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What Causes a Motorcycle to Backfire?

Most people don’t think about the fact that their motorcycle may have a backfire until it happens to them. It is a loud, sudden noise that can be startling and is usually caused by a rich or depleted air-fuel mixture entering the engine combustion chamber. An improper air-fuel mixture ratio causes some of it not to burn. It’s what’s not burned that detonates in the wrong manner somewhere along the path from the combustion chamber to the exhaust, causing a backfire.

There are several things you can do to fix the backfire. That’s what we’re going to talk about in this article. And let’s also take a closer look at the causes of this problem, so you can know what to look for first.

Also Read: What Does CC Mean in Motorcycles?

What Is Motorcycle Backfire?

This is a very common problem faced by many motorcyclists. A backfire is a pop or bump that you can hear coming out of your motorcycle’s exhaust pipe. Besides the fact that the sound can be very annoying, it can lead to serious problems. 

The cause of this problem is usually an improper ratio of air to fuel in the engine. If the mixture is too rich, it can cause unburned fuel to ignite in the exhaust system, resulting in backfiring.

Other causes of this could be:

  • loose Exhaust Header Pipe;
  • after Market Exhaust;
  • intermittent Spark;
  • bad Fuel Pump;
  • airbox Leak;
  • bad Fuel Filter;
  • dirty Carburetor.

Next, we will look in more detail at what causes backfire.

What Causes a Motorcycle to Backfire? – The Most Common Reasons

Based on our experience with motorcycle maintenance and troubleshooting-related issues, we will explain to you as clearly as possible the causes of the backfire.

If you know the root causes of engine backfires causes, you can solve them faster and prevent potential problems with your exhaust pipe or other parts.

Too Much Fuel

This is the most common cause of this problem. When there is more first in the mixture of fuel and air than there should be for proper engine operation, the propellant is not burned completely. The unburned fuel flows into the exhaust pipe and ignites there. This causes a loud explosion, and sometimes flames burst out of the exhaust pipe. Operating a motorbike with too much fuel leads to lower mileage and can damage the engine over time.

Too Little Fuel

The motorcycle is said to be idling when less fuel than required is supplied to the motorcycle engine cylinders. This usually happens when the air filter is replaced with a looser flowing air filter. When more air enters the cylinder than required, incomplete combustion of fuel occurs. The unburned fuel and air go into the exhaust, where it explodes and burns up.

If you change the air filter on your motorcycle, be sure to find out if the injectors need to be rebuilt to increase the flow of fuel into the cylinders or if the ECU needs to be adjusted to let more fuel in.

Running the engine at idle can be bad for the engine and needs immediate attention. If anything, it’s better to let the bike run rich than lean – if you have to choose the lesser of evils, that is too much fuel.

Loose Exhaust Header Pipe

It can also be caused by a loose exhaust manifold pipe. The manifold is the part of the exhaust system that connects directly to the engine case.

This happens because the pipe allows the exhaust gases to exit the cylinder earlier than they should. This causes the mixture to ignite prematurely, causing a backfire.

To prevent this from happening, make sure the exhaust manifold pipe is properly tightened. If it is still loose, replace it with a new one.

After Market Exhaust Backfire

Aftermarket exhaust can cause backfire for several reasons:

  1. The pipe may not be the right length for the motorcycle, which means that the fuel-air mixture is not being burned correctly.
  2. It may not be equipped with a baffle, which can also result in an improper fuel-air mixture.
  3. The aftermarket pipe may not be installed correctly, causing the exhaust to leak.

Intermittent Spark

When it comes to the engine, there are several key systems that must work for the engine to function properly. Spark plugs are one of these. They are used to ignite the fuel-air mixture inside the engine. If the timing and sequence of the spark plugs are not correct, it can lead to loss of power and unburned fuel. And it, in turn, will escape through the exhaust valve and burn up in the exhaust pipe and this is what causes a motorcycle to backfire.

Therefore, if you notice a loss of power when accelerating, it may be due to an intermittent spark plug. If this is the case, it is important to check the spark plugs and replace them if necessary.

Bad Fuel Pump

We have already pointed out that backfire can occur because the motorcycle engine is not getting enough fuel. The most common cause of this is a faulty fuel pump, which delivers either too much or too little fuel to the engine, eventually causing a backfire.

In addition, a fuel pump that runs intermittently also causes a loss of power. The fuel pump should be serviced regularly, and the fuel line should be checked as well.

Airbox Leak

If your motorcycle’s airbox is leaking, it will cause the engine to run lean and backfire. To fix this, check the airbox’s rubber packing for damage and ensure the screws clamping the two halves of the box are tight. Also, visually inspect the airbox for cracks.

