Idling speed adjustment screw
Idling mixture adjustment screw
Throttle cable clamp screw
Main adjustment screw
Choke cable clamp screw
Throttle lever shaft
Figure 21. Carburetor adjustment.
(2) Idling mixture adjustment screw. The idling mixture adjustment screw (8) controls the amount of air admitted
to the idling system, which operates only at low speeds. Turning the adjustment screw (8) counterclockwise
admits more air and makes the fuel mixture leaner. Turn the adjustment screw (8) clockwise or
counterclockwise until the engine reaches its smoothest running point and operates without missing, jerking,
or spitting. If a vacuum gage is available, attach the gage to the intake manifold (3) and adjust the
carburetor for highest manifold vacuum. This point will coincide with the smooth running of the engine.
(3) Idling speed adjustment screw. The idling speed adjustment screw (1) adjusts the idling speed of the
engine. Turn the adjustment screw (1) clockwise to increase the speed and counterclockwise to decrease
the idling speed.