Why Is My Lawn Mower Smoking? 9 Reasons & Solutions

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Lawn Mower Operational Issues

It’s a fine day and you plan to give your lawn the much-needed grooming, but as you start the mower engine, it starts billowing smoke. It’s the worst you can even imagine, right?

Even though the lawn mower smoking would be the last thing you would want to see, it’s not unusual for the lawn mower to emit a different color of smoke. But the immediate question that may strike your mind is, why is my lawn mower smoking? 

There are numerous causes why your lawn mower emits blue, black, or white smoke. The most common reason is oil leaking from the exhaust or spillage if you’ve overfilled the tank. Motor overheating is another cause for an electric lawn mower to smoke, leading to wire breakage and short circuit.

There are several other reasons for the lawn mower to smoke. In this article, I’ll discuss all the probable causes of lawn mower smoking and their solutions. Keep reading for more.

Key Takeaways

  • Lawn mowers smoking black, blue, and white smoke is very common. 
  • The primary cause of lawn mower smoking is oil leaking from the exhaust. 
  • Motor overheating is another cause of electric lawn mower smoking. 
  • There are multiple other causes for the issues like low oil levels, clogged air filters, worn out motor, dirty discharge chute, etc. 
  • You need to maintain your lawn mower and check for probable causes to keep the lawn mower protected from further damage. 

Top Nine Causes of Lawn Mower Smoking and Effective Solutions

Lawn Mower Smoking

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Mentioned below are some of the main reasons your lawn mower may emit smoke:

1. Low Oil Levels

Low oil levels are one of the causes of lawn mower smoke. Like your car, the lawn mower engine needs appropriate levels of oil to work smoothly. If smoke is coming out of the engine, this could be a sign of not enough oil. 

Operating the lawn mower at a low oil level may cause increased friction up to the point that it heats up the internal parts and causes smoke. 

Please note: Similar to low oil levels, overfilling oil can also cause smoking in the lawn mower. The smoke comes in the form of burning oil, which usually has a blue or white hue. 

The Solution

The simple solution to the problem is to fill the lawn mower tank to appropriate levels. Don’t underfill or overfill it. Use the dipstick to check oil levels if you notice symptoms like noise, overheating, engine heating up, etc. 

2. Motor Overheating

An overheating motor will also lead to smoking in an electric mower. But what causes the motor to overheat? There are several causes of the problem, such as:

  • You didn’t clean the inside of the motor, and it got too dirty. A dirty motor can’t cool itself, leading to overheating. 
  • If the grass is too tall, it can put force on the motor, causing overheating. 
  • Something has been stuck in the blade for a long time, leading to overheating. Make sure to inspect the blades regularly before and after using the lawn mower. 
  • A very old electric lawn mower can also overheat easily.  

The Solution 

Since a dirty engine is one of the primary reasons for overheating, keeping it clean is the top solution. To clean it, remove the mower casing and clean the inside using a soft brush or compressed air. 

Another way to prevent overheating is to keep the machine’s cutting height a little higher than where it’s set now. Pro tip: Never cut more than 3rd of the length of grass in one go. 

3. Clogged Air Filters

If your lawn mower is emitting blue or white smoke, stop the machine and check the air filter once the engine cools down. Clogged air filters are another common cause of lawn mower smoking, similar to having a stuffy nose. Clogged air filters mean that the combustion chamber isn’t getting enough oxygen, leading to a rich oil mixture and smoke being emitted. 

The Solution 

The easiest solution to the problem is replacing the air filters. You should anyway replace the air filter once a year as part of your yearly maintenance. 

If the smoke issue persists even after replacing the air filter, it means the lawn mower’s carburetor needs adjustment. You can either do it yourself or get help from a professional. 

4. Spark Plug Issues

The spark plug is an essential component in the lawn mower as it ignites the fuel and air mixture in the cylinder. Examining the spark plug regularly is essential because a dirty one can cause various problems, and smoking is one of them. 

If the spark plug is dirty or too old, or if the plug’s gap is too large, it won’t start the mower and will sputter black smoke. 

The Solution 

Many people would start adjusting the plug gap as an immediate solution, but getting a new one is the best thing to do as it’ll cost you only a few dollars. 

5. Carbon Build-up

Excessive carbon build-up can also lead to lawn mower smoking. But what is the cause of carbon build-up? Incomplete combustion is one of the top causes of carbon build-up. Carbon build-up can happen if the plug is designed to run at a cooler temperature or if you keep the machine idle more than when you run it at full speed, which the engine needs for proper combustion. 

If the carburetor sprays too much fuel into the combustion chamber, the fuel burns cooler. The smoke resulting from such a cool burn can ruin the air filter, plug, and the spark arrestor that covers the engine’s exhaust port. This ultimately can cause smoking in the lawn mower. 

