What Causes The Lawn Mower To Smoke And How To Fix It For Good?

Many people love taking care of their grass, and for many, a well-groomed lawn is a source of pride. However, maintaining a yard is not an easy task.

It involves careful planning and hours of work watering, fertilizing, dethatching, aerating, and mowing grass. And, when it is time to trim your lawn, the last thing you want is a smoking lawn mower. 

White Smoke from your mower looks pretty problematic, but usually, it’s a simple fix.

Smoke from a lawn mower is never a good sign, whether the smoke is white, blue, or black. It means something is wrong with your machine, and you need to figure it out and fix it.

The white or blue smoke is often caused by leaking oil from the exhaust. But, if the smoke is black, it might mean the engine is running “too rich.” The “rich” condition means the engine’s fuel/air mix has too much fuel.

Often these issues can be resolved without professional help.

Please continue reading to find out how!

Common Reasons Why Lawnmowers Smoke

Here are the most common reasons for smoke coming out of lawnmowers. 

Afterward, we will discuss colored smokes from lawnmowers, what sort of problems they indicate, and how you can fix them in the comfort of your home.

Make sure you stick around so you don’t miss anything! 

Nevertheless, Let’s get started.

1. Lawn Mower Tipped Over

smoking lawn mower

Tipping a mower too much might cause the engine oil to spill, making the lawnmower smoke.

Let’s start with the most fundamental reason for smoking in lawnmowers: mower tipped over. It is the most common reason for smoke coming out of lawnmowers, and this one is also the easiest to fix. Often, the smoke due to tipping over goes away on its own.

It often happens when people turn over or tip their lawnmowers to unclog the chute or clean the deck. And, when you tilt the mower machine too much or in the wrong manner, it allows the engine oil to enter the combustion cylinder from the oil pan or sump.

So, when you start the mower, the engine oil burns with the fuel, turning your backyard into an 80s disco. However, the oil can sometimes also leak from the muffler.

The fix to this mower problem is pretty straightforward. Check your mower for oil leakage and let it run until the white smoke clears. However, if you have a tractor mower and it is smoking, there could be other reasons too.

For example, it might be a blown head gasket, a faulty carburetor, or too much oil.

We will discuss these issues more later in the article.

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2. Too Much Oil

Too Much Oil

Overfilling the oil compartment is the second most common reason for smoking mowers.

If you read the manual that comes with mowers, you will see that most of these machines take only about 0.6 liters (or a quart) of engine oil to run. Therefore, you could very quickly overfill them. And many people do, which then causes problems with the mower.

Too many people also never check the engine oil level in their mowers and keep adding the oil, thinking that it would not do any harm. Wrong! It will affect the mower.

Too much engine oil can severely damage a mower machine, as many lawnmowers that are available to people operate on splash lubrication systems. So, when the oil compartment of a mower is overfilled, the lubrication system doesn’t work effectively.

The white smoke results from this excess oil spilling over into the combustion chamber and burning along with the air and fuel mixture. So, what is the fix?

Stop adding engine oil to the mower when it is not needed, and the problem will disappear. However, if it is already done, drain the excess oil and let the mower engine run idle for a few minutes till the smoke clears up.

The process can take about ten minutes, depending on the extent of oil contamination.

Also, depending on the model of your mower machine, draining the excess oil can often be daunting. Overfilling the oil compartment of a mower can also cause other problems for the lawnmower, such as engine damage, leaks, and poor performance.

All in all, you should only add engine oil to a mower when needed!

3. Gas In The Oil

smoking lawn mower

A failed carburetor seal can cause oil to mix with the gas, causing it to burn and the mower to smoke.

If the problem is not just the smoke coming out of the mower, but the mower is also stalling, sputtering, and then dying when you start it, the problem is neither too much oil in the oil compartment nor is you mistakenly tilting it too much or in the wrong direction.

The mower stalling and producing smoke is often a sign of failed carburetor.

And, if you think this is the problem with your mower, running it idle will not fix it. In fact, you should not even run it s the oil is too thin now since it has mixed with the fuel, and running it can severely damage the engine of your lawnmower machine. 

