that is that large screw you see on the engine...it has a slot for a flat blade screwdriver. these are preset at factory and i wouldn't mess with that until last resort. if your motor is new i would just set high end needle to 1/4 turn more then manual says (1 1/2?) and start it. you are supposed to adjust the motor when wide open with high speed needle only also. when it is correct you should be able to chop the throttle and it will idle (adjust with radio)perfect. be sure ya have yur tank full and the tank vent capped off with a removable plug. after running remove plug to depressurize your tank. these things run rich so let it smoke a bit and it will run just fine...[8D]