Why Does My Snowmobile Keep Fouling Plugs: (8 Causes)

Why Does My Snowmobile Keep Fouling Plugs

Spark plugs provide an electrical charge that allows combustion to happen inside your snowmobile engine, so when they stop working, you’re stuck. No one wants to get trapped in the snow, especially when you’re far from home or your vehicle.

You can’t avoid all spark plug problems, but you can learn to diagnose them. Why does my snowmobile keep fouling plugs?

The main reason most people keep fouling their snowmobile plugs is simply by adding too much oil. When the oil is overfull, it can get onto the plug, which causes it to misfire or not fire at all due to the blockage. When you have an oil-fouled spark plug, that’s easy to identify because it is covered in oil.

What Causes Snowmobile Spark Plugs To Foul Out

Snowmobile spark plugs foul out due to many different causes. Unfortunately, this is a delicate part, and anything that interferes with your plug’s operation can mess them up, causing a failure.

Below I’ll walk you through the top 8 causes of fouled spark plugs so you can figure out the root of the problem and hopefully prevent it from happening in the future.

1 – Overfull Oil

You should never overfill your oil. Sadly, when there’s too much in the tank, oil can get forced up against your sparkplugs.

A plug coated in oil won’t produce electricity the way it would normally, which can lead to fouled plugs.

Since it’s so easy to overfill, oily spark plugs are one of the most common reasons for a foul-out.

Happily, an oily spark plug is an easy fix. If you open the hood and discover a greasy-looking plug, it’s probably not a lost cause.

Often you can remove a little of that excess oil from the tank and clean off the plugs and area around them.

I recommend using a microfiber towel as they don’t leave debris behind as you wipe.

2 – Too Much Gas

When your engine runs too rich, it means that only some of the gas is burning off in the combustion process.

The rest of that gas has to go somewhere, which unfortunately means the leftover liquid collects in various locations around the engine compartment. One of those places is on top of sparkplugs.

Luckily, if you catch it quickly, the solution to gasoline on your sparkplugs is the same as it is for oil buildup. You can usually wipe the excess away.

3 – Excessive Idling

Idling isn’t something we generally consider a potential problem, but it can cause issues in your snowmobile if you do it too often.

The trouble is that, while idling, your engine doesn’t run at the same temperature.

This can lead to numerous issues, including fouled spark plugs since they are temperature-sensitive components.

4 – Carbon Fouling

A carbon-fouled spark plug is usually only dirty on the tip, where it will be black but not wet or greasy.

This means a deposit of carbon has built up there, and it is interfering with proper sparking.

Several things lead to carbon fouling. As AutoGuru explains, “Causes of carbon fouling include rich fuel mixture, clogged air filter, prolonged low-speed driving or idling, faulty ignition system, retarded ignition timing, and spark plug heat rating is too cold.”

Regrettably, you will have to check all these potential causes, but at least you can clean off the spark plug and reuse it in many instances.

5 – Engine Overheating

Sparkplugs are made from metal. We like to think metal is basically indestructible, but that’s not the case.

When your engine overheats, the parts inside do as well. The metal is expanding and contracting excessively and can crack or have warping issues.

High temperatures, especially if it happens repeatedly, will cause sparkplugs to wear out prematurely.

6 – Blocked Air Filter

You need an air filter to keep debris out of your engine, but when the filter gets too full and becomes blocked, your engine stops getting the air it needs to operate correctly.

A restricted air supply causes your engine to run as though it was too rich. Not all the fuel gets burned.

The resulting soot residue can foul the tip of your spark plug.

7 – Ash Fouling

Ash fouling can occur from overly rich fuel to air ratios and blocked air filters, but there are other possible culprits, so I’ve given this its own category.

Unfortunately, ash fouling can be indicative of significant engine issues. It also occurs when oil gets burned, or you use low-quality fuel and problematic additives.

8 – Riding Long Distance at Slow Speed

Continuous low-speed driving causes spark plugs to foul due to the cold.

