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How to Adjust a Riding Lawn Mower Carburetor

rasenmähertraktor image by Ideenkoch from

The carburetor on your riding lawn mower is set by the factory. The only necessary adjustments are to periodically adjust the idle speed and the idle mixture. Most mowers now have a limiter cap around the idle adjustment screws. Do not attempt to force the screws past these caps as it will damage your engine. Once you adjust the idle and the idle fuel mixture, you will maintain fuel efficiency and good engine performance.

Place the parking brake into the on position and the drive gear to the neutral position. Open the hood of your riding mower and locate the carburetor adjusting screws. The carburetor is near the air cleaner assembly and the two idle adjustment screws are on the top and side of the carburetor.

Start the riding mower engine and allow the engine to warm up for five minutes. Pull the choke lever to the slow position. The slow position will be toward the bottom and usually has a picture of a turtle.

Adjust the idle speed screw with a flat-head screwdriver until the RPM reading is at or near 1,750 on the gauge on the mower dash. The idle speed screw is toward the top of the carburetor. Turn the screw counterclockwise to decrease the RPMs or clockwise to increase the RPMs.

Turn the idle mixture screw on the side of the carburetor clockwise with the flat-head screwdriver until the engine starts to die. Immediately turn the screw counterclockwise until the engine begins to run rough. Find the center point between the two extremes. This will provide maximum fuel efficiency and optimal performance.

Adjust the idle speed again if necessary.


If you mower does not have an RPM gauge, listen to the engine. The engine has a distinct sound when the idle speed is correct.

Clean the air cleaner before adjusting the carburetor. Often the simple act of cleaning the air cleaner will solve any performance issue.


Do not wear loose clothing when making adjustments with the mower running.

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