The clearances on ZX6 J/A1P models are known to close up quite quickly as the head is supposedly quite soft. I checked my A1P at 18k and at least two valves on the exhaust side were out of tolerance and several of the intakes were on the tight side but still in tolerance. I prefer to set the valves on the loose side (a little tappety) then I can hear when they have closed up. Too loose is generally better than too tight. When they get tight, the valves will stay open damaging the valve seats, when they are very loose, the cams and buckets will be hammered causing premature wear. Some models are more prone to wear than others and require more frequent checks. A compression check can indicate valve problems and also stalling and or poor tickover could indicate valve clearance issues. I will be rechecking the clearances at 40k miles, 22k since the last check. If there's any doubt, get them checked for peace of mind.