Triumph Repair: Pushrod, triumph tr6, push rod

Question
I have a 1976 triumph Tr6, The problem I have it keeps throwing #4 intake push rod off when driving around 50mph. This has happen twice and both times I have properly lashed the rocker. any ideas??

Answer
Hi Tom,
There are several things that can make a pushrod jump out, like a weak or broken valve spring, a sticking valve, a bent push rod or a rocker arm that is binding on the shaft or with excess side movement.
Can't think of anything else.
Howard