Hey I've just bought a 2005 Trx300Ex and am having some idle issues, the idle is super high and the tail pipe is red hot and i checked in the tank after shutdown and it was boiling... im trying to figure out where the idle control on the carb is and have been experimenting with the big flathead screw in front of the carb facing the choke side and it's not doing anything. I dont think it's the throttle cable because i had it in neutral and turned the handle bars back and forth and the idle didnt change... Any ideas? Thanks

 

With the air filter off, see if you cover the intake port into the carb if it will bring the idle down. Choke it down completely, it should stall out. Does it pop when you let off the throttle while moving in gear (engine braking)? It sounds like you are burning very lean. This is very bad. I am not sure which one is the idle screw.

 

Sounds like a very ditry carb, that is leaving you lean. I would clean the carb (really clean it, not just spray some cleaner around in there and call it good), and pay particular attention to the idle (slow/pilot) jet.