Having problems with the valve train on my 1970 A50. Had the SRM roller bearing conversion and fitted a Spitfire cam at the same time. Put a few thousand miles on it no problem. Fitted a different head and barrels, did quite a few miles. Then out of the blue it packed up amid horrible metallic sounds and when I pulled it apart the right inlet rocker arm had snapped and the inlet pushrods were bent.
Rebuilt it and did about 500 miles before hearing some more nasty metal crunching sounds. The bike kept going so I made it home then found the top of an inlet pushrod had half cracked off, luckily there was enough of it left to still work the valve.
I fitted a new pushrod but only got about a mile up the road before more nasty noises and I limped home on one pot. This time both inlet pushrods had cracked at the top.
I've just got some one piece pushrods from SRM and am hoping maybe it was a dodgy batch of pushrods but that still doesn't explain the rocker arm breaking. I have found about 1/8" end float in the camshaft (manual says there shouldn't be any) and wondered if this could cause the cam to lift the wrong valve if it went out of line with the tappets? If so how can I eliminate this end float?