss JAP Special ¤ 50 years of Wasp
Inside Team Obsolete
Feb 2018 UK Jan 24-Feb 20
£4.30 USA $9.99
Two fingers on the
clutch? You’d want
more than that on
an earlier Jota...
words: Phillip Tooth.
Photography: tim keEton
Velocity is intoxicating, but when it’s combined with a noise that sounds
like a portent of the world’s end, it can only be one thing – a Laverda Jota
o say that the Jota comes with a
reputation is a massive understatement.
When it was launched in 1976, it was the
fastest road bike that money could buy.
While the Ducati GT I owned at the time
was good for about 115mph and my Le Mans’ top speed
was closer to 130, the legendary Jota was the first overthe-counter
production road bike to top 140mph. It
didn’t matter if it was too heavy and that you had to
bully it round bends, or that you
needed two hands to pull in the
clutch lever, the Jota blew the best
from Japan into the weeds, and
deafened them in the process.
Laverda’s 981cc triple had
launched itself from the Breganze
factory in 1973 with the uninspiring
model name 3C (Tre Cilindri). With
a bore and stroke of 75 x 74mm and
featuring the usual chain-driven
double overhead cams with two
valves per cylinder, designer
Some advertising lines are just hype – but not this one
Luciano Zen went his own way
with a 180° crankshaft. Because the middle piston was
at top dead centre when the outer pistons were at
bottom dead centre, the 3C wasn’t as smooth as a 120°
triple like a Triumph Trident, but it certainly wasn’t
rough – and the power pulses gave the exhausts a brutal
bark. Laverda claimed 80bhp at 7250rpm and a top
speed of 137mph... but you could take those figures with
a large grind of black pepper.
It was British importer Slater Brothers who unleashed
the Beast of Breganze. Richard and Roger Slater had
‘the Jota blew the best from Japan
into the weeds – and deafened
them in the process’
On the gas with the
fastest bike of its
been campaigning a 3C in production racing with some
success. Fork triple clamps from the SFC750 endurance
racer twin were used to give a shorter rake. The engine
delivered extra punch, thanks to a factory cam and
pistons designed for the endurance racers that first
appeared at the Bol d’Or, and the silencers lost their
baffles while the collector pipe was a bit bigger. Those
mods were enough for another 8-9bhp at peak revs, and
that meant harder acceleration. In 1975 Slater Brothers
built a small number of these
racers for the road, and called
them the 3CE (‘E’ for England).
Tested at the Motor Industry
Research Association track, the
latest Laverda recorded a mean
average speed of 133.3mph.
The Breganze factory had also
been busy, upgrading the 3C with
Laverda’s own cast wheels, triple
Brembo discs and a tail fairing to
produce the 3CL for the 1976
season. This was to be the bike
that the Slater Brothers would use
as the basis for the Jota, a name that music-loving Roger
chose after hearing Spanish folk dance songs with a
three/four beat – and they didn’t hang about.
Available from January 1976, the Jota’s engine was
factory-built to Slater’s 3CE specification. The
transmission featured a lower first gear ratio (9.51:1
instead of the 3CL’s 11.24:1) and closer ratios for the
other four, which made the Jota racetrack-ready and a
great bike to ride on fast, open roads. Claimed
maximum power was now 90bhp at 7600rpm. And that
1: High, wide,
and very fast
in the fun juice
are quality touches
4: Just so as you
5: Looks like a
silencer – but looks
can be deceptive...
was enough for a two-way average of 137.80mph, with a best
one-way of a benchmark-setting 140.04mph.
Those first Jotas were available in either red or green paint for
the tank and side panels, with a black frame. Silver was the
colourscheme for 1977, with gold an option the following year,
when the Ceriani suspension was replaced by Marzocchi.
Laverda’s official orange race livery and a silver frame graced the
Jota in 1979. For 1980 the cylinder head was redesigned, the
exhaust headers were increased to 36mm diameter and the
clutch got extra plates. There were more changes in 1981, when
the Series II Jota got a bigger-output alternator (up from a barely
adequate 140W supplied by Bosch to an impressive 240W
thanks to Nippon-Denso). The transistorised ignition was
moved to the left side of the crankshaft, and the primary
chaincase grew a bulge as big as mamma’s pasta pot to hide it.
