Lawn mower engine backfires. Lawn Mower Backfires When Shutting Off? (We Have A Fix! )

Why Is My Lawnmower Shooting Flames? Expert’s Interview

Lawnmowers are sensitive machines, and every part plays an important role in running the engine smoothly. If anything happens to any of the components, it may prevent you run the machine smoothly.

Why is my lawnmower shooting flames?

One of the main reasons could be that the exhaust system is filled with unburnt fuel, ultimately causing firing issues. Since it is a serious issue, you want to address it soonest to prevent damaging the exhaust manifold and other components.

• Why Is My Lawnmower Shooting Flames?

• Giving Pressure
• Cutting Tall And Thick Grasses
• Fuel Hazards
• Excessive Fuel
• Poor Performance Of Spark Plugs
• Using Old Fuel

• Imperfect Air/Fuel Mixture
• Bent Valve Or Valves
• Wrong Ignition Timing
• Older Lawnmower
• High Engine Temperature

• Adequate Oxygen
• Air leakage
• Replace Spark Plugs
• Maintaining A Healthy Exhaust

Why Is My Lawnmower Shooting Flames?

There could be several reasons your lawnmower is shooting flames. Since it could lead to dangerous accidents, you want to address it soonest. Here are all possible reasons when you want to know about “Why is my lawnmower shooting flames?”

Giving Pressure

Are you giving more pressure to the lawnmower? When you mow grass for several hours without any single break, the engine becomes excessively hot.

As a result, the piston moves slowly, and it fails to comply with the firing cycle of the spark plug. Some portion of fuel fails to burn and moves to the exhaust system without burning.

Finally, when the ignition system starts, your lawnmower is likely to shoot flames. The earlier you stop the machine, the better it is.

Cutting Tall And Thick Grasses

Do you cut tall and thick grasses often? Have you checked whether the mower deck doesn’t stick anything?

If the blazing hot muffler is completely filled with grasses, your lawnmower has a probability of shooting flames. At worst, this may burn out the lawn too.

Fuel Hazards

The normal stability of a lawnmower motor is compromised if fuel leaks in the engine. This can lead to flame. In addition, if a hot muffler is surrounded by fuel vapors, it can also cause a flame.

Excessive Fuel

Initially, if excessive fuel exits inside the combustion chamber, your mower may shoot flames. So, why it occurs? It occurs when the air-fuel mixture becomes excessively rich from the adjustability of the carburetor.

Poor Performance Of Spark Plugs

Are the spark plugs performing the way they should be? If there is a lack of oxygen, incomplete combustion occurs, making the spark plug weak or misfiring.

At first, this will lead to smoking. Then extra heat is generated, making the exhaust hotter. At last, flames will come out from the exhaust pipe.

Using Old Fuel

Are you using too old fuel for your mower? Changing fuel is necessary once a month. Old fuel may lose its quality when it sits idle for a long time. Using this old fuel can cause smoking issues and ultimately shoot flames.

So, these are the possible causes you want to check out if you wonder, “Why is my lawnmower shooting flames?”

What Does It Mean When Your Lawnmower Backfires?

Is your lawnmower backfiring? Not taking immediate action will lead to heavy damage to your mower.

What does it mean when your lawnmower backfires?

When your lawnmower engine backfires, it is failing to generate the same amount of power it used to do. As a result, fuel inefficiency occurs, and the machine uses more fuel to produce energy. You may also hear loud popping noise coming out from the mower.

So, what are the signs of misfiring a lawnmower? You can understand whether your lawnmower is misfiring or not by checking out these symptoms:

• The unpleasing smell coming from the mower
• The mower makes unusual sounds when it runs on
• The engine is losing its power
• You may struggle to start it
• the exhaust pipe is releasing an excessive amount of smoke

You have already learned about “What does it mean when your lawnmower backfires?” and “What are the symptoms of misfiring lawnmower?”

Here are the possible reasons you should check to learn to find the reason behind misfiring issues in your lawnmower.

Imperfect Air/Fuel Mixture

You should neither have a high or low air/fuel mixture. The ratio should be stable — not too low or too rich.

If there is a low air/fuel mixture, the engine has less fuel but high air. Imbalanced ratio. This may happen due to low fuel pressure. It is also known as “lean mixture.”