When your engine is always running below its optimum temperature, the components designed to run at a specific temperature tend to react.

For spark plugs, running cold can impact their ability to function. I would never recommend speeding, but you can hit the gas a little if your timidity and caution are causing fouled plugs.

How To Fix Fouled Snowmobile Spark Plugs

There are two ways to ‘fix’ fouled spark plugs. Depending on the root cause, you may be able to simply clean it off with a microfiber cloth and replace it.

However, it’s important to understand that this only works when the problem is oil, gas, or another substance, not the plug itself. Even so, it may be wiser to use the second method.

When in doubt, the second method for fixing fouled spark plug always works, at least temporarily, because the solution is to replace the plug with a new one.

Unfortunately, this may only be a temporary bandaid on the problem. Determining the root cause of your fouled spark plugs is the only way to ensure it won’t happen again.

If you are new to changing snowmobile spark plugs, I recommend checking out this video from RedLine Recreational Toys.

They go over the basic process and show you what to look for. However, it is essential to note that your model may differ slightly due to the variety of shapes, sizes, and engine configurations on snowmobiles.

The manufacturer’s website should have copies of the operator’s manual for every model if you still need help locating and removing your particular spark plugs.

Best Spark Plug To Prevent Fouling

NKG Br8es 5422 Snowmobile Spark Plug
  • Often specified as original equipment, NGK spark plugs are the best combination of performance and longevity.
  • Offering the Quality, Reliability and Durability You’d Expect from an OEM Manufacturer
  • NGK is the world’s largest supplier of OEM spark plugs
  • Research Applications Prior to Purchase To Make Sure This OEM Part Fits Your Vehicle, Including Engine, Drivetrain and Quantity Needed.
  • This Listing is for 10 Spark Plugs

Last update on 2024-04-20 / Affiliate links / Images from Amazon Product Advertising API

The best spark plugs to prevent fouling are the NKG Br8es 5422 Boxed. These simple but efficient spark plugs are built to last with a nickel core.

You’ll appreciate the high-quality, thoughtful design that helps these plugs offer optimal performance.

Over 80% of reviewers give these spark plugs five stars.

Tom says, “Awesome plugs perform flawlessly in my 2-stroke Kawasaki 220.”

Bob P adds, “I always buy NGK plugs for my SeaDoo. They work great.”

Not only does NKG make superb, cost-effective spark plugs, but they ship quickly.

Better still, this company has an outstanding reputation and excellent customer service.

See what everyone is raving about when you order a set right here.

Helpful Tips To Know About Why My Snowmobile Keeps Fouling Plugs

Fouling out snowmobile plugs is extremely easy. The good news is that they are also a quick and simple part to replace, and plugs aren’t very expensive.

Here are a few more helpful tips to know about why my snowmobile keeps fouling plugs.

  • There are a surprising number of things that can cause spark plug fouling. While I’ve listed the most common causes, there are others. For example, a moisture leak, riding short distances, or improper heat range sometimes causes fouled spark plugs. If the problem happens regularly, it pays to root out the cause, even if it is one of these less likely culprits.
  • Even when nothing goes wrong, and you don’t have fouled spark plugs, keeping some spares with you is still a good idea since spark plug fouling is a widespread problem for sledders.
  • Remember to change your spark plugs at least once per year. I recommend doing it right before your first ride of the snowy season since that’s when your sled has been sitting unused the longest, and you should be doing pre-ride checks and maintenance anyway.

Final Thoughts

When you ride a snowmobile, you will eventually have fouled plugs. It’s just a fact of life with machines.

However, now you should be able to determine the cause more quickly, which can help you take preventative steps to minimize future recurrences.

With so many possible ways to foul a plug, it’s a good idea to carry spares and a small piece of a microfiber cloth with you when you ride.

Doing this can save you from serious trouble if you’re on a long ride and your spark plugs fail.

Drew Thomas

My name is Drew Thomas and I’m the creator of Fun In the Yard, your one stop site for all your outdoor games, sports, party activities, outdoor gear, and lawn & gardening tips.

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