all carb adjustments must be made with engine warmed up to running temps and with air cleaner on, set idle to 450 to 475, with engine off, turn idle jet screws in all the way, then back off 1 1/2 turns, start engine and turn screws in till engine starts to stumble the back off screw 1/2 turn or till engine idles smoothly, to make sure carb is working right turn screws out till engine starts to stumble then back in till it runs smooth, if you dont get any change in engine idle going both ways with idle screws carb needs rebuilding, remmber turn idle screws in till engine stumbles then back out till engine runs smooth, when your done the idle speed should be 450- 475