Why is My Lawn Mower Smoking? (White, Blue or Black Smoke Explained)

It is worrying to see a cloud of white, blue, or black smoke from your lawn mower. While it could be minor, some cases imply a serious problem that needs to be inspected and fixed by an expert. Let’s get down to why your lawn mower is smoking and how to stop it.

Your lawn mower is smoking for several reasons depending on the color of the smoke. White or blue smoke is usually linked to an oil spill on the engine. On the other hand, black smoke implies a problem in the fuel system and the combustion chamber.

Why is my Lawn Mower Smoking?

A cloud of smoke around your mower’s engine is something that should not be ignored. There could be a major problem behind it which can lead to severe damage to your machine.

The following are potential reasons for this problem:

Lawn Mower Blue/White Smoke Meaning

A cloud of white or blue smoke from your mower usually indicates an oil spill on the engine. The oil will then burn to form a white or blue smoke cloud. Oil is an important addition to the engine; it minimizes friction and wears between components. Some types of oil are also designed to clean engines.

Oil spills to the engine usually happen during servicing as the old oil is removed and a new one is added into the crankcase. Overfilling the reservoir with oil can also result in leaking due to pressure. For every engine, there is always a mark at which oil should not go beyond.

Oil can also escape the crankcase when mowing on a slope greater than 15 degrees angle. The same can happen when a mower is tipped to the side during storage, cleaning the mower deck, or sharpening lawn mower blades.

No serious fix is required for this kind of problem other than just letting the oil burn until the smoke disappears.

Other reasons for oil spills on the engine include damages to the crankcase, a rapture in the breather tube, or worn-out cylinders and/or piston rings. A blown head gasket will also lead to an oil-soaked air filter.

Lawn Mower Smoking Black Meaning

Black smoke from your lawn mower means that the ratio of gasoline to air is not met for proper combustion. In other words, black smoke shows that your mower has more fuel than the air required for complete combustion.

Dirty air filters are usually the main reason for insufficient air in the combustion chamber. Cleaning or replacing air filters can help solve the problem.

If this does not help, then the carburetor is not supplying the right air/fuel mixture to the engine’s combustion chamber. A dysfunctional carburetor needs to be adjusted by a professional dealer.

Lawn mower smoking black could also happen due to low-grade fuel or impurities in the oil. Lawnmowers are recommended to use fuel with a minimum octane rating of 87 and with less than 10% ethanol.

Black smoke from your lawn mower is also a sign of bad spark plugs. They produce the spark that ignites the air/fuel mixture, creating the explosion that makes the engine produce power. If they are worn out or damaged, then a lot of fuel will escape unburnt in the form of black smoke.

How to Stop a Lawn Mower from Smoking

You can stop your lawn mower from smoking as follows:

1. Avoid overfilling the oil/fuel reservoir

Always check the level of oil using the provided dipstick on the reservoir. To do this, wipe the provided dipstick with a rag, reinsert it into the reservoir and remove it to check the oil level. Ensure it is not exceeding the ‘fill’ line on the stick.

2. Avoid tilting your mower

When storing or servicing your lawn mower, avoid tilting it. If this happens when mowing on slopes, ensure the spark plugs are facing upwards. This will help prevent oil from escaping the crankcase and getting onto the engine.

3. Use a recommended fuel

Always use the right type of gas for your lawn mower. Most four-stroke lawn mower engines require fresh unleaded gasoline with a minimum octane rating of 87 or higher and containing up to 10% ethanol. Two-stroke engines will use the same type of fuel but with the addition of 2-cycle engine oil in a recommended ratio.

4. Check the condition of the piston rings, cylinder, and the head gasket

It is normal for piston rings, cylinders,s and head gaskets to wear out. These parts should be inspected, especially during servicing, and be repaired or replaced where necessary. Professional service will be much helpful in inspecting and replacing the worn-out or damaged parts of your lawn mower.

5. Clean or replace air and oil filters

Filters help ensure that impurities are trapped in air and oil before getting into the engine’s combustion chamber. Dirty or clogged filters become dysfunctional, and this affects engine performance. Always replace or clean your lawn mower filter as directed in the manufacturer’s manual.

6. Adjust the carburetor

A carburetor provides the right air-to-fuel ratio before the mixture is taken for combustion in the engine. If your lawn mower is smoking black, then try to adjust the carburetor as directed in the user manual.

7. Clean or replace spark plugs

When servicing your lawn mower, you should also remember to check the state of your spark plugs. Clean or replace them to avoid high fuel consumption, stop black smoke from your lawn mower and increase your engine’s power.

8. Proper storage during winter

Lawnmowers are only deployed when the grass is actively growing. During cold seasons, little or no mowing takes place. Always winterize your lawn mower before storing it for winter. This will give you an easy start when the mowing season comes.

Final Thought

A black, blue, or white cloud of smoke from a lawn mower should be inspected, even if it doesn’t mean something serious. You could end up replacing the entire engine by ignoring this. If you don’t have the skill to deduce the problem, an expert should be able to help.

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