Is Your Lawn Mower Smoking? Here’s What to Do!

The sweet scent of freshly cut grass is a hallmark of summer. But what happens when that idyllic image is tainted by a plume of smoke rising from your trusty lawnmower? Suddenly, your carefree weekend chore becomes a stressful situation. Don’t panic! While lawnmower smoke can be alarming, it’s often a sign of a solvable problem. This article will guide you through the common causes of lawnmower smoke, provide practical troubleshooting tips, and empower you to tackle the issue head-on. We’ll cover everything from identifying the source of the smoke to understanding potential safety hazards, ensuring you can get your mower back in tip-top shape and back to enjoying your well-manicured lawn.

A Short Overview

Smoke from a lawnmower usually indicates an issue with the engine’s combustion process. This could be due to insufficient lubrication, faulty spark plugs, a clogged air filter, or a problem with the carburetor. Understanding the cause of the smoke is crucial for determining the necessary repair.

Identifying the Source of the Smoke

Before diving into troubleshooting, it’s essential to determine the type of smoke you’re seeing. The color and density of the smoke can provide valuable clues about the underlying problem.

1. Blue Smoke:

Blue smoke typically indicates burning oil, a sign of an internal engine problem.

Potential Causes:

  • Worn Piston Rings: Worn piston rings allow oil to seep into the combustion chamber, where it burns and creates blue smoke.
  • Valve Stem Seals: Deteriorated valve stem seals can also leak oil into the combustion chamber.
  • Overfilled Crankcase: If the crankcase is overfilled with oil, the excess can be drawn into the combustion chamber, resulting in blue smoke.

2. White Smoke:

White smoke usually indicates burning coolant, suggesting a serious problem with the cooling system.

Potential Causes:

  • Cracked Cylinder Head: A crack in the cylinder head can allow coolant to enter the combustion chamber, leading to white smoke.
  • Blown Head Gasket: A blown head gasket can also allow coolant to mix with the combustion process.
  • Faulty Radiator Cap: A faulty radiator cap can cause coolant to overheat and leak into the engine.

3. Black Smoke:

Black smoke often indicates incomplete combustion due to a rich fuel mixture.

Potential Causes:

  • Clogged Air Filter: A clogged air filter restricts airflow, resulting in a rich fuel mixture and black smoke.
  • Faulty Carburetor: A dirty or malfunctioning carburetor can also lead to an over-rich fuel mixture.
  • Improper Spark Plug Gap: An incorrect spark plug gap can hinder the combustion process, causing black smoke.

Troubleshooting and Repair: A Step-by-Step Guide

Once you’ve identified the type of smoke, you can begin troubleshooting and addressing the underlying issue.

Important Note: Before working on any engine, it’s essential to disconnect the spark plug wire and ensure the engine is completely cool to prevent burns or injuries.

1. Check the Oil Level

Start by checking the oil level in your lawnmower.

  • Low Oil: If the oil level is low, it could indicate an oil leak. Inspect the engine for any visible leaks and address them accordingly.
  • Overfilled Oil: An overfilled crankcase can contribute to blue smoke. Correct the oil level to the recommended mark.

2. Inspect the Air Filter:

A clogged air filter can lead to black smoke.

  • Remove and Clean: Carefully remove the air filter and check its condition. If it’s dirty, clean it thoroughly using a brush, compressed air, or a mild detergent solution.
  • Replace: If the air filter is severely damaged or beyond cleaning, replace it with a new one.

3. Check the Spark Plugs:

  • Inspect: Remove the spark plugs and inspect them for wear, fouling, or damage.
  • Clean or Replace: If the plugs are dirty, clean them using a wire brush. If they are damaged or worn, replace them with new ones of the correct type.
  • Gap Adjustment: Ensure the spark plug gap is properly set according to the manufacturer’s specifications.

4. Examine the Carburetor:

A faulty carburetor can contribute to both black smoke and blue smoke.

  • Clean: If the carburetor is dirty, clean it thoroughly using a carburetor cleaner and compressed air.
  • Replace: If the carburetor is damaged or beyond cleaning, replace it with a new one.

