Please don't tell me you are his mechanic!
It could come from a stretched cam chain.
I think that the shims that were in before might not be the correct thickness needed if the head got a valve job or the valves were at least lapped. They should be measured and shimmed accordingly.
Did the exhaust valves hit the piston?
I'm no expert so I'm just guessing. But if you are a mechanic you should know this?
'07 LTR 450 - Yoshi rs-5, Intake Hotcam cam, 08 exhaust cam, FuelAtv intake, PCIII, Sandtars all around.
'03 White Z400 - SOLD
Last edited by chinoduca; 05-28-2011 at 04:33 AM.