Electric lawn mower smoke. Bad Boy Mower Is Smoking 4 Possible Reasons

3rd August 2023

Lawn Mower Smoking and Sputtering- How to Fix [DIY Solution]

Have you ever experienced that your mower is smoking black or white? It’s truly an embarrassing situation for all who just started their lawn mowing but stopped due to smoking and sputtering. If you want to fix the problem, you first need to know why the lawn mower is smoking and sputtering.

Smoking and sputtering can occur in a lawn mower due to some possible reasons. It may happen due to incomplete combustion, overfilling the lawn mower with excessive oil, tipping it the wrong way, and inflating the gasket.

Don’t worry; if you find such problems in your lawn machine that can cause smoking and sputtering, you can fix them yourself. Let’s dive into the topic.

Reasons Why You Lawn Mower Smoking and Sputtering

Your lawn mower is misfiring, putting out black smoke? Let’s know the key reasons below.

Overfill With Engine Oil:

Like a car, you shouldn’t overfill your lawnmower with excessive engine oil because it can overheat the engine.

Your engine might get locked up due to excessive engine oil in your lawn mower. In that case, the engine will not run well and cause smoke. It is one of the most common things that you may come across.

Note: You will face the sputtering problem in your lawn mower due to using old or wrong fuel.

Tip: Check the air filter to ensure it isn’t overfilled with oil. You can use the dipstick to check the oil level.

Tip Over the Lawn Mower in the Wrong Way:

Another common reason for lawn mower smoking and sputtering is tip over the lawn mower incorrectly. If you tip the mower the wrong way, the chances are that the oil will leak into the tube and restrict the fuel line.

Or, if the oil moves into the breathing tube, oil can restrict the air filter. Thus the engine can’t run and cause the problem.

Tip: You can replace the faulty tube with a new one or replace the air filter.

Inflated Gasket:

If the gasket gets a little crack, it will start leaking out the oil, clogging the fuel line and restricting the engine’s running. Ultimately, the engine will be overheated and cause smoking.

Tip: You can repair the gasket crack or change the faulty one with a new head gasket.

Incomplete Combustion:

It happens because of incomplete combustion. Generally, sputtering or smoking is caused by two things.

The first one is your spark plug either fouling or not working properly. There is no appropriate gapping.
The second reason can be the air filter when it is dirty and not working properly. It can cause incomplete combustion.

Basically, the reason why it causes incomplete combustion (when the spark plug or filter is not working properly) is because of the fuel. The fuel is coming through the lawnmower, but it is not properly burning.

Because of the incomplete fuel burning, it blows out black smoke; your lawnmower will run roughly. You may also experience your lawn mower losing power or backfiring etc.

How to Troubleshoot the Lawn Mower Smoking and Sputtering? Easy 2 Methods

To sort out the problem, the first thing that you usually check is to check the air filter. You should ensure that it is clean and clear, and after that, you must check the spark plug.

Inspect if the plug is really black or carbonated. You may need to change the plug or clean it. Also, inspect the gap and ensure that there is an appropriate one on the spot.

Here, I will explain the process of checking and cleaning the air filter and then the Spark plug. So, let’s come to the diagnosis process.

Step 1- Check the Airport

First of all, you should check the airport. It is all nice. Ensure it should be clean enough. Unscrew the screws and tap the box to open the airport.

Step 2- Inspect the Airport

Once you have removed the airport, inspect it thoroughly. Make sure there should be no dust in excessive amounts.

Step 3- Take off the Foam

For proper cleanliness, take out the foam from the filter and check it thoroughly.

You can see old lawn clippings, dust, and everything like that. Such hurdles add to misfiring and incomplete combustion.

It is a non-effective air filter that deteriorates the overall performance. So you need to clean it. Clean it thoroughly and ensure all the debris and grass particles are removed.

Once it is properly cleaned, reinstall it at the previous place. Check the lawnmower; if it is still sputtering or smoking, then the problem is with the spark plug so check for the spark plug.

