How to Set the Automatic Choke

by Kevin Mclain

The automatic choke is the main component that regulates the air/fuel mixture while the engine is being cranked. As the engine warms up, the automatic choke adjusts to the temperature change to regulate the fuel/air mixture to the proper ratio. Over time, the automatic choke can become out of adjustment and will require readjustment to continue working properly. The opening and closing of the butterfly valves of the carburetor is also determines the amount of the fuel/air mixture.

Step 1

Park the vehicle and shut off the engine. Wait a couple of hours for the engine to cool completely.

Step 2

Raise the hood and lock it in place. Unscrew the wing nut from the air cleaner assembly with pliers and remove it from the top of the carburetor. Locate the automatic choke element on the right side of the carburetor. The automatic choke element is round, with three screws that mount it to the carburetor.

Step 3

Locate the throttle lever on the left side of the carburetor. Pull the throttle lever down until it touches the stopping arm. Hold the stopping arm out of the way of the throttle lever. Continue pulling the throttle lever down until it stops.

Step 4

Release the stopping arm and the throttle lever so that they both snap back into place. Ensure that the adjustment screw at the top of the throttle lever is resting against the stopping arm.

Step 5

Loosen the three mounting screws from the automatic choke element with a flathead screwdriver.

Step 6

Watch the butterfly valves inside the carburetor while turning the automatic choke element clockwise until the butterfly valves are standing straight up. Turn the choke element counterclockwise until the butterfly valves are fully closed. Tighten the three automatic choke element screws with the screwdriver.

Step 7

Crank the engine and watch the butterfly valves while the engine is warming up. Once the engine begins to warm up, the butterfly valves will move straight up and down. If the valves do not move in this manner, readjust the choke element as needed until they do.