Almost as important, the clutch cable was replaced by a
hydraulic system. The big news for 1982 was a new 120° crank,
but a year later the Jota was replaced by the RGS.
I’d have been happy to throw my leg over any Jota, but the
pick of the bunch has to be the 1981 orange-and-silver version
that owner Terry Sage wheels out of his garage before handing
me the ignition key. Before hitting the starter, I used to openand-close
the twistgrip on my Le Mans so that the pumper carbs
would squirt neat petrol into the combustion chambers. The
Jota also wears pumper Dell’Ortos, but Terry does things
differently. “Just pull back the choke lever a bit and press the
button. It’ll fire immediately, then ease the choke right off.”
The Jota’s soon ticking over reliably. It’s my first surprise.
This Jota is full of surprises. The second is that I can plant
both feet on the ground. The seat height might be a crotchstretching
32in, but the nose of the seat and the rear of the tank
are both slim. I think it was journalist Peter Watson who
described the Jota’s Brevettato ace bars as ‘adjustable to 27
different configurations, none of them comfortable’ – and I still
laugh whenever I see a Jota and think of him. Yet as soon as I set
off, I feel completely at home, easing through rush-hour traffic
and out of the city as if I’d owned this Jota as long as my Duke.
After a quick blast along a dual carriageway, I change down
1 laverda jota
into third entering a village and rumble through with
rock-steady needles recording 30mph and 2000rpm on
the Japanese clocks. Read that again: third gear, 30mph,
2000rpm. I didn’t believe it, either – and had to play
with the gearbox to make sure that I was right. Wasn’t
the Jota meant to be a right pain in the neck – and
wrists, and clutch hand – to ride slowly, and only come
into its own when you were thundering across England
at speeds close to twice the legal limit?
But when I crack on, the Jota begins to reveal its true
nature. The engine growls, the exhausts boom and as the
needle swings past 6000 my guts tell me that things are
getting exciting. The Jota can be safely revved to 8500,
but with 500rpm in hand that’s still 60 in first, nearly 90
in second and 110 in third. Two more gears to go...
You don’t ‘think’ a Jota through bends. At 236kg
(522lb) with a gallon of super unleaded, it weighs the
same as my old GT – but most of that weight is carried
much higher. Stay focused. Get your braking done early
and pitch it into the corner. Winding on the throttle
helps to pick the Jota up again and throws it out of the
apex. You’ll have to use muscles you forgot you had, but
it feels good. Who needs a gym when you’ve got a Jota?
On fast sweepers the steering is faultless. You can
relax at 70mph with the engine turning over at a lazy
4000rpm, or cross continents at the ton and still only be
using 5700rpm. Gears snick effortlessly into engagement
and the hydraulic clutch feeds the power in smoothly.
Brake and clutch levers were set up by Ricardo Oro’s
workshop in Breganze, so they are as good as you can
get, but after riding for four hours the thumb muscle on
my left hand was aching and I didn’t like the front brake.
Although it was powerful enough, it had as much feel as
squeezing a pick-axe handle. And the lever was too far
from the handlebar for the span of my dainty paw.
There was time for some cornering photos before we
headed home, and that meant turning around in the
road a half-mile from the bend. We were in the middle of
the country and there was only one house, so I didn’t
think we would disturb anyone, but I was making the
fifth turn when an old woman came out and said
politely: “You are making an awful lot of noise. Can you
please do that somewhere else?” Pointing out that I was
only using half-throttle wasn’t the way to respond, so I
apologised and we moved on. The Jota legend lives.
Terry Sage bought and fixed up a
crash-damaged 1976 Laverda 3CL
when he was 19. “I’d been riding
the 3CL for four years, but I really
wanted a Jota. When I saw a
secondhand orange-and-silver one
at Three Cross Motorcycles in 1985
I had to have it.” Terry was working
as a steel erector at the time: “I was
earning good money, but it cost
£3500 so I had to go to the bank
and get ticked up to the eyebrows.”
