Why Does My Snowmobile Keep Flooding?

You’ve been waiting all week to ride your snowmobile, then when the day comes, your sled won’t start. Is it out of gas? No, you just filled up the tank the other day. You’re not sure what could be happening then. One possibility is that you flooded the engine, especially if you’ve had this issue before. What causes repeated snowmobile flooding?

Your snowmobile might keep flooding if you over-prime or over-choke the engine on startup. In other instances, it might be an issue with faulty parts such as the inlet needle or float valve seats.

In today’s post, we’ll dig deeper into the reasons your snowmobile might flood, discuss what happens when you flood the engine, as well as how to assess and fix the issue. You’re not going to want to miss it! 

What Does It Mean When a Snowmobile Engine Floods Anyway?

First thing’s first, when you flood your snowmobile, what’s really happening?

Your snowmobile engine, like many internal combustion engines, needs to be fed fuel and air at a particular ratio, typically 12:1. In this case, the 12 is the quantity of air and the 1 is the quantity of fuel. Following this ratio optimizes the performance of your sled so your days on the snowmobiling trails are better.

Yet what if you were to add too little air or too much fuel to your snowmobile’s engine, thus destroying the ratio? Well, all sled fuel has an upper explosive limit, also known as the flammability limit. This is simply referring to how much oxygen and combustible materials in the fuel will burn if the fuel concentration is within that limit.

When your snowmobile’s fuel now surpasses the upper explosive limit, you’ve flooded the engine. The air-fuel mix is too rich and does not allow for ignition. Either your snowmobile won’t start at all, or it’ll start, but it will begin stalling out on you every so often, which is even more disruptive. 

Why Does Your Snowmobile Keep Flooding?

If your snowmobile floods once, it’s a pretty scary occurrence. We’ll talk in the next section about the signs that indicate sled flooding, but they’re not pretty. Unless you identify and rectify the reason your sled has flooded, then it’s very easy for the issue to continuously crop up. Maybe not every time you ride your snowmobile, but more often than not, your engine will flood. 

Here’s why. 

Over-Choking the Engine

Your sled’s choke is an integral component to startup, but there is such a thing as overdoing it. To turn on your snowmobile properly, you want to activate the parking brake, begin throttling, and then roll along slowly for a few minutes so the engine can warm up.

If your sled uses an electric start, then you should put the key in the ignition, turn it on, and let go of the choke when you hear the engine kick on. Then, once your engine has a couple of minutes to warm up, turn the choke off. 

Some sledders turn their snowmobiles on and ride them while the engine is still cold. We don’t advise this, as it puts strain on the engine. That said, you will have to prime or choke your engine more than you would with a warm sled engine. Otherwise though, limit too much choking. 

Remember, your choke produces the correct air-to-fuel ratio by limiting how much air gets to the carburetor. This lets more fuel in. When you over-choke the engine, you restrict the quantity of air to such a degree that engine flooding is very much possible. Fortunately, once you realize what you’re doing, this behavior is easy to fix. 

Using the Wrong Type of Fuel

You also want to check that your snowmobile fuel meets that appropriate air-to-fuel ratio requirements necessary for your sled. As we just mentioned, you can always choke the engine to reach that ratio, but the wrong fuel type will cause issues not just on startup, but when you try to ride your sled as well. 

Holding on to Old Parts

Certain parts of your sled can go bad that could cause your engine to keep flooding. One of these is the inlet needle and the other is the float valve seat. 

The inlet needle beneath the carburetor is attached to a float bar and connects the carb to the fuel line. If your inlet needle is dirty, you can use some WD-40 or a similar product to lubricate and clean it. If that doesn’t work and your engine is still flooding, then you should very much consider replacing the inlet needle. 

This isn’t super cheap, as one needle costs about $40 if you go through your snowmobile manufacturer. For such a small piece of metal, the price is quite high, but you still don’t want to push your inlet needle too far past its prime.

The other component that might contribute to your snowmobile flooding is your float valve seat, which is another part of your float valve. The float valve is a component that regulates how much fuel the carb receives. Within the float valve are the float, the needle, and the seat, which is a specialized orifice. 

When your carb becomes flooded by fuel, which can happen, and the fuel sits and sits, your float valve can go downhill. Surprisingly, you’ll probably pay less for a whole new float valve than for the inlet needle. The average price of a float valve is between $20 and $40. 