Method 2: Check and Fix the Lawnmower Spark Plug?

Here I will teach you three simple steps to check clean and then replace the spark plug if needed. It will boost the engine performance.

Things You Will Need:

Spark Plug Wrench
Hex turning tool
Spark plug wire brush
Spark plug gapping tool

Step 1- Read the Manual

It will help you to finish your job quickly and perfectly if you read the instruction manual.

Step 2- Check for Spark Plug

First, you must remove the spark plug to check it thoroughly.

Start with removing the spark plug wire. You can grip it and go ahead and pull it straight off of the spark plug.

Then move it out of the way, get a spark plug wrench, and place it over the spark plug until you feel it engaged.

Then install the hex turning tool and loosen the spark plug. You may need to turn it on for a few seconds.

Once it is removed, you can inspect the spark plug. You can see it is dark and covered with carbon. You can restore it after cleaning the carbon. Also, check for the gap.

Step 3- Clean the Spark Plug

Take a soft wire brush; it would protect your spark plug from damage.

While cleaning it with a brush, start from the outside edge of the spark plug and then turn it. You will be able to access the entire surface and also check for the spark plug gap.

That looks fairly good now; check for the spark plug gap. You should use the spark plug gapping tool.

Insert the tool between the open and gap in the spark plug on the smallest end; this is point zero to zero.

Then slide the spark plug up until it stops. Check the measurement; it should be less than zero

Reinstall it, but if needed replacement, go ahead to replace it with a new one.

Step 4- Replace the Spark Plug

Take a brand new Spark plug that should be compatible with your engine brand. Then take a spark plug wrench to remove the older one and install a newer spark plug.

Place the new spark plug at the end of the wrench and carefully turn the spark plug. Turn it until you feel the threat set, and keep it turning slowly until the spark plug stops.

Tighten it some more to ensure correct installation.

Once you have tightened it, finally reattach the spark plug wire.

Switch on the lawnmower to test, hope there will be no sputtering or smoking issue. You have done your job well.

Frequently Asked Questions(FAQs):

What are signs that a lawn mower air filter is bad?

You may notice poor engine performance if there is a problem with the air filter. Common signs include hard starting, random misfire or sputtering, stalling, smoking, and failure of fuel system parts.

What does it mean when my lawn mower smokes grey or blue?

If you notice your lawn mower is smoking blue or grey smoke, it means the problem is with the engine. Your engine is burning the fuel inside the combustion chamber. Maybe there is leakage of valve seals or bad piston rings.

There may be an issue with the combustion chamber. Coolant or water is vaporized in the combustion chamber, producing white smoke.

What happens if my lawnmower is sputtering or smoking?

If your lawnmower smokes, there is no harm except an unpleasant mowing experience. It may cause frequent engine stalling if you do not immediately remove the issue.

Final Verdict

Lawnmower smoking or sputtering is a common issue you can fix in a couple of minutes. Air filters, combustion chamber, spark plugs, fuel quality, and poor wiring can be possible reasons for smoking.

You should immediately identify and fix the issue for a smooth mowing experience. If you find it tough to solve the problem, then please don’t hesitate to take professional help.

Bad Boy Mower Is Smoking [4 Possible Reasons]

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I bet you despise hearing bad news. especially when you’re in the middle of cutting the grass and suddenly notice your lawn mower blowing of white smoke; it’s understandable if you have a lot of questions, the most important being: is this a serious issue? Will this problem be an easy fix?

You need to relax and take a few deep breaths because we have a straightforward answer for you. It doesn’t make a difference whether you have a 2-stroke mower or a 4-stroke mower; you shouldn’t run the mower and start looking into the common reasons for this issue.

Common Causes Your Bad Boy Mower is Smoking

Bad boy mowers contain an internal combustion engine, which can have many problems, one of them being smoke emitting from the engine or muffler. There are several reasons this may happen:

Air Filter is Plugged
Insufficient Engine Oil Level
Bad Gasket in Engine
Internal Engine Damage

Insufficient Engine Oil Level in Your Bad Boy Lawn Mower

Not only is it crucial to ensure that your Bad Boy lawn mower has enough engine oil, but it’s also crucial to avoid overfilling it. Your engine may suffer severe impacts and start to smoke if either of these oil levels is too low. Clean the foam air filter element of a Bad Boy.

