No longer intimidated by a 4 stroke. I took my project 2008 yz450f down to the last nut and bolt. Also removed all the valves replaced all valve seals and cleaned the head. Valves were still sealing. The piston, crank and bottom end bearings replaced. In about 25 hours im sending the head off for new seats and recut and replace the valves. For the people that are scared of a 4 stroke. They are super simple to rebuild with a manual. The hardest part was doing the torque on the head bolts. The 180 degree turn was hard with the motor out. Make sure and order a hot cams shim kit and a offset feeler guage. Overall fun easy project.