Learn How to Clean Your Carburetor and Get Your Mower Running Again!

Is your lawn mower not starting or running poorly? Did you know 2/3rds of all repair orders to small engine repair shops are linked to fuel-delivery issues, namely dirty carburetors? The following guide will help you avoid that trip to the small engine shop, as you can learn how to clean your carburetor yourself!

First, lets begin with the basics of what a carburetor is. Essentially, an engine cannot run on liquid gas alone. The gas must be mixed with air and 'vaporized' in order for the engine to run properly and at different speeds, with differing power demands.

In order for a carburetor to function, it must rely on pressure differences in order to provide the engine with both vaporized fuel and in the correct amount. Different ports, whether they are designed for air or gas (or both) must all be obstruction free. When cleared, they pull and draw the air and fuel in on their own. If any ports are clogged, the result is either a no-start mower or a poorly running one.

Here's where the problem with a no-start lawn mower lies. Gas is usually left in the fuel system long past its usable life, and when the gasoline begins to break down these 'ports' or tiny passages become blocked.

This all may seem complicated. The good news is, if you understand these concepts you will have a keen eye for 'ports' or 'passages' within the carburetor that must be cleared and clean in order for your machine to work.

The following are the main components of a modern gravity-fed, bowl-style carburetor. Similar to the one you may own. This particular model has the auto-choke function. Yours may not have an auto-choke, but the principles will still apply. Whether yours is older, follow these guidelines.

A gravity-fed style carburetor only means that the fuel tank is situated above the carburetor and a fuel line runs from the bottom of the tank to the carburetor inlet. Fuel simply flows down into the carburetor.

Use a quality carburetor cleaner and compressed air (if available). The cleaning solution can should be equipped with a small spray tube necessary, in order to direct cleaning spray into small openings.

When you have located a port to be cleaned, direct spray until cleaning solution can be seen through an adjacent or connected opening as this ensures the pathway is cleared (when applicable).

Pro Tip: Always wear protective glasses to protect your eyes when using carburetor spray cleaner, wear nitrile gloves to protect against unnecessary exposure to gasoline and the cleaning solution itself. Never direct compressed air towards yourself or others.

In order for you to locate your carburetor, look for the engine air filter cover.

View of intake, engine air filter cover; arrow points to the fuel line

Be cautious, once you remove the carburetor, gasoline (if present inside the fuel tank) will begin to pour from the fuel inlet line. Either plug off the fuel line using appropriate pliers or drain fuel into an appropriate container.

A great practice is to snap a photo of all linkages before disassembly! This makes reassembly a breeze.

Carburetor linkages prior to removal

Your air filter cover will be held down with either some kind of fasteners or simply by clips, like this one.

Air filter cover removed exposing air filter element inside

After removing the air filter element, remove the fasteners holding the air filter box to the intake of your machine (these steps may vary with your machine but the premise remains the same).

Air filter removed to expose bolts; remove bolts in order to access carburetor

View from behind air box; some of the carburetor ports that must be clean

Gently remove linkages, breather tube and anything else holding the carburetor to the intake manifold. Be sure not to bend any linkages.

Carburetor attached to engine; this is after air cleaner housing removed

Now that you have a visual reference of how the carburetor was arranged prior to disassembly, and hopefully taken a photo for future reference, you now have the carburetor separated from the unit; we can now begin strategically cleaning.

This is the choke side of carburetor, choke is in closed position (for starting)

The first step to cleaning your bowl-style carburetor is to remove the bowl itself. For the example plastic style carburetor shown, there are two fasteners holding the bowl down. Be cautious as gas will likely be present inside the bowl.

Bellow is the bottom of the bowl removed.

Arrow points to bowl O-Ring

Note the Drain Plug on bottom of bowl

Pro Tip: If your carburetor is off an older lawn mower, the main jet may be in the bowl nut itself! Look for small holes going through the bowl nut on your mower and make sure that light can pass through, ensuring it is properly clean.

First, gently grab the hinge pin holding the float to the carburetor using needle nose pliers, to remove.

Study this picture before removing the components to be aware of how they are to be reassembled

Hinge pin removed

Bowl float; Sometimes these can become gas-filled, check that it is properly sealed and dry inside

Be careful, when removing hinge pin not to lose it as it is a small component as well as the needle valve.

Inspect the circled portion of needle valve for pitting or deformation

A symptom of a deformed or improperly seating needle valve is leaks from the carburetor bowl, or no starts due to flooding or fuel starvation! If you see any dents, to the needle valve tip or pitting, this component must be replaced.

This is the needle valve, hinge pin and bowl float assembled together

The needle valve and float regulate the amount of fuel reaching the carburetor from the fuel tank. It rises and falls based on the amount of fuel inside the carburetor bowl. When enough fuel enters the carburetor bowl the needle valve must properly seat and prevent any more gas from entering the bowl.

Ensure main jet is clear in these ports and passages

Ensure all ports are clear and free of obstructions; air or liquid of carburetor cleaner must pass through

Throttle plate side of carburetor (throttle is open)

Be sure not to lose the retainer and O-ring found on the throttle side of the carburetor!

When reassembling carburetor ensure that the needle valve is properly seated inside the needle seat, and that the float moves freely on the hinge pin. Ensure that the bowl and its O-ring is properly seated onto carburetor body and not kinked. Do not over-tighten the bowl fasteners to the carburetor body.

Ensure that the auto choke linkage is holding the choke closed upon reassembly and that it is not binding on anything.

After you are confident that the carburetor is reassembled, introduce gas to the gas tank or reattach the fuel line to the fuel inlet. If you see a leak check tightness of the bottom of the bowl fasteners. If they are sufficiently hand tight, leakage from the bowl can point to a needle valve not properly seated. Do not over-tighten bowl fasteners to stop a leak! Locate source of leak first as this may damage the carburetor body threads, or warp the carburetor body and or bowl.

Carburetor passages and ports are very small and must be cleared to allow fuel and air to pass through. When aware of this you can strategically clean your carburetor using the methods outlined above.

If you found this post helpful consider enrolling in our free Online Program designed to transform novice lawn mower operators into knowledgeable and independent troubleshooters, and maintainers of their own equipment! Avoid the expense and hassle of untimely breakdowns! All that is required to enroll is an email, and it is completely free of charge! Click here to be directed to the enrollment page: Online Program

Never the Norm!