I read that one of your readers had problems with the gear shaft moving forward and causing damage to the rod. I had the same problem with a VT49 purchased 'NIB'. I put it down to incorrect assembly, replaced the rod , made sure the securing strap was really tight and carried on.
Unfortunately the problem reoccurred very quickly.
You suggest that the trouble is caused by excessive drag on the valve, due to valve damage or incorrect shimming. The valve is definitely OK
so the prob could be the shim?? How do I check the correct clearance for the valve and what should it be? The engine is fitted with the roller bearing on the valve.
Yours Hopefully Ted Hatton Matakana N.Z.