You need to take out the carburetor and fix it to solve this issue. And, if the carburetor isn’t fixable, you will need to replace it if you want to keep using your mower.

Sometimes the carburetor only needs to be cleaned, and the problem goes away. However, there is only one to find that out. You will need to take it out of the mower, clean it properly, install it back into the mower, and run it again.

If the problem is gone, very good. Otherwise, you will need to fix it but fixing a carburetor is no easy task; you will most likely have to take it to a pro.

4. Head Gasket Failure

Head Gasket Failure

If the head gasket becomes damaged, the oil will begin to leak; this will cause white smoke.

The failure of a head gasket on a lawnmower is a rare occurrence. However, it can happen, and when this happens, the mower will produce enormous amounts of smoke. In the case of head gasket failure, any other cause cannot justify the amount of smoke released.

Unlike the abovementioned issues, fixing a broken or faulty head gasket will take a lot of work. A head gasket is a graphite and metal part that plays a crucial role in sealing the engine’s combustion chamber to avoid engine oil leaking into the cylinders.

It can be located between the cylinder head of an engine and the cylinder block.

The most common sign of the failure of a head gasket is a mower that will not start, and if it starts, it runs on very little power. And without proper power, the mower is useless.

If you hear puffing sounds when the compression escapes from the combustion cylinders, chances are it is a fault head gasket. Other common signs of a head gasket failure include oil leakage and high crankcase pressure in your lawnmower machine.

So, how can you fix a broken head gasket? Well, you will have to replace it! It is not worth fixing a faulty or damaged head gasket as it is inexpensive, and the effort and hassle of fixing or repairing it simply do not make any sense.

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5. Oil In The Gas Tank

You may wonder who puts oil in the gas tank or how that happens. But let me tell you, it happens more often than you would expect and is very common.

There are some mowers in which oil and gas go into the same compartment. However, the mowers widely used today have a four-cycle engine in which gas and oil go to separate containers, and putting them in one place can cause issues.

So, if you accidentally put engine oil into your mower’s gas tank with a four-cycle engine, it will start to produce white smoke. However, do not worry! It isn’t the end of the world. With a bit of patience, some tools, and some knowledge, you can fix it.

To fix an oil and gas mix, drain the oil and fuel, clean the gas tank, and add fresh gas to your mower to get it up and running again. I also recommend you check and clean the spark plug and air filter when cleaning the gas tank.

Sometimes these parts could also cause the mower not to start correctly or the fuel to burn incompletely, which also results in the release of smoke from the mower.

Smoke Color And What That Means

smoking lawn mower

Now let’s discuss the different colors of the smoke coming out of a lawnmower, what problems they indicate, and whether there is a way to fix the issue.

Lawn Mower Blowing Blue Smoke

You probably have seen white or black smoke coming out of engines, but did you know sometimes they can also blow out blue smoke? When this happens, it can be quite concerning, and it is especially true when you see it for the first time.

What Causes Blue Smoke In a Lawnmower?

If your mower is releasing blue smoke, there are many possible causes. You will have to pinpoint the problem and then fix it to stop the blue smoke.

Nevertheless, some of these causes are:

  • The lawnmower has a damaged head gasket
  • The lawnmower is being stored improperly
  • The lawnmower has leaking seals
  • The lawnmower is using the wrong type of oil
  • The lawnmower has an engine problem
  • The lawnmower has a fuel system problem
  • The lawn mower’s spark plugs are fouled
  • The lawn mower’s air filter is dirty
  • The lawnmower is overfilled with oil

How To Fix A Mower Blowing Blue Smoke?

If you see blue smoke coming out of your mower, first of all, consult its manual.

If you see your problem mentioned there, great! Just troubleshoot the mower according to the instructions, and soon you will have your mower all fixed and ready to go. If, however, yo problem is not mentioned there, check for the cause mentioned above.

Most of those causes also have simple fixes. If you cannot fix a mower part, get a replacement. And, if you are still not sure, get professional help!

