ouch

I'm fairly certain that the headers are all in place, since i inspected them not long ago and tightened all four bolts.  I'm curious to see if removing and re-intalling the gas-tank does anything for the problem.

having that valve too tight for spec, could that cause any noises or vibrations?  I've been hearing a little top end 'clink'-ing during warmups latey too.  could it all be connected?

Oh, just the valve potentially contacting the piston...

Seriously, what I've done in the past is get the next size smaller shim and measure the clearance using that. If you're running a 365 and go to a 360 you may still be within spec .03mm - .08mm. Now, if you can find a 362 shim, buy it, they aren't usually easy to just find. Like tools, you can never have enough shims. I'd like to buy a whole box of shims so I can service everybody in the bay area who is a member of GStwin.

Valves that are too tight aren't able to dissapate heat into the head due to not enough cantact time with the valve seat. Carbon deposits may begin to form on the face of the valve further interfering with face to seat contact. This is also how valve guide seals go bad, by the valve stem getting so hot and expanding in the guide, extreme heat and pressure wears the guide out. And more oil is allowed to seep by.