I had my freshly rebuilt 03 yz450 out for alot of weekend riding. Broke it in the first day with a long steady trail ride at or around half throttle for a good 1.5 - 2 hours. I did how ever notice in 4th gear it seemed to slip when I took it hard from 1/4 to past half throttle. We put on about 150 miles this weekend all at 40-50 mph with some faster runs (60+) back to camp at sunset. Question is will 4th gear be where I start to notice the clutch going out?? the plates looked fine when I had it all apart, nothing was burnt looking ect... It doesn't seem to slip in any other gear. I am going to try some better oil too I had used just plain 15w40 to get it broken in and have that in now. My free play is in spec as well I tried playing with it either way and made little or no difference. I haven't had a chance to study the manual on it yet will do that tonight.