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Why is My Lawn Mower Smoking? 5 Reasons Why

Mowing your grass can bring great pleasure to us lawn connoisseurs and is a great way to keep your yard looking neat and tidy. It can be frustrating when your mower might not want to keep up its end of the deal, though, and especially you start seeing smoke. 

Why is my lawn mower smoking you ask? Here are five common reasons why.

Why is my lawn mower smoking
Lawn mower smoking – via Youtube

Why is My Lawn Mower Smoking?

The wrong fuel type

There are three types of push mower motors available for everyday folk to purchase; Electric motors, two-stroke, and four-stroke. 

Two-stroke and 4-stroke are the two combustion engine types. Here’s a quick explanation of the difference between the two. So why is my lawn mower smoking?

Because the engines work in different ways, they require slightly different fuels.

  • 2-stroke engines need their oil mixed into the fuel to keep the motor lubricated.
  • 4 -stroke engines get their oil from a separate reservoir in the mower, and they run on regular unleaded fuel. 

If you use a 2-stroke oil and fuel mix in your 4-stroke engine, there will be too much oil during combustion, and your mower can billow with smoke. 

If you use regular unleaded fuel in your 2-stroke engine, there’s no oil present, which causes your engine to struggle, strain, and seize. 

You can also get too much oil in your fuel if you use the wrong ratio when mixing your 2-stroke fuel.

As a side note, electric motors should never smoke unless something catastrophic has happened. You should immediately stop work and take your electric mower to a repair shop if you see any smoke when using one.

Fuel and oil getting onto your mower

Another possible reason why your lawn mower is smoking again comes back to fuel and oil.

When filling your mower with fuel or oil, make sure you don’t spill any. Not only will spilled fuel kill grass, or stain anything it’s spilled on, it also runs the risk of igniting when your engine gets hot.

If you’ve ever seen fuel or oil on fire, you’ll know that it’s a smoky affair.

If you do happen to spill anything when refueling, wipe it off as best you can with a rag. Always give your mower a visual check over before mowing to check for any leaking fuel or oil as well.

Built-up grass is burning

Depending on where you live, dry grass and leaves that get caught up in between the engine and the body of your mower can catch fire and begin to smoke. 

While not a common scenario, it can be a reason why your lawn mower is smoking. 

Dry organic matter that is pressed hard against a hot combustion engine can begin to smolder and smoke as you push your mower along. If it catches fire it can cause grease and oil on your mower to ignite. This can then even begin to melt any plastic parts of your mower.

To help stop this, always wash or blow down your mower after use. Having a nice lush green lawn, and avoiding mowing on hot dry days can also help stop this from happening. 

Dirty air filters.

Your combustion engines run by igniting a fuel and air mixture via the spark plug to make the motor turn your mower blades. But why is my lawn mowing smoking?

Oxygen gets into the combustion chamber through air-intakes in your mower. The engine sucks in air for use in combustion as it turns over. Air intake inlets are covered by air filters, which stop dust and grit from getting inside the engine and causing damage.

If your air filter is dirty and is becoming blocked, your engine won’t get enough air, and the air-fuel mix with be too rich with fuel. This will mean that the fuel won’t burn properly. Too much fuel in your mix will cause the engine to begin to smoke, and eventually, it will stop running.

You can help solve this by removing and cleaning your air filter regularly. You can also have your mower serviced by a mechanic every year.  

If you’d rather keep it to DIY, you can easily find replacement air filters for your mower.

Engine problems.

Obviously, smoking mowers can be from something more serious and harder to fix than just some poor fuel or a bad air filter.

Internal components of your mower that become worn or damaged over time can have smoking as a symptom. 

Damaged piston rings, carburetors, exhausts, or head gaskets can all cause smoke to waft out of your mower.

Unless you’re a mechanic, a lot of these issues will need professional repair. To help avoid your mower getting to this point it’s important to do proper lawn mower maintenance. It also really pays to get your machines serviced by a professional regularly.


Summing it all up.

If your asking yourself the question “Why is my lawn mower smoking” consider these five things.

Make sure you’re using the correct fuel for your mower. Two-stroke engines need fuel with oil mixed in. Four-stroke mowers need regular unleaded but need their oil added to a separate reservoir. 

Check that your two-stroke fuel blend is the correct ratio for your mower.

When filling up your fuel or your oil, make sure you clean up any spills so that they can’t ignite and smoke while you’re mowing.

Clean your mower after each cut to make sure no caught grass can dry out and build up in the nooks and crannies of your mower body. If these get stuck against a hot part of the engine, they can begin to smolder or even catch fire.

Have your air filter checked, cleaned, and replaced regularly to ensure that the engine can get the correct airflow for proper ignition. Blocked air filters will cause your engine to sputter, smoke and stall.

Get your mower regularly serviced to keep on top of any issues before they become serious.

Internal problems like worn rings and seals, damaged carburetors, and exhausts can cause smoking.  

So over to you? Do you have any other reason why your mower might be smoking? Let us know below!