Dirt Bike Spark Arrestor – Don’t Burn Your Trails Down

What is a spark arrestor? Do I need one for my dirt bike, and why? This article will answer these questions in detail, and why they can help prevent more riding areas from being shut down.

Yes, having the required equipment on your dirt bike is extremely important in certain riding areas. Whether you agree with the rules or not does not change the fact that you may need a spark arrestor on your dirt bike…

What Is A Spark Arrestor On A Dirt Bike & What Does It Do?

SuperTrapp Spark Arrestor end cap on CRF230F muffler
SuperTrapp Spark Arrestor end cap on CRF230F

A spark arrestor is a screen or device that prevents sparks or flames from escaping out the exhaust of a dirt bike muffler or silencer. They are usually located just before the outlet tip because that is the most convenient location, especially if it’s an add-on part.

When Do Sparks or Flames Come Out The Exhaust?

Sparks or flames come out the exhaust when there is a backfire. A backfire is a combustion or explosion of fuel that was not burnt in the combustion chamber. The unburnt fuel reaches the exhaust and causes a “Popping” or loud “Bang!” noise. This can be frightening if you have never heard it before because it sounds like a gunshot going off right behind you.

What causes a backfire?

A backfire can be caused by a number of things. The number one cause is a rich jetting condition and can be corrected with some simple tuning of the carburetor. Here’s some other possible causes of a backfire:

  1. Incorrect cam timing
  2. Incorrect ignition timing
  3. Lean air/fuel mixture; too much air from incorrect jetting or a dirty carb can cause backfiring
  4. Electrical problems; faulty spark plug or wiring.
KX250F shooting flames from backfiring = this much backfiring means there’s tuning issues.

What Does A Spark Arrestor Look Like?

Dirt bike spark arrestors can come in various forms. Even though most of them are screens, they are sometimes difficult to see. 

How Do I Know If My Dirt Bike Has A Spark Arrestor?

Motocross bikes have a muffler/silencer, but do not come with a spark arrestor. A muffler or silencer is only for lowering the decibel output of the exhaust system. Motocross bikes are designed for off-road closed-course competition only. While they are legal to ride on trails with all the properly fitted required equipment, they are not legal to ride on state trails in stock form.

Most trail dirt bikes and enduro bikes come with a factory installed spark arrestor. This information will be stamped or etched on the outside of the muffler or silencer. You can shine a flashlight in the end of the exhaust too look for the mesh screen.

However, sometimes an owner will remove the baffle/insert from the stock exhaust to change the sound output. Most spark arrestors are built-in to the baffle, so if the baffle insert is removed then there is no spark arrestor.

Do I Need A Specially Approved Spark Arrestor?

In the United States, state trails require you to have a properly installed and USFS-approved spark arrestor on your off-road motorcycle/dirt bike. Factory installed exhaust systems with a spark arrestor should be permanently stamped and USFS approved and are legal for trail use. They are necessary on all dirt bikes no matter the size.

What is the USFS?

The US Forest Service is a government service that manages public land throughout the United States. They maintain these lands for public use of viewing and various recreations, such as our dirt biking recreation. Any public land or trail must be ridden within the legal requirements. A spark arrestor is one requirement, and a DNR trail sticker is another depending on your state laws and regulations for off-highway motorcycles.

FMF Turbinecore spark arrestor on KTM 200XCW that is USFS approved
FMF Turbinecore on KTM 200XCW that is USFS approved

Our Trails Are Getting Shut Down!

What is one of the biggest reasons that causes the dirt biking community to decline? Besides the cost of new dirt bikes, the lack of places to ride are what kill this sport. If you live in the city, chances are you have to drive at least an hour just to get to the nearest local riding park or trail.

There are many variables for why dirt bike riding areas are getting shut down, but there’s one thing that we as dirt bike riders can easily do to help change this. 

