17 Reasons Your Lawn Mower Is Smoking(+Quick Fix)

A lawn mower can develop issues after getting used for a long time. A lawn mower releasing smoke is a major problem, and maximum house owners complain about it. 

The primary reasons behind a smoky lawn mower are excessive oil, clogged filters, damaged engine components, an overloaded mower, gasket issues, or wire issues. To fix the issue, diagnose the problems individually, then take the necessary steps to repair/replace the damaged parts.

You can analyze some problems from the smoke color. This guide will share the smoke colors, explain the major behind the smoke, and provide some quick fixes. 

Different smoke colors released by the lawn mower

A lawn mower can release different types of smoke colors, and you can identify the real problem in your lawn mower from these colors:

The mower releases 4 common smoke colors:

Blue smoke 

• Excessive oil throughout the engine
• Oil split on the engine case
• Damaged head gasket
• Lawn mower upgradation

Gray smoke 

• Burning oil due to worn-out engine
• Depleted oil levels
• Oil burning in the combustion chamber

White smoke

• Excess oil in the lawn mower
• Overflowing of the oil affects the crankcase’s functions

Black smoke 

• The fuel and air mixture is unbalanced
• Dirty air filters
• A problem with the carburetor

Let’s discuss these issues one by one. 

1) The motor is overheating.

An overheated motor is a common cause behind a smoky lawn mower. Some common reasons behind an overheated motor are:

• Dirty motor: The mower motor becomes dirty over time and will overheat. 
• Something caught in the blades: If something gets caught in the blades, it struggles to work and overheats. Make sure the blades are free of dirt and debris.
• Tall grass: Tall grasses put extra strain on the motor and overheat it.
• Old mower: An old mower struggles to work efficiently and overheats.

Some signs of an overheated motor include:

• The mower blades stopped spinning.
• Mower started to smell like burning.
• Mower smoking. 

How to fix the problem?

If you see it smoking, you must take the lawn mower to the repair shop. 

The technician will fix the problems behind the overheating and fix your machine.

Besides that, you can follow some steps to keep your mower from smoking:

• Clean your lawn mower regularly, especially the underside of the deck and around the blades. 
• Remove the dirt and debris from the blades. 
• If the grass is taller than 3 inches, cut a few inches from the top and start mowing. 

2) Worn-out motor

The lawn mower’s motor wears out over time and releases smoke if not replaced. It struggles to work and ends up releasing smoke. 

Some signs of a worn-out motor include:

• The mower is not running efficiently
• Mower smoking every time
• You have an old mower

How to fix it?

If the motor is damaged, replace it with a new one. 

Before replacing the whole motor, take the lawn mower to a professional to confirm that the motor is the main issue. 

Professionals can detect the right cause and repair the damage instead of replacement. 

Since getting a new motor is a huge investment, you should confirm whether the machine requires replacement or repair. 

In that way, you can save money. 

If you replace the motor, here are a few tips:

• Select a motor having the same voltage as the previous one. 
• Select the motor from the same manufacturer. 
• Please ensure the motor’s model number is the same as the old one, or at least it matches the make and model of the lawn mower. 
• Go through the owner’s manual for the motor and mower compatibility. 

Also read:

• 9 Reasons Your Lawn Mower Is Turning Over But Not Starting
• 3 Reasons Your Lawn Mower Won’t Start After Winter (+Quick Fix)
• 4 Signs That Your Lawn Mower Engine Is Blown (+Fix)

3) Overloaded mower

An overloaded mower struggles to function, gets overheated easily, and releases smoke after some time. 

Some causes behind an overloaded mower include:

• Tall grasses
• Dull blades
• The mower machine is running too fast. 

How to fix it?

If your lawn mower is smoking due to overheating, follow these tips:

• Try mowing your garden often to prevent tall grass. If the grass becomes taller than 3 inches, cut it short and mow. 
• Sharpen the mower blades in time. 
• While mowing, be slow and take your time instead of hurrying. 

4) Wire shorting

Another reason behind a lawn mower releasing smoke is short in the wiring. 

Wire shorting occurs when the wires are damaged or frayed. 

It can further cause the electrical current to arc.

The current will create a lot of heat and cause the insulation to burn. 

Additionally, the short circuit will damage the internal components of the lawn mower and lead to its failure. 

How to fix it?

If the wiring is damaged or frayed, you must repair or replace them. 

So, before working with the lawn mower wiring, you should disconnect the mower from the main power source. 

After disconnecting the mower, follow the steps below:

• Check the wiring in the mower. If there are signs of damage, like frayed or exposed wires, you should repair or replace them. 
• Reattach the loose wires tightly. 
• If the wire damage is beyond repair, purchase new wires and install them with the help of a professional. 

Also read: Why Is My Lawn Mower Spark Plug Wet? (3 Possible Problems+Fix)

5) Worn-out blades

When the blades have worn out, the motor will overwork, leading to overheating and smoking. 

Some signs behind worn-out blades are:

• The mower does not cut the grass properly. 
• The mower leaves streaks in the grass. 
• Noisy mower.

