White Smoke From
Lawn Mower

What We'll Cover

White Smoke From
Lawn Mower

What We'll Cover

Your Problem Will Likely Be Loose Battery Connections, Flat/Faulty Battery Or Faulty Starter Solenoid.

Causes

01. Too Much Oil

02. Mower Tipped Over

03. Faulty Carburetor

06. Blocked Crankcase Breather

07. Head Gasket Failure

08. Engine Worn Out

Most Common Causes

This commonly happens after you've tipped your mower over to clean it, or after you've over filled it with oil.

 

White smoke from your lawn mower looks serous, but usually it's a simple fix. 

 

Mower Tipped Over

Mower tipped over is the most common reason for white smoke. Usually, the customer turns over the mower to clean the deck or unclog the chute.

 

This allows oil to enter the cylinder, and when the mower is restarted, the oil burns and turns your yard into a 70s disco. Sometimes oil will also leak from the muffler.

 

The fix is simple, check the mower for oil, and let the engine idle until the smoke clears.

 

 

 

mower tipped over

Tip Over

Tipping the mower on its side for maintenance or cleaning causes oil to move into the cylinder.

Disco

When you fire up the mower the oil in the cylinder burns causing white smoke.

It will clear after a short while.


mower smoking
mower tipped over

Tip Up

I hook the handlebars under a bench.

Turing your mower to the side is fine as long as you turn it with the carburetor side up.

Tip Over


mower maintenance

Tipping the mower on its side for maintenance or cleaning causes oil to move into the cylinder.

Disco


mower smoking

When you fire up the mower the oil in the cylinder burns causing white smoke.

It will clear after a short while.

Tip Up


mower smoking

I hook the handlebars under a bench.

Turing your mower to the side is fine as long as you turn it with the carburetor side up.

Too Much Oil

Lawnmower engines usually take a little over half a quart (.6lt), and so it's easy to overfill them. Lots of my customers add oil, without ever checking the level. They do this thinking it won't do the engine any harm. 

 

Wrong! Too much oil can damage the engine, as most operate a splash lubrication system. When the oil level is above the splash paddles, they don't work efficiently. Check out " How to check oil level ".

 

The white smoke is the engine burning off all the excess oil. The fix - drain the excessive oil, and idle the engine until the smoke clears. This may take 5 minutes or so.

 

Depending on your mower type, draining the oil can be a bit messy. My favorite tool for oil draining is the oil extractor, makes life easy and the job mess free.

 

 

Too Full


mower oil level

Too much oil will cause other problems, smoke, poor running, no running, leaks, engine damage.

Check out "How to check oil level".

Drain


mower oil drain

Drain excess oil and check and top up if needed.

mower oil check

Too Full

Too much oil will cause other problems, smoke, poor running, no running, leaks, engine damage.

Check out "How to check oil level".

Drain

Drain excess oil and check and top up if needed.


mower oil drain

Gas in Oil

If your oil level is overfull and smells of gas, it's likely you have a failed carburetor seal. Don't run the engine as the oil is too thin and offers no protection. Change the oil after making repairs to the carburetor. Check out "Lawn mower tune-up".

 

If you think this sounds like your problem, go ahead and replace the carburetor, it's faulty. Check out "Carburetor gas flow".

 

 

Gas Smell


mower oil level

The oil level will be overfull and stink of gas.

Carburetor


mower carburetor

The fix is to replace the float needle and seal, or replace the whole carburetor.

Consider fitting a fuel tap, and don't forget to change the oil.

mower oil check

Gas Smell

The oil level will be overfull and stink of gas.

Carburetor

The fix is to replace the float needle and seal, or replace the whole carburetor.

Consider fitting a fuel tap, and don't forget to change the oil.


mower oil drain

White Smoke & Dies

This is a sure sign that oil has made its way into the carburetor, and is blocking the gas feed jet. Most times repeated starting and running of the engine will clear the oil.

However, if you are unable to run the engine long enough, you may need to clean the carburetor. 

 

First, try removing the plug and turning over the engine a few times to expel oil from the cylinder. Clean or replace the plug and try starting again.

 

If this fails, you can check out "Carburetor Cleaning" where I show you how to remove and clean the carburetor.

 

 

 

mower plug clean

Clean Plug

Remove the plug and clear the cylinder by turning over the engine with the pull cord.

Clean the plug before refitting.

Clean Plug


Mower plug

Remove the plug and clear the cylinder by turning over the engine with the pull cord.

Clean the plug before refitting.

Oil in the Gas Tank

In addition to overfilling with oil and tipping mower on its side, putting oil into the gas tank accidentally is very common. Using the trimmer 2 cycle mix in the mower is quite common too, but won't produce the dramatic white smoke like engine oil.

 

The fix - drain the gas tank and refill with fresh gas and run the engine to clear the system. If the engine fails to start, Check out "carburetor cleaning".

 

Head Gasket Failure

A failed head gasket is much less likely but it will produce lots of smoke. Unlike previous solutions, it's a little more work. A head gasket is a metal and graphite material. It's fitted between the cylinder block and the cylinder head of an engine. Its job is to seal the combustion chamber.

 

 

High crankcase pressures and oil leaks are a sign of head gasket failure, you may also hear a slight puffing noise as compression escapes from the cylinder. The fix - replace the head gasket. 

 

A blocked crankcase breather will cause oil in the cylinder and white smoke, clearing the breather pipe is a simple fix. 

 

Failed or worn piston rings is the end, sadly a rebuild is needed. A new engine is most likely a cheaper option and it comes with a guarantee. 

 

 

 

 

Head Gasket


mower head gasket mower head gasket

Head gasket failure can cause white smoke.

This will only be an issue with ohv (over head valve) type engines, and will also depend on where the gasket fails. 

Ohv engines are usually well marked with ohv on the front engine cover.

When it fails and depending where it fails, it will suck oil into the cylinder and blow gases into the crankcase. 

Mower Head gasket Mower Head gasket

Head gasket

Head gasket failure can cause white smoke.

This will only be an issue with ohv (over head valve) type engines, and will also depend on where the gasket fails.

Ohv engines are usually well marked with ohv on the front engine cover.

When it fails and depending where it fails, it will suck oil into the cylinder and blow gases into the crankcase. 

Engine Wear


Mower engine test

Last on the list is engine wear or ring damage.

A compression test will confirm if you have internal damage.

This condition is rare.

Wear

Last on the list is engine wear or ring damage.

A compression test will confirm if you have internal damage.

This condition is rare.


Mower engine test