A 'hanging idle' is when the bike will not return to a regular idle and instead remains elevated. It may come down after a bit or a few blips of the throttle can sometimes coax it back to normal. But it does not have to be. Usually, it is caused by a slightly lean idle mixture combined with a slightly high idle speed adjustment. We will assume you have already properly set your fuel screw and yet, your idle 'hangs'. Often turning the idle speed knob a tiny amount, like 1/8th of a turn will fix it. The procedure is with a hot bike, turn it CCW 1/8th turn, blip the throttle four or five times. You may find that it is a very narrow range where the idle does not hang and the bike does not stall. In some instances, opening the fuel screw an additional 1/4 turn helps too. Do not open the fuel screw much more than that (assuming you are starting from the correct point as identified in the fuel screw sticky).