How to Rebuild a Lawn Mower Carburetor

A carburetor is a mechanical device that combines air and fuel in an internal combustion engine. The carburetor controls the flow of air into an engine. The speed of the air entering the engine determines the amount of air pressure in the engine. The air pressure affects the amount of fuel being drawn into the jet stream and ultimately entering the engine. A lawn mower carburetor is smaller than the carburetors found in motor vehicle engines but operates according to the same mechanical principles. This article will provide you with step-by-step instructions for rebuilding your lawn mower's carburetor.

Difficulty: Moderately Challenging

Instructions

Things You'll Need:

• Carburetor air filter
• Flathead screwdriver
• Filled oilcan
• Wire scrub brush
• 8-inch steel swivel screw
• Phillips-head screwdriver
• Adjustable wrench
• Dry cloth
• 6-inch steel bolt

Rebuilding a Lawn Mower Carburetor

1. Remove the air filter from the top of the carburetor. If the filter is corroded, pry it loose with the flathead screwdriver.

2. Scrub the area around the filter with the wire brush. Pop the new air filter into place.

3. Unscrew the choke valve using the Phillips-head screwdriver and remove the old screw.

4. Oil the choke valve in the area around the screw with the oilcan and refasten the choke valve to the inside of the carburetor using the new swivel screw. Tap the choke valve a few times to make sure it rotates freely.

5. 
   Carburetor Metering Rod

   Open the fuel delivery compartment and, using the adjustable wrench, remove the metering rod. Discard the old bolt that was used to attach the metering rod to the mechanical linkage.

6. Clean the metering rod thoroughly using the dry cloth to remove oil and other residue. If necessary, apply some WD-40 or baking soda to loosen the residue.

7. Oil the mechanical linkage that attaches to the top of the metering rod. Make sure that the mechanical linkage moves freely by tapping it a few times.

8. Reattach the top of the metering rod to the mechanical linkage using the new 6-inch steel bolt and the adjustable wrench.

9. Unscrew the float valve using the adjustable wrench. Check the attachment area for corrosion. You may be able to clean the attachment area using the dry cloth, but if there is too much corrosion, the float valve will need to be replaced.

10. Scrub the inside of the fuel nozzle with the wire brush to ensure that the nozzle's pathway to the air intake area is clear. Also scrub the inside of the float chamber using the wire brush. Re-attach the float valve to the inside of the float chamber using the adjustable wrench.

Tips & Warnings

• You can order replacement parts for a lawn mower carburetor from a distributor of small motor parts, such as Outdoor Distributors. If the dry cloth does not remove the corrosion on the various pieces, you may want to spray the pieces with WD-40 or coat them in baking soda.
• Always wear appropriate clothing when working with engine parts. Long pants, gloves, closed-toe shoes and eye protection should be worn at all times.

References

• Outdoor Distributors

Resources

• Small Engine Carburetor and Repair Parts