Does the tapping noise stay in the engine even when it warms up? I had a ZR750 with a tapping problem, it was noisy when cold but fine when warm. I replaced the camchain & tensioner, did the shims, compression test etc, etc.
It was hard to tell where the noise was coming from but it sounded like it was from the top-end, it turned out that one of the big end bearings was shot.
Do as M says & check the valve clearances first, if they're okay then you could getting into the expensive stuff.
steo, May 2010
