Need help to find problem with my 06 LTZ250 idle. Starts up nicely but after few minutes seems to struggle and will not idle with choke on or off. Pulled carb and cleaned out everything but same prob. I pinched off vacuum line from fuel valve to carb and it seemed to idle better but engine would not rev properly. Spark plug looks black (rich?) but I have searched all over carb for fuel mixture screw but no luck. Is there one? I would appreciate any advice because I am getting frustrated.

 

The air/fuel screw is probably hidden behind a brass plug. Carefully drill the brass plug out. If it doesnt just pop out as you are drilling, screw a screw or an easy out into the drilled hole to remove brass plug. Now you can adjust the air/fuel screw.

 

Thanks. Great place to put the air mixture screw. Even after adjustment, engine seems to idle high then (after turning idle screw down) it will bog and die. I'm calling it the High and die syndrome. Any ideas?