Your Bad Boy Mower’s Engine Oil Level Is Too Low

Running the mower with insufficient engine oil is one of the most frequent issues that might happen. Although it appears to be a little problem, your laptop could suffer significant damage.

The engine’s moving parts start to produce friction when insufficient oil is present. As a result of this heat buildup, the oil itself may eventually begin to burn. Additionally, the engine parts may start to melt, resulting in white or blue smoke from the exhaust. In some circumstances, the damage can be irreparable, necessitating a complete engine replacement.

It’s crucial to give your mower a thorough checkup, including checking the engine oil level, before each mow: Checking the oil level in your lawnmower takes a few minutes, but it could prevent you from having to make costly repairs later. Before each usage, make sure to check the oil and add extra if necessary.

It’s also crucial to pay attention to the oil’s color; if it begins to appear black or abrasive, it’s time for a replacement.

It’s best to identify this issue quickly and avoid operating your mower under these circumstances: As with most things, it’s considerably simpler (and less expensive) to remedy an issue as it first arises than it is once it has already caused significant harm.

If you have any reason to believe your mower might not have the recommended amount of oil, proceed with caution and wait to use it until you’ve checked (and potentially replaced) the oil.

You should send your lawnmower to a qualified small engine mechanic for analysis and repair if the level lowers quickly once more because there might be a leak somewhere in the system.

The Engine Oil Level in Your Bad Boy Mower Is Too High

Generally speaking, you should always check the oil level in your lawnmower’s engine before using it. However, a lot of individuals are unaware that using too much oil might lead to issues.

Too much oil in the crankcase increases the pressure, which can then push oil into the cylinder and even into the air intake through the valve train. Your lawnmower may sustain severe harm as a result, necessitating pricey repairs.

If you discover that your crankcase has too much oil, adjusting the quantity as quickly as possible is critical.

You can accomplish this by draining a little amount of oil through the oil filter or drain plug. A tiny amount of oil from the fill area can also be sucked out using an oil evacuator or turkey baster.

After removing some of the extra oil, check the level again with the dipstick and drain the oil as necessary until it is at the proper level.

It’s crucial to check your air filter to make sure it isn’t clogged with smoke or covered in grease. If so, swap it out for a fresh air filter to stop your lawnmower’s engine from suffering any more harm.

Bad Gasket in Your Bad Boy Mower Engine

If your mower’s gasket is damaged and engine oil leaks, it may be the cause of the smoke coming from your Bad Boy. A heated surface, such as your muffler, will burn off any excess oil that has spilt onto it and emit a lot of smoke.

Internal Engine Damage on Your Bad Boy Lawn Mower

Without disassembling the engine and carrying out leak down and compression checks, it might be challenging to pinpoint the precise cause of an internal engine issue.

However, there is a straightforward test you may perform to see if your internal engine is malfunctioning.

Remove your spark plug(s) and look for any evidence of oil to finish this inspection. Oil on the spark plug may indicate a piston ring or valve train issue. Even though this check is unable to diagnose your specific issue, it will let you know that a mechanic is required to fix it.

Taking your lawnmower to a small engine repair is crucial to assess the issue and determine the cause if you carry out this inspection and discover oil on your spark plugs. Ignoring an internal engine issue could cause major harm or possibly the engine’s demise.

Your Bad Boy Mower’s Piston Rings Have an Engine Problem

Your engine must be disassembled in order to detect a piston ring issue. Damaged piston rings or scoring is found inside the cylinder wall, oil could enter and burn off, which could cause your Bad Boy lawnmower to start smoking.

Your Bad Boy Mower’s Valve Train Has An Engine Problem

An overheated Bad Boy lawn mower can have a burned valve. Only the cylinder head may be removed and tested for leakdown, which is the only technique to detect burn valve problems.