Lawn Mower Blowing White Smoke

White is the most common smoke color that comes out of mowers, and most of the time, it means there is oil in the fuel or combustion cylinder, and it will go away on its own when the oil is burned. All you have to do is start the mower, let it run idle for some time, and wait for the white smoke to disappear. But the problem can sometimes linger!

In that case, you will have to figure out the cause and fix the issue. Failure to do so can result in significant or irreversible damage to your lawnmower.

What Causes White Smoke In a Lawnmower?

Like blue smoke blowing out of a lawnmower, white smoke coming out of a mower also has many causes, many of which are similar to the reasons for blue smoke.

Here is a complete list of what might cause white smoke in a mower:

  • Damages to the cylinder/piston rings
  • An obstructed or crimped breather tube
  • Exceeding the engine’s oil capacity shown on the dipstick
  • Turning/tilting the machine on its side for storage
  • Worn cylinders or rings
  • Blown head gasket
  • Crankcase air leak
  • Inoperative crankcase breather
  • Incorrect oil grades
  • Overfilling the crankcase with oil

How To Fix A Mower Blowing White Smoke?

As already stated, white smoke blowing out of a mower will typically go away once you run the mower for a bit. Even if there is an issue, you can fix it quickly. The only time you should worry is a blown head gasket, as repairing and replacing it is pretty tough.

RELATED: How To Fix Lawn Mower Sputtering: Common Reasons & Easy Fixes!

Lawn Mower Blowing Black Smoke

If your lawn mower is blowing out white smoke, it typically means that the fuel or carburetor systems are not working as they should. These systems are responsible for adequately mixing gas and air before the fuel burns in the combustion chamber.

So when any of these systems malfunctions, the result is an air-fuel mixture that is unsuitable for burning into the combustion engine. And when this air-fuel mixture has a higher fuel ratio than required, the fuel burns “too rich,” creating black smoke.

However, there could also be other problems causing black smoke, such as:

  • Blocked Air Filter
  • Choke Set or Stuck “On”
  • Fault Carburetor Adjustments

So, what can you do to fix the problem? Well, first of all, figure out what is wrong with the lawnmower. If it is a clogged air filter, replace or clean them. If it is a stuck choke, get it fixed.

However, more often than not, the problem lies within the carburetor. And to fix it, you will have to take it to a pro, as setting it requires skill and proper knowledge.

Final Thoughts

Lawnmowers are amazing machines. They are easy to use, require little to no maintenance, and often last for years if taken care of properly. However, they can sometimes run into problems, and the emission of white, blue, and black smoke is widespread.

The issues that cause smoke in lawnmowers are often simple to fix. You can do it yourself. However, even if trying everything you read in this article, the issue stays; you must take your mower to a professional and seek assistance before it is too late.

If you don’t know what you are doing, you could end up doing more harm than good.

Frequently Asked Questions

What would cause a lawn mower to smoke?

An engine on a lawnmower will typically start belching out blue or white smoke if the engine oil has made its way to the combustion engine, where it will burn and produce smoke.

How do I fix white smoke from my lawn mower?

If you want to fix white smoke from your lawnmower, you first need to consult its manual. Then, troubleshoot according to the instructions. If the problem persists, I highly recommend you seek professional assistance before it is too late.

Why is my electric mower smoking and smelling like burning?

The four most common causes of smoking and burning smell from an electric lawn mower are a jammed blade, overheating, worn-out engine, and faulty wiring.

Sources for Further Reading

Lawn mower tune-up | University of Delaware. (2023). Retrieved 1 January 2023, from https://www.udel.edu/udaily/2022/march/lawn-mower-tune-up/

Electric Lawn Mowers – SEDAC | Smart Energy Design Assistance Center at The University of Illinois, Urbana-Champaign. (2022). Retrieved 1 January 2023, from https://smartenergy.illinois.edu/electric-lawn-mowers/?utm_source=rss&utm_medium=rss&utm_campaign=electric-lawn-mowers

Mowing practices for healthy lawns. The University of Minnesota Extension. (2023). Retrieved 1 January 2023, from https://extension.umn.edu/lawn-care/mowing-practices-healthy-lawns

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