Bad Fuel Filter

The fuel filter is an important component in any motorcycle and is responsible for keeping impurities out of the fuel system. If it becomes clogged, it can cause a lean air-fuel mixture, leading to an engine backfiring. If you notice any of the following symptoms, it is time to replace your fuel filter:

  • engine backfires;
  • poor engine performance;
  • rough idling;
  • engine stalling;
  • difficulty starting the engine.

Dirty Carburetor

The carburetor is one of the most important parts of the bike. It is responsible for mixing air and fuel in the correct ratio and delivering them to the engine. If it is not cleaned or the jets are not installed correctly, it can cause the engine to backfire.

If your motorcycle has been idle for a while, the carburetor will probably have to be removed and cleaned before the engine will start running properly.

Is Backfiring Bad for Motorcycles?

Yes, backfire is bad for motorcycles. And this answer is indicated by the following reasons:

  • it’s a sign that the air-fuel mixture in the engine is disproportionate, which can lead to a loss of power and efficiency;
  • it can cause the engine and exhaust to overheat, leading to further damage;
  • the noise can be very annoying and even cause complaints from neighbors.

Therefore, backfire should not be ignored, and the cause of the problem should be found as soon as possible.

How To Fix Backfire On Motorcycle?

Now that we know what causes a motorcycle to backfire, we can look at how to fix it. But these tips are more suitable for those who know at least a little bit about bike mechanics. If you are not confident in your abilities, it is better to ask for help from a professional.

1. Adjust the Carburetor

If the backfire is caused by a rich or depleted air-fuel mixture, you need to tune the carburetor. It should be tuned at least every six months. If you take your iron horse in for maintenance, then ask for it every time it falls into the hands of professionals.

2. Check the Air Filter

A clogged air filter can prevent air from flowing into the system, causing the engine to malfunction. You should have the air filter checked for dirt. If it is blackened or has too much dirt clogged in it, you need to replace it.

3. Clean the Jets and Carburetor

If the problem is caused by dirt in the jets and carburetor, you must remove it and clean it with the jets. The carburetor should be cleaned at least once a year to avoid potential problems. Try to do it more often.

4. Check the Spark Plugs

You should also check your spark plugs for fouling, as a clogged spark plug can cause a backfire and affect engine power and mileage. If the gap between the spark plugs deviates from normal, they should be replaced.

5. Add or Replace a Muffler

This is unnecessary, but if the backfire is caused by the heavy exhaust, you may consider adding or replacing the muffler or even the entire exhaust pipe. You may not have to do this unless the backfire is excessively loud and annoying.

Difference between Backfire vs Afterfire

The terms “backfire” and “afterfire” are often used interchangeably, almost without distinction. But this is only partially true.

While the phrase “backfire” refers to improper combustion anywhere from the engine cylinder to the tailpipe, “afterfire” refers specifically to the detonation of the fuel in the tailpipe. In other words, afterfire is a type of backfire.


How do I stop my motorcycle from backfiring?

A backfire is usually the result of an insufficient air/fuel mixture in the engine. This can be caused by a number of things, including a dirty air filter, a clogged fuel line, or a faulty carburetor. To fix a backfiring motorcycle, you will need to clean the air filter, clear the fuel line, and adjust the carburetor.

Will backfiring affect the fuel mileage of a motorcycle?

No, backfiring does not affect the mileage of the bike. It is itself a symptom of a motorcycle problem and does not cause a loss of mileage on its own. But the gas leaking into the exhaust pipe and making that annoying and sometimes frightening popping sound is the cause of the reduced mileage.

How do I install new exhaust pipes?

If you have new pipes and everything you need to install them, then follow these steps:

  1. Park your motorcycle on a level surface and prop it up securely so you can work underneath it.
  2. Use a wrench to loosen the clamps securing the old exhaust pipes to the manifold and exhaust pipe.
  3. Carefully remove the old exhaust pipes, being careful not to damage the gaskets.
  4. Clean the mating surfaces of the manifold and exhaust pipe and inspect the gaskets for damage.
  5. Install new exhaust pipes, using new gaskets if necessary.
  6. Tighten the clamps to secure the pipes in place.
  7. Start the engine and listen for leaks.


If you’ve experienced a motorcycle backfire before, you already know that it can be annoying and potentially dangerous to your exhaust system. If you are experiencing this problem, it is important to diagnose and correct it as soon as possible. Use this article to learn about the potential causes that you need to look at first. Our guide will also help you fix the problem without harming your two-wheeled friend.

More often than not, to solve your motorcycle’s backfire problem, you will need to – adjust or clean the carburetor and jets, check the air filter and inspect the spark plugs. You may have to replace a faulty air filter or spark plugs.

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