This examination and repair should be done by a small engine mechanic. The technician must precisely cut the seat and the valve to finish the combustion chamber.

You Bad Boy Mower is Blowing Black, White or Blue Smoke: What’s the Difference?

I always advise using the aforementioned techniques to locate the source of smoke coming from your lawnmower. By examining the hue of the smoke, you might be able to determine most likely its source.

Blue or white smoke is frequently produced when burning excessive amounts of oil. Oil leakage from a harmed piston ring, the valve train, the combustion chamber, or an engine gasket might cause this.

A clogged air filter may potentially be the reason oil is being driven into the cylinder.

When changing the oil, don’t forget to look for oil burning off the muffler or engine as a result of an oil leak or spill.

Black Smoke: Black smoke is produced when fuel is burned too thoroughly. This happens as a result of a clogged air filter, which permits a higher fuel concentration in the fuel-to-air ratio.

The Bad Boy lawnmower can produce dark smoke when operating heavily. Check your mower for another air limitation if the filter is not the problem.

Conclusion

Mowing your lawn should be a relaxing and satisfying experience, but it can quickly become a nightmare if your lawn mower is blowing white, black or blue smoke. If you’re experiencing this problem, you can do a few things to diagnose and fix the issue.

First, check the oil level and grade to make sure that they’re correct for your model of mower. Next, inspect the air filter to see if it needs to be replaced.

Finally, take a look at the angle at which you’re mowing—mowers can start smoking when tilted at angles greater than 15 degrees.

If all else fails, remember that regularly conducting an oil change is one of the best ways to prevent smoking issues (and extend its life overall).

FAQ (Frequent Asked Questions Bad Boy Mower Is Smoking)

How do I fix white smoke from exhaust?

There may be a few possible causes for white smoke coming from the exhaust of your lawn mower. According to two possible explanations, your engine is burning oil or coolant has entered the combustion chamber.

How do I fix blue smoke on my lawn mower?

If your lawn mower is smoking blue smoke, it may be because the oil is too old or dirty. Try changing the oil and see if that fixes the problem.

Can spark plugs cause blue smoke?

Spark plugs that are damaged or worn out can cause blue smoke.

Can low oil cause smoking?

Yes. If the oil level is low, it can cause the engine to run hotter than normal and this can cause increased smoking from the exhaust.

Hey, I’m Zane. I’m a passionate DIY’er who uses my own embarrassing journey to help anyone fix, improve or create their own badass projects one tip at a time.

I’ve kickstarted over 27,600 men women through free guides and videos to help them achieve truly epic results.

I eat a healthy balance of homegrown vegetables and beer. I live in Michigan with my wife and 3-year-old son, who both love and tolerate me!

White smoke from a lawnmower? What the pros say

Every lawnmower owner experiences odd-colored smoke from their mower’s exhaust at some point. Among the different colored smoke, your mower may produce white smoke, which is the most common. It is natural to get worried when you see any smoke coming from your mower’s exhaust, especially if you have a 4-stroke mower because 4-stroke mowers aren’t meant to smoke from their exhaust. Most of the time, white smoke from your mower’s exhaust will go away on its own, but other times, it might not go away, indicating that something is wrong with your mower.

The most probable cause of white smoke is that your lawnmower’s engine burns oil. This can happen due to any of the following reasons:

Tipping the mower on its side or using the mower at a steep slope
You have overfilled the mower with engine oil
Damaged head gasket
Piston ring failure
The petrol you used in your mower had engine oil in it

Some causes of engine oil entering the combustion chamber of your mower’s engine can be resolved by simply letting the mower idle for a while until the smoke clears out. While other causes might require a little more effort to fix, and you may need help from a professional small engine mechanic to stop white smoke from your mower’s engine.

In this article, I will explain the possible causes of white smoke from your mower’s exhaust and how you can fix them.