The Solution 

Regular cleaning of the air filter and the cylinder is essential to prevent carbon build-up. Additionally, you should only use quality oil to run the engine. Maintain regular oil changes as recommended by the manufacturer, and you can use a fuel additive like AFC to improve combustion and engine efficiency. 

A good quality additive reduces the amount of engine deposit and keeps the engine in pristine condition. If you’re already facing the carbon build-up issue, try increasing the engine’s RMPs to let the engine burn off carbon build-up within the machine. 

Other solutions you can adopt to cure the problem include chemical cleaning, special fuel additives, fuel treatments, etc. 

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6. Fuel Issues

Seeing smoke from the lawn mower could be due to various fuel issues. As I mentioned before, leaking oil from the exhaust is a reason for the problem. If you have recently changed the oil and overfilled the tank, it could be a probable reason for oil leakage, causing blue or white smoke. 

The Solution 

You should change your lawn mower oil after every 50 hours of operation. If you are using old, contaminated fuel, it can cause the engine to smoke and further damage the engine. Additionally, if the carburetor is dirty or damaged, it can also cause fuel issues as it’s responsible for the correct combination of fuel and air. 

To prevent damaging the engine, make sure to change the oil at regular intervals. Also, you should use good quality oil to prevent easy and smooth functioning of the engine. Also, check the oil level using the dipstick located at the reservoir. 

To check the oil level, remove the dipstick, clean it with a rag, and re-insert it in the reservoir. Remove the dipstick again to check the oil levels. If you have overfilled it, drain the oil completely and start refilling it following proper instructions from the user’s manual. 

7. The Deck Has Gathered Debris & Grass

Cleaning Lawn Mower's Deck

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The deck of a lawnmower is responsible for keeping grass and debris away from the motors and blades to help them run smoothly. Therefore, cleaning the inside of the deck regularly is important to keep it running smoothly. 

If you don’t, the deck will start accumulating grass leading to motor overheating and smoking. Moreover, it can also interrupt the smooth rotation of the blades, which will ultimately affect the grass cut. 

Some common signs of a dirty deck are: the mower leaving grass clumps and trails of debris behind, the deck accumulating lots of debris underside of the deck, or the deck being visibly very dirty. 

The Solution 

If you see the above symptoms, you should immediately clean the deck. To do so: 

  • Disconnect the mower from the power source. 
  • Tip it to the side to access the inside of the deck, and use a brush to get rid of all debris and grass. 
  • Clean it further using a hose and let it dry before using the mower again. Make sure there is not even a single droplet of water before you use the lawn mower again. 

8. The Discharge Chute Is Blocked

Lawn Mower Discharge Chute

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Just like the deck, the discharge chute also plays an important role in keeping the grass clipping away from the blade. But if the discharge chute gets blocked, it can cause grass build-up inside the deck. And as you already know, excessive grass build-up will cause overheating and smoke. 

Hence, keeping the discharge chute clean is paramount to avoid the problem. 

The Solution 

The cleaning procedure of the discharge chute is quite similar to cleaning the deck. Here are the detailed cleaning steps: 

  • Turn off the mower and disconnect it from the power source. 
  • Next, remove the discharge chute from the mower and thoroughly clean it using a hose. 
  • Once the discharge chute dries, reattach it. 

9. Worn Out Motor

If you have an electric lawn mower and it’s smoking, an old or worn-out motor is one of the main reasons. Some early signs of a worn-out motor, apart from the smoke, are that the motor isn’t operating as smoothly as it used to. 

The Solution 

The solution in such a case is replacing the motor and getting a new one. However, you can also ask a professional to inspect the motor and see if minor repairs can be done. But it’s better to replace the motor to save additional costs in the future. 

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Why Is My Lawn Mower Smoking? FAQs

1. How Do I Fix White Smoke From My Lawn Mower?

White smoke isn’t very harmful, so you can fix the issue by allowing the spilled oil to burn completely. 

2. Why Is My Lawn Mower Smoking Blue?

The usual cause of blue smoke is burning oil, and the reasons for burning oil are- incorrect oil grade, overfilling the oil crankcase, or operating the engine at higher than 15 degrees.

3. Why Is My New Lawn Mower Smoke When I Start It? 

Overfilling the oil tank is again one of the common causes for even a new lawn mower to smoke. So always be careful while filling the oil tank. 

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Final Thoughts

The lawn mower plays a crucial role in keeping your lawn spick and span, hence it’s important to maintain it in the best possible condition. There are many reasons that can cause your lawn mower to smoke. And there’re, of course, some simple ways to fix the issue. Keep in mind that the earlier you diagnose the problem with your garden equipment, the easier and more cost-effective the solution will be. And if you can’t resolve the repair yourself, it’s best to turn to a professional in the field. 

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