Why do ATVs Backfire?

There are few things that get my heart pumping like the shock of hearing a backfire when I’m out riding an ATV.  It happened enough on an older ATV I had, I decided I had to put an end to it.

Why do ATV’s Backfire? ATVs usually backfire because of a short, sudden moment where the engine is running too rich or too lean.  That means that it’s either getting more fuel than it needs for the amount of air it takes in, or else not enough. 

There are different reasons this can happen. Let’s look into what those are and what you need to do about it.

What is backfiring on an ATV?

First let’s look at what backfiring actually is.  If you’re reading this, you probably already know what backfiring is—or at least what it sounds like.

But what backfiring actually is, is a little explosion—yes, I said explosion—in the intake or exhaust of your ATV’s engine.  But don’t worry.  These explosions are supposed to happen, they’re just supposed to happen in the combustion chamber…

When the little explosion happens elsewhere, you get a pop and a really short interruption in your ATV’s normal operation.  Sometimes, it can be bad enough to shut off the engine and you have to restart, but usually it’s just a sudden “pop” sound with maybe a short pause that can make you lurch forward slightly in your seat.

Most of the time it’s pretty harmless, but if it’s happening a lot on your four wheeler, you should probably try to figure out what’s causing it.

Why does my Four Wheeler Backfire?

We already talked about backfiring being caused by either too much or too little fuel compared to air.  But let’s explore that a little more.

For the fuel in your ATV to burn—which is how it makes your four wheeler actually go—it needs 3 things.

  1. Fuel
  2. Oxygen (air)
  3. Ignition

The fuel and some air enter the combustion chamber in just the right amounts and are ignited by a spark plug.  But if there’s too much or too little fuel for the amount of air that comes in, then it can’t actually burn—or really, explode—inside the combustion chamber.  So the explosion takes place either on the intake side or on the exhaust side.

So four wheelers backfire whenever there’s too much or too little fuel.  Now obviously it’s not a problem of constantly running too rich or too lean.  If you were constantly running that way, then the engine wouldn’t run at all.  Remember, it’s caused by short moments where there’s too much or not enough fuel, which means the problem with your ATV is pretty small.  Most of the time, it’s running correctly.

So what’s causing it?  Here are a few of the most common causes.

  • Changing the Muffler or Exhaust on your ATV—this isn’t as common on four-wheelers as it is on motorcycles, but any change you make to the exhaust of your ATV will change how your fuel and exhaust system operates.
  • Clogged Fuel or Air Filter—If the fuel filter or even the air filter on your four wheeler is clogged, you won’t get enough fuel to the combustion chamber and you’ll be more likely to get these sudden backfires.
  • Gummed-up Carburetor—If you let fuel sit in your fuel tank for months without using it and your ATV has a carburetor then the fuel in the tank will start to degrade. As it does, it gets a little thick and can clog up the jets in your carburetor.
  • Low Fuel Pressure or Weak Fuel Pump—Like a clogged fuel filter, this would cause your engine to not get enough fuel to the combustion chamber.
  • A Hole in the Exhaust—If there’s a hole in your exhaust system (muffler or tailpipe) near the engine, this would cause backfire.
  • Fouled up Spark Plug—Over time, your spark plugs will get build-up on them and that can prevent them from igniting the fuel consistently in the combustion chamber. So it ignites in the exhaust and causes a backfire.

When do four wheelers usually backfire?

Most of the time, I find that ATVs backfire when I let off the throttle.  I’m slowing down or even coasting and then “POP”—I get a backfire.  That’s probably because the engine is trying to idle just to keep running and not enough fuel is getting to the engine.

Sometimes I get a backfire when I’m accelerating or just riding along but not very often. It’s usually when slowing down or right after I let off the gas.  That’s because for just a moment, the engine is running a little extra rich.

Does backfiring hurt my ATV?

If backfiring is happening in the exhaust (after the engine) then it will cause damage to the muffler and exhaust system over time.  A backfire here and there isn’t usually a big deal but having those explosions over and over again in a place where they’re not intended is going to cause some damage.  It usually leads to leaks in the muffler or exhaust.

On the intake side, regular backfires can lead to engine damage.  You could blow the intake valves or even ruin a carburetor.  But this kind of damage appears to be pretty rare, so unless it’s happening pretty often, I wouldn’t be too worried about the occasional backfire on my ATV.

How do I stop my four wheeler from backfiring?

Because backfiring has so many possible causes, it’s not really practical to try to fix everything at once.  Especially because some of the fixes can be pretty spendy.  So when troubleshooting, I find that it makes sense to start with the simplest and least expensive fixes first.

  • Add fuel injector cleaner to your fuel tank. The fuel injector cleaner will mix with your fuel and help clean out dirt and debris in your fuel line that might be gumming up your fuel filter or pump.  I also like to add fuel stabilizer to my fuel any time I don’t expect to ride again within a few weeks.  This keeps my fuel from degrading.  Just add the amount recommended on the bottle and drive your four wheeler around for a few minutes.  This will get the stabilizer all through the fuel system.  Then it’s safe to sit for several months.
  • Prevent it by using better fuel. Using a higher fuel grade will help prevent backfire because it will cause a lot less gunk and debris from piping up in your fuel system.
  • Check your throttle settings. Do a google search for your model of ATV plus the words “throttle settings” to find a diagram or even a video showing you how to adjust your throttle on your four wheeler.  It’s usually really simple, like the turn of a dial, to increase or decrease the amount of fuel that goes into your engine when idling.  Make really small adjustments one way and test it out.  Then it will probably be better or worse.  If it’s worse, try going the other way.
  • Change the air and fuel filters. You may or may not be comfortable doing this yourself.  That’s okay.  Just start by googling the model of your ATV and the words “replace fuel filter” and it’s pretty likely you’ll find good content showing you exactly how.  Otherwise, you can seek the assistance of a mechanic to take care of it for you.
  • Clean the Jets in your Carburetor. This one isn’t very easy if you’re not very mechanical.  Removing and disassembling your carburetor to get to the jets can be a pretty quick job if you’re comfortable following instructions from a YouTube video.  But if not, then it’s best to leave it to the pros.  Take your ATV in to a shop and ask them to do it.  It probably won’t be real cheap, but if the easy fixes haven’t worked this probably will.
  • Take it to an ATV mechanic. If none of these solutions has worked, it’s probably time to let a professional troubleshoot it.  Again, if you’re mechanically inclined you could try things like changing the fuel pump.  But at this point, you’re probably better off paying a pro.  You can sink loads of time and money into this if you’re not careful, so you might as well get it figured out and fixed right.  You can also check out how much you might expect to pay for these repairs in our guide to ATV repairs.

And that’s it.  Just remember that the occasional backfire is actually really normal and nothing to really worry about.  But if it’s a common occurrence on your four wheeler, then it’s worth looking into.

Brent Huntley

Brent Huntley is the owner of ATV Man and is responsible for almost all the material on the website. He also runs photographyandtravel.com and loves to travel and ride ATVs with his family. When he isn't playing, his day job consists of owning Huntley Law.

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