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Catastrophic camshaft and follower failure - any ideas?


Well Known and Active Forum Website User
VOC Member
Evening All,

Oh dear - isn't Vincent ownership fun......

I wondered if any members have any ideas on what caused pretty catastrophic camshaft and follower failure on my 4000 mile old engine. Pictures embedded below.

The story is that I came to re-start the bike after re-fitting my refurbished dynamo, only to find it fire on the rear cylinder and not on the front. I traced it to a stuck open exhaust valve and suspected the valve lifter mechanism.

On stripping the timing side today, sure enough the front and rear linkage had become seperated and the front had stuck open the exhaust valve.

However, then things get worse. On checking for other damage/issues we found that all four cam lobes were heavily worn/scored and all four followers were deeply scored and worn - see the pictures.

Everything was invoiced as new in the top end and timing side before I bought the bike. More new parts than would sink a Battleship.

The work was done in Australia - I don't yet know the origin of the new parts which were fitted, but we have narrowed down the problem to one of three causes, I'd be very grateful for any other ideas, comments or advice from members on what to check/look for in advance of fitting the new parts I ordered today (ouch!):

1 - Parts failure
Perhaps the cams or followers weren't properly hardened

2 - Oil Failure
I have been meticulous in checking the oil return immediately on firing the bike, changing oil and cartridge filter at 500 mile intervals including priming the cartridge and keeping to recommended running in speeds and loads. The timing case is lovely and oily throughout, the valve caps have always had a good covering of oil in them when I have removed them and the new stainless rocker feed bolts are all clear and running through when you blow them - no metering wires fitted. So whilst of course it is always a possibility - I just can't see it myself.

3 - High Lift Cams
The lower valve guide is visible in the picture attached - we were wondering whether such damage could have been caused by a mechanical problem, perhaps the valve collar is bottoming out on the top of the lower guide before full cam lift and this is causing the damage. The cams which have come out are stamped "3" but the profile does not look anything like some spare old "3"'s I've compared them to.

Have we missed something?




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Well Known and Active Forum Website User
VOC Member
Stuart. If you make the Annual, I will gladly buy your BBQ for all the interest and problems that you have had and solved. I have always read them, thanks.


Well Known and Active Forum Website User
Non-VOC Member
1929 scott tt

Ring dings are fine for dirt bikes but too compromised otherwise. Narrow power bands , burning their own lubricant , high fuel consumption and emissions , limited engine life and they sound rubbish !!


Mine has a nice wide power band and burns less oil than some Vincents I know of.

Emissions were unheard of when she was new, (except the nocturnal ones), and she makes a very nice "Youl" on the pipe thank you.!! And still going well at 80 years young.

I rest my case, you Bloody 4 stroker# you.
(Tongue firmly in cheek) ;)

Ken Smith
(Had her out today. Still a joy to ride!)


greg brillus

Well Known and Active Forum Website User
VOC Member
Greg Brillus

Hi ther, a couple of thoughts that come to mind. I have just fitted two new mk 3 cams to a fellow club members Rapide engine. Being here in Australia, the cams are from Terry Prince, and their specs differ slightly from std mk 3's only in slightly more lift and also in duration for a bit of extra torque. I found the lift messured at the tappet adjusters on the inlets to be no more than 0.330", so i dont see the small increase in lift being a problem. However if the cam and follower materials are different i believe that can cause an issue, and also, i have found the oilways through the new components need to be checked by passing the correct drill sizes through them as Big Sid correctly advises. I found the holes in the cam lobes passing through to the bushes dont always align so well. Anyway good luck, i'm sure you will get it sorted... cheers.. Greg.
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