Why Does My Snowmobile Smoke So Much?


For as long as you’ve owned your snowmobile, you’ve always known it to smoke a little, especially when turning it on or when the sled is idling. Yet lately, there seems to be more smoke than you’re comfortable with. Why is this happening?

Your snowmobile could be smoking excessively for the following reasons:

  • Antifreeze has traveled to the cylinders and is burning, especially if your smoke is white
  • Old fuel in the gas tank 
  • Heavier parts of the oil are stuck in the engine and need to burn off
  • Months of inactivity 
  • Oil injection pump sending too much oil, which then burns and smokes

In this article, we’ll elaborate on the issues above so you can determine what may be causing your snowmobile to smoke so much. We’ll even offer some suggestions you can try to fix the issue. You’re not going to want to miss it! 

How Much Smoke Is Too Much?

First, let’s make one thing clear: more than likely, your snowmobile is going to produce smoke from time to time. Like we said in the intro, this is indeed normal. If you see some smoke behind you (as it’s typically coming from your engine or gas tank) but the smoke isn’t getting in the way of your ride, then you’re okay.

The same is true if the smoke is whiter or grayer than black, as black smoke is usually something burning. That signals to you that an internal component of your sled has gone bad or is in the process of doing so.

If you’re sitting on your snowmobile ready to go or you’ve just taken a break and the sled produces so much smoke that you’ve lost visibility, that’s too much. The same is true if the smoke gets excessive to the point where you’re coughing and your sledding buddies are as well.

When your snowmobile begins smoking that severely, it’s telling you that you need to stop riding, check things out, and get to the bottom of the issue. 

Why Your Snowmobile Is Smoking So Much

Discerning when your snowmobile smokes the most will go a long way towards figuring out why it’s happening. For instance, is your sled smoking more when you start it up or after it’s been running for a while but you’re sitting idly? 

Depending on when you see the most smoke, here are the issues that could cause the smoking.

Snowmobile Smoking When Idle

  1. Antifreeze in the Cylinders

Your snowmobile antifreeze, also known as coolant, comprises ethylene glycol, methyl alcohol, glycerol, or propylene glycol as its main ingredient. If the antifreeze is made primarily with ethylene glycol, then it has a higher boiling point than most. That said, ethylene glycol is also quite toxic, so watch how you use it as well as where you dispose of empty containers.

Methyl alcohol, also known as methanol antifreeze, has no color but a noticeable smell. This antifreeze is very flammable, but in some instances can also be used as a fuel or solvent.

Glycerol antifreeze is non-toxic, so it’s safer to use, and it can handle very high temps without breaking down. Its freezing point is low as well, and glycerol antifreeze is even non-corrosive. Then there’s polypropylene glycol, which is less toxic but can corrode.

No matter which type of antifreeze you favor, you should pour it into your snowmobile’s cooling system. In the warmer months, the antifreeze boosts the engine fluid boiling point temperature so the engine doesn’t overheat. Over the winter when you use your sled the most, the antifreeze will drop the engine fluid’s freezing point so your engine stays warm.

That’s what should happen, but what if the antifreeze ends up somewhere else, such as in your engine cylinders? That’s a possibility, typically due to a leak somewhere near the cylinders. 

When antifreeze travels to an unintended location, it can’t control your sled’s temperature as well anymore. Also, the antifreeze burns, and when it does, it produces plentiful quantities of white smoke. 

Snowmobile Smoking at Startup

Using Old Fuel

Perhaps this scenario sounds familiar to you. 

The snowmobile season ended, and you didn’t feel like draining the gas tank because there was so much fuel left in there. You figured you’d let it sit in the tank for a few months. When you come back to your sled in the winter, you run your snowmobile on that same old fuel. Your sled starts, but then it begins smoking like crazy.

Here’s another situation. You’re about to fuel up, either at home or at the pump, yet the gas added to your snowmobile’s tank isn’t very new. Once more, your sled will start, maybe with some difficulty, but upon startup, the amount of smoke you see is very concerning. 

Old fuel can definitely contribute to your snowmobile’s smoking issue. 

Improper Fuel Separation

Using old fuel is not only a bad idea because it causes your snowmobile to smoke, but because it can contribute to improper fuel separation. So too can smoking occur if your fuel source is suddenly richer than what you typically use. 

So how does fuel separate like this? We’re glad you asked! When you start up your engine, especially while it’s still cold, the engine is holding onto heavier parts of your oil from the last instance in which it was running hot and you powered the engine off. These heavier fuel parts occur because your crankcase, which is also hot at this time, can evaporate some of the oil, but only the lighter portions. 