The Importance of Having A Spark Arrestor On Your Dirt bike

Don’t Follow The Rules

That’s right, if you want more riding spots to get shut down, disobey all the laws and regulations, including trespassing on private property or exceeding a sound limit. Doing these things are the quickest way to get places shut down and having less spots to go to and enjoy our free time on a dirt bike.

CRF230F EPA noise emission requirement info
Stock mufflers and silencers have stamped EPA or sound info on them.

This is why it’s important that you learn and follow the laws and regulations for dirt biking at whatever location you ride, whether it be a local state trail, a public motocross track, or in your backyard.

Do Spark Arrestors Actually Work?

Spark arrestors actually do a good job of keeping sparks contained within the exhaust. This will prevent any fire from accidentally being started because you got too close to a tree or plant that is easy to catch on fire.

2-Stroke Dirt Bike Spark Arrestor

While all dirt bikes can produce sparks from a backfire, it is a lot less common on a 2-stroke. This is simply because the exhaust temperatures are not as high as a 4-stroke exhaust. The lower the temps, the less likely unburnt fuel will ignite outside of the combustion chamber.

With that said, you still need to follow the law and install an approved spark arrestor on your 2-stroke exhaust system if the place where you’re riding requires one. This will help give dirt bikers a better name because it is following the rules, and you’re less likely to get a complaint from the law or outsiders.

4-Stroke Dirt Bike Spark Arrestor

4 stroke dirt bikes backfire way more often. This is because the higher exhaust temperature is more likely to burn the fuel that went unburnt from the internal combustion chamber of the engine.

Whether you have a two or four stroke, check your local riding trail, park or spot and see if it requires a spark arrestor on your bike to ride there.

What are the odds of a fire actually starting from your dirt bike?

Statistically speaking, I couldn’t even find stats for the number of fires started from dirt bike exhausts without a spark arrestor. Realistically, the electrical or fuel system is more likely to catch fire than sparks from a backfire coming out the exhaust is to cause a fire. 

So why do we need them?

For the sole reason that the law requires them. Whether or not you appreciate the DNR Forest Service, they are still the people and organizations that allow us to ride on public trails and property. 

If we can’t follow their simple rules, then that says that we are too proud or ignorant. These are the traits of the ‘so called riders’ that give this sport a bad reputation. 

Where Do I Get A Spark Arrestor Screen?

There’s a couple ways to get a cheap spark arrestor screen for your dirt bike exhaust. You can make your own, or there may be a bolt-on screen that fits your exhaust. However, if you want to ride legally at a riding spot that requires a USFS approved spark arrestor, then you need to buy a muffler or silencer that has one built-in or has an approved insert.

Homemade Spark Arrestor Screen?

You can make your own spark arrestor using a stainless mesh screen and bolting/riveting/welding it inside the end of the muffler or silencer on your dirt bike.

While this may get you by a simple “stick poke”, it’s technically not legal at riding areas that require a stamped USFS approved spark arrestor plate. 

Universal Spark Arrestor Insert/Screen

There isn’t much available for universal spark arrestors because not all exhaust systems have the same outlet on the muffler or silencer. 

You either have to buy an aftermarket exhaust that has a screen built in to it, or see if the company that makes the exhaust you have sells a screen spark arrestor insert that you can bolt on.

Spark Arrestors Require Maintenance Too

The screens get clogged after so many hours from carbon deposits of unburnt gas. Cleaning the spark arrestor will ensure that you are getting maximum performance out of your exhaust system. 

A dirt bike with poor jetting will cause the spark arrestor, as well as the rest of the exhaust to get dirty much quicker. This is why it’s best to learn how to do your own jetting. Adding a spark arrestor will often require some carb tuning to run properly. For a complete guide on how to test and tune the jetting of your dirt bike click here.

Kelley Fager

Kelley started riding a Honda 50 at the age of 6 years old. The passion for dirt bikes started there and grown into a lifelong pastime of riding and learning how they work. Motocross Hideout is the result of sharing his past, present, and future knowledge and experience.

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