When it happens, some fuel and air fail to reach inside the exhaust valves at the right time as they burn slowly. As a result, backfiring occurs.

Bent Valve Or Valves

A lawnmower has several cylinders, and each cylinder includes one exhaust valve and one intake valve. The job of an exhaust valve is to pass burned gases from the cylinder.

On the contrary, the intake valve enables an ideal air-fuel combination to enter the cylinder.

However, when a valve vent, it doesn’t have a perfect close or opening. As a result, the fuel fails to pass through the exhaust or intake valve to combust. This leads to backfiring issues.

Wrong Ignition Timing

This is the best ignition coil for a lawnmower available in the market.

When wrong ignition timing occurs, the spark will fire either too late or too late. In both cases, the intake or exhaust valve may combust, causing backfiring. You can’t diagnose this problem unless you are a professional mechanic.

Older Lawnmower

Are you using an older lawnmower? Latest lawnmowers are tuned up finely through computer systems. That’s why they can constantly adjust their internal system to make the mower run smoothly.

However, the older lawnmower may not do this like the latest models. They often fail to control the sparks when it is fired and the perfect air-fuel ratio.

High Engine Temperature

Commonly, your lawnmower temperature will rise when you use it. But if the temperature increases unusually, there is something concerned.

When this happens, you may notice the engine is backfiring and automatically shut down after running for several minutes.

Can A Backfire Damage An Engine?

The backfiring issue occurs for several reasons, which we have already discussed above. It will prevent you from running the machine normally.

Can a backfire damage an engine?

A backfire can damage the engine heavily if neglecting the issue for a prolonged time. You want to address the problem as early as possible to prevent damaging it completely.

How to stop backfiring issues for your lawnmower? Here are a few points you want to apply if your lawnmower is backfiring and save from extra damage.

Adequate Oxygen

Does your lawnmower have the perfect amount of oxygen? An ideal amount of air fuel is required to run the mower smoothly. It should be neither too rich nor too low.

When the oxygen level drops, excessive fuel will enter the system. Also, a high level of oxygen (air) will prevent entering an adequate amount of fuel.

Air leakage

Is Your Mower Has Air Leakage? If there is any leakage issue, you want to solve it soonest.

Replace Spark Plugs

Replacing spark plugs after a certain time is necessary. Over time, its construction weakens due to long-time use.

Using new spark plugs ensure perfect spark firing at the right time, also preventing backfiring issues.

Maintaining A Healthy Exhaust

The exhaust system is one of the most common parts where backfire occurs. This mainly happens when the exhaust system is unhealthy.

Proper functioning will be carried out because of this. That’s why maintaining a healthy exhaust system for your lawnmower is necessary.

Hopefully, you have learned about “Can a backfire damage an engine?” and how to stop this issue.

Can A Lawn Mower Explode?

Explosion for any engine can damage it and even make the owner heavily injured.

Can a lawnmower explode?

Yes! A Lawnmower can explode if it is a gas-powered rotary mower. If a leakage issue is seen in the gas tank, it may fire and create a small explosion.

While filling the gas tank, you want to make sure no spelling issues. Being uncareful, you may splash it on the hot muffler, causing firing issues and explosion.

Replace your muffler with the Best muffler for lawnmowers.

The tall grass is one of the primary reasons that could lead to a fire in the lawnmower. That’s why it is better to mow your lawn regularly, ensuring good conditions for your lawn and mower.

So, why do tall grasses cause firing and explosion issues?

The taller the grasses, the bigger the grass clippings. As a result, bigger grass clippings will stick inside the deck and enter the hot motor, muffler, or exposed parts.

When the clippings contact with the hot parts, they start to burn. After a certain time, they will catch fire and may result in an explosion.

Weather condition is another important thing you should note down. You need to choose a perfect time to mow your lawn, especially in the summer season.

During the season, the temperature becomes excessively hot, especially in the afternoon hours. That’s why you want to either mow the lawn in the early morning or evening hours to prevent excessive heat.

Conclusion

Everyone wants to run their machine without any issues. Sometimes unwanted problems pop up from the engine. Resolving it soonest is what we are supposed to do. Hopefully, you have learned everything about “Why is my lawnmower shooting flames?” and how to deal with the problem.

