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A common problem encountered by many homeowners is finding that their lawn mower engine won’t start when they try to mow after a long winter season. This can be a sign that your mower’s carburetor is gummed up or even corroded, so it’s important to perform annual maintenance at the beginning of the mowing season to address any problems that could have been created over a long period of disuse.
Other signs of a dirty or restricted carburetor include the engine starting but stalling during use, the muffler emitting black smoke, a significant increase in fuel consumption, or the engine running rough during regular use. Keep reading to find out how to clean a lawn mower carburetor, as well as how to diagnose if you need lawn mower carburetor cleaner or more involved carburetor repair.
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BEFORE YOU BEGIN
In the event a dirty carburetor isn’t the reason your lawn mower won’t start, it’s important to first make sure something else isn’t causing the issue. Double-check that there’s fuel in the tank, the fuel valve is on, and the spark plug is in decent condition before spraying aerosol lubricant or carburetor cleaner into the throat of the carburetor. After spraying the carb cleaner, attempt to start the engine. If the engine runs at all, then the issue is with the fuel system. If the engine refuses to start after several tries, however, then the problem may be more serious. In that case, take your mower to a small engine repair shop.
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STEP 1: Clean the outside of the lawn mower engine.
The purpose of learning how to clean a carburetor on a lawn mower is to remove any dirt and debris that could be causing the engine to run rough, so begin the lawn mower carburetor cleaning process by cleaning the outside of the engine while it is turned off. This makes it easier to keep the internal parts of the carburetor clean during disassembly.
Also, it’s necessary to take the time to clean your work area, which should be well-lit to avoid losing any small parts while you work. Have a clear space on your workbench where you can disassemble, clean, repair, and reassemble the various parts of the carburetor.
STEP 2: Remove the air filter to access the carburetor.
In order to access the carburetor in your lawn mower, you need to remove the air filter housing. The air filter typically sits overtop of the carburetor. Inspect the air filter to determine if it’s attached with clips or screws, then use a screwdriver to loosen the fasteners and place them in a safe location for reinstallation. Next, remove the air filter. It’s a good idea to inspect the air filter and either clean or replace it if necessary. If you have difficulty removing the air filter, you should be able to find detailed information in your lawn mower’s manual to help with this part of the process.
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STEP 3: Remove the carburetor.
Wearing durable gloves for skin protection, use a carburetor cleaner for lawn mowers to spray into the throat of the carburetor or clean the part’s exterior. To clean the internal pieces of the carburetor, though, you will need to remove it entirely from the engine. Use a nut driver or socket set to remove the two bolts that hold the carburetor to the engine, then disconnect the throttle and choke linkage cables from the carburetor.
Make sure to place any fasteners or small pieces in a safe location for reinstallation, and note (or photograph) the location of any cables or hoses so you can put them back in the proper place. Prepare a bucket or bowl to catch the fuel before removing the fuel lines from the nipples of the carburetor housing with needle-nose pliers. If no gas comes out of the fuel line, you may have a plugged fuel line or fuel filter, which will have to be addressed before reassembling the lawn mower.
Once the carburetor is disconnected, pull it off of the mounting studs, taking care to avoid damage to the main gasket between the carburetor and the engine. Also, make a note of the position of the carburetor so that you don’t reinstall it upside down. Place the carburetor in a bucket to allow any fuel to drain.
STEP 4: Disassemble the carburetor.
A key reminder before disassembling your carburetor is that every piece you remove needs to be put back in the same position. Prepare an appropriate place to disassemble the carburetor if you haven’t already, and consider taking pictures while you work to prevent confusion during reassembly.
With the carburetor in the middle of your clean work area and while wearing gloves, start the disassembly process by cleaning around the bowl with a carburetor cleaner. Next, unbolt the fuel bowl and ensure the hole in the nut is clear of any obstructions by poking a paper clip or piece of thin wire through it. Then, remove the float, which should be attached to the carburetor with a hinge pin, and also remove and replace the needle, if necessary. Keep all of the parts grouped together.
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STEP 5: Replace any worn-out parts.
Even the best carburetor cleaner cannot repair worn-out parts. Should you spot significant wear and tear on any parts, including the float, pin, needle, or gaskets, then you should get a carburetor repair kit for your specific carburetor to make necessary repairs. Some carburetor parts, like gaskets, wear out more quickly than other parts. When planning your annual carburetor cleaning, it’s recommended to have spare parts ready on hand to avoid taking the carburetor apart more than once. Simultaneously replacing the mower air filter also helps to streamline the maintenance process.
STEP 6: Clean the carburetor and carburetor parts.
With the carburetor disassembled and your gloves on, you will be able to spray carburetor cleaner inside the carburetor housing and clean the various parts. Carb cleaners come in aerosol cans that are great for quick, efficient cleaning, but you can also purchase carburetor cleaner in a bottle or jug.
If you prefer to use a liquid carburetor cleaner over a spray cleaner, then you will need to pour the cleaner into an empty bucket where the parts can soak. Wire the larger parts of the carburetor together, then carefully lower them into a bucket filled with carb cleaner. Use a piece of aluminum screen or a fine-mesh basket to wrap the small pieces of the carburetor before placing them in the bucket, as well. Leave the parts to soak for about an hour before removing them from the cleaning solution.
STEP 7: Reassemble the carburetor.
Rinse the carburetor parts with water to remove excess carburetor cleaner. Then, blow dry the parts with compressed air or let them air dry. It’s essential that the parts are completely dry before reassembly.
When you’re confident that the carburetor parts are dry, you can begin putting the carburetor back together. Use any pictures you took during disassembly to ensure that you are correctly reassembling the parts.
Once the carburetor is reassembled, mount it on the lawn mower, reattach the throttle and choke linkage cables, and reinstall the fuel lines. Fasten the bolts on the carburetor and reattach the air filter to the mower.
STEP 8: Test the lawn mower.
After you have reassembled and reinstalled the carburetor and air filter, add fuel to the gas tank and start the lawn mower to ensure that the maintenance was a success. Ideally, cleaning the carburetor should allow the engine to start up easily, but if you continue to experience problems with starting your mower, take the lawn mower to a small engine repair shop for further diagnosis.
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Final Thoughts
To get the longest life possible out of your mower, it’s necessary to perform regular maintenance throughout the year. This includes cleaning the carburetor at the beginning of the mowing season, winterizing your lawn mower at the end of the mowing season, and changing oil, replacing spark plugs, and sharpening blades as needed. If you neglect regular mower maintenance, it may break down in a relatively short period of time, costing you more in expensive repairs.