How to Fix a Backfiring Lawn Mower & How to AVOID it?

A backfiring lawn mower is a common problem. Fix it by using a fuel with lower alcohol content, you can also adjust the carburetor settings and improve the cooling system of your lawn mower’s engine. If that doesn’t work, open up your engine and check the timing. If not, you may have to replace certain engine components.

Backfiring can do a lot of damage to the lawn mower and decreases the life of the machine. This article aims at answering how a backfiring lawn mower can be fixed and avoided.

How to Fix a Backfiring Lawn Mower

Read on while we explain these points in detail, helping you tackle your backfiring lawn mower with ease in the future.

How to Fix a Backfiring Lawn Mower

While owning a lawn mower helps you maintain your lawn easily, there are some occasions when your peace is disturbed by a loud bang, similar to the sound of a gunshot.

However, the most likely source of the bang is your lawn mower backfiring. It can be a nuisance to both the operator and the people around, thus needing an effective solution to the problem.

  • During deceleration, gradually reduce the speed of your engine. Do not allow the throttle to rebound to the rest position immediately. Controlling the deceleration will ensure that the mixture does not get lean due to a sudden reduction in fuel flow. 
  • Change your fuel to one with lower ethanol content. Fuel with high ethanol content is more combustible. As a result, you could have premature explosions outside of the engine chamber while the lawn mower is in operation, which causes the engine to backfire.
  • Changing your carburetor settings can help curtail engine backfire. The carburetor controls the fuel-to-air ratio of the mix that is then combusted within the engine. Changing the setting to allow more fuel into the engine chamber will ensure that your combustion process is more efficient, while also ensuring that backfires are avoided.
  • Cooling systems must be made better. If your engine is running at hotter than normal temperatures, the combustion process will not utilize the mixture efficiently within the chamber. Not only does this lead to poor fuel efficiency, but fuel particles will remain in the exhaust as well. When it comes in contact with hot components like the muffler of the exhaust, this could lead to an ignition outside of the chamber, causing a backfire.
  • The timing of the engine must be checked to ensure proper ignition. If your timing is not proper, this will also lead to inefficient fuel consumption. This can have an adverse effect on the fuel mix within the engine, eventually causing it to backfire.
  • Worn-out components like spark plugs, valves, and ignition coil must be replaced if none of the above work. These are the primary components involved in the combustion process of an engine. Worn-out spark plugs and ignition coils can disrupt the timing of the engine by failing to ignite the fuel mix, causing the engine to operate very roughly. Check out the article When to Change Spark Plug on Lawn Mower, to learn more about spark plugs. Failure of the valve system can also lead to improper fuel intake and exhaust flow, causing the engine to backfire.

What Causes a Backfire in a Lawn Mower?

A lean fuel mixture is the primary reason for an engine backfire. The fuel mix has more air than the optimum fuel-to-air ratio, resulting in incomplete fuel combustion inside the engine. 

When the by-products of the process enter the exhaust system, the remaining fuel spontaneously combusts, causing the engine to backfire. This is characterized by a long pop-like bang.

Another probable reason for your engine backfiring is the engine tuning itself. The timing may be too advanced or your fuel mix is slightly leaner than normal. This could lead to backfires when specific operators who are not used to these changed settings operate the machine.

What causes a fuel mix to become too lean

Decelerating your engine too quickly is one of the most common reasons. Due to the rapid closing of the throttle, the engine’s timing goes out of sync with that of the throttle. This has an adverse effect on the fuel mix, eventually resulting in a backfire.

Lean fuel mixes can also be the result of high alcohol content in the fuel and increased operating temperature. These result in the engine operating outside of its optimum conditions and tend to advance its timing. The resulting out-of-sync combustion results in your lawn mowers engine backfiring.

Tuning of a lawn mower engine

Learn more about the timing of fuel engines in the video below. It demonstrates the concept in an easy-to-understand manner.

Does a Backfire Damage an Engine?

No, a backfire does not damage the engine. Despite how terrifying the term may sound, a backfire occurs when the combustion occurs outside of the engine chamber. As a result, it has no direct impact on the engine.

However, it could have a negative impact on your exhaust system in the long run. This is because they are not designed to handle the heat and energy produced from the combustion that occurs during a backfire

Can a Lawn Mower Explode?

Yes, only gas-powered lawnmowers have the slight possibility of exploding. Although it is a very rare occasion, it takes multiple factors going wrong at the same time to result in something as bad as an explosion. So what exactly can cause a lawn mower to explode?

— Also read: Is it bad to leave Gas in Lawnmower over Winter?

Due to the hot temperatures of the engine, there is a chance of fires breaking out while in operation. If the fires are not extinguished quickly, they could spread to the fuel tank. Large amounts of fuel can combust very quickly in the tank, which is not designed to contain the release of energy. As a result, your lawn mower can explode.

How to avoid Backfiring

Preventing engine backfires from occurring does not take specialized care or skilled operation whatsoever. All you need are a few basic steps to take care of your lawn mower.

Regularly service and maintain your lawn mower

Replace internal components of the engine on time and ensure the fuel you use is good quality. These will not only help your engine run smoothly but will also ensure that the fuel mix is rich enough for optimum combustion

Do not operate the lawn mower when the outdoor temperature is high

This could cause more volatile fuels to evaporate easily, while also increasing the engine temperature. The combination of these factors can result in an incomplete combustion process while in operation, leading to a backfire.

Don’t deaccelerate to quickly

As the throttle is suddenly shut, engine timing becomes misaligned with the throttle. This adversely affects the fuel mix and eventually leads to a backfire.

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