The Knowledge - Velocette Owners Club

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
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