Where Is the Carburetor On Your Lawn Mower (And What Does It Do)?

Key Takeaways

1. You can find the carburetor on your lawn mower underneath the air filter compartment.
2. Carburetors ensure the correct air-to-fuel mixture for your lawn mower.
3. If your carburetor starts going bad, you’ll notice issues such as diminished engine performance and reduced fuel economy.

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Where Is The Carburetor On Your Lawn Mower?

Generally, you can find your lawn mower’s carburetor directly below the air filter housing compartment on the side of the engine (the same side as the fuel tank). You will also find it by locating the fuel lines coming out of the tank and following them to the engine. Before you reach the engine, you will come across the fuel filter and the carburetor. 

Every lawn mower is different, though (even in minor ways), depending on the brand. So, you can also use your owner’s manual to locate your lawn mower’s carburetor.

What Does Your Lawn Mower’s Carburetor Do?

A carburetor is a mechanical device used in internal combustion engines to mix air and fuel correctly before delivering the mixture to the engine’s combustion chambers. It plays a crucial role in the engine’s overall performance by providing the fuel-air mix for combustion.

Mixing Air And Fuel

Your carburetor’s primary function is combining the correct amount of air and fuel to create a combustible mixture. Your carburetor draws air in through the air intake while the fuel tank supplies the fuel. A carburetor’s design allows it to regulate the flow of both air and fuel, ensuring the ideal mixture for combustion.

Atomization

Your carburetor atomizes (converts) fuel, breaking it into fine droplets and dispersing it evenly within the incoming air. This process enhances fuel vaporization, allowing it to mix more effectively with the air. Efficient atomization results in a matching mixture combusting efficiently within the engine cylinders.

Throttle Control

Carburetors also control your engine’s speed and power output through the throttle valve. The throttle valve regulates the amount of air entering the carburetor, affecting the fuel the engine draws in.

When you open the throttle, more air and fuel enter the engine, increasing power output. 

You can locate your lawn mower’s throttle control by looking for the rabbit and turtle emblem, showing high speed and low speed, respectively.

Enrichment For Cold Starts

In lawn mower engines, a choke mechanism enriches the air-fuel mixture during cold starts. This provides a richer mix that is easier to ignite in colder starts.

What Happens When The Carburetor Fails?

A failing carburetor significantly impacts the performance and functionality of an internal combustion engine. A failing carburetor creates various issues affecting your engine’s operation and efficiency. It will either run poorly or not at all. 

Signs And Symptoms

Most times, there will be warning signs of a malfunctioning carburetor. Here are some common effects to look for when your carburetor goes out.

Diminished Engine Performance

A failing carburetor results in poor engine performance, including reduced power output, sluggish speeds, and decreased fuel efficiency. The carburetor’s inability to properly mix air and fuel leads to an imbalanced combustion process, causing your engine to run rough or not deliver its expected power level.

Unstable Idling And Stalling

A malfunctioning carburetor causes your engine to run roughly or stall unexpectedly. Incorrect air-fuel mixture ratios lead to unstable engine idling, which might result in the engine shutting off when your lawn mower is stationary.

Challenges In Starting

If your carburetor is not providing the right mixture for combustion, starting the engine might become difficult. Your engine may require several attempts to start, especially when colder conditions strain your lawn mower’s battery.

Rich Or Lean Running Conditions

A failing carburetor causes your engine to run too rich (excess fuel) or lean (insufficient fuel). Running too rich increases fuel consumption, fouled spark plugs (needing cleaning or replacing), and excessive exhaust emissions. Running too lean results in overheating, increased wear on engine components, and more.

Backfiring And Popping

An improperly functioning carburetor leads to unburnt fuel entering your lawn mower’s exhaust system, causing backfiring or popping noises during a decrease in speed or transitioning between throttle positions.

Excessive Exhaust Smoke

If your carburetor delivers too much fuel, the exhaust may emit black smoke. This indicates incomplete combustion and leads to poor fuel efficiency.

Reduced Fuel Economy

A failing carburetor causes your engine to consume more fuel than usual due to improper fuel-air mixture ratios. This results in decreased fuel economy and higher fuel costs.

Inconsistent Speed Control

Inconsistent air-fuel mixture delivery makes maintaining a steady speed while driving your lawn mower challenging, leading to surging or fluctuating engine performance.

Engine Overheating

A lean air-fuel mixture caused by a failing carburetor leads to higher combustion temperatures, potentially causing your engine to overheat.

Emission Issues

An improperly functioning carburetor leads to increased emissions of pollutants, causing your lawn mower to fail and contributing to environmental pollution.

Carburetor Maintenance Tips

Here’s what to do to ensure the efficiency and longevity of your lawn mower’s carburetor:

1. Regular Cleaning: Periodically clean your carburetor to prevent dirt, debris, and fuel residue accumulation. Use a carburetor cleaner specifically designed for small engines. 
2. Fuel Quality: Always use fresh, clean, and properly mixed fuel. Stale or contaminated fuel leads to carburetor clogs and poor engine performance.
3. Fuel Stabilizer: If you plan to store your lawn mower for an extended period, consider using a fuel stabilizer (you’ve got lots of great options). This prevents fuel from breaking down and causing carburetor issues during storage.
4. Air Filter Maintenance: A clogged air filter affects your carburetor’s performance. Clean or replace your air filter at least once a year to maintain proper air intake and combustion.

My Experience With Carburetors

Over the last two decades, my main issue with carburetors is the trash and gunk accumulating over time. Cleaning is a complex job, but the gaskets will last longer if you get away without removing the carburetor. Removing the carburetor for cleaning and maintenance issues should always be a last resort. 

However, there are always those caked-up moments where I’ve had to remove the carburetor. I always check the gasket while it is removed to see if it needs replacement because leaks from air and fuel are imminent with the constant removal. 

If you must remove a caked-up carburetor, let it sit in a bucket of Pine-Sol All-Purpose Cleaner solution with the right amount of water for 30 minutes to an hour (see the back label). Clean it with a toothbrush and a rag and install it back in place. 

Remember to wear gloves and eye protection while doing so.

For quick engine and fuel system clean-ups and maintenance, I recommend using Sea Foam. It goes into the fuel tank and acts as a stabilizer and cleaner for the fuel and entire fuel system. It also works for diesel engines and mixes with the oil to clean the whole engine. 

I’ve rarely found anything else causing problems with the carburetor other than a few throttle cables breaking or needing to adjust them. Other than these issues, if you follow proper maintenance advice and lawn mower use, you should rarely have problems with the carburetor.