Why Does a Lawn Mower Backfire & How to Stop It?

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When you know how to start a lawn mower and you’re finishing up your yard work and turning off the lawnmower, a lawnmower backfire generates an unexpectedly loud noise, taking you by surprise.

When gasoline ignites outside the engine, generally in the muffler, a backfire occurs. Although a backfire won’t harm your engine, it’s typically a sign of a technical issue.

Backfire can happen at any time, when you are turning off your mower, after you have turned off your mower, or even when you are turning on your machine.

So, do you have questions like what is a backfire, what does a mower backfires, and how can you prevent it from happening to your lawn mower engine?

Well, let us discuss it one by one in this article.

lawn mower back fire

What Does Backfiring of Lawn Mower Means?

A popping sound produced by gasoline-burning outside of the engine’s combustion chamber is referred to as backfiring by a lawn mower.

Why Does a Lawn Mower Backfire?

A backfire is common when the engine tries to get its timing in line with the dropped throttle during sudden deceleration. It might result in an excessive amount of air in the mix, resulting in the creation of a  lean blend.

The lean blend is driven into the exhaust system, which was caused due to incomplete combustion, and mistiming. Where it spontaneously combusts with the popping sound heard.

This appears to be a lengthy procedure, but owing to the engine’s perfect timing, everything happens in a fraction of a second.

Usage of an improper gas can for a lawnmower sometimes leads to a backfire.

How Can You Stop Your Mower From Backfiring?

There are a lot of things you may do to create a backfire when running your mower, and there are ways to avoid them.

  1. Decelerating too rapidly is the major cause of a backfire. The simple solution is to slow down the engine speed a little more gradually. If you use a throttle to lower speed, let it up gently rather than letting it rebound rapidly.
  1. Sometimes it’s the fuel that’s causes the issue. Due to the skewing of the mix, gasoline with a greater alcohol content might cause your mower to backfire.

Mowers are designed to run on certain fuel mixes, and using the wrong one might throw the system off. Simply alter your mix to remedy this.If a no-alcohol mix isn’t available, look for one with reduced alcohol content.

When you start a lawn mower, it’s not meant to backfire. 

  1. If your lawnmower backfires when you try to start it, it means the mower is broken in some way, therefore replace the appropriate parts.

Many mowers feature components that serve to protect more expensive components. These low-cost components, such as the flywheel, are sacrificed to safeguard the more expensive components, such as the crankshaft.

If your mower goes over a huge rock or its blades contact an object while mowing, the flywheel will break and won’t engage when you restart it. When you try to start your engine, it will stutter or backfire.

  1. Backfires can also be caused by the engine running at a higher temperature than usual, which can be easily remedied by boosting airflow over the engine to cool it down, or by halting the engine and allowing it to cool down.  To draw better conclusions, it is necessary to undertsnad how does the engine of lawn mower works.

Consider modifying the engine casing to reduce air restriction across the engine for a long-term solution.

  1.  Finally, backfires might occur simply owing to the muffler’s structure and the sensitivity of internal channels. There is no solution in these circumstances other than changing the muffler.
  1. Anti-after fire solenoids are specific devices in certain mowers that help avoid backfires after the engine has been shut off, so you should consider adding this on your mower.

These allow you to shut off the engine at any speed without spilling gasoline into the exhaust system.

If you suspect a malfunctioning anti-after fire solenoid, contact a qualified repair shop.

Steps to start back fired lawn mower

Despite their name, backfires are neither harmful to humans nor the engine. Hence you should not worry that it can burn your home or might hurt your family.


Engine backfires appear to be frightening, especially when they occur unexpectedly.  Although an explosion in the lawnmower seems weird, it is not anything to be concerned about.

This article discusses the reasons for engine backfires. You may use this information to figure out why your mower is backfiring and hunt for solutions.

So, the next time your mower backfires, apply what you’ve learned to correct the problem before it permanently harms your mower.

About Tom Reynolds

My name is Tom Reynolds, and I like lawn mowing. When I was a kid, I used to help my dad in cutting grass using a reel mower, now, I have my own 6 different lawn mowers. Keeping my lawn healthy and beautiful gives me satisfaction, and I still enjoy working in my lawn.