How the Idle Circuit Works
Hesitation Off Idle When accelerating and just off idle, the idle mixture adds a bit more fuel/air mixture to get over the hump and let the accelerator pump circuit take over. Keep in mind that the accelerator pump circuit can cause the same problem, because it isn’t easy to know when you are off idle and into the accelerator pump mode. At idle the air fuel mixture enters the carburetor bore via the idle passage as marked. During acceleration there is a bit of a gap between idle and when the accelerator pump circuit takes over. As the throttle valves opens, a slot is exposed allowing more air fuel to enter the bore. Remove the idle mixture screws to make sure the passage to the idle is clear. Also follow the slot openings up through the carburetor (with air) to make sure it is open. This image is looking at the top of the float bowl with the top removed. Air is introduced from the top of the carburetor idle air vent. Fuel enters from the main jet through the fuel idle jet. The air & fuel then mixes before moving down into the idle passage. Notice that the fuel idle jet hole is very small. This hole is easily get plugged.