2005 Yamaha yz450f hot start problems

[damien1350]

So I got my 450 about two months ago. Ive taken it to the track and trails about 4 times and probably have a solid 12 hours on it. When i got the bike it started first kick everytime hot or cold. On my last trip out the bike starts first kick when cold, but after the bike gets warmed up I have a hard time getting it restarted or to idle on its own. I took the carb apart and everything was good, I cleaned all the jets regardless. Anyways, Im not sure what the issue is and would appreciate any help or advice.

 

[dirt bike dave]

Have you checked the valve clearances?

They tend to tighten up over time, and get tighter still when the motor is hot.

Basically, if the valves are not closing all the way or for long enough, it can make the bike very difficult to hot start.

It could be other things, but tight valves are a common problem and a likely culprit if it starts fine when cold.