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E: Engine Exhaust Tappet

Peter Holmes

Well Known and Active Website User
VOC Member
I have probably had a lucky escape, I am not sure when I last rode my Comet, but it was probably towards the back end of last year, wherever I went I got home without a hint of trouble, well none that I noticed anyway. So with nothing better to do today I thought I would check a few of the usual things, when I get to the exhaust tappet it is loose, and I mean loose, I immediately started to think savage cam or follower wear, probably both, but then I find the bulb on the end of the pushrod virtually worn away and the tappet adjuster snapped in half, but somehow hanging into to rocker by just a single thread, has anyone experienced this before, should I investigate further down or just replace the pushrod and adjuster and see how we go, any suggestions.

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Martyn Goodwin

Well Known and Active Website User
VOC Member
How do I find OVR, did a forum search, but nothing comes up.
Here you go

The Oz Vincent Review is a totally independent, non-profit, email distributed magazine about all things Vincent as well as the broader classic motorcycling scene. OVR is distributed free of charge to its readers. OVR may be contacted by email at OzVinReview@Gmail.com . OVR is not intended to compete in any way with MPH - rather I try to complement it.

On my web site you can sign up for a FREE subscription to OVR and also access the OVR Archive where all past editions can be found and if you want downloaded to your own device

Martyn Goodwin, Editor Oz Vincent Review (Melbourne, Australia)

My web site: https://ovr270.wixsite.com/ozvincentreview

My Phone: +61 419 499 901
 

Peter Holmes

Well Known and Active Website User
VOC Member
Having read Tim's section review on Cadwell Park VMCC 75th Anniversary I thought I would resurrect this post, in Tim's review he mentions evaporating pushrods, which is how my original post started.

After a fairly exuberant ride out with my son Jamie, he riding my Rapide and myself on the D Comet, I felt the Comet was a little underpowered, not unexpected, but perhaps a little more pronounced than I would have expected, I decided to check the engine over, when stone cold of course, only to find that the inlet pushrod had gone exactly the same way as my previous exhaust pushrod, with the tappet adjustment end almost completely worn away to the point that all that was left was something resembling a very small mushroom, but in both cases, inlet and exhaust, the cam follower end was relatively unworn, so this set me thinking, I would imagine that in both cases the cam follower end gets a fairly liberal feed of oil splashing around, perhaps not so at the tappet end, as this has never happened on my Maughan rebuilt twin engine, at least 35 years ago, and loads of miles since, I can only presume that scarcity of lubrication is not the sole cause of this phenomenon, but if the pushrod ball end is in anyway substandard, it will fail at the tappet end first.

Previously people on this forum far more knowledgable than me have suggested lapping the pushrod and the tappet adjusting screw together, but does that not destroy the hardened, highly polished ball end surface , or is it through hardened, in any event, I purchased from Maughan's 2 x pushrods and 2 x tappet adjusters, they look and fit so perfectly together that I have decided not to lap them in, but I did install them with a generous coating of Graphogen that I have had in my tool chest for many years, so are my pushrod problems at an end, I sincerely hope so, I have also given the bike a filter and oil change, but where does the worn away pushrod material go in these circumstances, what route will it take, does it hit the filter before it can damage any bearing surfaces, I would assume from the way it is worn that it is little more than metal dust, but presumedly still not that desirable being pumped round the engine.

So fingers crossed as they say.
 
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vibrac

Well Known and Active Website User
VOC Member
I admit the 3 pushrods in question came from my 'store' and not VincentSpares one remained from the original build and that was OK my guess is is a material fault from whenever. I havent stripped the engine (Its a big build this winter) Ben has come second in the championship this year missing two and 1/2 meetings all on my road engine from 1999 so I cant grumble (well not much anyway :) )
 

Nigel Spaxman

Well Known and Active Website User
VOC Member
I am using Smith Brothers aluminum push rods. They have inserted hard steel radiused ends that are not undercut. Some people undercut them so they look more like the original Vincent push rods. What I did instead was open out the hole in the tapped adjusting screw and the hole in the follower so that the push rod could pivot around without interfering with the sides of the push rod. This has worked really well for about 18,000 miles now. I don't have to adjust the valves more than once a year.
 

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