Is White Smoke from Lawn Mower Dangerous? (6 Things You Must Check)

Gasoline-based lawn mowers occasionally emit white smoke from their engine or crankcase. But what does white smoke emission indicate?

It indicates that something went wrong in the system and caused oil to either burn or spill on the mower engine. But is white smoke from lawn mower dangerous?

Emitting white smoke is a clear sign of danger and can damage major internal parts of your lawn mower if left neglected for a while.

Keep reading this article that reveals the reasons behind such white smoke discharge & guides to resolving the problem:

Is White Smoke from Lawn Mower Dangerous
Is White Smoke from Lawn Mower Dangerous

What Causes White Smoke from Lawn Mower?

The most common reasons behind white smoke coming from your lawn mower are:

  • Tilting on the mower’s side incorrectly or turning it upside down/Operating at a higher than 15-degree angle
  • Incorrect fuel mixture or overfilled with engine oil
  • Stuck Float Needle
  • Defective Head Gasket
  • Faulty Breather Tube
  • Damaged Piston Rings

Is White Smoke from Lawn Mower Dangerous?

Yes, it is dangerous.

Especially, when you see a big wave of white smoke coming out of your mower, it is unsafe and it needs to be taken care of.

Remember, smoke emission is never good news whether you witness white, blue, gray, or black smoke, and requires immediate attention.

Whether it’s a 4-stroke or 2-stroke lawn mower, users commonly witness two scenarios:

Either white smoke from the lawn mower when starting or when blades are engaged.

White smoke emission means either you have overfilled the engine crankcase with oil, oil got mixed into the fuel, or you have tilted the mower wrongly while performing regular maintenance.

A faulty exhaust, carburetor, and engine parts also can cause white smoke.

In their feigned ignorance, people forget that it can be health hazardous for both humans & environment because any smoke generated by an oil spill or burning is also poisonous to the environment.

Therefore, if you do not diagnose the issue promptly and keep running the mower with such conditions, you are likely harming the major driving elements of your mower.

Related Post: Riding Mower Blowing White Smoke When Blades Are Engaged

How To Fix White Smoke Emission from Your Mower?

As soon you notice that your mower started to release white smoke, immediately check these 3 facts and fix them as required:

1. Wrongly Tilting the Mower on its Side or Turning it Upside down/ Operating at a Higher than 15-degree Angle: 

Many users prefer doing their mower’s regular maintenance by themselves, and they accidentally tip the mower inaccurately while cleaning the deck area.

This especially happens with push or self-propelled mowers.

Later, when you start the mower again, the oil slips into the engine cylinder and burns to cause white smoke emissions.

If you accidentally or intentionally, run the mower higher than a 15-degree angle on a steep slope, it will also cause white smoke.

Make sure to tilt the mower on the air filter side up and the smoke will stop once the oil has completely burnt off.

In most cases, it takes 10 minutes maximum to stop smoke emissions. Therefore, let your mower stay idling until there’s no smoke coming out.

Also, avoid operating your mower at a higher than 15-degree angle on any steep slope.

2. Check if there’s too much Engine Oil, or Incorrect Fuel Mixture:

White smoke can emit from your mower if you have too much oil in the crankcase reservoir. It can also cause by incorrect fuel mixture or if oil gets mixed with the fuel.

Therefore, make sure that you are not overfilling the fuel tank while refilling it and using the correct fuel mixture recommended for your lawn mower.

In that case, the fuel-to-air ratio should be accurate, and if it’s a 2-stroke lawn mower, be sure to refill it with the fuel mixture needed for a 2-stroke mower.

If you own a 4-stroke lawnmower, put on the right fuel mixture recommended for the 4-stroke mower.

If oil got mixed with the fuel, drain the gas out of the fuel tank and use a Siphon or Performance Additive to clear the system before putting in fresh gasoline.

Generally, keeping the mower at idling for 5 to 10 minutes helps to burn out all the extra oil.

But if that does not work in your case, remove the excess amount by tilting the mower down or using a Fuel Transfer Pump to pump the oil out.

3. Look for a Stuck Floating Needle:

When the floating needle (responsible for regulating the amount of fuel that goes into the engine) in the carburetor gets stuck, you will see white smoke emission because gas gets into the engine.

Undo the drain plug and drain all the bad oil out. Refill it with fresh fuel and add a new fuel filter.

If possible, insert a fuel shut-off valve.

Tips: Always leave the throttle adjuster at a slower speed.

Take the carburetor off and clean it.

Also, spray some carb cleaner onto the floating needle.

Put everything back together securely.

Still, White Smoke Emitting from Your Lawn Mower?

If the problem still remains the same, try these…

4. Diagnose the Head Gasket & Repair it: 

A blown or failed head gasket will also lead your mower to release white smoke, but you cannot be sure unless you diagnose it first.

First, diagnose whether it’s a head gasket that blew up and caused the smoke or not.

While inspecting, if you see that one of the head bolts is missing, you can replace the head gasket without even removing the entire engine shroud.

Remove the head bolts and loosen the engine shroud bolts a little bit to get access to the gasket.

Make sure to scrap all the gasket surfaces and then reassemble the new head gasket before putting everything in place securely.

5. Check the Crankcase Breather Tube: 

When the oil enters the cylinder, it indicates that you have a blocked or faulty breather tube and the engine is running rich.

If that is the case, you will also encounter white smoke released from your mower.

Check the crankcase breather and clean the pipe.

If that does not solve the problem either reroute or replace the crankcase breather tube.

If you have a small engine lawn mower, follow this step-by-step tutorial to repair or replace the breather tube:

6. Check the Piston Rings: 

Damaged or worn-out piston rings on the cylinder can also cause this smoking problem.

So, do not forget to check on them.

If damaged piston rings are the main culprit, you have to replace the piston rings.

If you do not want to change the piston rings, either rebuild or replace the engine.

Read Also: 5 Lawn Mower Bad Spark Plug Symptoms to Look Out For!

Frequently Asked Questions (FAQs):

What Does It Mean When My Lawnmower Suddenly Blows White Smoke?

It indicates oil burning in the engine crankcase, and you have to investigate all the possible areas to find which faulty element caused the engine oil to burn.

Can White Smoke Cause My Lawnmower to Die? 

Yes, it can. When you have been ignoring the early signs for too long, you will end up witnessing your mower die after emitting smoke for a long period.

Why Is My Mower Smoking Every Time I Try to Start It Up?

It mainly happens when the mower has turned old, and the internal parts, such as the spark plug, carburetor floating needle, crankcase breather, head gasket, or valve seal deteriorates.

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