Why Is My Snowmobile Backfiring?


Your sled’s engine usually purrs as smooth as a tiger, and then you hear it. Bam! You see sparks, possibly even fire coming from where your engine is. It seems like your snowmobile just backfired, but why is this happening?

Snowmobiles can backfire for many reasons, including the following:

  • The catalytic converter is damaged
  • There’s an animal like a mouse in your snowmobile’s exhaust system
  • The spark plug has misfired or could be faulty 
  • You’re using the wrong ratio of fuel
  • Your fuel has additives or air mixed in
  • You don’t turn off the engine properly when you’re done riding 

Seeing your snowmobile backfire can be a terrifying ordeal, but once you know what’s causing it, you can address the root problem. Keep reading for more information on the above issues as well as what to do when you experience sled backfiring. 

What Is Backfiring?

First, let’s start with a little definition. What exactly happens when your snowmobile backfires? Sure, you see sparks or flames, but why?

The engine of your sled must be running for a backfire to occur, as that’s the location of most backfires. This problem is also more prevalent with internal combustion engine types. 

So here’s what happens. One of the issues from the list above occurs. For example, maybe the gas has a lot of air in it. When you turn on the ignition of your sled, it likely won’t work because the fuel ratio is incorrect. 

Since there is some fuel in the gas mixture, the fuel will exit your snowmobile, igniting on its way out. All the fuel has to do is make contact with any of the exhaust pipe parts. These are very hot, as you’ve tried to turn on your engine (or maybe even did so successfully).

Beginning in the internal combustion engine, the backfiring transpires externally, which is why you can see it. Backfiring is an explosion, albeit a small one, but that doesn’t make a backfiring snowmobile any less dangerous. 

Why Is My Snowmobile Backfiring?

As we explained in the intro, the reason your sled could backfire comes down to many internal components being old or outright failing. Here’s a more thorough list of culprits you want to look at the next time your snowmobile starts backfiring. 

Catalytic Converter

The duty of a catalytic converter as part of your exhaust emission system is to limit the amount of pollutants and toxic gases in the exhaust gas coming out of your sled. These toxins, which emerge from the internal combustion engine, undergo a redox reaction. This is a type of reduction and oxidation occurring at once for fewer emissions.

Should your catalytic converter fall out after a particularly rough ride, that’s a huge problem. The same is true if the converter is seriously banged up. The pipe of your sled becomes more prone to backfiring when you have catalytic converter issues, not to mention you’re breathing in who only knows what kind of fumes.

Don’t sleep on catalytic converter issues then. Bring your sled to a snowmobile repairperson, stat. 

Exhaust System Blockages

This isn’t necessarily super common, but it is a possibility, so we have to mention it. That is, in some instances, you could have mice and other small creatures make your exhaust system pipes their home.

On their part, this isn’t a bad idea at all. Think about it. If you live in a cold environment, wouldn’t you like to seek a nice, warm place to settle down as well? Your exhaust system pipes are that warm place. 

We’d recommend at least once or twice a season that you remove your exhaust pipe from your head pipe and look inside. If you see any small, fuzzy critters living within the pipes, give them the boot. You might just have your backfiring issues stop altogether! 

Spark Plugs

Without spark plugs, your combustion chamber can’t receive electricity via the ignition system to ignite the air and fuel mixture. The curious thing is, sometimes your spark plugs aren’t even faulty and yet you have backfiring.

How can that happen? Well, it can all come down to timing, or lack thereof. The spark plug is supposed to open at a precise time to ignite your fuel source. If it opens too early, then the exhaust pipe releases unburnt fuel that is going to explode. 

This can be a coincidence if it happens only once. However, if you often have the same issue with your spark plugs, then the chances are higher that they are indeed faulty. It’s likely a wiring issue, so either get your plugs to a snowmobile mechanic or change them out. 

Other spark plug problems are also possible. If yours are especially wet, the plugs could malfunction. You could also have snowmobile backfiring if your spark plugs are filthy or if you have yet to ever replace them.  

Fuel Ratio

Your sled’s fuel is another major contributor to snowmobile backfiring. You can experience several issues with your fuel source that cause explosions, the first being an incorrect fuel ratio. Your sled needs an equal ratio of air and fuel in the gas. If the gas has more air than fuel or vice-versa, then the ignition gets affected. 

You’ll try to power your snowmobile on and feel like it’s the Fourth of July with how many sparks you’re seeing. The best thing to do in a situation like this is to refuel as soon as you can and avoid going back to wherever you bought your gas from. 