1 Tipping the mower or using it at a steep angle

1.1 Fix: Tipping the mower or using it at a steep angle

2.1 Fix: Overfilling the engine with oil

3.1 Fix: Damaged or leaking head gasket
3.2 Step 1: Get a replacement head gasket
3.3 Step 2: Remove the cylinder head
3.4 Step 3: Remove the gasket
3.5 Step 4: Add the new gasket
3.6 Remark: check if you have an overhead valve engine

4.1 Fix: Failed piston rings

5.1 Fix: Oil in the fuel of a 4-stroke mower
5.2 Step 1: Locate the fuel line
5.3 Step 2: Remove the fuel line
5.4 Step 3: Collect the spilled gas
5.5 Step 4: Drain the carburetor
5.6 Note 1: Do not tilt the lawnmower
5.7 Note 2: Check for stuck oil

Tipping the mower or using it at a steep angle

If you tip a mower the wrong way or use it at a very steep angle, it can cause the engine oil to make its way into the cylinder and start burning. This is one of the most common reasons why lawnmowers produce white smoke.

People tip the mower to its side or back the wrong way so they can take a look under the deck or replace the blades. Or the lawnmower might have been used at a surface that is too steep. Both of these situations may result in the cylinder filling up with oil and white smoke being produced from the exhaust.

Fix: Tipping the mower or using it at a steep angle

If your mower has started smoking after being tipped over or using it at a steep angle, you can get rid of the white smoke by simply letting the mower run on idle until it burns up the oil that has gotten into the combustion chamber. To know the correct way to tip the mower on its side, read the owner’s manual of your lawnmower.

Similarly, I recommend avoiding using your mower at a surface with a slope of more than 15 degrees, as too steep can cause excess engine oil to enter the cylinder and start burning, resulting in a Cloud of white smoke. Most lawnmowers should be fine if tipped on the side for maintenance with the carburetor and air filter facing upwards.

Overfilling the engine with oil

Engine oil is your friend if you want to make your lawnmower’s engine last as long as possible and keep it running smoothly. Changing the engine oil after regular intervals is part of the normal maintenance routine for your lawnmower. But the important part of every oil change is to avoid filling the mower’s engine with oil and, simultaneously, not to put in less oil than needed.

Oil in the fuel of a 4-stroke mower

If you own a 4-stroke lawnmower, mixing oil in your mower’s fuel is a big no. Many modern-day lawnmowers come with 4-stroke engines because they are more reliable and last much longer than 2-stroke engines. Besides being reliable, 4-stroke lawnmowers have fewer maintenance needs, and unlike a 2-stroke lawnmower, you don’t have to mix oil in its fuel.

If the fuel you put inside your lawnmower has oil in it, then as the lawnmower starts running, it will burn the oil that has been mixed in the fuel and produce a lot of smoke. And if you keep running the engine with engine oil in the fuel tank, it can lead to damage and premature engine wear.

Fix: Oil in the fuel of a 4-stroke mower

Depending upon how much oil got into the fuel tank, you might be able to get rid of oil in the fuel tank by simply running the mower till it burns off the contaminated gas and then filling it with fresh, clean gas in it. If you are certain that very little oil went inside the mower’s fuel tank, it will get dissolved in the gas and get used.

Of course, you will get white smoke from your mower’s exhaust until all the oil has been burnt. But if you are unsure how much oil got mixed with the fuel and want to be on the safer side, then you will have to remove the fuel from the fuel tank and carburetor before filling it with new fuel. You can remove oil-mixed fuel from your lawnmower by following these simple steps:

Bad Boy Zero Turn Overheating?

Step 1: Locate the fuel line

Locate the fuel line that exits the fuel tank and feeds fuel into the engine.

Step 2: Remove the fuel line

Remove the fuel line from where it exits the fuel tank by undoing the clip that holds the fuel line in place and pulling the fuel line off. Or you can follow the fuel line where to the shut-off valve and remove the fuel line where it connects with the shut-off valve.

