Looking for reliability. I've got a 2010 YZ450F that I rode this year in 10 USRA desert races. I ride track usually once a week and usually trail ride another 2 hours one evening and again on Saturdays. I estimate I've put 140-160 hrs on it and I purchased it in January with 20 hrs.... it's time for a full top end. I've ordered Pro X stainless Steel intake and exhaust valve kits with new valve springs, a Yamaha Timing Chain and Top End Gasket kit and valve seals. Wondering which piston I should order for the best reliability? The bike has plenty of power for me, so I figure I'd like to stay stock 12.5:1 compression. Pro X? $119 Wiseco? $126 Stock Yamaha? $109 Something else? What are the differences between them? The last piston I did was in my 99 Yz400f and the stock piston was junk sintered powdered aluminum. While the new Wiseco was a beautiful forged piece. Is the stock piston in my '10 a nice forged piece or should I buy another Wiseco? I've been having stalling problems off and on all season and hard hot starting. Even with my Rekluse EXP 3.0 Two races I wasted 15-20 minutes with it not wanting to hot start for me and was stuck watching on the side of the trail until the bike cooled down enough to start again. I've reshimmed the valves 3 times on the intake and 1 time on the exhaust. Intake valves are down to .145 shim and they are going out of spec in 20-30 hours which is unacceptable at this point. I'm inspecting/ adjusting valve clearance every 2-3 weeks. I figure I'll do it all myself but have the local shop recut the valve seats and match them to the new valves for me. Anything else I should do? I can check the valve guides and crank for movement.