Last update on 2023-01-28 / Affiliate links / Images from Amazon Product Advertising API

Lee Safin was born near Sacramento, California on a prune growing farm. His parents were immigrants from Russia who had fled the Bolshevik Revolution. They were determined to give their children a better life than they had known. Education was the key for Lee and his siblings, so they could make their own way in the world. Lee attended five universities, where he studied plant sciences and soil technologies. He also has many years of experience in the U.S. Department of Agriculture as a commercial fertilizer formulator.

Thoughts on Why Is My Lawnmower Shooting Flames? Expert’s Interview

Lawn Mower Backfires When Shutting Off? (We Have A Fix!)

Loud and unruly noises when shutting down your lawn mower engine is not normal. Bangs or pops as your engine quits running are an indication that something is amiss with the engine. The cause can be a mechanical problem or incorrect operating procedure. It is important to learn and remedy the cause of your lawnmower engine backfires.

If your lawnmower makes loud bangs or pops on shutdown, afterfire may be the problem rather than a backfire. Backfires typically describe a bang or explosion while the engine is running or as it is shutting down. Afterfire happens after the engine has stopped. Neither is harmful or dangerous but do indicate something may be wrong.

Diagnosing and remedying both backfire and afterfire is relatively easy on most lawnmower engines. Following a few tips and tricks can get your lawnmower running smoothly without annoying bangs and pops.

Understanding the Problem – Backfires in Small Engines

In most cases, the cause of a small engine backfire is related to the Rapid deceleration of the engine. Several factors can contribute to the problem.

• Rapidly lowering the engine speed after running at top speed. Jerking the throttle back suddenly from high speed to low speed can cause the mixture in the carburetor to be too rich. The unburned gas can ignite in the cylinder and a backfire through the carburetor can occur. If the gas passes through the cylinder unburned, an afterfire in the hot exhaust pipe or muffler can happen.
• Using blended gasoline with higher levels of alcohol may cause your engine to backfire or to afterfire. Alcohol behaves differently in small engines at different ratios when blended with gas. Always follow the manufacturer’s recommendations when using alcohol blended gasoline.
• Carburetor adjustment can be a cause of backfire or afterfire. If the carburetor settings are too lean, backfires may result. If the carburetor is adjustable, follow the directions in the user manual to reset the carburetor to the proper adjustments.
• The design and construction of some small engine mufflers can induce backfires. Short of replacing the muffler with a new unit or a different muffler style, you can’t do much to prevent this type of backfire.
• High operating temperatures in your small engine can contribute to backfires. Make sure that the cooling fins on your small engine are clean and free of dirt and debris. Check under the cowling for any built-up grass. Air must be free to circulate around the engine at all times.
• Some carburetors can backfire due to design issues. If the small passages inside the carburetor are not properly sized or become clogged, backfires may result. Unfortunately, many carburetors found on small engines are not repairable and you must replace the carburetor if this condition exists.

Even if your small gasoline engine on your lawnmower is perfectly tuned and you are using the right gasoline, backfires may still occur. Unless the problem becomes, recurrent backfiring is not a big issue. It shouldn’t damage your small engine and it isn’t dangerous.

On the Other End – Afterfiring in your Small Engine

Aftefiring usually occurs after the engine is shut off and has stopped running. Many small engines are prone to this problem and some manufacturers apply a solution by including an afterfiring solenoid to prevent these occurrences. Understanding the causes of afterfiring gives some ideas on how to prevent this annoying situation.

• On engines equipped with a separate shot down switch, activating the shut down while the engine runs at full speed can cause an afterfire. In this situation, the engine continues to pump gas as if the engine were still firing, which causes a fuel-rich condition. Never turn off the engine with the throttle at full speed. Throttle the engine down to an idle speed before hitting the shutdown switch.
• Using alcohol blended gasoline can lead to afterfires. Alcohol ignites easier than gasoline, and any unburned fuel may ignite from the engine’s heat alone. Always use the manufacturer’s recommended fuel in your small engine.
• Some small engine manufacturers offer re-designed muffler and exhaust designs that can mitigate the problems with afterfires.
• If your small engine has an anti-afterfire solenoid, ensure that the solenoid is operating. If the solenoid seems to work properly, make sure you follow the shutdown directions in the user manual. A few small engines equipped with anti-afterfire solenoids have quite different shutdown routines.

