the airscrew should always start at 1.5 turns out, then go both directions 1/4 turn at a time, giving it 20-30 seconds between turns to catch up to the adjustment, do this till it idles the highest, then re-adjust the cable to get it to where you like it to idle, then fine tune the airscrew with 1/8th inch turns, in or out, till it revs cleanly, and fine tune the idle with the choke knob
keep the cable adjuster jamb nut loose to make a quick adjustment if it revs too much, turn the adjuster in, to loosen cable tension, to calm it down