Why Does My Lawn Mower Backfire?

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For those who have experienced a lawn mower backfiring before, you’ll know that it’s not a particularly pleasant sound. In fact, it can be completely frightening and catch you off guard whilst you’re busy daydreaming whilst conducting your weekly yard work. 

Although a lawnmower backfiring might sound scary, it won’t harm you in any way. But, the bad news is that it could harm your engine.

To make sure that your lawn mower works properly, you’re going to need to sort out your engine so that it doesn’t cause any further damage. 

But in order to fix a backfiring lawn mower, first of all you have to determine what the cause is. There are a couple of different reasons why this might be happening, all it takes is some patience and assessment. 

Below, we’ve provided a helpful guide that you can refer to when diagnosing your lawn mower issue. To find out more, simply keep reading below, as we take a closer look. 

The Key To Determining The Cause Of Your Lawn Mower Backfire 

When it comes to determining the cause of your backfiring lawn mower, there is one question that you should always ask yourself. This question is, when does your lawn mower backfire? 

This simple question will show you everything to know about the root cause of the problem, and help you to in turn, solve it. 

Perhaps your lawn mower backfires when you’re just turning it on, or maybe during use? Maybe it doesn’t backfire until the job is done and you’re just switching it off?

Either way, each of these specific scenarios have a different cause that we’ll be taking a look at below. 

Keep reading to find out more. 

Backfiring Whilst Starting Up

The first scenario that we’ll be taking a look at is if your lawn mower is backfiring just as you’re starting it up. This is an extremely common issue, and oftentimes, it won’t even power up properly. 

We need to emphasize that this shouldn’t happen, and if you see that your lawn mower is backfiring as soon as you power it up, then this is a sign that there may be some kind of damage that’s been done to the machine. 

The most common cause in this scenario is that you’ve inadvertently mowed over a sharp object that’s done some damage to the engine.

Although there are typically safe guards in place to protect your engine, some smaller items such as rocks might still get through. 

The first thing that will be broken in this case is the flywheel.

This is one of the most replaceable elements of the lawnmower, and if you suspect that this might be the issue, you can simply take it in to have the flywheel replaced. It’s a very common issue with lawn mowers, and is easy to fix. 

Why Does My Lawn Mower Backfire?

Backfiring During Use 

The next scenario that we’re going to take a look at is if your lawnmower is backfiring whilst you’re using it. This can be incredibly frightening, and it is one of the most stressful moments at which your lawn mower backfires. 

When you first power it up, it might run perfectly for a while, only to create a massive backfire halfway through the process.

If this is something that’s been happening to you, then you can pretty much guarantee that it’s being caused by your carburetor. 

Carburetors are prone to issues, and yours might either have become too lean, or too rich. Essentially, in simple terms, your lawnmower has an air to fuel ratio that is uneven, and this is what’s causing it to backfire. 

Again, don’t worry, as this is another common problem, and can be fixed.

If you’re feeling confident enough, you can try to fix this one yourself by adjusting the gas in the engine. If not, take it to a professional to solve. 

Backfiring After Use 

Some of you might find that your lawn mower is backfiring after you’re done using it. This can be quite shocking, especially if you’ve been using it for hours without running into any problems. 

We would, however, urge you to fix this problem as soon as possible, even if it runs fine for the most part. This way you can prevent any further damage to the engine and ensure the longevity of your lawn mower. 

So, if your lawn mower is backfiring after you’re done using it, this is usually caused by the speed at which you’re driving the engine.

It’s a common mistake, but many people don’t realize that they actually need to bring the speed of the lawn mower down before they shut the engine off. 

If you’re guilty of this, then this is probably why your lawnmower is currently backfiring. To solve this problem, bring the speed down gradually before shutting it off. 

Final Thoughts 

To sum up, the key to determining the cause of your lawn mower backfiring is to simply assess when it’s happening.

If it backfires when you first turn it on, then it’s likely that the flywheel has incurred damage and needs to be replaced. 

If you find that the lawn mower is backfiring during use, then the cause is likely to be an imbalance between the air and fuel. 

Finally, if it backfires after use, this is probably because you’re shutting the engine down too quickly after intense usage.

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