He was still running his Jota in
1998, but was being left behind by
his mates who were all riding
modern supersports. So he sold the
big triple and bought a Ducati 748.
“I realised I’d made a mistake as
soon as I sold it,” says Terry. He
chopped in the 748 against a 996,
then a 999 and finally 1098S – but
he still hankered after a Jota. “I
know it was loud, heavy and slow
compared to modern sports bikes,
but it was something special.”
He bought another Jota, but had
top-end oil feed problems. Ged
Shorten at GCS found that the six
long studs which fix the cam
bearings, cylinder head and barrel to
the crankcase had been fitted
upside down. As they were
tightened, some of the threads had
been ripped from the crankcase.
The studs are 9mm diameter and fit
in a 10mm hole. Oil is pumped up
the gap to feed the cam bearings
but now the lubricant was simply
returning to the sump.
After the crankshaft was rebuilt
by Keith Nairn of Laverda Scozia,
Ged repaired the crankcase and
rebuilt the engine using Omega
ceramic coated pistons.
With the Jota properly sorted,
Terry is enjoying the good times
again. “My friends all admit that she
can get a move on for an old girl!”
‘The engine growls, the exhausts
boom, the needle swings past
6000... things get exciting’
The legend lives on –
and Phillip survived
the experience, too
The Bravest Indians
The recent revival of the Indian marque has brought it back into the
spotlight, so here’s a reminder of its first incarnation. We look at
some of the legendary models that forged the famous firm’s identity
words & Photographs: phillip tooth
▲ 1905 Camelback
On May 24, 1901 Oscar Hedstrom sent a telegram to George Hendee to
tell him that the first Indian was finished. Six days later he was riding the
prototype around Springfield before towing his friend Brooks Page, who
was on a bicycle, up a long hill. Hedstrom’s engine had a capacity of
260cc and was fitted into a bicycle frame, with chain drive and a top
speed of 25mph. The first production Indian was assembled at the
Springfield factory and was on the road in May 1902, with a total of 143
built that year. Three years later a bigger single-cylinder engine rated at
2.25hp was offered, with a bore and stroke of 67 x 82.5mm adding up to
a capacity of 290cc. When this 1905 red Indian (a colour option to the
standard Royal Blue) was first pedalled into life, there was a spring fork
and a twistgrip control to the carburettor. Production rocketed to 1181 in
that year. Speed had increased dramatically and a tuned version covered
the flying mile at 52mph. That was really flying...
▲ 1912 Hedstrom Racer replica
Headline news in 1906 was the addition of the 633cc V-twin racers to the
catalogue, soon followed by the road version (still with a camelback tank).
A single-loop cradle frame replaced the bicycle-style diamond frame in
1909, and there was a coiled spring in a cartridge mounted horizontally
above the mudguard to provide suspension for the forks (although the
famous leaf-spring forks were introduced for the 1910 season. There was
also a new 988cc F-head engine with a mechanical oil pump, and these
engines were reduced to 585cc to make them eligible for the 1911 Isle of
Man Senior TT, the first time the race was run over the Mountain course.
With all-chain drive, a clutch and a two-speed gearbox the red Indians
swept the board with a 1-2-3 finish. At the end of 1911, Indian held all 121
American speed and distance records. For the motodromes, Hedstrom
developed an eight-valve engine but these rare beasts were for the
chosen few. Mere mortals used a tuned F-head like this 1912 racer replica.
When a road tester arrived back at the Indian experimental department
after a hard, fast ride Charlie Gustafson, who designed the new V-twin,
and Frank Weschler, in charge after founders Hendee and Hedstrom had
retired, stubbed out their cigarettes and walked out to meet him. “What
does she go like?” asked Gustafson. “Man, this motor has power –
plus!” replied the tester. The 998cc side-valve used the same 42° V-twin
angle as the Hedstrom engine. Two years of rigorous testing were
carried out before it would go into production in 1916, but to prove just
how good the Powerplus was, Erwin ‘Cannonball’ Baker fitted a
Powerplus engine to his 1914 Hedstrom chassis to attack the Three Flag
record by setting the shortest time to ride from Canada to Mexico. He
left Vancouver on August 24, 1916, reaching Tijuana on August 27 –
1655 miles of treacherous roads in three days, nine hours, 15 minutes.