Afterfire and backfire are remarkably similar in their causes and their remedies. Often, it may be hard to distinguish one from the other. Fortunately, many of the same solutions work for both backfire and afterfire.

Backfires when Starting – Not a Good Sign

Lawnmower engines should not backfire when you try to start the engine. Backfires especially backfires through the carburetor as you start a small engine, indicate a bigger problem. Most often, the problem is a timing issue.

The single largest cause of timing issues in lawnmower engines is a damaged or broken flywheel. This type of damage can occur from running over a large object with the lawnmower or simply due to age. Be careful if your Briggs and Stratton backfires through carburetor.

Is the Flywheel Broken?

A small engine with a broken flywheel probably won’t start at all. Most of the time, you cannot budge the engine with the starter rope. The broken parts of the flywheel usually lodge in the engine’s internal parts and prevent the movement of the crankshaft and pistons.

A flywheel that is missing teeth may still turn but probably won’t run well, if at all. The missing teeth can throw the timing of the engine off enough to prevent the engine from starting. Even if it starts, the operation will be rough and erratic.

The only solution to this problem is to have the small engine rebuilt and the flywheel replaced. A reputable small-engine mechanic can do this job at a reasonable cost. Some homeowners may be able to affect this repair but, be advised it is challenging and messy.

Preventing Backfires and Afterfires

Many backfires and afterfires are preventable. In most cases, a bit of maintenance and following proper operating procedures will reduce or eliminate most backfires and afterfires. Here are some tricks and tips to keep your lawnmower running smoothly all season.

Follow the Manufacturer’s Recommendations

Every small engine comes with a user manual. The manufacturer includes in the manual a schedule of recommended maintenance for your lawnmower and engine. To ensure the longest life possible and the best operation of your lawnmower, you should follow this maintenance schedule

Learn the Proper Operation Techniques

The user manual supplied by the manufacturer with your lawnmower also has guidelines for the operation and use of your lawnmower and small engine. Following these guidelines will give the best performance and easiest operation of your small engine. Learn the proper techniques of operating your lawnmower and follow them with each use.

Don’t Abuse your Lawnmower

Lawnmowers are for cutting grass. Using your lawnmower to cut extremely tall or large weeds, brush, or fallen limbs and twigs can damage the blade and possibly the engine. Before each use, walk the area to be mowed and pick up anything that might damage your lawnmower.

Keep it Clean – Reduce Heat, Wear, and Tear

One of the biggest enemies of small engines is overheating. Small lawnmower engines are air-cooled and depend on air circulation around the engine to prevent overheating. Keeping the engine and lawnmower clean is the easiest way to prevent overheating.

Make sure that there is no dirt or debris built up between the cooling fins on the engine. Grass can lodge under the cowling or pile up against the engine on the lawnmower deck. All these conditions can cause a small engine to run at excessive temperatures. These debris build-ups can cause backfiring, premature wear, and even engine failure in some extreme cases.

Never use a water hose to clean a hot small engine. The cold water may cause the engine block to crack or warp. Wait until the engine is cool to the touch. Even then, avoid spraying water into the engine. Heavy water sprays can damage the electronics in the ignition systems.

Keep the Air Filter Clean

Surprisingly, many problems with small engines are traceable back to a dirty air filter. If the air filter is clogged, the engine can’t get enough air to operate properly. Old or improper air cleaners can allow dust and debris to enter the engine, causing premature wear and failure.

Many professional landscapers recommend changing or cleaning the air filter on your small engine each time you fill the lawnmower with gasoline. If your lawnmower uses disposable paper filter elements, check with the manufacturer for a replacement foam-style filter that you can clean many times before replacement.

Backfiring, Afterfiring, and Small Engine Operations

The occasional backfire or afterfire is normal with most small lawnmower engines. If the backfire or afterfire problem becomes constant, you should take note and discover the cause. The most important thing you can do for your small engine is to adopt a regular maintenance schedule and use the engine as the manufacturer intended.

Dennis is a retired firefighter with an extensive background in construction, home improvement, and remodeling. He worked in the trades part-time while serving as an active firefighter. On his retirement, he started a remodeling and home repair business, which he ran for several years.

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My Lawn Mower Made A Loud Pop And Won’t Start – Now What?

