How do you set idle screw?
Crank the engine, let it idle. If it dies, turn the screw in 1/4
turn. Crank it. Repeat until it doesn't die. Then turn it in one
additional 1/4 turn.
Now if you mean the mixture screw, typically 1 1/2 turns out.
After you set that, rev it up. If it revs clean, leave it. Another
method is to set the idle screw and set the mixture screw 1 1/4
turns out and back it out in 1/4 turn increments until further
adjustments cease to increase revs at idle, then turn it 1/4 turn
in.