Just with any other piece of equipment, lawn mowers have the capacity to break or fail. Whilst backfiring isn’t necessarily an issue on its own, it can be used to diagnose a larger issue, or could be a precursor to an issue that is about to arise.
Backfiring is often something not to worry about, as it can easily be avoided by decelerating slowly. If the problem persists, further diagnostics may be needed to determine a cause.
Lawn mowers can be an expensive bit of kit and if problems are left unsolved, can lead to expensive repairs or part replacements.
What is Backfiring?
Backfiring is when a lawn mower ignites gasoline outside of the combustion chamber. Whilst this sounds dangerous, it generally isn’t, due to the speed of which the ignition takes place and how quickly the gasoline burns up. It usually occurs in the muffler, just outside the combustion chamber, and is still contained within the lawn mower’s system, meaning that it shouldn’t lead to any harm involving the individual pushing the mower.
How to Tell your Lawn Mower’s Backfiring
You can tell that your lawn mower’s backfiring due to the loud, startling noise that it makes when it does backfire. It sounds like a loud popping sound, and has the potential to make you jump or catch you off guard. This noise often occurs when the lawn mower is being shut down, or when it is being slowed down during use.
What Causes a Backfiring Lawn Mower?
A lawn mower will backfire for a few different reasons. Whilst most of the time it isn’t an issue to be worried about, it can occasionally lead to or be caused by a mechanical problem within the body of the lawn mower.
Most of the time, a lawn mower will backfire during shut-off due to rapid deceleration, leading to an excess of air making its way into the system as the throttle tries to fall in time with the engine. This creates a lean blend, which is brought into the system via the exhaust system, where it ignites and creates the loud popping sound which is synonymous with backfiring.
This process can take seconds to occur, providing conditions and the deceleration speed are correct.
Why is my Lawn Mower Backfiring?
You can sometimes diagnose the reason behind your lawn mower backfiring based on when the backfiring occurs. Whilst these reasons may not be wholly accurate or representative of your specific situation, they can provide you with a basis of where to begin looking for a diagnosis.
Backfiring During Shut-Off
If your lawn mower backfires during shut-off, the chances are that it is due to the speed at which you are decelerating the lawn mower. By decelerating and shutting down quickly, you’re allowing for excess air to make its way into the lawn mower’s engine, thus leading to a backfire. If you find yourself shutting your mower off abruptly or doing it at an unreasonable speed, you will be more likely to suffer from backfiring as a result. One way in which this can be avoided is by shutting the lawn mower down in a timely manner, and allowing for any excess air to pass through before shutting down. This means allowing the mower to run for approximately 15 seconds before powering it off completely.
This should be a solution to the problem, but if backfiring persists during shut-off, it could potentially be due to an overheating problem. In that case, it is ideal to speak to a professional who can suggest ways in which to increase airflow to cool the system off.
Backfiring After Shut-Off
Backfiring after shut-off can be a symptom of issues pertaining to the muffler or carburetor. This could be down to the carburetor settings, or problems within the muffler and its attachments. Both of these components can be looked over and any changes can be made to them to make them more compatible with your mower if need be. In addition to this, the type of gas being used by the lawn mower can also cause backfiring after shut-off. Alcohol gas is more likely to ignite outside of the engine, and instead ignite in the muffler which can cause backfiring. Using low alcohol or non-alcohol gas may also alleviate this issue.
Backfiring When Starting
Backfiring when starting a lawn mower is rare and shouldn’t occur unless there is actual damage to the system in play.
If your lawn mower is backfiring when trying to start, cease trying and book it in for a repair or speak to a professional before attempting again.
Backfiring when starting up is a sign of physical damage being taken to the lawn mower, often by an obstruction or other object that has damaged it. Lawn mowers are designed with parts in mind, so most of the more expensive and necessary parts are hidden away, guarded by inexpensive and replaceable components such as the flywheel. A broken or damaged flywheel can result in backfiring or stuttering when trying to start a lawn mower, and should be fixed before it is put to work again.
How to Avoid Backfiring
Depending on when the lawn mower backfires, the means in which to avoid it can be varied. In a majority of cases, the cause of backfiring is due to the speed at which the lawn mower is powered down, and occurs when shutting the system off.
To avoid this, the solution is rather simple. When finishing off your lawn, make sure to gradually lower the engine speed over a longer period. If you use a throttle to reduce speed, make sure to slowly and steadily let it up instead of rebounding quickly. Leave your engine running for an additional 10-15 seconds before shutting it down.
If your lawn mower backfires after being shut off, it’s possible that the issue is regarding the carburetor or muffler. A lawn mower runs smoothly providing a lean mix isn’t being produced by an excess of air. A lean mix could be caused by a carburetor running incorrectly, and can be adjusted by reading the lawn mower’s manual or by consulting a professional. If your lawn mower is producing a lean mix due to an issue with the carburetor, you may need to adjust the carburetor for a richer mix.
Your gas may also be to blame for persistent backfiring. Alcohol-based gas is more combustible and likely to ignite within incorrect parts of the machine, such as the muffler, which will lead to backfiring. If this is the case, swapping to a low-alcohol or non-alcohol gas could yield better results and reduce any backfiring that may occur.
Lawn mowers can also be finicky when working in temperatures that they are not used to. Hotter temperatures may lead to overheating, which may also lead to backfiring. One way to avoid this is by ensuring that the airflow to the undercarriage is adequate for your lawn mower, or by using the lawn mower during cooler times of the day, such as mornings or evenings.
Is Backfiring Dangerous?
Despite the rather imposing name, a lawn mower backfiring is hardly dangerous as the ignition takes place within a contained area or the lawn mower and should see no exposure to the person behind the lawn mower. Backfiring is also not dangerous to the engine either, as the engine is well-equipped and protected from any sudden ignitions. Backfiring, however, can be annoying, distracting, and the noise may lead to dismay from neighbors. It’s definitely an issue worth diagnosing and sorting as soon as it arises, and taking further measures to prevent it from happening again.