“It’s a bear, a big, husky lick-all-comers machine!” Baker enthused. That
rugged useability led to Indian supplying the US Army with nearly 50,000
Powerplus motorcycles after America entered World War I.
▲ 1917 PowerPlus Boardtrack
Somehow, Charles Franklin managed to extract more power out of a
Powerplus engine than Harley’s top tuners could squeeze out of their
eight-valve engines. While the 1917 road bike now featured leaf springing
front and rear, the earliest board track and dirt track bikes used a cut-down
frame and were often raced in rigid form. Later there would be special
Marion frames for the Powerplus racers. The tube that ran under the
engine on the loop cradle frame was cut out, and the engine held in place
with steel plates. It seemed like a backward step when these bikes were
debuted at the 200-mile national championship race in Marion, Indiana in
1919, but the pundits were proved wrong. A Daytona version of the
Marion frame, complete with lowered top tube and headstock, was
adopted in 1920. These frames are easily recognisable because the seat
tube had to be bent into an S-shape in order to make the engine fit
properly. The Daytona soon became the factory riders’ favourite bike, but
there were plenty of farm boys and garage mechanics who raced
stripped-down Powerplus cycles.
ABOVE: Spring forks
went on road bikes;
racers were rigid
xxxxxxxxx xxx xx xx
xxxxx xxx xxxxx xx
▲ 1930 Scout 101
‘You can’t wear out an Indian Scout’ was the boast long before the 101
was launched in the spring of 1928. Capacity had been hiked from the
original 600 to 750cc for the 1927 Police Special, and it was this ’45 cubic
inch’ engine that went into the 101. One of the best Indians ever, the new
Scout was about 3in longer, 1in lower at the saddle and even had decent
brakes. Big ‘balloon’ tyres were standard and handling exceptionally good.
For 1931 there was a twistgrip-controlled oil pump to vary the delivery rate
of lubricant. The 75mph 101 Scout was popular for amateur racing and
Wall of Death. Despite the Depression, some 14,000 were sold before it
was (unpopularly) replaced by the 203 Scout – a 750cc using the heavy
Chief chassis – in 1932. The sporting image was regained with the 1934
Sport Scout – a winner for Ed Kretz at the first Daytona 200-miler in 1937.
▲ 1938 Type 438
There was a new four-cylinder engine for the 1936 model year, but it was
a flop. Called the ‘upside-down’ engine because the exhaust valves were
now on the top, it looked ugly and the high exhaust pipe needed a steel
guard to stop it burning the rider’s leg, so for 1938 the Model 438
reverted to the original overhead inlet/side exhaust configuration. The
cylinders were now cast in pairs – testing proved that eliminating some of
the air gaps between cylinders allowed the heat to be pulled into the
airstream more quickly. The aluminium cylinder heads were detachable
with the valve mechanism fully enclosed and automatically lubricated.
There was a streamlined muffler to keep things quieter on this 95mph
motorcycle. Although a left-hand throttle and right-hand gearshift was
standard, a right twistgrip and left gearshift was a factory option.
ABOVE: Indian Big Chief
was a response to the
▲ 1925 Big Chief
For the 1920 season a radically different Indian was launched: the 600cc Scout, with semi-unit construction – the engine,
primary drive, clutch and gearbox were locked together. The primary drive consisted of three helical gears, each on roller
bearings, all enclosed in an oil-tight alloy casing. Instead of a single camshaft to operate all four valves there were now two
camshafts, each with a single-lobe cam to operate both inlet and exhaust valves of one cylinder through pivoted cam followers.
