Hi, I have read some very informative information on this site. Now I am in need of some.I have a 2000 yz426f. When I first start it I let it idle on choke, then I take the choke off and rev the engine to warm it up. This is when the bike starts spitting, sputering and throwing flames out of the exhaust. After about 2 minutes it seems to have warmed up and runs great the rest of the day. Next day of riding I have the same problem. Any ideas would be appreciated.