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What To Do If Your Lawn Mower Starts Smoking? – Easy Guide

Written by William
Last Updated on January 24, 2023

What To Do If Your Lawn Mower Starts Smoking?

Seeing smoke coming out of an engine is always scary, especially if it's from a potentially dangerous machine such as a lawn mower.

Lawn mowers shouldn't smoke when you start them up. A lawn mower should be able to run without smoking. 

Was your lawn mower working just fine, and then suddenly started smoking?

Don't know what it means and what to do?

Fret not! We're here for you.

Knowing the cause of the smoke will teach us how to fix it. The color of lawn mower smoke indicates the problem.

Lawn mowers emit different colors of smoke. The smoke from your lawn mower could be white, blue, or black.

What Different Smoke Colors Mean

White or Blue Smoke

White is the most common color in lawn mower smoke. It could also appear blue.

The smoke should disappear by itself if you run the lawn mower for about 15 minutes. If it doesn't disappear after running the lawn mower for around 15 minutes, then you should check out the manual for your lawn mower.

White or blue smoke could mean that the engine needs repair. You need to turn off your lawn mower and take it apart to check if there's something wrong with it.

Typically, white or blue smoke indicates the following issues:

1. Incorrect use; lawn mover tipped over or tilted too much.

Lawn mowers should always use oil, even if it's just a little bit. Oil helps prevent damage to the engine.

Tipping the mower on the side is dangerous because oil moves into the engine.

This smoke could be caused by burning oil.

Fix: Don't tilt your mower at more than 15 degrees angle.

If you do, the oil moves from the crankcase to the cylinder. It may even cause a leak. 

Always put your mower upright, even when stored. You should check the oil in the crankcase. You can fix this issue by just letting the engine run. After a while, the smoke will dissipate. 

2. The engine is overfilled with oil.

Lawn mowers should be filled with about half a quart (0.5l) of oil. Overfilling causes problems because the engine doesn't get enough oil to run properly. Splash lubrication systems work better when there is less than half a quart (0.5l) of oil in the tank. Always check your manual about the right oil to use for your unit.

Overfilled lawn mower oil reservoir can cause your engine to burn oil. 

Overfilling the crankcase can cause an engine to seize up. This should never happen because it could lead to a fire. Oil spills can damage your lawn mower. You should always check the oil level before using your mower. Drain excess oil and check and add more if needed before using.

Fix: Drain excess oil and idle the motor until the smoke clears.

Depending on your mower type, you may need an oil extractor.

If the oil smells like gas, you should stop the mower and check the carburetor. You want to fix the carburetor and change the oil before using it again.

Adding proper oil and fixing the problem with the carburetor before you run the engine. Otherwise, you'll damage the engine.

3. Head gasket failure

Head Gaskets are important parts of engines. They're made out of metal and graphite. They seal the combustion chamber. They're used to prevent oil leaks. 

Oil leaks, high pressures in the crankcase, and a strange noise are some common symptoms of head gasket issues. White smoke could mean that there is a leak or something wrong with the engine. 

Fix: Replace the head gasket that failed with a new one. 

4. Using the wrong type of oil 

Check if you've put oil in the gas tank by mistake. It's a common mistake. 

Fix: Run the engine after you drain the oil and put the gas properly.

After a while, the remaining oil will clear out, and so will the white smoke.

5. Worn out engine or faulty or damaged parts.

Just like a car engine, you should check your lawn mower regularly. Make sure that everything works properly. Sometimes, you might have to replace certain parts such as crankcase breather, head gasket, cylinder head, piston rings, etc.

Fix: Determine and replace broken or damaged parts.

You may need a will need a compression test. This should be done by an experienced mechanic. 

6. Electrical Problem

Smoking may also be caused by carbon buildup in your spark plug.

Fix: Pull out your spark plug and check. If it's carboned up, clean it.

Ensure to also double-check the gap in the plug according to the unit manual. You can always just replace it. Make sure you don't use the wrong plug type. 

Black Smoke

A black smoke issue in mowers typically indicates carburetor and fuel systems problems. 

1. Clogged Air Filter

Black smoke coming out of a mower means that the engine is overheating. It may be due to a clogged air filter.

Fix: Check your air filters. Clean or replace as necessary.

To check, remove the air filters and start the engine. If you don't see any smoke, then it's the problem.

You can clean the air filter and remove dirt and other particles. 

But, replacing the air filter is more effective. After you clean the air filter or replace it, start your lawn mower and let it go for a few minutes to check if the problem has been solved.

2. Faulty or damaged carburetor

Black lawn mower smoke could mean your carburetor isn't working right. Black smoke can be caused by an unsuitable fuel-to-air mixture. There may be more gasoline than there should be.

Fix: Check your unit manual and tune or change the carburetor as appropriate.

You can also change your entire carburetor after confirming that it's failing.

Final Thoughts

White smoke could be just normal when starting up a new lawn mower.

Blue or black smoke indicates a problem.

To summarize, you can troubleshoot the most common lawn mower problems by:

1. Checking the mower for oil issues 

2. Checking the air filter

3. Checking the angle which you're mowing

4. Checking the mower engine and its parts if it needs cleaning, adjusting, or replacing.

If you want to fix the issues yourself, always refer to your unit's manual or, better yet, consult a professional at your trusted lawn mower repair shop.

About the author
Written by William
I have always had a passion for gardening and that with a background in selling lawn mowers for the past 10 years, I have become very knowledgeable in all types of gardening tools. The site was created as a hub where I can review and write about all of the tips around gardening.
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