Heads and barrels were cast in one piece. The double-loop cradle frame had a flat platform to mount the engine/transmission.
But there were those who demanded more power. Enter the Chief, launched on Labor Day, September 1921. The 998cc
engine delivered about 20hp, enough for brisk acceleration to a top speed of 65mph. But Harley had gone supersize with a
1200cc engine in 1921. The Chief was more technically advanced, but Indian needed something bigger for the 1923 season –
enter the 1200cc Big Chief. In November that year Hendee Manufacturing Company became Indian Motocycle [sic] Company.
▲ 1925 Ace Sport
What’s Ace got to do with Indian? Rather a lot. William Henderson, the
technical brains behind the Henderson Four, had fallen out with Ignaz
Schwinn, whose Excelsior company had taken over Henderson in 1917.
Henderson found new backers and formed the Ace Motor Company in
Philadelphia in 1919, with the first high-performance F-head Aces rolling
out for the 1920 season. But then tragedy struck. In 1922 William was
killed while test riding his latest creation, the very rapid Sporting Solo
model Ace. Ace riders set new cross-country speed records and won
numerous hillclimbs, but financial troubles were never far away. In
December 1927 Indian purchased the Ace assets and marketed the
1300cc Four as the Indian Ace, and up to 1935 all Indian Fours were
essentially Ace, which were essentially Henderson...
▲ 1929 Type 401
While Indian initially produced the Ace virtually unchanged, the 1929
Model 401 adopted more of the parent company’s trademark features.
As well as deleting the Ace name, the tank became a compact teardrop
design. Indian’s famous leaf-spring fork replaced the Henderson-Ace
plunger type and a drum front brake was fitted, complementing the
contracting-band rear. The 401 initially shared the Ace’s single downtube
frame, but vibration issues prompted a twin-tube design based loosely on
the Scout models but using heavier tubing. The new frame was fitted to
the Model 402, available from spring 1929, which also featured a fivebearing
crank to replace the Ace’s three-bearing unit, along with a better
oil pump, redesigned cylinder heads and alloy pistons. The 402 gained
50lb, so riders needed all the available 30hp to stay with the old Ace.
ABOVE: Military Chief
‘These 75mph bikes
were painted in a drab
olive with no hint of chrome’
▲ 1940 Military CHief 340B
Although the US Army selected Harley-Davidson for World War II, in 1940 Indian received an order for 5000 Chief sidecar
outfits from the French army. When events overtook France, most were diverted to other forces, including the Polish Army,
many ending up in Britain - some allegedly ending up at the bottom of the North Sea in torpedoed ships. These 75mph bikes
were painted a drab olive with no hint of chrome, but at least the dispatch riders had the comfort of plunger rear suspension.
▲ 1942 Scout 741B
The British, Canadian, Australian and other Allied forces chose the Indian
Model 741B to be used alongside BSA M20 and Norton 16H dispatch
bikes. Designed in 1939, with a capacity of 500cc, the 741B was lighter
and almost as fast as its bigger brother. It revved to almost 5000rpm and
topped out at 65mph. Production ran through to 1944, with about 35,000
made. After the war, many – like this 1942 model – were stripped of their
army uniform and dressed for Civvy Street with a coat of fresh paint.
▲ 1943 Type 841
In 1941 the US Army offered Harley and Indian a $350,000 contract to
build 1000 shaft-driven 750cc twins to rival the WWII BMW. Harley’s XA
was a boxer, but Indian offered a transverse 745cc V-twin., using Sport
Scout cylinders. Put through their paces in summer 1942, Army testers
reckoned the low-centre-of-gravity 841 handled better than the H-D with
a 70mph top speed. A tough call, but there could be only one victor... the
Jeep. They were sold off as war surplus in 1944 for $500 each.