How Do You Know Your Snowmobile Engine Is Flooded? (How To Fix It)

If your sled is acting up, how can you tell whether it’s an issue with your snowmobile’s engine flooding or something else? Be on the lookout for the following symptoms. 

Your Engine Is Extra Noisy

No snowmobile engine is noiseless, especially on startup, but yours is making some extra strange sounds, some that you’ve never heard before. For example, you hear a sound almost like a crank, especially when you turn on your snowmobile. This may be the only noise or it could be accompanied by other disconcerting sounds.

Either way, the cacophony of noise is your snowmobile’s engine reacting to the improper air-to-fuel ratio in the sled. 

The Engine Starts but Doesn’t Stay On

If you’re a common over-choker of your snowmobile, then those first few minutes after startup can be especially dicey. Like we talked about before, your sled turns on, but then a couple of minutes later it cuts out on you. You might choke it again to get the sled up and running, which only makes an already bad problem even worse. 

Should your day proceed like this, where your engine stops, you choke it more, and the engine stops yet again, you’re not going to get very far on your snowmobile because you’ll have majorly flooded the engine. 

The Engine Doesn’t Start at All

In some instances, things never quite get that far because you can’t even make your snowmobile power on. Too many repeated instances of the above behavior can flood the engine so significantly that it can’t run.

You Can Smell Gas

The last symptom to beware of a flooded snowmobile engine is the smell of gas. Especially when you first turn on your sled, it’s normal to smell some gas, but if the odor is overwhelming, that’s no good. Another sign that’s indicative of engine flooding is if the gas smell is more prominent around your sled’s exhaust than elsewhere on the vehicle. 

How to Troubleshoot Snowmobile Flooding

You’re pretty sure your snowmobile engine has flooded again, but what can you do about it? Try the following troubleshooting measures to get your sled running healthily once more. 


Your first method isn’t really a method at all, as you do nothing for a little while. Yes, we’re serious. Pull over to the side of the road, power down your snowmobile, and wait it out for 20 minutes. You can go inside to warm up, take a bathroom break, or get something to eat.

By the time you come out, the extra gas in your engine should have had time to evaporate. Your spark plugs, which were saturated in gas, should also have dried out by now. That said, if you seriously flooded the engine, then waiting for a while might not work, so keep that in mind.

Provided it’s not a significant issue, after 20 minutes or so (you can always wait longer if you think it will help), turn on your snowmobile engine again. Avoid priming the engine too. The restart and the time off may have fixed the issue, but if not, you have plenty of other options. 

Remove the Extra Gas

Not all gas will necessarily evaporate, so you might want to manually remove it. We recommend turning the choke and motor off and letting your engine cool down. Next, take out your spark plugs, drying and cleaning them as needed. 

Check your crankcase, which can also get saturated in gas, and look for the drain plugs. By opening these, you can let the excess gas out. You also want to clean your carbs. 

Choke Sparingly

By learning the correct way and the right times to choke your engine, you can prevent future instances of flooding your snowmobile. This is worth doing, as you can save yourself a lot of the work we’ve discussed in this guide! 

Replace the Float Valve 

To change out the parts of the float valve, including the seat and the inlet needle, you’ll need a 5/8-inch wrench. Put it on the adjustor nut and begin loosening your screws using a flat-blade screwdriver. Rotate your screwdriver counter-clockwise to release the screw. It doesn’t have to come all the way out unless you want it to. Repeat this for all the screws in the set until they’re loose enough to work with. 

Next, use an adjustor nut to thread your needle, rotating the nut in a counter-clockwise direction. This should pull both the seat and the needle up and out of your float bowl. Again, don’t expect complete removal here, as the seat and needle will rise up about 3/8 inches since the O-ring will keep everything relatively in place.

You need to disengage the threads for complete removal if that’s what’s necessary. Then, you should be able to lift the seat and the needle from the float bowl. Add your new parts and follow the above steps backwards to get everything screwed into place as they should be. 

See a Repairperson 

If the above measures haven’t stopped your snowmobile flooding problem, then it’s never a bad idea to see your favorite sled mechanic. 

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Final Thoughts

Frequent snowmobile flooding involves sending too much fuel to the engine, which ruins the necessary air-to-fuel ratio that your snowmobile needs for top performance. By over-choking the engine, you could flood it, as is the case if the float valve parts are old. 

Now that you know how to fix your flooded snowmobile, you shouldn’t keep having these issues going forward. 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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