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Catastrophic camshaft and follower failure - any ideas?

BlackLightning998

Well Known and Active 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?

Regards

Stuart
 

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pifinch

Well Known and Active Website User
VOC Member
Hi Stuart,what a chamber of horrors, your cams must be lifting too high (lower valve guides not relieved) or someone has hand ground your cams with an angle grinder, I do not see why you have so many crude flats on the surface of the cams, you can knock the peaks off but the cams must always be turning, so you should not have flats on them.
Sorry, I could well be wrong but this looks to be an accumulation of earlier damage, good luck. dont lose heart
 

BlackLightning998

Well Known and Active Website User
VOC Member
Here's the picture of the valve guide I meant to add

Steve,

I meant to add this one originally, it should show the lower guide and valve collar.

PS I didn't do the dremel re-modelling to drain the vale guides - found it today......

Hi Stuart,what a chamber of horrors, your cams must be lifting too high (lower valve guides not relieved) or someone has hand ground your cams with an angle grinder, I do not see why you have so many crude flats on the surface of the cams, you can knock the peaks off but the cams must always be turning, so you should not have flats on them.
Sorry, I could well be wrong but this looks to be an accumulation of earlier damage, good luck. dont lose heart
 

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martinamotor

Well Known and Active Website User
VOC Member
Valve springs to heavy?

Hello Stuart,

How strong are the valve springs?

Changing the oil and filter every 500 miles is a bit overkill, every time the filter is changed there will be a delay in oil supply unless you prime the filter chamber via A22/1, banjo bolt.
I change the oil ones a year no matter how many miles.
In 36 years never had any problem with cam/follower wear. Apart from a loose spindle.

I have seen a lot of worn cams and folowers, but your cams are really bad.

Peter
 

BlackLightning998

Well Known and Active Website User
VOC Member
Oil Change

Hi Peter,

I wouldn't change oil so regularly other than I'm running in a brand new engine - I always fully fill the oil filter housing through the banjo - "prime the cartridge" and use the kick starter to help get things started.

The valve springs are new parts on the invoice as well - I have been told of difference between some manufactured from 4.00mm stock as oppose to 3.76mm (sorry for new money) but can't discern the 1/4 mm difference with the spring in place (can't get a gauge on them that accurately). However I'm told they have been used in many other engine re-builds - as have the cams and followers.

Thanks very much for your reply.

Cheers

Stuart

Hello Stuart,

How strong are the valve springs?

Changing the oil and filter every 500 miles is a bit overkill, every time the filter is changed there will be a delay in oil supply unless you prime the filter chamber via A22/1, banjo bolt.
I change the oil ones a year no matter how many miles.
In 36 years never had any problem with cam/follower wear. Apart from a loose spindle.

I have seen a lot of worn cams and folowers, but your cams are really bad.

Peter
 

martinamotor

Well Known and Active Website User
VOC Member
Using kick starter

Hi Stuart,

A couple of years ago , an Austrian friend of mine, Micheal Schartner, bought a complete restored Shadow in the UK. The bike was not started and was trailered back via my place. The engine was completely rebuild (bills to prove) and not ridden since. We looked it over and started the bike up, ran fine but was very noisy. We took the timing cover of and found cams and followers very worn. The reason for this was the previous owner kicked it round every month or so previnting seizing up.;)
Doing so he ground the cams and followers away.When cams are turning slowly the load is very high. New engines when started up should not tick over slowly but revs at approx 2500 rpm.good oil supply and no load on the cams.
In short, turning the engine over slowly to get the oil going is bad practice.

All the best Peter
hope you are not disapointed in Vincents. :)
 

hrdsuper90

Well Known and Active Website User
VOC Member
Installation ???

Dear Stuart,
What a sad sight - commiserations !
One group of possible problems associated with installing high lift cams like Mk2, are clearances. Guides need to be flush with the lock ring but there are a number of further variables associated with valves, such as position of the collar etc. Mk2's have a lift (at the valve) of .365" but I did install eccentric rockers that raised that to .405" , this looked like the maximum in an original head.
As a matter of course after a build I pre-load the tappet by .050" - .065" and gently turn the engine over and check the clearances. This checks everything, ensures the springs aren't coil bound and valve clearances to the piston. It's a simple check that served me well.

Regards, Chris
 

Peter Holmes

Well Known and Active Website User
VOC Member
Cams

I can only imagine that your machine has suffered complete lubrication failure to the cams or the quality of the parts used were sub standard, I think in the first instance I would get the cam followers checked with a rockwell tester (if you can find an unworn surface). Maughan had a tester last time I was up there.It will not solve your problem I know but at least you might eliminate one reason for this carnage
 

BlackLightning998

Well Known and Active Website User
VOC Member
Hi Peter, you can run a file across them easily

Hi Peter,

Trust you're well?

Thanks for your interest and reply.

One of the problems with the Rockwell Test I'd imagine is that the followers have clearly got hot (friction/damage/loss of oil - take your pick) and I suspect that may have distorted any reading we'd get on hardness - however you can easily file them - and when I tried the same on an old rocker you can't do that on the working surface.

There appears no indication of lubrication failure, I meticulously check the oil return in the tank immediately upon starting -always working, I always fully prime the filter housing on oil change, the rocker feedbolts are all clear with no metering wires, there is a goodly amount of oil in the timing case and the insides of all the rocker covers are well oiled - there is no wear anywear else in the timing case, including the cam follower spindles which are perfect - so while I can't yet rule it out, I can't see how it has happened (and to both camshafts too). Any thoughts on what else I might check to see if I can identify lubrication problems?

You are right on the money though - I really do want to find out why this happened - I really don't fancy putting in some rather expensive new cams and followers only to have it happen again - that would be rather foolish (and expensive!).

The level of damage is such that my inexperienced thoughts and deduction, coloured by advice from the chap who is now helping me fix it, plus Forum and Jtan are tending to lean me towards narrowing down to one of two things now:

1 - insufficient mechanical clearance between the valve collar and the top of the lower guide causing the valve to bottom out before the cam reaches the top of the lobe. We're going to check that on re-assembly.

2 - insufficient care/inappropriate care when the engine was first started and run after the re-build which (may or may not be linked with suspect parts) then caused damage to the cams/followers which has then simply done what you'd expect it to over time after that once the hardened surfaces were damaged/compromised.

Any further thoughts, ideas or observations most welcome.

Cheers

Stuart


.
I can only imagine that your machine has suffered complete lubrication failure to the cams or the quality of the parts used were sub standard, I think in the first instance I would get the cam followers checked with a rockwell tester (if you can find an unworn surface). Maughan had a tester last time I was up there.It will not solve your problem I know but at least you might eliminate one reason for this carnage
 

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