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vincent clutch-pd24 mod?


Well Known and Active Forum Website User
VOC Member
Hi All, I am pawing at the clutch of my Shadow as the restoration gets underway,and have read articles on the Vincent Free Classified Website relating to the bush PD24, and oil leaks through seal PD25 into the clutch housing.There is a theory that the oil grooves in some PD24 bushes,when facing "forward", scoop up oil and push it through the bush (surely desirable)but then the oil backs up behind seal PD25 and pressurises it slightly leading to leaks,which we dont want.Some bushes have the scrolled grooves facing the other way and thus theoretically scavenge the oil away from the bush. The (original?) bush in my clutch chainwheel has grooves facing "away" i.e. "scavenging" and indeed, the inside of the bush is a bit worn and looks a bit blued as if it has been a bit short of oil.The replacement has scrolled grooves facing forward and so will "pump" the oil into the bush.My question is this, there is room to drill one or perhaps two small relief holes, say 0.75mm through PD24, to enable any "pumped"oil to escape from behind the PD25 seal back into the primary case, thus providing a complete circulation of oil, improving lubrication of the bush and preventing subsequent pressure on the seal .The holes would have to be on a sufficiently large PCD to emerge clear of collar PD21 of course.PD24 is meaty enough to accomodate, has anyone tried this before? and if so was it a sucess ? cheers, Bob Cottam.

Tom Gaynor

Well Known and Active Forum Website User
VOC Member
PD whatever

I know that Sid Biberman knows more about clutches than any normal four people, so sent him your question. Here is his reply.

[FONT=font-family:segoe tv,Arial,Verdana]First thoughts are -- this bushing only sees heavy use while at traffic stops . caution lights , while sitting with the clutch held in - blipping the throttle - low gear ingaged . The stationary shaft within the rotating chainwheel . Drag starts were punishing to the bush as one screamed the motor while standing at the start line awaiting the flag to blast off . So careless riding skills , heavy traffic or long standing with the clutch lifted create the problem . The face of the bush can be lightly grooved to improve lubrication if the scrolling is ineffective. Sid . [/FONT]
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