▲ 1946 Chief
If Indian couldn’t compete with Harley’s Knucklehead in the performance
stakes, the 80mph Chief certainly could when it came to style. The big
news for 1940 was the skirted fenders introduced by engineer and stylist
George Briggs Weaver. Although not everyone was impressed with the
look, there were others who thought the skirted fenders made the Chief
the most beautiful bike on the planet and today they are iconic Indian
wear. Also new that year was a plunger-sprung frame, although the forks
retained the leaf spring – that all changed in 1946, however. Indian had a
new owner named Ralph Rogers; times were tough and the Chief was
the only model produced that year, but it came with a new double-spring
girder fork with a hydraulic shock absorber, basically a slimmer version of
the fork developed for the military 841. The Indian head and war bonnet
fender light was introduced for the 1947 model year, but Rogers’ business
was struggling – he was developing a range of lightweight vertical twins
to take on the Brits and finances were tight. The Chief wasn’t listed in
1949, but returned in 1950 with new telescopic forks and a capacity hike
to 1300cc. Three years later production of Indian motorcycles ended and
the Roadmaster Chief was sent to the happy hunting grounds. But today
the Chief and the Scout are back – big time. And you can even buy one
with skirted fenders and that war bonnet light...
▲ 1947 ‘Rainbow’ Chief
In 1933 the Chief went to dry sump lubrication from the old total loss. A
year later it lost the helical-gear primary drive, replaced by a cheaper and
quieter four-row chain – Harley riders joked that the whine from the
geared primary drive sounded like a built-in police siren. The 1935 Chief
looked bang up to date with smooth ducktailed fenders and a striking
Indian chief‘s head decal on the tank. Performance was improved with
cylinder heads designed to increase midrange torque with a small
sacrifice in top speed. But Harley had their own ideas, and in 1936
launched the legendary 1000cc ohv ‘Knucklehead’. Indian’s response?
A tank-top instrument panel and custom paint features – but these did
become a useful selling point, with colour options running to practically
anything the customer wanted. This was a side benefit of Dulux paint
manufacturer E Paul duPont having taken over struggling Indian in 1930.
In 1938 Rollie Free set stock class records at Daytona Beach with
109.65mph for the Chief and 111.55mph for the Sport Scout.
‘harley riders said The primary
drive sounded like a siren’
Rick Parkington welcomes you
to our Classic Workshop
Rick’s Fixes Your problems solved 92 Project bike Martinsyde cases 98 Wiring Pt2 Looms for beginners
our classics 1?????????????
Make vintage bike grips
You can adapt a regular handlebar grip like this...
Solving the problems
of the classic world
1Here’s the problem – most handlebar grips have a closed end. If you
have a vintage bike with inverted levers – or a more recent bike with
handlebar weights – you need to make a neat cut.
knife makes a mess of the job, but a wooden or nylon bar makes
it easy to use a wad punch – the bar gives the necessary support
of an ‘anvil’ against which the punch can do its work.
If the bolt doesn’t fit
the hole, it’s worth
making one that does.
stammered the Sunbeam’s engine as I peeled off
the main road into a lane. Oops, that doesn’t
sound good. It’s engine speed… piston? Big end?
It’s loud, so more likely piston, but (despite
having opened up a bit to shake off a tailgating
car) there’d been no sign of any seizure.
I limped gently along, home still ten miles
away… Try a hand-pumpful of oil. No
difference, hmmm... I’d expect a splurge of cold
oil to take the edge off a noisy big-end or
piston. Try a bit of ignition retard; taking the
punch out of the combustion usually quietens –
or at least alters – rattles. Not this time...
Not as bad as it sounds
A ride on Rick’s latest acquisition results in a noise that sends alarm bells ringing...
‘it would be Just my
luck to blow it up so
soon after buying it’
Who Is Rick?
has been riding
and fixing classic
bikes for decades.
He lives and
fettles in a fully
tooled up shed in
his back garden.
My thoughts turned to the events I’ve
booked the bike in for this year – and
what I’d take instead. Just my luck to
blow it up so soon after buying it;
whatever the trouble it can be fixed,
but it will take time and money.
Spotting a lay-by, I pulled in for a
quick look and bingo! The rocker
support plate bolts had come loose, allowing
the rockers to jump about on the head; the
noise was that and the consequent slack in the
tappets. After a few spanner tweaks, we
completed the journey in (relative) silence.