Lawn mower engines, while not entirely complex, have a certain number of issues that can arise. One is the engine backfires, or you hear a loud pop, and the machine no longer starts. Several different things can cause a lawn mower engine to pop, dealing with the spark plug, engine timing, and more.

You were excited to mow your lawn. Well, maybe not, but you had plans to do it anyway. However, the mower made a pop, you jumped, and now it won’t even start. We know what you’re thinking, but no, this is not an excuse to forfeit mowing for a cool glass of lemonade. What it is time to do, is release that inner mechanic (we know you have it in you). Roll up your sleeves, and let’s take a look at why that engine won’t start.

What causes a lawnmower engine to pop?

Your lawn mower may have worked perfectly fine until the engine pops, but why? Ok, maybe you don’t have an inner mechanic in you, or if you do, they aren’t all that knowledgeable on lawnmower engines. Thank goodness for google, hey? Let’s dive in.

The popping noise you hear is commonly known as the lawnmower’s engine backfiring. This happens when gas ignites outside the combustion chamber of the engine. It is a rather loud noise and can come across as very startling. To further understand how to fix it, let’s take a look at the fine print.

Inside of the mower is an engine (obviously). It is a combustion engine, producing power through an air-fuel mixture. The air-fuel mixture combusts to start the engine, creating a spark. This ignites the moisture, causing an explosion and your engine to fire up. All of this takes place in the combustion chamber, where it is specifically designed to take place. We begin to have issues when the combustion occurs outside the combustion chamber.

Perhaps it’s all a bit confusing, and that’s ok. Now that we have a better understanding of the inner workings of a lawnmower, the solutions are a bit easier to find.

Why Does My Lawn Mower Backfire And Not Start?

When it comes to your lawn mower backfiring and then not starting, it most likely has to do with the engine’s timing. When it comes to poor engine timing, most of the time, the flywheel is at fault.

Flywheels get damaged as time passes from regular use. However, if you tangled with a sizeable rock the last time you were mowing, there is a very high possibility something is wrong with the flywheel.

To check this, you must disassemble a portion of the mower. Keep in mind that all lawn mowers are slightly different when it comes to taking parts off, so be sure to check the manual before disassembling the mower; anything from Craftsman to John Deere mowers has slightly different builds.

Fixing A Flywheel

• To begin, disconnect the spark plug connector.
• Remove any screws holding the housing in place.
• Remove the flywheel nut. A socket wrench will effectively remove the flywheel nut in most cases.
• Remove anything preventing a clear view of the flywheel key.
• The key should be in line with the keyway hole. If it is not, the flywheel is damaged, and the spark plug is not in line with engine valves, which causes the engine to backfire
• Replace the flywheel key.

Because the flywheel is connected with the timing of the lawn mower, once replaced, the timing of the mower will also improve, causing the engine to start correctly.

Why Does My Lawn Mower Backfire When Starting?

Now, if your mower will start but still backfires, check the flywheel first. If you ensure the flywheel is working properly, it could be the carburetor.

The carburetor provides the air-fuel charge the engine needs to run correctly. As a rule of thumb, routine maintenance on a carburetor is essential to prevent backfires and keep the engine running smoothly.

Backfiring usually occurs when the carburetor is not properly adjusted. To fix this, use a carburetor cleaner. Another option is to disassemble the carburetor, clean it, and then reassemble it.

Carburetor problems occur on many mowers and are common on pull start engines and weedeater engines.

Other Common Issues That Cause An Engine To Backfire

Many things can cause a lawn mower engine to work improperly. Here are a few other things to check if your engine continues to backfire.

• High Engine Temperature- Engine temperatures are essential to keep an eye on. Most lawn mower engines are air-cooled. If you are dealing with a continuously heated engine, this is a sign of a clogged air-port. To fix this issue, clean and check the air filter and air intake.
• Spark Plug- Over time, spark plugs become worn and do not produce an adequate spark. This is a simple fix; replace the spark plug.

Why Does a Lawn Mower Backfire? (and how to prevent it)

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Is your lawn mower’s engine popping, hesitating or backfiring? Maybe the engine just doesn’t sound right. At this point you may be wondering why lawn mowers backfire. You’ll also be interested to know if this is this causing any damage to your engine and what you need to do about it.