A shut-off valve is a small knob that allows you to stop the flow of fuel to the engine, and it is pretty simple to locate.

Step 3: Collect the spilled gas

After the fuel line is removed, the fuel will start pouring out of the gas tank, and you can collect it in a pan to avoid spilling it since spilled gasoline can be a fire hazard, so you would want to prevent any spillage on or around the lawnmower.

Step 4: Drain the carburetor

As the fuel tank is emptied, go ahead and locate the carburetor of your lawnmower to drain fuel from it. Lawnmower carburetors have a carburetor bowl underneath the carburetor, containing a small screw or nut that can be used to empty the carburetor.

Simply undo the screw or nut on the bottom or side of the carburetor bowl and let the fuel drain into a pan.

Note 1: Do not tilt the lawnmower

Avoid tilting the mower to drain the fuel out of the mower because this can result in engine oil spilling into the cylinder or the carburetor.

Note 2: Check for stuck oil

If you notice the oil is stuck inside the mower’s fuel tank, you will have to remove the fuel tank and clean it using dishwashing soap or liquid. Pour the soap inside the fuel tank and shake it well so the oil stuck inside it is removed.

Use a can of carburetor cleaner to clean the carburetor by spraying the carburetor cleaner on it. You can find a good carburetor cleaner here.

Final remarks

White smoke coming from the lawnmower should never be ignored as it can potentially be a sign of a serious problem with your mower’s engine that needs immediate attention. Using the details provided in this article, you can easily pinpoint the exact cause of white smoke from your mower, and the troubleshooting process will be much simpler. But one thing is common among all the causes of white smoke from your mower; it mostly occurs due to your lawnmower’s engine somehow burning engine oil.

White Smoke From Lawn Mower: What It Means And How To Fix It

If there’s white smoke coming from your lawn mower, don’t freak out!

There are two common causes – spilled oil or too much oil – and both have simple solutions. You’ll either need to burn off the oil on your engine, or drain some oil from your reservoir.

Is your lawn mower smoking? Here’s what that means and what you can do to fix it.

Why is My Lawn Mower Smoking?

There are a lot of different reasons for your mower to spew smoke. Common causes include excess oil, a blown head gasket, not enough air in the gas tank, or a dirty air filter.

What Does White Lawn Mower Smoke Mean?

For lawn mowers spewing white smoke (or even blue smoke), the likely culprits are an overfilled oil reservoir or oil spilled onto the engine.

You may have overfilled your mower with oil, which then spilled over and caused engine smoking.

Alternatively, if you’ve been mowing on a slope greater than 15º or if you’ve tipped your lawn mower sideways to inspect the mower deck, the oil will spill.

If you’ve accidentally turned your lawn into a DIY rave, there’s no need to panic. White smoke is generally harmless and easy to fix.

Quick Fixes for a Smoking Lawn Mower

Step one, if there’s smoke from a lawn mower, is to shut off the engine immediately. Your safety is the main priority here, so turn off your mower until the smoke clears.

For electric mowers, take out the spark plug so you don’t risk a fire hazard.

After the mower cools and the haze is gone, check the air filter.

For a dirty or clogged air filter, you’ll need to clean it. For a worn-out air filter, you’ll likely need to change it out.

If that’s not the case, replace the parts and restart the mower. Let it run for about 5–10 minutes to burn off any oil that could have entered the lawn mower engine.

If there’s no more blue or white smoke, you should be fine.

How to Fix White Smoke from Lawn Mower

If the quick fixes don’t work and you’ve run your engine for about 10 minutes, then it’s time to get down and dirty. Identify the cause of your white smoke and use the appropriate solution.

White smoke from spilled oil

Oil spills in mowers have a few common causes:

Worn-out seals in the combustion chamber
Cracked crankcase or air leak
Mowing a slope of over 15º incline
Tipping the mower on its side
Overfull oil reservoir
New mower with leftover oil residue

The excess lubricant will leak out onto the mower’s engine, where the oil burns and causes smoke.

In this case, just restart the engine and let it run. Eventually, all the oil will burn off and the engine will stop producing white smoke.