How to fix it?

Replace the worn-out blades. 

While replacing, you can understand whether the blades need sharpening or replacement. 

Check the manufacturer’s website or the owner’s manual to get the correct blade size for your lawn mower. 

Also read:

• Is It Better To Sharpen Or Replace Mower Blade?
• 9 Ways To Sharpen A Lawnmower Blade Without Removing It (+Mistakes To Avoid)
• How Often Should Lawn Mower Blades Be Changed? (+Mistakes to avoid)

6) The deck has gathered too much grass and debris.

The deck removes the grass and debris from the blades and mower motor and encourages smooth functioning. 

Without regular cleaning, it will accumulate grass and debris over time, making your motor struggle, overheat, and release smoke. 

The blades will struggle to spin properly. 

As a result, it won’t be able to cut the grass effectively. 

Some common signs of a dirty mower deck include:

• The deck is visibly dirty. 
• The grass and debris accumulated on the deck are visible. 
• The mower leaves grass clumps and debris trail. 

How to fix it?

If the mower deck is too dirty, you should clean the underside of the deck properly. 

Some tips for cleaning the mower deck are:

• Please turn off the mower and disconnect it from the main power source. 
• Tip the lawn mower on the side to access the deck. 
• Use a putty knife or a stiff brush to clean the deck properly and remove the accumulated grass and debris. 
• Take a garden hose and rinse the deck to remove the remaining dirt and debris. 
• Let the deck dry before you use the mower again. 

Also read: 10 Reasons Your Lawn Mower Is Not Cutting Well (+Quick Fix)

7) Worn-out or broken mower belt 

The belt drives the mower blades. So, the blade gets affected when the belt is worn-out or broken. 

As a result, the machine will overwork, overheat, and release smoke after some time. 

Some signs include:

• The blades are not spinning. 
• Mower makes a squealing noise. 
• Visible damage in the belt. 

How to fix it?

If the belt is damaged, replace it with a new one. 

The good thing here is that the cost of the mower belt is cheap and easily available. 

Some tips for the right belt type are:

• Check the manufacturer’s website or owner’s manual to select the right belt size and type. 
• Measure the old belt to buy the right size for your lawn mower. 
• You can also take the old belt to the market to receive the exact belt. 
• Ask the sales associate for the best belt recommendations. 

For better results in the mower, consult a professional to install the new belt. 

You can assure that it is correctly installed and won’t face any further issues. 

8) Blocked discharge chute

The discharge chute helps remove the grass clippings away from the mower blades and out at the back. 

If the discharge chute is blocked, the grass will build up under the deck. As a result, the mower’s motor will overheat and release smoke. 

A few signs of a blocked discharge chute are:

• The grass is not discharging from the back of the mower. 
• The engine is working hard and overheating. 
• The grass is building up under the deck. 

How to fix it?

Clear the lawn mower’s discharge chute if it is clogged. Here are the steps to clean the discharge chute:

• Turn off the mower at the main power source. 
• Remove the discharge chute. 
• Take a garden hose to rinse the discharge chute and remove the buildup of grass and debris. 
• Reattach the discharge chute back in place. 

Avoid causing any damage or tear to the discharge chute while clearing. Otherwise, you will have to replace it. 

9) Old mower

Since the lawn mower is a machine, it will have a lifespan. 

Once the machine has completed its shelf life, it won’t work efficiently as before. 

As a result, it will struggle to work, overheat, and release smoke. 

So, when your old mower starts to smoke, it is time to buy a new one. 

Some common signs include:

• The mower becomes harder to start. 
• The mower does not run efficiently and smoothly as before. 
• The mower leaves behind clumps of grass. 

How to fix it?

Though mower replacement is not the cheapest option, it can save you from the hassle of several repair costs. 

Besides, the new mower will not cause any smoking issues after a replacement.

When you shop for a mower, please read the reviews first to find out how well it can perform. 

One good option is EGO Power+LM2101 21-Inch 56-Volt Lithium-ion Cordless Lawn Mower 5.0Ah Battery and Rapid Charger Included.

It works for about 45 minutes without any interrupted runtime. It also contains a 21-inch cutting deck for fast mowing. 

10) Mowing for too long

An electric mower can start smoking if you have been mowing for too long. 

These machines are not designed to run for hours without any interruption. 

So, if you use it for a long time, it will overheat and release smoke. 

How to fix it?

The only fixation here is to give your mower a break between the mowing. 

Please turn off the mower and let it cool down for some time. After that, start mowing again. 

Frequent breaks will prevent damage and give your mower a prolonged shelf life. 

11) Overfilled oil reservoir

Using new oil in the lawn mower can accidentally fall too much and cross the fill line. 

When this occurs, your machine will burn the extra oil and release smoke. 

It will last for a couple of minutes and then fade away. 

How to fix it?

Do not panic if you see this. 

It is better to be careful while filling oil and avoid filling too much oil. 

Some lawn mowers work fine even with over-filled oil because they have a line to siphon the excess oil during overage. 