One of the most nerve-racking sounds you can hear when starting a lawn mower is a backfire which tends to be a common problem after winter storage. Most commonly, lawn mowers backfire because of a failing spark plug or a dirty air filter resulting in incomplete combustion.

Let’s look into what that means and what you should do about it.

What Happens When a Lawn Mower Backfires?

When you try to start your lawn mower and it backfires, there may be ab engine timing issue but most likely it’s a result of incomplete combustion of the fuel. In other words, the fuel is not being burned properly which can cause stuttering, unusual sounds and even black smoke being blown out of the mower.

You may find that your mower will not start at all, lose power or run rough.

This can certainly be a cause for concern, so let’s dive a little deeper into why you may be experiencing some of these problems.

Why Does a Lawn Mower Backfire?

Engines often backfire when there is an improper air to fuel mix. It can be difficult to know what exact component of your lawn mower is causing the problem but we’ve found some of the most common causes and put them together below.

Of course, with most mechanical issues, a certain level of troubleshooting is required to get to the root cause of the problem.

We’d recommend starting by checking the fuel supply, the air filter and the spark plug first. Removing the carburetor and checking for a malfunction there is probably the last thing you should check since it can be tricky to remove and put back on.

Air Filter

Sometimes after running your mower for some time, the air filter can become blocked with all kinds of debris like crud, grass clippings or paint chips. The air filter in a lawn mower acts to prevent these particles from entering the engine as a first line of defence. Once it becomes clogged, you may experience strange engine sounds, a misfiring engine, reduced fuel efficiency or even black smoke from the exhaust.

Spark Plug

Over time your spark plug will accumulate wear and tear. A failing spark plug is one that is unable to produce enough current to spark the fuel. A light gray color is usually a good indication that it’s operating properly. Sometimes it can become chipped or black and carbonated over time. A worn or damaged spark plug can the engine to stall or have poor fuel economy.

Fuel Filter

The fuel filter screens out dirt and debris from entering the fuel. Old fuel can clog up the fuel filter which may prevent it from effectively filtering out any impurities. If you’re unable to see any light through the filter, this may be an indication that it’s gone bad.

Fuel

The fuel you’re using in the mower may be old or have a higher amount alcohol than necessary.

Incorrect fuel maybe preventing the proper function of your engine by clogging up essential components.

You might also want to check that there is no water contaminating your fuel. A good way to do this is to take off the float bowl to take a look inside. You may see tiny droplets of water in the bottom and if this is the case, you need to drain the fuel out and replace it.

Carburetor

Your carburetor is responsible for creating the right fuel to air mixture in order for complete combustion to take place.

Sometimes, the residue from old fuel can create problems in the carburetor. The holes may become clogged with debris resulting in malfunction and of course, could result in incomplete combustion so they will need to be addressed.

Does a Backfire Damage the Mower’s Engine?

Overtime it could cause extensive wear to the engine and other essential components of your lawn mower.

A backfiring lawn mower will result in suboptimal lawn mowing and wasted fuel so there’s plenty of reason to get it fixed straight away.

How to Stop a Lawn Mower From Backfiring?

Proper maintenance and regular service of your lawn mower can go a long way to help your mower’s engine to run smoothly.

Below are some steps that you can take to in order to prevent your mower’s engine from backfiring.

Before you replace anything on your mower, it’s best to consult the owner’s manual for the best practice although we do appreciate this may be long gone for some of you out there!

Unclog the Air Filter

You can start by making sure the air filter is unclogged. Dust, grass and other debris can block it up. A dirty air filter can stop good air flow from reaching the engine so you’ll want try and remove the air filter and use some compressed air to clean it up.

You may even want to replace the air filter if it’s really dirty. They are cheap and it’s not difficult to do.

Clean the Spark Plug

This probably needs to be replaced about once a year or so but you may just need to clean it rather than put a new one in. You can also use an ignition tester to see if it’s faulty. Double check the lead while you’re at it too. A damaged lead could cause the circuit to be incomplete.

If the plug is fouled with oil and sand, the best tool to clean it with is a pneumatic spark plug cleaner. You can connect this to an air compressor and it can be used over and over. On the other hand, spark plugs aren’t that expensive. If only have one mower it may be worth just replacing it.