Fuel Type

Besides the fuel ratio, you also have to worry about the quality of your fuel. Again, this comes down to buying your sled gas from a trusted source. Watery or airy fuel can interrupt ignition and cause backfiring. The same is true if your fuel source is bogged down with additives, butane especially.

Butane is a type of hydrocarbon gas that’s extremely flammable. All it takes is a heat source and sparks will fly, and not in the romantic sense, either. 

Engine Misuse

You’ve checked each of the above components of your snowmobile. They all seem to be in running order, yet you still have backfiring more often than not. Is it time to take your sled to a mechanic?

Not necessarily yet. Your problem could come down to user error. 

How do you turn off your engine? Do you come to a stop and then immediately power down your sled when you’re done riding? This is the wrong technique. You should stop your sled and let it go for a minute or two. This crucial time lets your engine get back to idle mode, cooling down a bit before you hop off the vehicle for the day. 

Try doing this the next time you ride your snowmobile and you could say goodbye to backfiring. 

What Should You Do When Your Snowmobile Backfires?

Your snowmobile just backfired for the first time. You’re appropriately spooked. The incident has kind of ruined your mood and you’re not even sure if you want to continue riding for the day. What if it happens again?

An occasional backfire isn’t often anything to worry about. As we mentioned in the last section, it could be spark plug mistiming that led to the backfire, a small animal in your exhaust system, or even you not letting your engine idle before turning it off. Most of these issues rectify themselves.

Frequent misfiring will call for an early end to your day though. You shouldn’t ride a snowmobile in that condition until you can get it assessed by a mechanic. Please don’t try to ignore the issue, either, as doing so will cause a lot more harm than good.

Here’s what prolonged snowmobile backfire damage can do to the internal components of your sled.

Crack Plastic and Fiber Shells

Many parts of your snowmobile are encased in protective shells. Some of these shells or cases are made of a very durable material like metal, while others are cheaper plastic or fiber. The latter materials will absolutely fry if they’re exposed to a strong enough heat source frequently enough. Now the inner component is unprotected and much more likely to be damaged.

Converter and Pipe Malfunctions

Since fuel remains unburned during backfiring, it can get stuck in the converter and pipes. These parts can also break down if backfiring becomes a regular enough issue.

Carburetor and Related Parts Damage

Not only does regular backfiring destroy the carburetor, but any other components associated with it. These include the supercharger and the intake manifold. Without a functioning carburetor, your gas will not have the right ratio of fuel to air, which will just make the backfiring problem even worse. 

Engine Failure

Since the backfiring occurs around your sled’s engine, you’d have to expect the greatest amount of damage to occur here. Indeed, with enough regularity, the engine could be destroyed to the point of failure. 

Replacing a snowmobile engine can cost well over $1,000, so take care of your engine as best you can!

Burns and Other Injuries

You didn’t think your sled backfiring can affect only the vehicle, right? Since you’re in such close vicinity to the flames and even fire, at any time, you could be burned or otherwise seriously injured. 

How to Prevent Future Snowmobile Backfiring

Once you see fire coming out of your snowmobile, it’s a sight you can’t quite erase from your mind. You will feel inclined to do whatever it takes to never have to see that vision again, which means learning a few backfiring prevention tips.

Check Your Airflow Sensors and Valves

Too much air can be bad for the fuel, but your engine’s system needs air to travel through and keep the components cool. If any valves or sensors are acting up, take your sled to a mechanic immediately to get the issue addressed.

Care for Your Spark Plugs

As part of your sled maintenance routine, make sure you pay special attention to your snowmobile’s spark plugs. If these are old, dirty, or just malfunctioning, it’s time for them to go. Unlike a new engine, you can buy spark plugs for well under $10 a pop, so don’t hesitate to replace the plugs if need be.

Prioritize Your Catalytic Converter

You also have to keep your sled’s catalytic converter running well. Check on it every few months, look for signs of damage when you do, and bring the vehicle to a mechanic if the converter is going bad.

Keep Your Exhaust System Spotless

When the exhaust system gets gunked up, it’s to the detriment of your snowmobile’s health. You’ll want to check the exhaust system about monthly (maybe every two months depending on how often you ride your snowmobile) and give it a thorough cleaning if it’s dirty. 

Final Thoughts 

Your snowmobile can backfire because of problems with the catalytic converter, spark plugs, or the exhaust system. Using the wrong type of fuel is a no-no, as is not letting your sled’s engine idle before turning it off.

Now that you have a checklist of sorts for snowmobile backfiring issues to check for, you can fix your problem faster. Best of luck! 

Geoff Southworth

I am a California native and I enjoy all the outdoors has to offer. My latest adventures have been taking the family camping, hiking and surfing.

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