It’s normal for a push mower carburetor to fail over time because old fuel sits in the carburetor causing gumming and crusty buildups.
This will cause parts to stick and clog the fuel jet preventing the engine from getting the fuel it needs. Running old fuel and fuel with ethanol is hard on a carburetor.
Symptoms of a Bad Push Mower Carburetor
The carburetor is a key component that helps regulate the amount of fuel mixed with air to create a combustion. When the carburetor becomes dirty and components stick, you will likely experience one of these symptoms:
- Push mower won’t start
- Push mower backfires from running lean
- Push mower engine sputters and runs rough
- Push mower engine surges
- Push mower consumes too much fuel
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Follow all safety instructions provided in your equipment operator’s manual before diagnosing, repairing, or operating. Consult a professional if you don’t have the skills, or knowledge or are not in the condition to perform the repair safely.
10 Steps to Clean a Push Mower Carburetor
Before you start removing the carburetor from your push mower and disassembling it, you should check these two things that will help narrow down the problem to the carburetor:
- Make sure the push mower is getting fuel to the carburetor. Check the fuel line running to the carburetor to ensure good fuel flow. Refer to the guide if you need help with the steps to check the fuel lines.
If you are not getting fuel to the carburetor check for clogs or kinks in the fuel lines. If your mower uses a fuel pump or fuel filter, you will need to check these components for a restriction.
- Make sure the engine is able to start and run well. To identify the carburetor’s lack of releasing fuel is the cause of your problem, remove the fuel filter from the filter housing. Spray carburetor cleaner into the air intake and then start your mower.
If it starts and runs well and then shuts off, your problem is likely in the carburetor. The carburetor should be taken apart and cleaned.
If the engine does not start or run well, the problem may not be fuel related. Check for an air restriction or electrical problem preventing the push mower from getting air or spark.
1. Gather Items Needed to Clean Your Push Mower Carburetor
- Socket/ratchet set
- Carburetor Cleaner
- Thick wire
- Needle nose pliers
2. Take Photos of Your Push Mower Carburetor
It’s a good idea to take photos while taking your carburetor apart. You don’t want to start removing parts and then forget where they go. Because most people have a cell phone with a camera readily available, it is convenient to take photos before and during the tear-down process.
I recommend taking these photos even if you have a great memory. You’re better off having these photos available and not needing them over not having the photos at all.
3. Shut off Your Push Mower Fuel Supply
Stop the fuel flow on your push mower. Use the fuel shut-off valve located on the bottom of your fuel tank. If you don’t have a shut-off valve, crimp the fuel line using pinch pliers.
4. Remove Your Push Mower Throttle & Choke Cable
Detach the throttle and choke cables from your carburetor.
5. Remove your Push Mower Air Filter Housing
Remove the hardware that attaches the carburetor to the air filter housing so it is detached.
6. Remove the Springs from Your Push Mower Carburetor
Slowly remove the springs from the carburetor. Do not stretch the springs or you’ll have to replace them. You may have to twist the carburetor a bit to get the springs to come off the carb.
Be careful not to rip the gasket between the engine block and the carburetor or you will have to replace it with a new gasket.
7. Remove the Bowl from Your Push Mower Carburetor
Now locate the bowl on the bottom of your carburetor. This is the place a small amount of fuel is collected once it leaves the fuel tank. Have a rag available to soak up any remaining fuel in the bowl.
Remove the screw located at the bottom of the bowl and lower the bowl to remove it from the carburetor. You will find a gasket located between the bowl and the carburetor.
It looks like a rubber band. Do not get any carburetor cleaner or other substance on the gasket as it will ruin it. If you do, the gasket must be replaced before the bowl is reattached.
8. Check Your Push Mower Carburetor for Clogged Holes in the Stem
You will find a stem that hangs down in the center of the push mower carburetor. The holes in the stem can become clogged with the gumming of old fuel. With a flashlight to better see the holes, use a thick wire to unclog them.
9. Remove White Crusty Buildup and Gumming in Your Push Mower Carburetor
Check the other components in your carburetor along with the carburetor itself for additional gumming and a white crusty buildup.
Remove the gummy deposits along with as much of the crusty material as possible using a carburetor cleaner and a clean cloth. Note: It is almost impossible to remove all the crusty material.
10. Reassemble Your Push Mower Carburetor
Once you have finished cleaning the push mower carburetor and ensured all the components are in good working order including your float needle and float, go ahead and reassemble the carburetor.
Reverse the steps you went through when you removed your carburetor. Use the photos you took earlier for reference.
Replace or Rebuild Your Push Mower Carburetor When Cleaning is Unsuccessful
Sometimes cleaning your carburetor doesn’t make it carburetor function correctly. You may have small components in your carburetor that must be replaced or old fuel has caused so much damage you need to replace the carburetor.
Fill Your Push Mower Fuel Tank with Fresh Gas and a Fuel Additive
Only use fresh gasoline in your gas-powered push lawn mower. Add a fuel additive like Sea Foam Motor treatment to stabilize your fuel, reduce moisture and clean the fuel system.
Read more about using Sea Foam Motor Treatment as a fuel stabilizer and why it is what I use in my lawn mower.
If you are using an older push mower that is using a two-cycle engine, make sure you are using good fuel along with the correct fuel-to-oil ratio mix.
Still Having Problems with Your Push Mower?
Push mower owners encounter many common problems over a mower’s lifespan. Every mower develops issues over its lifespan even when purchasing a top-of-the-line lawn mower.
To help you identify the causes of these problems and how to fix them, I put together this guide to help: Common Push Mower Problems & Solutions.