Use the Correct Fuel for Your Mower

Always use fresh fuel when filling the fuel tank along with a stabilizer to make sure the fuel quality remains optimal. Always remember to following the manufacturers recommendations on what fuel you should be using. If you have too much water in the fuel, you will need to drain it out and start over. This can be caused by leaving your lawn outside which can cause you to accumulate water in your float bowl.

Once you’ve checked the air filter, spark plug and added a little fuel to make sure there’s plenty to get down into the carburetor, it’s likely a fuel flow issue. You can start by spraying some starting fluid into the throat of the carburetor to see if it will run in short bursts. If it will run, it’s probably something to do with the carburetor which you’ll need to take out.

Clean the Carburetor

When you remove the carburetor, be sure to take note of how the mechanisms attach together so you can put it back in the right order.

You can also try cleaning the carburetor with carburetor cleaner to eliminate any clogs. Use a paperclip or a guitar string to help clean out the holes, and combine this with an air compressor for the best results.

This should be enough to get the job done, but if it wasn’t effective, you may need to purchase a carburetor repair kit in order to either replace any faulty components or put in a brand new carburetor.

Replace the Fuel Filter

A degraded spark plug will need to be replaced to prevent the engine from stalling. You will need to check it for any damage and replace if necessary.

Winterize Your Lawn Mower

If you’re planning to put your lawn mower away for the winter, you’ll want to winterize it before doing so. This is a great yearly practice that you should do to keep your mower in the best condition possible. If you’re unsure on how to do this, we have an extensive guide here to walk you through what you need to do.

In Summary

The above steps should cover any issues that might be causing your lawn mower to backfire. If the problem persists, you may need to get someone to look at it. Nevertheless, troubleshooting on your lawn mower can save you a lot of money and can actually be quite rewarding too!

Why Does My Honda Lawn Mower Backfire?

This post may contain affiliate links. As an affiliate of retailers(like Amazon), we earn from qualifying purchases.

When it comes to lawn mowers, Honda is among the most popular brands in the business. Occasionally during use, you might find that your Honda lawn mower backfires. A backfire is a pop or loud boom that occurs when gasoline ignites outside the engine’s combustion chamber; so, what causes a Honda lawn mower to backfire?

A lawn mower backfires when burning fuel enters the exhaust or the engine. This happens when s of unspent gasoline enter the engine or exhaust system before the valves close. Backfires occur due to Rapid deceleration, faulty components, and even incorrect fuel blend, among other causes.

Want to know more about why your Honda lawn mower is backfiring? Read on as we discuss proven ways to fix a backfiring lawn mower.

Causes of Engine Backfires in Lawn Mowers

Below are some of the leading causes of backfiring in Honda lawn mowers.

Decelerating Too Fast

Lawn mower backfires mostly occur during Rapid deceleration when the engine attempts to align its timing with the lowered throttle. In most cases, this tends to lead to excessive air in the mix, which in turn creates a lean blend. The lean blend is consequently forced into the lawn mower’s exhaust system, where it makes the infamous pop sound when it combusts.

Slowing down a small engine should be gradual. Therefore, if your Honda lawn mower is backfiring when you’re looking to shut it off, chances are you’re decelerating too fast. The engine speed increases when using a lawn mower, and shutting it abruptly means the engine could pump some stray gas into the muffler, which could lead to combustion.

To prevent backfires when turning off your Honda lawn mower, reduce the mowing speed gradually, and allow the motor to idle for roughly 20 seconds before turning it off.

Fuel Blend

Fuel blend is a crucial aspect to consider when dealing with small engines. You’ll find that some gasoline contains ethanol or alcohol as part of the fuel blend, which can prove troublesome over time. Most Honda lawn mowers struggle to burn this blend effectively, which often results in power loss and occasional backfires.

Since lawn mowers are designed to handle specific blends of gasoline, using a wrong blend can lead to system imbalances. Due to this, it is advisable to use gas containing zero alcohol levels. If zero-alcohol blends are hard to come by, go for blends that contain low levels of alcohol.

Water Contamination

Water is another major cause of backfiring and loss of power in mowers. To remove water from your Honda lawn mower, you’ll need to start by removing the spark plug. Afterward, carefully remove the carburetor and clean it thoroughly. You should also check on the combustion chamber’s moisture levels before adding some fresh engine oil to coat the walls of the piston chamber.

