White smoke from a lawnmower? What the pros say. With Fixes

Are you dealing with white smoke from your lawnmower? We understand your concern. Our expertise will provide the necessary insights to address this problem effectively.

White smoke can result from oil in the combustion chamber, caused by tipping mower, overfilling oil, head gasket damage, piston ring failure, or oil in fuel. Fixes are burning off excess oil by running the mower, replacing the head gasket, rebuilding the engine, draining contaminated fuel, and proper maintenance.

Is Your Lawnmower Smoking? Is your lawnmower spewing white smoke, and you’re at a loss about what to do? This could be due to various reasons, including overfilled oil or contaminated fuel.

We provide a detailed analysis of these issues and their solutions. Keep reading to learn how to tackle this problem effectively.

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 causes 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 on a too-steep surface.

Both of these situations may result in the cylinder filling up with oil and white smoke being produced from the exhaust of the lawn mower.

● 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 off the oil that has gotten into the combustion chamber. To know the correct way to fix it, 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

While a lawnmower engine with less than an average amount of oil will face a lot of friction due to lack of lubrication, if you have excess oil in your mower’s engine, the oil will enter the cylinder and start burning along with the fuel.

This results in white smoke from the exhaust; sometimes, excess engine oil can come from the exhaust muffler.

If you have too much oil in your mower, it will start leaking, and when the engine gets hot, it will produce white smoke as the oil burns. Excess engine oil will cause the mower to have white smoke, which can drown the crankset and hinder its motion.

In most cases, a mower overfilled with engine oil won’t start, or it will take too long to start up and will be challenging to idle because of burning engine oil in the combustion chamber.

● Fix: Overfilling the engine with too much oil

Preventing accidental overfilling of engine oil is relatively simple, and it is best to avoid filling excess oil in your mower in the first place.

When it is time to change the engine oil, refer to your mower’s user manual to find the exact amount of engine oil your lawnmower needs. Usually, a lawnmower will not require more than 20 ounces of engine oil.

Once you have put engine oil in your lawnmower’s engine, use the dipstick to ensure the oil level is within the indicated mark on the dipstick.

If you have already put too much engine oil in your mower, the only solution is to remove the excess oil. You must drain all the engine oil and pour in the recommended amount.

Although filling a lawnmower engine with oil isn’t as bad as underfilling it, most use splash lubrication. A small amount of oil is systematically splashed on different engine components to lubricate them, while the rest stays at the engine’s bottom. 

Here you can find good oil for your Lawn Mower.

Damaged or leaking head gasket

While the first two causes of white smoke would not cause worry or require you to do a serious repair, a leaking or blown head gasket is one of the more severe reasons your lawnmower might be producing white smoke.

A Head gasket is a seal used to keep the engine closed off, located in the area that joins the cylinder with the rest of the engine.

If your lawnmower has a damaged head gasket, then the white smoke won’t go away if you run the mower for a while as it does if the mower is tipped on the side or overfilled with engine oil.

• How Oil Leaks into the Cylinder

 When the head gasket is not sealing the cylinder head properly, oil can leak into the cylinder from the crankcase.

It doesn’t take a massive crack in the gasket to suck oil into the combustion chamber since there is a lot of compression in the cylinder that sucks oil from the crankcase, even if there is a tiny leak in the head gasket.

As the oil starts to enter the cylinder, it can start burning and cause white smoke, and the number of smoke increases if the engine keeps running since more oil is being sucked into the combustion chamber through the damaged gasket.

In addition to consistent white smoke from the exhaust, you can hear the air being blown from the leaking gasket and loss of compression, which causes low power output from the mower.

If a lot of oil is rushing into the cylinder, the engine may fail to start or stop running after a while. Moreover, you will notice oil around or under the head gasket and on the body of the lawnmower that is leaking from the damaged head gasket seal.

– The Importance of Engine Oil in Lawnmowers

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 critical 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.

You must also ensure enough air for the engine to function correctly. In case of any problems, check the seals for any spilled oil. If you notice black smoke instead of white, your mower might have other smoke problems.

● Fix: Damaged or leaking head gasket

A Head gasket is found in an overhead valve (OHV) engine, and if it is damaged or starts leaking, you can only fix it by putting a new head gasket in because gaskets are not repairable once they become damaged.

A head gasket is inexpensive, and you can get a new, good, quality one for a few dollars. If you have worked on a small engine before, you can easily replace your lawnmower’s head gasket by yourself by following these simple steps:

● Step 1: Get a replacement head gasket

Purchase a replacement head gasket. Your local dealer can get you the correct one or find one online.

Here, you can find head gaskets for your Lawn Mower.

● Step 2: Remove the cylinder head

Before you start using a socket, you must remove the sparkplug wire and the bolts that hold the cylinder head onto the engine block.

● Step 3: Remove the gasket

The damaged gasket on the engine block where the cylinder head connects. Take the gasket off and use a tool to scrape off any hard-to-remove pieces of the gasket, but be careful not to damage the smooth surface when scraping off the debris.

● Step 4: Add the new gasket

Place the new gasket on the engine block and the cylinder head back before bolting it back onto the cylinder head and putting the sparkplug wire on the sparkplug. You can purchase head gaskets here.

● Remark: check if you have an overhead valve engine

Only overhead-valve engines have gaskets, so before you take your lawnmower’s engine apart, ensure that your lawnmower has an overhead-valve engine.

When you have an overhead valve engine, you will see the valves and cylinder head above the combustion chamber. The valves are below the combustion chamber if your engine is a flathead engine.

Failed piston rings

Of all the causes of white smoke in lawnmowers, a  failed piston ring is probably the worst one, and it is usually seen in older, worn-out lawnmowers or if the mower is poorly maintained. Piston rings to control the engine oil and supplies minimal oil to the piston to move smoothly inside the cylinder.

Piston rings of your mower’s engine also remove excess oil from the combustion chamber and flow it back into the engine block. But when these piston rings fail, nothing stops the engine oil from entering the combustion chamber and burning up to produce white smoke.

Piston rings may get damaged due to any number of reasons, but the most common ones include:

• An unclean or worn-out air filter may allow dust and other particles to enter the combustion chamber and damage the piston rings.
• Not replacing the engine oil on time or dirty oil will cause poor lubrication and damage to the piston rings.

If your mower is burning up a lot of oil and producing white smoke as it runs with little to no power, it can have bad piston rings.

● Fix: Failed piston rings

Unfortunately, repairing failed piston rings is not simple; it will require a complete engine rebuild, and the whole engine must be opened up. If your lawnmower has lousy piston rings, the head cylinder will also have signs of damage and must be replaced.

This kind of repair requires special tools and a lot of expertise, and it is best to leave it to a professional repair shop or install a brand-new engine since rebuilt engines don’t tend to work as well as new ones.

Here, you can find lawnmower piston rings.

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 dependable, 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. If you are sure that very little oil went inside the mower’s fuel tank, it will dissolve 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 safer, remove it 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:

● 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 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, 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.

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 the oil is stuck inside the mower’s fuel tank, you must remove it and clean it using dishwashing soap or liquid. Pour the soap inside the fuel tank and shake it well to remove the oil stuck inside it.

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.

Remarks

White smoke coming from the lawnmower should never be ignored as it can be a sign of a severe problem with your mower’s engine that needs immediate attention.

Using the details provided in this article, you can quickly pinpoint the exact cause of white smoke from your mower, and the troubleshooting process will be much simpler.

But one thing is shared among all the causes of white smoke from your mower; it mainly occurs due to your lawnmower’s engine somehow burning engine oil.