KH500 Pushrod Failure

[JohnReilly]

Good. day,
Rode thew bike into the garage on Sunday, normal operation.
Wednesday tried to start, spiting and farting ensued so investigations led to port side exhaust valve pushrod issue.
The valve itself was fine, stem was lubricated and free. with no sign of seizure or other malfunctioning.
Has anyone experienced this type of failure and/or is there an explanation?
Regards
John

[Roger Gwynn]

Happened to me once coming home from club night, in the forest, in the dark. Luckily I was carrying a spare push rod, don't know why. I think the valve may stick open, leaving the push rod flapping about and when the valve is knocked back into place by the piston the rod is not in the correct place and has a chunk taken out of it by the rocker

[JohnReilly]

Roger,
I would agree that in the absence of other evidence that would seem most likely.
However the valve stem was free in its guide and not any sign of scuffing or seizing and it was lubricated.
My only other thought would be metal fatigue around the spherical end.
Anyway, awaiting spares from Rob so we will see what the future holds

[simon.holyfield]

I saw a very similar failure on my W/NG, though in the cam follower. The pushrod cup had worn very thin & fractured.

[KenS]

My VG500 exhaust pushrod upper end was so worn that there were two tiny holes that had permitted the pushrod tube to fill with oil, and would undoubtably have failed had I not discovered it by accident after washing the rods and a day later, noticed oil on the work bench! Once I had removed he upper end, the metal thickness in the center was paper thin.

[JohnnyBeckett]

hi i have had the exhaust rocker arm sticking and done the pushrod in coming back from Devon on a nh 350 1953 it was a blockage in the oil feed in the rocker shaft