I put a YZ 450 exhaust cam in my WR 450. Now the bike won't start. When I was disassembling, I lined the crank up on the "H" mark, and the cam marks were pretty close to the top of the head. When I went to reassemble, I found the "I" mark, and timed the cams to it, the way the manual shows. The manual also shows 14 chain pins between the upper cam marks, but I have 13 with the YZ cam.