5. Inspect the Cooling System:

  • Check Coolant Level: Check the coolant level in the radiator and ensure it’s at the proper level.
  • Inspect for Leaks: Look for any signs of coolant leaks in the hoses, radiator, or engine.
  • Pressure Test: Consider taking your mower to a repair shop for a pressure test to check for leaks in the cooling system.

6. Seek Professional Help

If you’re unable to identify the cause of the smoke or the problem persists after troubleshooting, it’s best to seek professional help from a qualified lawnmower repair technician. They have the tools, experience, and knowledge to diagnose and fix more complex engine issues.

Safety Precautions When Dealing with Lawn Mower Smoke

Working on a smoking lawnmower requires caution. Here are some safety precautions:

  • Wear Protective Gear: Always wear safety glasses, gloves, and long pants when working on any machinery.
  • Work in a Well-Ventilated Area: Ensure adequate ventilation to prevent inhaling potentially harmful fumes.
  • Fire Extinguisher: Keep a fire extinguisher nearby in case of a fire.
  • Consult the Owner’s Manual: Refer to your lawnmower’s owner’s manual for specific safety instructions and warnings.


While a smoking lawnmower can be alarming, it’s not necessarily a cause for despair. By understanding the different types of smoke and following these troubleshooting steps, you can often identify and fix the problem yourself. Remember, if you’re unsure about any repair or the issue persists, it’s best to consult a professional lawnmower repair technician. With a little knowledge and caution, you can get your lawnmower back in working order and enjoy a well-manicured lawn in no time.


1. Why is my lawn mower smoking?

There are several reasons why your lawn mower might be smoking. The most common culprits are:

  • Engine oil: If you’re seeing blue smoke, it’s likely that your engine is burning oil. This can be caused by worn piston rings, valve seals, or a bad head gasket.
  • Fuel: If you’re seeing black smoke, your lawn mower is probably burning too much fuel. This can be caused by a clogged air filter, a faulty carburetor, or a dirty spark plug.
  • Overheating: If you’re seeing white smoke, your lawn mower might be overheating. This can be caused by a lack of coolant, a clogged radiator, or a faulty thermostat.

2. Is lawn mower smoke always a problem?

Not necessarily. A small amount of smoke during startup is normal, especially if your lawn mower is older. However, if you’re seeing excessive smoke, or if the smoke is accompanied by other symptoms, like a loss of power, it’s important to address the issue as soon as possible. Ignoring a smoking lawn mower can lead to further damage and costly repairs.

3. How can I prevent my lawn mower from smoking?

The best way to prevent your lawn mower from smoking is to perform regular maintenance. This includes:

  • Changing the oil regularly
  • Cleaning the air filter
  • Inspecting the spark plug
  • Checking the fuel lines and carburetor
  • Ensuring the coolant level is adequate

4. What if I see blue smoke coming from my lawn mower?

Blue smoke typically indicates that your lawn mower is burning oil. This is a sign of wear and tear on your engine, and it’s important to address the issue right away. If the smoke is excessive, you might need to replace worn components like piston rings or valve seals. A qualified mechanic can help you diagnose the problem and recommend the necessary repairs.

5. What if I see black smoke coming from my lawn mower?

Black smoke is a sign that your lawn mower is burning too much fuel. This can be caused by a number of factors, including a clogged air filter, a faulty carburetor, or a dirty spark plug. It’s important to clean or replace these components as needed to ensure proper combustion. In some cases, you might need to have your carburetor adjusted by a mechanic.

6. What if I see white smoke coming from my lawn mower?

White smoke is often a sign of overheating. If you see white smoke, you should immediately stop your lawn mower and allow it to cool down. Once it’s cooled, check the coolant level and add more if necessary. If the coolant level is adequate, the problem might be caused by a clogged radiator or a faulty thermostat. You may need to consult with a mechanic to diagnose the issue.

7. What are some common mistakes that cause lawn mower smoke?

Several common mistakes can lead to your lawn mower smoking. These include:

  • Using the wrong type of oil: Using oil that’s too thick or too thin can lead to engine problems, including excessive smoke.
  • Overfilling the oil tank: Overfilling the oil tank can cause the engine to burn oil, leading to blue smoke.
  • Neglecting regular maintenance: Regular maintenance is crucial for preventing lawn mower smoke.

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