I checked my valves last weekend (I'm at 26k). From what I could tell, the easiest (and probably only) way to get to the vales is through the radiator.
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FYI, there's a small bolt in the bottom pipe coming from the water pump used for draining the coolant. I didn't see this and decorated my garage floor with the beautiful Yamaha blue coolant
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My exhaust valves were all pretty tight. As a tip, any engine questions can also be pointed at the mt07/fz07/xsr700 forums, sharing the CP2 engine. There's a lot more info for those bikes
Intake is 0.11 - 0.20mm
Exhaust is 0.24 - 0.30mm