What to Do If the Choke on a Lawn Mower Doesn't Work

Carburetor Cleaner

• Aerosol cans of carburetor cleaner specifically designed for lawn mowers are available from mower manufacturers, but automotive carburetor and choke cleaner is a good substitute. Heed all precautions provided with the cleaner. Remove the air filter housing to gain complete access to all areas of the carburetor, and use the spray to clean the exterior surfaces. Clean the choke and throttle linkage, and check for freedom of movement. Ensure the carburetor is firmly attached to the engine.

Choke Action

• Move the choke blade into the fully closed position by hand. The blade should move smoothly and close completely with light hand pressure. Spray cleaner on the choke blade pivot points to restore free travel. Adjust or continue cleaning choke linkage if sticking or binding occurs. Observe the carburetor throttle plate while operating the throttle control. Adjust the control cable if the throttle plate does not open completely. It should appear to be on edge when fully open.

Inside Information

• Full choke action is no guarantee of complete carburetor function. Tiny passages inside the carburetor must be clear for proper fuel delivery to take place. Spray cleaner down the carburetor throat to remove varnish or dirt that may be clogging fuel ports. Use the cleaner sparingly to avoid flooding the engine. Allow 20 to 30 minutes for the cleaner to evaporate before installing the air filter and housing. Block the choke blade open, if necessary, to speed the drying process.

Cheating the Choke

• Carburetor cleaner is more volatile than gasoline, and small amounts of it in a carburetor can provide the "kick" needed to start a cold engine. If the mower must be used before it's repaired, direct a one-second blast of carburetor cleaner down the carburetor throat before cold starts. You may have to open or remove the air filter housing before spraying, but it must be put back in place before mower operation to safeguard against engine damage and backfires.