That keeps all the heavier parts of the oil stuck in your crankcase, typically overnight and in some instances, over the course of several days or longer. During this time, your engine will hit ambient temperature. Then, the next time you go to turn on your sled, the engine heats up again. Since the crankcase still has heavy oil parts, these have to go somewhere, and thus, they’re burned as the engine warms, causing lots of smoke. 

Lack of Activity

A similar thing can happen if you’re about to use your snowmobile for the first time since dusting it off since the warm season. In all that time it’s had to sit, especially in the warm weather, you can expect that your engine was at ambient temperature at the very least. It may have been even warmer depending on the heat and humidity.

If any heavy oil parts are left in the crankcase from the last season or if you didn’t empty out your old fuel before adding new gas, then all that leftover junk will be burned off as explained above, generating smoke. 

Malfunctioning Oil Injection Pump 

Your snowmobile includes an oil injection pump, a component that manages how much oil your sled receives at any one time. The oil injection pump is controlled by a throttle type cable, which tells the pump which fuel ratio to operate at depending on how much rotations per minute (rpm) of fuel the pump receives. For example, if the rpm is 3,000 or under, then the ratio is 70:1, if that. 

You need a well-functioning oil injection pump in your sled, as without it, you’ll breathe in a lot of exhaust emissions when you run your snowmobile. What do you think all that smoke is, after all? 

If your oil injection pump stops, then your snowmobile may won’t even turn on because it’s not receiving the necessary supply of oil. Yet what if things swing the other way and your oil injection pump now suddenly has an influx of oil?

The pump sends oil to the engine at a faster rate than the engine knows what to do with. The fuel will almost assuredly leak out of other parts of your snowmobile, burning off while your sled is running and creating smoke. 

How to Stop Your Snowmobile from Smoking

Now that we’ve discussed why your snowmobile may be smoking, we want to share some troubleshooting tips you can try to solve the issue.

Drive for a Bit

If you believe that inactivity has caused your snowmobile to smoke, then your first course of action is to drive your sled. Yep, that’s it, simply ride for a little while. Once all the temperatures of the internal components, including the engine, are regulated through a bit of activity, if you have any smoking, it should be far less.   

Remove Old Fuel 

If after a day of snowmobiling you still see more smoke than you’d prefer, then riding around isn’t enough. It could be that you have old fuel left in the tank, so you want to get rid of that next.

What some sledders do is cut a rubber garden hose to create a siphon. Then, you have to generate upward pressure so the fuel is sucked into the siphon by well, putting your mouth over the hose. This isn’t the safest nor the most hygienic solution, but it can work. 

You can also try using a hand pump kit and a siphon. You may also need a socket set, gas additive, a drip pan, and a gas can.

Set up your hand pump and siphon per the assembly instructions. Next, access your snowmobile’s gas tank, connecting your tube to the gas tank and the other end to your drip pan or gas can. Begin squeezing the pump as much as you can to siphon the gas out of your tank and into the can. Then, when all the fuel tank is empty, use a fuel additive and add new fuel. Problem solved! 

Be Picky about Your Fuel Going Forward

You also want to make sure you’re not creating a situation where gas parts can separate and get stuck in the crankcase. Always buy and use new fuel, not old stuff. Also, if you often fill up with a type of snowmobile fuel that’s not very rich, don’t switch to a new kind of fuel and expect your sled won’t smoke more. 

Look for Cylinder Leaks

What if you don’t suspect it’s an issue with your fuel, but rather, an antifreeze leak somewhere in the cylinder? You’ll want to remove the cylinder from your sled and check out the base gasket underneath. This gasket encircles the cylinder. 

If there’s a leak in the cylinder, the good news is it’s usually pretty easy to tell. Using a siphon, you now need to remove the excess coolant. You can also try a hose, some duct tape, and a portable vacuum like a Shop-Vac, which some sledders have pulled off.

Once all the antifreeze is out, give the bearings and oil crank a thorough cleaning. It also doesn’t hurt to fog your crankcase if you haven’t done that in a while.

Get Your Oil Injection Pump Replaced

Your oil injection pump, as important as it is, is not infinite. If it’s been several years since you’ve even looked at yours and you think it’s acting up, you’re better off replacing the pump. 

See Your Snowmobile Mechanic 

If all else fails, or if you don’t feel comfortable with some of the above measures we’ve discussed, that’s okay. You can always bring your sled into your preferred snowmobile mechanic and let them look over the vehicle. They can surely figure out why your sled is smoking so much and suggest a fix. 

Final Thoughts

Your snowmobile may smoke some when it’s in idle or during startup, but when the smoke gets to the point where it’s choking you, it’s too much. The problem could be due to coolant leaks in the cylinder, a faulty oil injection pump, old fuel, or heavy parts in the fuel clogging up the crankcase. 

Now that you know why your snowmobile may smoke a lot, you don’t have to delay in fixing the issue and getting your sled in running condition once more. 

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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