Back home, instead of simply reaching for the
Loctite I had a closer look and the true cause of the
problem became clear. One hole in the side plate is
oversize and a loose fit on the bolt. Without the location
of being a snug fit in the hole, the clamping force of the
bolt will struggle to hold it from shifting and working
loose. I made a shouldered bolt and hopefully that will
be the last I hear of that problem.
3Lucky me, I have an arbor press which makes it simple, but a
hammer would also do the job. It may be necessary to turn the
punch after the first blow to ensure a clean cut all the away round.
THE BIG FIX
Do the maths
Bob Covey emailed with what he called a
‘simple’ question. “Rick, my BSA B44 is
stripped for rebuild. It should have a
compression plate, but I can’t find out
what thickness it should be for the correct
9.4:1 ratio. Do you know, or can you tell
me how to work it out?”
I don’t know – and I failed maths
O-level twice before giving up. But thanks
to mechanical problems like this, I’ve
picked up a bit since.
To work out the compression ratio, you
need to know the volume of the
combustion chamber at TDC, measured
by tilting the engine and filling the plug
hole to the bottom threads with a
Higher-tuned Victor had a scary 11.4:1 compression ratio
measured quantity of oil. This, added to
the swept volume of the cylinder and
divided by the combustion volume, will
give you the ratio. For example, if the
combustion volume is 100cc on a 500cc
engine, 100 + 500 = 600. Divide that by
100 and you get 6, or 6:1.
4There we go – a nice, neat job that doesn’t look like it has been
chewed out by mice. One other tip: hairspray makes a good
lubricant for handlebar grips and sticks ’em in place when it dries.
So can you adjust the equation to work
out the combustion volume from the CR
and the capacity? Suppose the 441cc BSA
chamber was 50cc, then 491/50 gives a
ratio of 9.82:1 – close. Trying again, I find
52.5cc chamber volume would give a
441cc engine a 9.4:1 ratio. The next thing
is to work out by how much volume is
increased by, say, a 1mm shim. The B44 is
79mm bore, so using Pi x R sq x H, we
can work out that a 79mm x 1mm
cylinder has a volume of 0.49cc (which is
hardly surprising since a 490cc Norton’s
bore and stroke is 79 x 100).
So, for instance, if Bob’s current volume
is 51.52 (working out at 11.7:1) he would
need a 2mm shim to correct it.
I reckon my maths teacher should eat
his cruel words…
RICK answers your queries
Studying studs Pt1
Tony Dodsworth in Johannesburg is
building a pre-unit 500cc Triumph
for which he acquired a nice set of
late Speed Twin crankcases, but
there’s a catch: “None of my 500cc
barrels fit them – but 650 barrels do!
Any ideas what’s going on?”
As it happens, Tony, yes. Because
I ran into a similar problem building
my Tribsa scrambler. The answer is
to be found in Harry Woolridge’s
excellent Triumph Speed Twin and
Thunderbird Bible. Prior to 1956,
the barrel stud spacing was different
between 500 and 650 but from then
it was standardised to the 650 pitch
so pre-’56 500 barrels won’t fit.
In my case I had mismatched
cases – one pre-’56, one post – but in
the 30-odd years since I bought
them I only realised when I fitted
cylinder base studs in the empty
holes, having already rebuilt the
bottom end. Luckily I had another
bottom end with the right stud
spacing – but that led to another
problem. Although it appeared to be
the ‘big-bearing’ crankcase I needed,
it turned out to be the big-bearing
casting – but machined for a smallbearing
crank. I managed to
machine it out OK, but it underlined
the fact that although these engines
all look the same, there are
significant changes that need to be
borne in mind.
corroded to a
head may require
recourse to a press
LEFT: Late 500cc
stud spacings with
the 650, but early
ones do not
Studying studs pt2
Tony Allanson has a particularly
nasty problem to resolve. Corrosion
has stuck his BSA A65 cylinder head
fast onto its studs. After
unsuccessfully trying a spanner on
the crank nut with the combustion
chamber filled with rope (via the
plug hole), he has now removed the
top end as a unit but is unsure where
to go next, heat and penetrating oil
having already failed.