Water contamination is a serious problem that, if not addressed early enough, can lead to long term damage to fuel lines, the tank, and carburetor.

Lean Carburetor

The carburetor is crucial to the functioning of a lawn mower as it regulates the volume of gas and air required for combustion. The balance must be perfect for proper combustion. While some Honda carburetors come with an electrical solenoid to control fuel flow, most come with two adjustment screws that are usually mounted on the exterior. One screw is for controlling the mix, while the other is for idle adjustments.

If the carburetor produces a lean mix, chances as the lawn mower will backfire during deceleration or even during normal operation. The good news is that carburetors are easily adjustable. However, consulting with a professional is advisable if it’s your first time attempting to adjust your Honda lawn mower’s carburetor.

Dysfunctional Valves

Valves are essential parts of a lawn mower that need to function correctly for successful outcomes. The valves help to seal off the firing chamber or cylinder of a small engine. One valve allows air and gas to make way to the cylinder while the other opens to allow the exit of exhaust gases from the cylinder.

If one of the valves malfunctions (even for a second), then the lawn mower will backfire. But fixing valves on your own isn’t recommended since they are internal parts of your Honda mower. Consider outsourcing the valve repair job to experienced service professionals.

Damaged Spark Plug

A damaged or worn out spark plug will create a weak spark that might fail to ignite the cylinder. This means that instead of igniting in the cylinder, the fuel might ignite once it reaches the exhaust muffler, which results in a backfire.

Also, an incorrectly set gap between the spark plug’s electrodes tends to result in weak sparks that make the mower unreliable. Replacing the spark is necessary if your Honda lawn mower is backfiring as a result of weak sparks.

Poor Airflow in the Engine Area

When the engine runs at a higher than normal temperature, your Honda lawn mower might gradually start to backfire. This explains why most lawn mowers require enough space in the engine housing to allow for adequate airflow.

Your engine needs enough air circulation for it to cool. Therefore, besides turning off the engine and allowing it to rest, you can consider modifying the engine’s housing to improve air circulation inside the mower.

Copyright protected content owner: ReadyToDIY.com and was initially posted on 2020-08-14.

Damage to Internal Components

Your Honda lawn mower shouldn’t backfire when starting, and if it does, then one or two components are not functioning correctly. You’ll find that a broken flywheel often leads to stuttering or backfiring when attempting to start a mower.

Luckily, the more sensitive areas of a lawn mower, such as the crankshaft, are usually surrounded by their inexpensive counterparts that cost a lot less to repair. Therefore, if your Honda lawn mower is backfiring when starting, you’ll need to call in a professional to identify and repair the damaged components.

How to Keep Your Honda Lawn Mower From Backfiring

Avoid Cutting Wet or Damp Grass

Mowing the lawn when the grass is wet or damp can damage your mower, consequently leading to long term problems. As mentioned earlier, you should remove water once you suspect either the tank or carburetor has been contaminated.

Read the User Manual Before Use

Lawn mowers function differently. Take enough time to read the instructions before putting your new Honda lawn mower to good use. Generalizing the function of different brands of lawn mowers can lead to backfiring or malfunctioning when wrongly used.

Clear Debris Before Mowing

Large stones, toys, twigs, and branches might damage your Honda lawn mower. Although most mowers come with adequate safety-enhancing features, exposing them to extra hard surfaces and conditions might lead to backfiring and even total damage.

Copyright article owner is ReadyToDIY.com for this article. This post was first published on 2020-08-14.

Check the Fuel Blend

Gasoline with high alcohol concentration is more likely to lead to backfiring compared to using pure gasoline. Go for fuels with little to no alcohol concentrations to eliminate the chances of backfiring due to fuel.

Final Thoughts

While it’s normal for lawn mowers to backfire every once in a while, you should always take your time to determine the cause of backfiring. Factors such as fuel blend and water contamination can gradually damage your yard-maintenance device, leading to serious defects.

Although backfires aren’t dangerous to the engine or users, the large pop noises can be annoying. And to prevent a backfire when you’re done mowing, be sure to turn off the mower gradually, specifically 15-20 seconds after the blades have come to a halt.

Remember, since backfires tend to indicate underlying issues with your mower, you should consider reaching out to an expert if you can’t determine the cause(s) of backfires.

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ReadyToDIY is the owner of this article. This post was published on 2020-08-14.