Your SCAG Lawn Mower is Blowing White, Blue or Black Smoke (Find Out Why)

It is alarming to find smoke rolling out of your lawn mower. Your mind immediately goes to the worse things that can happen to cause such smoke. How much money is it going to cost to fix this?

A SCAG lawn mower will begin smoking when the air filter is plugged; the choke is stuck or set incorrectly; the engine level is too high or too low; an engine gasket is bad, or there is an internal engine failure with the valve train or piston ring.

Smoke is not always a sign indicating great damage. However, it can develop into a significant problem if you don’t find and fix the root cause. Do not continue to run your mower while it is smoking.

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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.

This is Why Your SCAG Mower is Blowing White, Blue or Black Smoke

Blowing Black Smoke

Black smoke coming from your SCAG mower is typically a sign of your engine running rich. Running rich means there is a higher concentration of fuel and less air than is required to burn in the cylinder.

When you notice black smoke, check for items that can restrict airflow. These are things like a plugged air filter or an incorrect choke setting.

Blowing White or Blue Smoke

White or blue smoke coming from your SCAG mower is usually a sign your engine is burning oil. Follow the steps below to find reasons why this is happening to your mower.

It could be due to an incorrect engine oil level, worn piston rings, a valve train problem, a bad engine gasket, or the wrong oil viscosity.

7 Reasons a SCAG Lawn Mower is Smoking

Plugged Air Filter

An air filter is a component used to prevent dust and debris from entering the air intake and wearing the engine. When the air filter isn’t cleaned or replaced regularly, it can become so plugged with dirt that sufficient air isn’t able to flow through the filter.

This lack of airflow can cause the mower to run rich emitting black smoke. Not only does a plugged air filter cause the mower to run rich, there is the possibility it can cause oil to be pulled into the cylinder.

When there is a lack of air available, the engine may look for any available. This means air and oil can be pulled from the crankcase. Black smoke will come from your SCAG mower when the oil begins to burn off in the hot cylinder.

Replace your air filter when you find it is not allowing air into the air intake. To prevent this from happening in the future, replace your air filter annually and check it several times per season to clean it.

You may have to clean and replace your SCAG air filter more often if you use your mower more than the average homeowner or in very dusty conditions. If you are using your air filter for commercial purposes, check your air filter before each use.

Clean a SCAG mower paper air filter

• Remove the air filter from the air filter housing.
• Wipe out any dirt remaining in the housing with a clean dry cloth. Don’t allow any dirt to fall into the air intake.
• Tap the filter against a solid surface to knock it loose and remove as much dirt as possible. Don’t use compressed air as it can damage the filter.
• Hold up your filter to a light source to see if the light is shining through the paper.
• Reuse the filter if you do see light through the paper. Install a new filter if you cannot see light, it is extremely dirty, damaged, or covered in oil.
• After you install your filter, reattach the filter housing cover.

Incorrect Choke Setting

Black smoke will come from your SCAG mower when the choke setting is not correct. If you have a manual choke and it sticks remaining in the choke position, lubricate the choke cable so it moves freely.

Low Engine Oil Level

There are several ways you can have a low engine oil level on your SCAG. It may be you didn’t use enough oil when you refilled the crankcase after an oil change; you’re using the wrong viscosity of oil; or you have developed an oil leak.

You need to keep your engine oil at the level required by the engine manufacturer. Having a low level in the crankcase will not provide the lubrication required for the internal engine parts to move freely.

Friction will begin to build increasing the temperature of the engine. This heat can become so intense that it begins to burn oil and melt the engine parts.

If a low oil level is a reason your SCAG lawn mower is smoking, you can attempt to correct the problem by adding fresh oil. However, this will most likely not help. If your mower started smoking because of a low oil problem, you probably incurred some engine damage.

Bring your mower to your local small engine mechanic to be diagnosed. Get an estimate for the repair so you can make an educated decision as to whether you should rebuild or replace the engine.

Too Much Oil

While most people know a low engine oil is not good, they don’t know that having too much engine oil in your SCAG can cause problems as well.

Filling the crankcase with more oil than recommended can cause oil to get pushed into the cylinder or even up to the air intake through the valve train. When the oil gets hot in the cylinder, it will burn off and your mower will begin smoking.

To fix this, first, replace the air filter if you find it covered with oil. Then correct the engine oil level to bring it to the proper level indicated on your oil dipstick.

There are several different ways to drain the oil to fix the oil level. You can remove a little oil out of the drain plug; the oil filter; or use an evacuator or turkey baster to suck a little oil out of the oil fill port.

Bad Engine Gasket

A failing gasket can cause oil to leak from the engine. This oil will begin to smoke when it burns off the hot engine or muffler. You must locate the bad gasket and replace it.

The difficulty of this task depends on the location of the failed gasket on your SCAG.

Piston Ring Problem

A quick check you can perform that may indicate you have an internal engine problem is looking for oil on the spark plug. When you find oil on the spark plug, I advise you to take the push mower to an experienced small engine mechanic for diagnosis.

Excessive oil on the spark plug indicates you may have a piston ring or valve train problem. Either problem will result in having to take the engine apart.

You may find a scoring inside of the cylinder wall or worn rings causing oil to enter the combustion chamber and burn off.

If you have this type of problem, you may have to make the choice between replacing your engine or buying a new mower depending on the age of your SCAG.

Valve Train Problem

A valve train problem is not always the worse problem to have. The only way to detect this is by removing the cylinder head and performing a leak-down test. This should be performed by an experienced mechanic at your local repair shop or SCAG dealership.

A problem with the valve train can develop when the valve gets burned by being overheated. The heat can cause the edge of the valve to fall apart.

This is known as a burnt valve. An indication you have a burnt valve or timing problem is a muffler that is glowing red due to extreme heat.

The valve and seat will have to be cut at certain angles to make sure the valve seats correctly. It needs to make good contact with the engine block to complete the combustion chamber.