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Is it normal for my motorcycle to backfire?

You may think that backfires sound cool, but in some cases, this may be harmful to your bike’s engine.

Is it normal for my motorcycle to backfire?

We motorcycle enthusiasts certainly appreciate the sound of a well-tuned engine. This is partly why an aftermarket exhaust is one of the first modifications we install on our trusty bikes. Indeed, we’ve discussed in great detail why getting an aftermarket exhaust comes with a variety of benefits. However, there are also a few drawbacks. Today, let’s talk about backfiring, or more specifically, afterfires, and determine whether or not these seemingly cool sound effects are normal.

Deceleration pops are normal

To start with, deceleration pops and crackles are normal. As Ari Henning explains in the video above, even the best-tuned motorcycle engines let some unburnt fuel into the exhaust. As such, manufacturers intentionally let some air into the exhaust to burn the excess fuel to reduce emissions into the environment. This is what we hear when high-performance engines such as Yamaha’s CP4 inline-four engine, or Ducati’s Teststretta V4 engine is decelerating. 

Backfires are bad

Is it normal for my motorcycle to backfire?

As for backfires, well, this is where things take a turn for the worse. If your motorcycle makes a loud—similar to that of a shotgun—when letting off the throttle, chances are you have a bigger issue at hand. Now, a backfiring engine can be caused by a multitude of things, but one of the scariest is when the backfire makes its way to your motorcycle’s intake. Although this is very rare, and usually happens only when something’s seriously wrong with your bike, and can cause your air filter to catch fire. Remember, your bike’s air filter is usually located right under your fuel tank, and fire and gasoline are two things that should definitely be kept as far away from each other as possible. 

How to fix a backfiring engine

Is it normal for my motorcycle to backfire?

When it comes to exhaust-related backfires, however, there are lots of things that could cause them, but nearly all of them are a result of your bike either running too rich or too lean. For instance, if your air filter is clogged due to dirt or debris, this could cause your bike to choke and run too rich. You’ll also probably smell a lot of unburnt gasoline from the exhaust. Conversely, installing an aftermarket exhaust system has the tendency to result in much leaner mixture.

To address this issue, especially if you’ve installed either a high-flow air filter or aftermarket exhaust, chances are your motorcycle will be in need of a tune. For modern fuel-injected motorcycles, you’re going to want to consider having an ECU reflash done to your bike. Reflashing the ECU allows the programmer to set certain parameters of the engine, such as the air-fuel ratio, to better accommodate any aftermarket modifications you’ve done to your bike. As for carbureted bikes, you may need to do a little research and experiment on variously sized jets for the carburetors. Either way, a backfiring motorcycle engine is not a happy engine, and something has to be done to make sure it’s running smoothly. 

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