I have an 03 yz 450 and i adjusted the valves on it. well when i put it back together it went exactly the same as when i took apart, the cam timing marks lined up, piston is at top dead center. went to start wont fire but shoots flames out the exhaust. How many degrees timing change is it if i happened to be off a tooth by chance? will it even start if its off a tooth on the cam? Whats the best way to re-time the bike?