To stop this issue from reoccurring, target the source. Check the owner’s manual for ways to limit oil leaks.

If your lawn has a steep slope, consider levelling it so it places less stress on your mower.

White smoke from too much oil

Double-check the oil level to ensure you didn’t overfill the reservoir.

Use the dipstick to check the engine oil (remember to wipe the dipstick clean first so you get a good reading). Compare the level to the “fill” line on the stick.

If the level is too high, you’ll need to drain oil from the reservoir. Follow the instructions in the owner’s manual for draining and refilling the oil to the fill line.

You may also be using the wrong grade of engine oil, which could cause lawn mower smoke.

Maintain Both Your Mower and Your Lawn

If the smoke problems persist, or you discover a deeper engine problem that you can’t fix, it’s better to take your mower to a repair shop.

You may also need expert help to change the seals on the combustion chamber or fix an air leak in the crankshaft.

For those who hire professional mowing services. keep yourself available in case they report smoke issues with your mower! You can also check to make sure they know these solutions in case a problem arises.

Check your lawn mower regularly to ensure everything is in working order, from the engine lubrication system to the oil seals.

Frequent check-ups let you catch malfunctions or damaged mechanisms before they can cause bigger problems.

Knowing how to tackle white smoke from lawn mower will save you some stress in the long run. Not only will it help your mower last longer, but your lungs will be more thankful – and you’ll get fewer complaints from neighbours too!

Jamie Donovan

Jamie is an Australian horticulturalist and landscape designer. He enjoys writing about landscape architecture, garden design and lifestyle topics.

Why Your Lawn Mower is Smoking (Black, Blue or White Smoke)

The first thing you should do when you notice smoke coming from your mower is to stop the engine to avoid potential engine damage.

A lawn mower is smoking due to a plugged air filter, low engine oil, too much engine oil, a bad engine gasket, a blown seal, an oil spill, or problems with the valve train or piston ring.

You should start with the simple items to check before moving on to the more complicated diagnostics. Wait for the engine to cool and remove the spark plug boot(s) before making repairs.

This post may include affiliate links. Purchases made through these links may provide a commission for us, at no extra cost to you. As an Amazon Associate, we earn from qualifying purchases.

Follow all safety instructions provided in your equipment operator’s manual before diagnosing, repairing, or operating. Consult a professional if you don’t have the skills, or knowledge or are not in the condition to perform the repair safely.

Reasons a Lawn Mower is Smoking (Black, Blue or White Smoke)

Clogged Air Filter

If my engine was smoking the first Item I would check is the air filter system. This is the easiest thing to check so why not start there?

First, remove the air filter cover. The cover is always located above the carburetor so that it can pull in clean air. Depending on the type of mower you have, the cover usually has a single screw or two knobs holding it down.
Some air filters will be along the side of the engine next to the carburetor.
Pull the filter out being very careful not to let any dirt fall into the intake pipe when you remove the filter.
Inspect the filter and check to see if it is full of dirt and grass. If it is, the engine will not be able to breathe. Instead of pulling in the fresh air, a clogged filter will bring in air from the engine crankcase or the internal part of the mower engine.

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Insufficient Engine Oil Level

If the air filter is not the problem, the next thing you are going to check is the engine oil. Now you may be asking yourself why you are checking the oil. If your engine oil is lower or higher than the manufacturer’s recommended oil level it can result in a smoking lawn mower.

Low Engine Oil Level

If your engine oil is low, you could be burning up the engine due to extreme heat causing lawn mower engine to smoke. In this case, the engine is having a meltdown and burning up the small parts in the engine.

You can try to add fresh oil to see if the smoking stops, but most of the time, at this stage, it is often too late for this simple solution.

High Engine Oil Level

Having too much oil can cause too much crankcase pressure which causes oil to get back into the cylinder or even up to the air intake through the valve train.

In this case, the oil is getting into the cylinder and begins to burn off when the engine is running at full speed creating smoke. You need to drain some oil out of the engine to resolve this problem.

