Why Your Husqvarna Lawn Mower is Smoking

It can be alarming when you see smoke pouring out of your Husqvarna mower. You may think there’s an expensive repair bill in the near future.

In some instances, you can easily resolve your Husqvarna’s smoking problem with some simple steps. If you’re not lucky enough to have your smoking problem fixed with these steps, you may need to have a professional look at your engine.

Your Husqvarna lawn mower may be smoking because the air filter is plugged; there is an insufficient level of engine oil; an engine gasket has failed; or there is a piston ring, valve train, or another internal engine failure.

Keep reading and I’ll share with you some simple steps to take to determine what kind of problem you have with your smoking mower.

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Follow all safety instructions provided in your equipment operator’s manual before diagnosing, repairing, or operating. Consult a professional if you don’t have the skills, or knowledge or are not in the condition to perform the repair safely.

Reasons Why Your Husqvarna Lawn Mower May Be Smoking

Air Filter is Clogged

Your Husqvarna mower uses an air filter to filter out the dirt and debris that gets kicked up when you are running your mower.

Dirt in your engine can cause extensive damage so it’s important to always run your lawn mower with an air filter. Not only do you have to run an air filter on your Husqvarna, but you also need to keep that air filter clean.

A plugged air filter can hurt your engine. When the filter is packed with dirt and grass, the air is no longer able to pass through the filter.

The lack of air being mixed with fuel can cause your engine to run rich causing black smoke. Running rich means you are running a heavily weighted fuel-to-air mixture so more fuel is being burned off in the cylinder than air.

If your engine can’t draw air through the filter, it may begin to overheat and will look for air anywhere it can find it. This air may come from the crankcase. When the air is pulled, oil is also pulled into the cylinder. The oil will begin to burn off creating smoke.

It’s very important to run clean air filters. Purchasing replacement air filters is a lot less expensive than the damage that will incur when you don’t use a clean filter.

Check your air filter at least a couple of times a year and more often when operating your mower in dry dusty conditions.

Clean your paper air filter using the following steps:

• Remove your Husqvarna air filter cover. Depending on the type of mower and style air filter you have, the cover will usually have one or two thumbscrews or knobs holding it down.
  
• Remove your air filter from the filter housing. Be careful to not knock any loose dirt into the air intake. Wipe any dirt remaining in the housing with a dry clean cloth.
  
• Knock the dirt out of the filter by tapping it against a hard surface until all the loose dirt has been removed. Never use compressed air to blow out the dirt as it can pack the dirt into the paper and damage the filter.
  
• Hold the air filter up to the light to check for light shining through the paper filter. If you are unable to see light through the paper, you must replace your filter.

If your lawn mower is using a different type of filter, read my article explaining how to clean different types of filters.

Insufficient Engine Oil Level

The engine oil level shown on your dipstick is not just a recommendation. It is a requirement. When your engine oil level is above or below the required level for your Husqvarna mower, your engine can begin smoking.

Low Engine Oil Level

Oil is used in your engine to lubricate the fast-moving parts that move in your engine. When there is a lack of lubrication, friction builds and your engine becomes very hot. Components may begin melting down from the heat and oil begins to burn off creating smoke.

You can attempt to add fresh engine oil to your engine to try to salvage it. Most likely, when extensive heat has built up in your engine to this extent, a simple fix like adding engine oil won’t help.

You should bring your mower to your local Husqvarna dealer or a small engine shop to determine if the engine can be rebuilt or if it must be replaced.

High Engine Oil Level

Having too much oil can cause too much crankcase pressure can cause oil to get into the cylinder or even up to the air intake through the valve train.

In this case, you’re noticing smoke from the oil that is in the cylinder and begins to burn off when the engine gets hot. To correct this problem, you need to drain some oil out of the engine.

There are several different ways you can drain a little oil from your Husqvarna mower:

• Loosen the drain plug and then quickly tighten it to only allow a little oil to drain
• Remove the oil filter and take some excess oil from the filter.
• Use a turkey baster (like the one from your kitchen) to suction out some oil from the oil fill area. Don’t reuse the baster for cooking purposes.
• Use an oil evacuator to vacuum out a little oil

Piston Ring Problem

Next, you are going to perform a step to help identify an internal engine problem. It’s hard to know exactly what type of internal problem you are having by performing this step, but it can lead you to potential problems that can be further diagnosed by a small engine mechanic.

An easy check for internal damage is looking for oil on the spark plug. You need to remove the spark plug with either a 3/4” or 5/8” socket depending on the mower you own.

Pull out the plug and check the tip for oil buildup. Oil on the spark plug will indicate you have an internal problem.

Oil on the plug may indicate you have a piston ring or valve train problem. To identify either problem, you will need to have your engine torn down and checked. There may be scoring inside the cylinder wall causing oil to enter the combustion chamber and burn off.

Valve Train Problem

Another internal problem that you could have is a valve train problem where the valve gets burned by being overheated. This is known as a burnt valve. If you find your muffler glowing red hot, this can indicate a burnt valve or timing problem.

The only way to verify your valve train problem is by removing the cylinder head and performing a leak-down test. This should be performed by a small engine mechanic at your local repair shop or a Husqvarna dealership.

If a burnt valve is found, the mechanic will have to cut the valve and seat at certain angles so it seats correctly and makes good contact with the engine block. The valve seat needs to be installed right so it can complete the engine combustion chamber.  

Bad Engine Gasket

A bad engine gasket can cause oil to leak out of the engine and possibly land on your hot muffler causing your Husqvarna to begin smoking when the oil burns off.

Sometimes the failing gasket isn’t that hard to find and replace, but it can get increasingly more difficult depending on its location.

Difference Between Blue and Black Smoke

I recommend going through the list above to identify your smoking problem. However, the color of the smoke can give you a clue as to what area on your mower you need to focus on.

Black Smoke

This color usually is due to your Husqvarna’s engine running very rich. This is when there is more fuel being burned than air so the first thing to check is the air filter and clean or replace it.

If this isn’t the issue check for another air flow restriction.

Blue or White Smoke

This color of smoke is due to the burning of excess oil. It is best to follow the steps above to identify the root cause starting with checking the engine oil level followed by checking for damage to the piston rings, valve train, or engine gasket.

You invested a considerable amount of money in your Husqvarna lawn mower. Checking your engine oil level and air filter before each mowing could prevent costly repairs.