12) Gas or oil spilled on the engine.

While filling the mower, gas or oil can accidentally spill on the engine. 

Whenever you start the engine, the gas or oil spilled on the engine will burn off the gas and the oil from the surface and cause smoke. 

How to fix it?

You need to be careful while pouring the oil through the tiny holes. 

There is nothing to panic about here as it is harmless. 

Once the gas or oil has been burnt off, the smoke should disappear. 

Also read:

• 16 Easy To Follow Steps To Clean Lawnmower Fuel Filter
• 7 Ways To Drain Gas From Push Lawn Mower Without Siphon?
• How Much Gas Can A Lawnmower Hold? (+Average Gas Usage)
• How to Transport Gas For Lawn Mower? (Ideal Storage+Safety Instruction)
• Should You Use Premium Gas In Your Lawn Mower?

13) Lawn mower used over steep slopes

When you use your lawn mower for steep slopes for a very long time, the liquid inside the machine will run downwards, pool around the areas, and come out of their respective reservoirs. 

As a result, the lawn mower will burn off these excess liquids and release smoke. 

It is the same as tank overfilling and gas or oil spills. 

How to fix it?

Avoid using the lawn mower over steep slopes for a very long time. 

Instead, you may have to clean those areas yourself, especially yards with sharp gradients. 

However, if you must run it, be careful. 

If your lawn mower releases smoke, it should fade after some time.

14) Bad oil seals

Bad engine seals or gaskets are a serious reason behind a smoky lawn mower. 

These seals are called piston rings that form a seal between the piston and the cylinder wall. 

The gasket or seals are made of graphite and metal. 

One common sign behind a problematic seal is a popping sound from the engine. 

When the seals crack and erode, they leak the oils into the combustion chamber and create smoke. 

Corroded oil seals will become a serious problem because the oil will keep leaking into the engine and get burnt off until it fades. 

Over time, your engine will lose all the lubricant it needs. 

How to fix it?

You need to get your seals checked and buy a new one. 

Take the old one to the shop or consult the expert or manufacturer’s manual to get the right seal matching your machine’s make and model. 

15) Clogged air filter

When the air filter gets clogged, the air cannot flow to the engine. 

Due to this, it will create a fuel imbalance and lead to smoke during use. 

Clogged filters will also let grass and debris fall into the engine. 

This dirt and debris will burn up and create smoke. 

If your machine releases a small amount of smoke, you should check the air filters for dirt and debris. 

How to fix it?

You should replace or clean the filters if it is clogged. 

Replacing or cleaning the air filter is easy and should be done every three months. 

You will have to change the filter cover for most machines. 

Pull out the cover, line up the new air filter at the base, and reassemble the cover. 

Also read: Can You Run A Lawn Mower Without An Air Filter?

16) Dirty or ill-adjusted carburetor

A dirty carburetor will make your lawn mower release smoke. 

When the carburetor gets filled with grime, it will create a flake-off and burn, thus the smoke. 

An ill-adjusted carburetor will have the same issue. 

How to fix it?

Clean the carburetor with a carburetor spray. 

You can get it from any local auto shop or home improvement shop. 

Also, go through the owner’s manual and figure out how to adjust the carburetor. 

17) Gas in oil and vice versa

A mixture of fuel and oil will cause the lawn mower to release smoke. 

It occurs when you accidentally pour oil into the fuel tank. 

When the fuel gets mixed with the oil, it will sip into the oil chambers. 

It indicates that the carburetor oil has failed. 

As a result, your lawn mower will release smoke. 

You can detect defective engine oil when you smell gas from it. 

How to fix it?

If you have poured oil into the fuel tank, drain the fuel tank completely. 

After that, wash it with fuel and replenish it. 

If the fuel gets into the oil chambers and mixes with it, change the oil and clean the carburetor very well. 

How to prevent the lawn mower from smoking?

To prevent the lawn mower from releasing smoke, follow the following tips:

• Check the oil levels from time to time. It will keep the lawn mower balanced at ground level and reduce the possibility of tilting or oil spilling. 
• Use oil suitable for your mower. 
• Keep the crankshafts free from oil leakages. 
• Ensure that the gaskets, rings, and cylinders are in good shape. 
• Check and replace the air filters every 3 months. 
• Examine the tilting angle of the mower engine. It should not be greater than 15 degrees. 
• Give your mower a break after every 45 to 60 minutes. 
• The grass should not be taller than 3 inches. If it is, cut them short and then use your mower. 
• Perform regular maintenance of your lawn mower. 

Final thoughts

There are various reasons behind a smoky lawn mower. 

Some reasons are quite common, while others need an expert’s attention. 

To prevent the lawn mower from smoking, consult preventive measures. 

Since the engines differ based on the mower’s make and model, consult the owner’s manual before proceeding with troubleshooting steps. 

Wear protective gear before troubleshooting the mower issues

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Reference: Lawn Mower Technology, Lawn Mower Safety, Lawn Mowing, Lawn Care, Mowing your lawn.