The Knowledge - Velocette Owners Club

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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