i have an 09 yz 450f. its been running fine up until yesterday. Its really hard to start. it feels like i have lost some compression, and it backfires when I'm starting it. So i adjusted the valves, the two exhaust valves were out and the intakes were borderline. Now they are all in spec. When i put it together i marked my timing chain with the dots on the cams with a paint marker to make sure it goes back together the same way. what i noticed when i took it apart was one of the cams was off a little by a tooth. my question is, can timing get thrown off, especially when the bike has never been took apart. I put it together exactly how i took it apart, and the bike is still hard starting and backfires when kicking it.