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Why Would Your Mower Blow White Smoke? Find Out Here!

Written by William
Last Updated on March 23, 2021

Lawnmower & White Smoke - Our Troubleshooting Guide

If you own a lawnmower, you will likely experience some smoke coming out of it at some point, this white smoke can be a little worrying and might cause you to panic, but not to worry, most of the issues that cause this white smoke can be easily fixed.

Your lawnmower may be blowing white smoke for several different reasons such as the oil being overfilled or a blown gasket. Your mower may additionally have been tipped or the engine is just simply worn out.

To make fixing your mowers dreaded white smoke issue easier, we have listed out the typical problems that might be causing this smoke and how to fix them below.

So without further ado, let's get into it and stop that white smoke!

Reasons For White Smoke From Your Mower

To fix the white smoke coming from your lawnmower, we need to figure out what's causing it, most of the time this white smoke is because of burning oil, which can be caused by many factors.

You may want to try running your mower for a while to see if this clears the white smoke that has come from your combustion chamber, this can often fix the issue and clear the smoke, however if not, have a look at our causes and solutions below.

Tipped & Angled Mower

One of the first and most common reasons as to why your mower is producing white smoke could be due to your mower being tipped or being used at a very steep angle.

When doing lawnmower maintenance you may have tipped the mower over to access its cutting deck or change the blades, when doing this you are meant to tip your mower in the right way to avoid oil leaking into your engine's cylinder.

If you have tipped your mower the wrong way recently this could be causing the white smoke from your machine.

Using your lawnmower at a steep angle can also produce white smoke, this may likewise cause engine oil to enter your mowers cylinder and burn, causing the white smoke.


Luckily, fixing this issue is pretty simple. All you need to do is let the lawnmower run idle to clear the oil that has entered the combustion chamber of your mower, this help burn the rest of the oil out and get rid of the smoke.

To avoid this issue in the future you should further avoid using your mower at a steeper angle than 15-degrees and also correctly tip your mower with the air filter facing up next time you want to look under your lawnmower.

Your Head Gasket Needs Replacing

One of the more serious issues that could be causing white smoke in your lawnmower is if the head gasket of the machine is broken.

The head gasket helps close the cylinder of your mower, when damaged this oil from the cylinder can easily enter the combustion chamber of your mower due to the compression in the cylinder that takes oil from the crankcase.

Signs that this is happening to your lawnmower could be the sound of air being blown and a loss of power output from your mower in terms of performance. Your mower will probably have oil around the head gasket and the mower itself too.

If your engine is running for a long time, this can suck more and more oil into your mowers combustion chamber which could completely stop the mower from running after time.


So, if it turns out your head gasket is damaged on your mower then you will need to get a new one as you cannot repair them.

These gaskets are normally affordable and can be fitted into the engine of your mower by a professional or by yourself if you have some experience with your lawnmower's engine.

The Engine Oil Is Too Full

Having a well-kept oil reservoir in your mower is important as it makes sure the mower performs to its maximum potential and can help your mower last longer overall.

Two common problems can happen with putting oil in your mower, the first one is putting a smaller amount of oil than required into your mower's engine, meaning the mower will have friction which can cause white smoke.

You should also make sure you are maintaining your mowers oil right when putting the oil to fuel ratio, as excess oil can cause it to enter the cylinder and burn, resulting in white smoke once again.

Too much oil in your mower could potentially ruin the crankset and stop it from moving, as well as an oil leak, this excess oil could result not only in white smoke but the mower not starting up too.


To fix this you should know the exact amount of oil your mower needs (typically no more than 20 ounces) and use a dipstick to measure it out before filling.

In terms of stopping the white smoke that has already started from overfilling the oil, you will have to drain the excess.

You should also ensure that you are using the correct type of oil for your mower as the wrong grade could potentially cause white smoke too.

Bad Piston Rings

Damaged piston rings tend to occur in very old mowers or mowers that have not been looked after properly.

For the piston to move correctly inside of your engine it uses the piston rings to control how much engine oil enters the cylinder, providing very small amounts at a time. They can also help to remove excess oil if needed.

When these rings fail, oil can flow freely into your mowers combustion chamber and cause white smoke. This tends to happen due to dirty engine oil or worn out air filters.


There is no simple fix for your mower if it has bad piston rings, you will have to take it to a professional who will likely need to rebuild the engine of your mower as the rings could have caused damage to other parts on your mower.

You Need To Adjust The Carburettor

If all else fails above, you may need to adjust the carburettor on your lawnmower. Adjusting the carburettor can help with the fuel to air ratio which could be causing the white smoke.

When your carburettor is completely damaged you may smell gas and have to replace the whole thing entirely.

Frequently Asked Questions About White Smoke Coming From Lawnmower

What side should I be tipping my mower? 

When performing maintenance on your lawnmower you should tip your mower in the direction of the air filter facing up and the carburettor facing up to stop oil leaking into the engine of the mower.

How can I fix it if I have put oil in my 4-stroke mower?

Four-stroke engine lawnmowers don't require you to mix oil with there fuel unlike two-stroke engines, if this happens you can try running your mower till this oil is burnt and the white smoke stops.

What are the steps to replacing a head gasket on a mower?

To replace an OHV head gasket on your lawnmower your first need to remove the spark plug and the cylinder head on your mower, then remove the gasket and put a new one on to the engine block with the cylinder head, then put the spark plug back on your mower and check all is working.

Final Words

Overall, although white smoke is scary, it's not the end of the world and most of the time can be fixed by following the troubleshooting guide above.

However, if you find running your engine till the oil burns off does not fix your white smoke problem and the other solutions above don't help, you should never keep using the mower as this can result in even more damage to your mower which can become costly in the long run.

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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