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.