Piston Ring Problem

After checking the easier troubleshooting steps and not finding any problem with the air filter or oil level, the next thing to do is check for oil on the spark plug. To do this, you will need a socket to remove the spark plug.

You may need a 3/4″ or 5/8″ socket to remove the plug. Inspecting the plug isn’t going to tell us a lot about the type of engine problem you have but pulling out the spark plug and checking to see if there is excessive oil buildup on it indicates you have a larger internal engine problem.

If you are mechanically inclined, you could check for internal engine damage. I recommend bringing your mower to a small engine dealer repair shop if you are not. If you find a lot of oil on the spark plug you may have a piston ring or valve train problem.

Either problem will result in you having to take the engine apart. A spark plug with oil build-up can indicate there is a ring problem and a score inside the cylinder wall.

If the cylinder has a score in it, the engine can bring up the oil to the combustion chamber and begin burning it.

This will create your lawn mower to begin smoking while in use. You may have to replace the engine in this situation.

Valve Train Problem

Sometimes having a valve train problem is not that bad of a problem to have. The only way to detect this is by removing the cylinder head or performing a leak-down test. This should be completed by a small engine mechanic.

The cause of a valve train problem is the result of the valve getting burned by being overheated. The edges of the valve begin to fall apart due to the heat. This is what is often referred to as a burnt valve.

You can also see a burnt valve or timing problem if the muffler is glowing red from heat while the engine is running. In this case, you will need to replace the valve and grind the seat.

The seat is where the valve contacts the engine block to complete the combustion chamber.

Both the valve and the seat will have to be cut at certain angles in order to make the valve seat correctly.

Bad Mower Engine Gasket

A bad engine gasket may leak oil onto the muffler and make the lawn mower engine smoke as it burns. You will need to find the bad gasket and replace it.

This may sound easier than it actually is. It becomes increasingly more difficult depending on the location of the bad gasket.

Difference Between White, Blue and Black Mower Smoke

Sometimes the color of the smoke can give you an idea of what kind of engine problem you are dealing with. It is best to go through the checklist above to narrow down the issue, but here is a quick list of items that could be causing the smoke.

Blowing Black Smoke

This color usually is due to the engine running too rich. The ratio of fuel to air is incorrect with more fuel being burned than air.

If you see black smoke coming from the mower, the first thing to check is the air filter. A plugged air filter must be cleaned or replaced. If the filter isn’t the issue check for another air flow restriction.

Blowing Blue or White Smoke

This color smoke is due to burning excess oil. It is best to follow the steps above to identify the root cause starting with checking the engine oil level followed by checking for damage to the piston rings, valve train, or engine gasket.

It is essential to continue to check your engine oil level and air filter before each mowing use to avoid large expensive repairs. For a checklist to perform before each mowing, I explain it in my Lawn Mower Checklist.

Complete Regular Engine Oil Changes

It may seem like a lot of work to change your engine oil, but changing your oil is necessary. To keep your lawn mower running and not shorten the life of the mower’s engine, you must change the engine oil regularly.

Read more about the damaging effects of skipping your oil change, Engine Damage is Likely if You Skip Mower Oil Changes.

Still Having Problems with Your Lawn Mower?

Lawn mower ownership doesn’t come without its frustrations. Own a mower long enough, you are bound to run into many lawn mower problems including starting, smoking, leaking, cutting, and overheating.

For mower troubleshooting, check out my guide Common Lawn Mower Problems: Solved.

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Sources:

https://lawnask.com/why-is-my-lawn-mower-smoking-and-sputtering/
https://yardsimply.com/mower/bad-boy/mower-is-smoking/
https://www.gardentoolexpert.com/white-smoke-from-a-lawnmower-this-might-be-why/
https://lawn.com.au/white-smoke-from-lawn-mower/
https://poweredoutdoors.com/5-reasons-your-lawn-mower-may-be-smoking/

Lawn Mowers electric, lawn, mower, smoke