How To Clean A Lawn Mower Carburetor?

The carburetor on a lawnmower plays a critical role in the combustion process that powers a gasoline lawn mower. It’s the place where fuel and air mix moments before they combust. Of course, this also makes them somewhat prone to developing carbon buildup and other residues.

It’s also possible for things like dust, pollen, and small grass particles to make their way into the carburetor. This can be the result of a dirty air filter or lawn debris that finds its way into the fuel tank. If you have a bad habit of letting old fuel sit in your lawn mower’s gas tank or you sometimes run the tank empty, lawn debris and other tank sediments can be sucked into the system and into the carburetor.

Left unchecked, this unwanted debris in your lawn mower’s carburetor can start to drastically affect the engine’s performance. As time goes on a dirty carburetor can even start to affect the performance of the spark plug, causing it to fail.

Two-stroke engines tend to be more prone to carburetor problems, as they are a less efficient combustion process. Though even a high-quality 4 stroke lawn mower engine can develop dirty carburetor problems over time.

Signs Of A Dirty Lawnmower Carburetor

The internal workings of a lawn mower carburetor aren’t all that easy to see. If you aren’t mechanically inclined, it can be hard to tell when the carburetor is gumming up and needs cleaning. Though there are a few red flags to watch out for. This includes things like:

  • Dark smoke coming from the exhaust
  • Performance issues like bogging down or struggling to stay running smoothly.
  • Backfiring while starting or while running, especially after bogging down
  • Frequently overheating
  • Hard starting

How Often Should I Clean My Lawn Mower’s Carburetor

If you’ve noticed any signs of a problem it’s probably a good idea to set aside some time to give the carb and other parts of the fuel-air system a thorough cleaning. Though a lot of small engine mechanics will also recommend cleaning the lawn mower carb every two or three years as part of your spring maintenance.

How To Clean A Lawn Mower Carburetor

Whether you’re having a problem with your lawn mower’s performance, or it’s simply a good time to clean give the lawn mower’s carburetor a good cleaning, you should also set aside time to take care of other essential maintenance tasks. Skipping one of the following steps could make it hard to diagnose problems in the future.

Step One: Thoroughly Clean The Lawn Mower’s Air Filter

A clogged air filter can have a staggering impact on the entire engine’s performance. The combustion process relies on the careful balance of the fuel to air ratio. When things like dust, pollen, grass clippings, and other lawn debris clog up a lawn mower’s air filter it can lead to poor combustion and excess fuel residue in the carburetor. In a severe case, the debris might even make its way past the air filter to physically clog the carburetor or prevent the spark plug from working properly. This is even more likely to be an issue in two-stroke lawn mower engines.

Most lawnmower air filters are in some type of housing and are made from a foam material. You might need to back out a bolt or two to release the housing. When pulling the air filter out make sure not to let any loose debris fall into the throat of the air system.

Physical debris can be picked away by hand. Canned air can help blow the air filter out.

Step Two: Check All The Connections On The Lawn Mower Engine

Loose connections and pinched throttle cables can all affect the lawn mower engine’s performance. Take the time to look at carburetor’s throttle as well as the choke plates, and the spark plug wire. Dirt and debris, or physical damage to these components can affect carburetor performance, which can lead to excess residue building up.

Step Three: Use Carburetor Cleaner Spray To Remove Debris & Clogs

Carburetor problems are so common with small engines like you find on most lawn mowers, that manufacturers offer a wide range of carburetor cleaner sprays. They’re relatively easy to depending on your lawnmower, you might not even need to open up the carburetor.

Just follow the directions on the can, according to the manufacturer’s specifications and the recommendations in your lawn mower’s owner’s manual.

Step Four: Change Oil And Replace The Fuel

Lawn mower fuel tanks have a nasty habit of collecting lawn debris. Especially if you have a large yard and need to refuel in the middle of a mowing session. When you open the cap, dust, pollen and other types of lawn debris can find their way into the tank, where they lay in wait for the chance to be drawn into the carburetor in the future.

It’s also worth noting that old fuel is more likely to separate into low-grade octane chains, water, and even tank varnish. Even if you add fresh fuel on top, these unwanted compounds can still find their way through the fuel system to the carburetor. As long as you are already cleaning everything, you might as well siphon out any old fuel and try to clean any physical residue you see out of the fuel tank.

If you have a four-stroke lawn mower, this is a good time to give it a complete oil change.

Tips For Keeping Your Lawn Mower’s Carburetor Clean & Functioning Properly

There are a few things you can do to help keep your lawn mower’s carburetor clean and functioning correctly. This includes:

  • Using high-quality, high octane fuel
  • Changing the oil every spring or every 50-hours
  • Periodically cleaning the air filter
  • Checking the spark plug for signs of corrosion
  • Removing any debris you see in the lawn mower’s fuel tank
  • Properly winterizing the lawnmower
  • Using fuel stabilizer if the lawnmower won’t be used for 2-weeks or more
  • Making sure to mix the oil properly for a two-stroke engine



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