I think the only way to do this is
with a press. The barrel will need to
be supported on flat bars, upside
down. Then I would use two pistondiameter
pieces of aluminium (or
wood) that can be bridged at the
exposed end with a strong plate and
see if the head can be pushed off
Hopefully, the even pressure
would cause the head to throw in
the towel – but if it’s stubborn,
beware breaking off the cylinder
flange. It may be necessary to have a
thick plate laser cut and drilled to
replicate the crankcase mouth so
that the barrel can be bolted
through all its holes for strength.
Rick’s top tips
Call that sturdy? Lever it out, mate!
I’m not impressed with this new inverted lever, bought by a friend on the
internet. Compared to an original it’s very spindly – little thicker than a
teaspoon handle. You wouldn’t need to be Uri Geller to bend it – as you
might discover under emergency braking...
This is not what I call boxing clever
My mate Bruce showed me a customer’s Monet Goyon gearbox that
jumps out of gear. Despite being a matched pair, the machining was way
out, with the selector shaft misaligned by 5mm! It’s all fixed now, but be
aware – just because it’s original doesn’t necessarily mean it’s correct...
Taking a peak
Pete Grogan emails from Australia,
asking about the headlight peak
he’s spotted on one of my bikes.
“Was there any benefit in these or
were they just cosmetic? I like the
look and am trying to find one for
my BSA Super Rocket,” he says.
These peaks were an anti-dazzle
accessory, first seen on acetylene
lamps in the vintage era and
re-introduced in the 1950s – despite
the improbability of dazzling
anyone with a 6v 30/24watt
Adding a bit of ‘bling’ to the
front end, they regained popularity
during the Rocker era. Very hard to
find by the time I started looking, I
managed to get the odd one here
and there until I had one on every
bike I owned – including a little one
on my 98cc Excelsior. My dad
regarded them as bolt-on junk that,
if anything, slowed the bike down
and I eventually gave in and
stopped using them. But finding I
had a couple left recently, I fitted
them for old time’s sake.
These days they are popular
accessories for British classic cars of
the ’50s and ’60s, which also used a
7in headlight, so they fit just the
same. They have a turned-up lip
that clips in between the lamp glass
and the rim, retained by the
headlight W-clips – although the
peak sometimes slips round to a
jaunty angle, so I usually glue them
in place with some silicone sealant.
You can probably find them at
car shows or online, but avoid ones
for VW Beetles – the laid-back
headlight position means the peak
points down when fitted to a bike.
Love them or hate
peaks have been
around a long time
RICK’s final word
Signed and sealed
Bill Hannah writes to suggest I retract my advice
about machining pre-unit Triumph timing covers to
accept an oil feed seal instead of the standard
phosphor bronze bush (Fixes February). He says
although this conversion is alleged to improve oil
pressure, he has seen the seal lip ‘blow out’, resulting
in zero pressure and a wrecked engine. The original
bush, he points out, can wear but cannot fail
completely, adding that if the cover has been cast
off-centre, the hole will ‘daylight’ if machined,
needing an ally-welded repair (see above).
Well, I understand your concern, Bill, but this is
not my experience. I had my first cover converted in
the mid-’80s after finding that new bushes were no
longer available. My casting was off-centre, causing
the circlip groove to break though at one point but it
worked perfectly for years on my Tribsa before
getting ‘borrowed’ for a ’59 Thunderbird. It’s still on
there and I have never even changed the seal since.
In my feature on ‘Rockerbox’ a while ago, I
passed on their warning about cheap pattern seals –
apparently there have been some very flimsy ones on
the market, and suspect these caused Bill’s problem.
Triumph fitted garter seals to all big twins from ’63-
on and I don’t remember hearing of any problems –
even with the 750’s uprated oil pump. The seal
conversion may not be an improvement but it’s an
easy fix and I still can’t see anything wrong with it.
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