4 Steps to Clean a Lawnmower Carburetor

Whether you use a push mower, a self-propelled mower, or a riding lawnmower, a carburetor is included as a means of helping the engine. However, regular use can cause the carburetor to become dirty and it will need to be cleaned to preserve engine performance. The purpose of the carburetor on a lawnmower is to ensure that the right mixture of air and fuel moves into the engine cylinder so combustion can occur. Through ignition by the spark plug, the mixture of fuel and air will combust. This causes the engine to piston downward and rotate the crankshaft. When that occurs, the blade on the lawnmower will spin and the wheels on the mower will start to rotate.

If bad or old fuel is left in the lawnmower, this can create a sticky residue inside of the carburetor. In some cases, this will cause a clog or a restriction that makes it challenging for the right mixture of air and fuel to enter the engine cylinder. This is often what is referred to when someone says a carburetor is “dirty.” In many cases, cleaning the carburetor will take care of this problem. Follow this step by step easy guide to learn how to diagnose a dirty lawnmower carburetor and get in back in great shape.

Symptoms of a Dirty Carburetor

If the carburetor is restricted or dirty, it’s typically simple to diagnose. It can cause any of the following problems to occur:

  • An obvious increase in gasoline consumption when the lawnmower is being used.
  • Trouble with the engine starting when turning on the lawnmower.
  • Black smoke that can be seen visually coming out of the area of the muffler.
  • An engine that starts but experiences stalling when the lawn is being cut.
  • An engine that runs roughly during the mowing process.

Before we get into the in-depth process of cleaning the carburetor, be aware that there are methods to prevent these kinds of issues. Making sure fuel is fresh when you fill the tank is a simple way to avoid a dirty carburetor. Adding a fuel stabilizer to the fuel is also a useful option. However, if the carburetor starts to become clogged, cleaning it will be the best option.

When to Inspect and Clean the Carburetor

Recommendations vary based on many factors, but most experts agree that the lawnmower carburetor should be inspected and cleaned at least a few times a year. There’s a simple reason for that. When the lawnmower is being used, twigs, grass, and other bits and pieces will be passed through the blade and can end up in the engine. Some of those things will end up inside of the carburetor. When they do, they can get into air and fuel passages. This can create a reduced performance for the engine.

Steps to Clean a Lawnmower Carburetor

Before you get started with the cleaning process, you want to be sure you are totally safe. The lawnmower should have a cool engine when you start to clean it. Put the lawnmower on a flat surface and remove the engine cover so you can get close to the carburetor. All of these things will help you prevent injuries or damage while working on the carburetor. Next, you can move on to the actual cleaning process.

Some of the tools you might need include a socket set, a nut driver, needle-nose pliers, clamps, an adjustable wrench, and screwdrivers. Other things to have with you include a vapor respirator, plastic gloves, a carburetor rebuild kit, and carburetor cleaner.

Before you start taking apart the carburetor, make sure you confirm that this is where the problem is coming from. Make sure the fuel valve is on, the spark plug works, and there is gas in the fuel tank. Use a burst of carburetor cleaner or an aerosol lubricant inside of the carburetor. If the engine starts or sputters and then dies, it’s a fuel issue. If not, there may be a more serious issue and you will need to follow the steps to clean outlined in this guide.

1. Check the Air Filter

Sometimes, the air filter might be dirty and could be causing the engine to have bad performance. It’s important to double-check whether that is the case. If the air filter is clogged, that can cause black smoke to start coming out of the exhaust. When this happens, the carburetor may not be able to draw in enough air to mix with its fuel.

Before going any further, open up the air filter cover and see if the filter is dirty or damaged. If there is an issue, it’s time to replace the air filter before moving on. Remove the cover, the filter, and the housing and do any needed cleaning before putting in a new filter and securing all the parts back on the lawnmower.

2. Inspect the Connections

The next thing you want to check are the connections to the carburetor. These areas can get dirty and cause issues. The connections are located at the carburetor throttle and the choke plates. Before you move to this step, it’s best to turn off the fuel valve. If that isn’t possible, make a crimp in the fuel line before taking it out of the carburetor. Have a rag or cloth around because this may create a small spill.

Take the throttle and choke linkages and detach them from the carburetor throttle lever. At this time, you can also remove the carburetor from the mounting bolts so it doesn’t need to be done later in the process. At the connection areas mentioned early, you want to see if there is any debris or dirt. If so, it should be cleaned off. Also, be aware that the use of the lawnmower can cause wear and vibration. This can cause screws to loosen, which need to be tightened.

3. Use Carburetor Cleaner

Since the small engine in a lawnmower encounters twigs, grass, and debris regularly, it’s far from uncommon for the passages inside the component to experience damage. Deposits that get stuck inside of the carburetor will clog the air and fuel passages and create bad engine performance or an engine that will not start at all.

Thankfully, in many cases, these problems can be dealt with easily and quickly without large, expensive repairs. Carburetor cleaner is a common item that comes in a spray can and is useful for cleaning out the exterior and interior of the lawnmower carburetor. If problems are already afoot, there are a few steps to this process to ensure the entire carburetor is cleaned fully.

If the carburetor has already been taken off the mounting bolts, the first step is to unthread the screw that will remove the carburetor bowl. Next, take the float pin out so the needle and float are both released. Those who wish to disassemble the entire carburetor will want to unthread several screws to release the primer base and bulb. Finally, remove the gaskets, diaphragms, and a metering plate.

Now that the carburetor has been disassembled, it’s time to take your carburetor cleaner (WD-40 can also be used for the process) and clean out all of the ports that have any visible residue. Clean each area thoroughly and don’t forget to also clean out the carburetor bowl if it has any debris or stains. If the carburetor has rust on it, a piece of sandpaper can be used to remove it.

4. Reassemble the Carburetor

After you have cleaned the carburetor, it’s time to let the component dry. Wait until it is fully dry before you reassemble its parts. While you do this, make sure that you take your time with the parts. The metering plate, gaskets, and diaphragms all need to be positioned correctly to ensure the carburetor is in good shape and ready to be used. Other parts to put in place include the primer base, the float, and the float needle.

The next step is putting the bowl gasket back in place before you reinstall the carburetor bowl. Once that is complete, the cleaned and rebuilt carburetor should be slid back up onto the mounting bolts. Take the throttle linkages and place them onto the throttle lever. After that, the fuel hose can be reattached to the carburetor. Replace the air filter housing, as well as the air filter and the filter cover. The only thing left to do is reinstalling the cover on the engine.

Additional Tips for Keeping the Carburetor Clean

As we mentioned earlier, the carburetor should be cleaned a few times a year to keep it in the best working order. However, having a carburetor repair kit around can also be useful. This kit will come with the most commonly replaced items of a carburetor, such as the diaphragms, gaskets, and a float needle and float.

If cleaning and replacing parts isn’t helping the small engine issues with your carburetor, the next step is to replace the existing carburetor with a replacement lawnmower carburetor. Just remember that replacing the air filter, cleaning the carburetor, or replacing bad parts will often stop the issue while being less expensive and quicker to manage. As always, if you have any questions we are always here to help at AppliancePartsPros.com.