White Smoke from Lawn Mower (Why + How to Fix)

Lawnmowers have a small engine capacity ranging from 140-cc to 190-cc. You can troubleshoot and fix engine problems in lawn mowers because of their engine size. Learn how to fix white smoke from a lawnmower.

The lawn is a sacred space for any homeowner because it is the first place visitors see when they walk by or towards your house. The state of your lawn spaces speaks volumes about your personality/character. You must always keep your lawn in tip-top shape to ensure visitors have a good impression of you. Lawnmowers are one of the essential tools you require to trim and maintain the grass on your lawn.

Lawnmowers come in different shapes and sizes, but most have an engine to run. The engine capacity in lawnmowers is relatively compact compared to car engines. You can maintain it yourself if you know what to do. Learn how to fix: white smoke from lawn mowers by reading the content below.

Table Of Contents

Common Causes of White Smoke In Lawn Mowers

Troubleshooting white smoke in lawnmowers is the first step before attempting to fix the engine problem. Below are some common issues that can cause your lawnmower to emit white smoke while the engine is running.

Engine overfilling with oil.
Engine overfilling with excess oxygen.
The engine contains incorrect oil grades.
The engine has air leaks.
The engine contains worn-out cylinders/rings.
The engine contains a blown head gasket.
The engine is worn-out.

You can jump to the solutions below if you know the exact cause of white smoke on your lawn mower. Follow the steps below (in order, beginning with the first one) to troubleshoot and fix the white smoke problem if you can’t pinpoint the cause of the white smoke on your lawnmower engine.

How to Fix White Smoke from Lawn Mower?

Solution 1: Burn Out Excess Oil In the Engine

The first common cause of white smoke in lawnmowers is tipping over the engine incorrectly. Most people tip the lawnmower over when cleaning the deck or unclogging the chute. However, tipping over the lawnmower engine can cause oil to enter the cylinder. Starting the lawnmower engine with oil inside the cylinder can result in excessive white smoke while the engine is running.

You can fix the oil spillage into the cylinder by letting the lawnmower run idle. The engine will burn off the oil spillage inside the cylinder after a few minutes, and you will be able to see the density of the white smoke reduce gradually until it returns to normal. You can proceed to the next solution if the white smoke doesn’t start disappearing even after 5 minutes of idly running the engine.

Solution 2: Check the Oil

The second troubleshooting tip is to check the oil on your lawn mower. First, check the oil grade in your lawnmower and ensure you are using the recommended type/grade of oil. You can read the user manual for the lawnmower to identify the recommended oil grades. You can also do an online search for the recommended oil grade from the official manufacturer of your lawnmower.

It is also a common misconception that the more oil you put inside your engine, the better it will run. However, lawnmowers utilize a splash lubrication mechanism to ensure your engine runs smoothly. Overfilling the lawnmower engine with oil (above the splash paddles) can cause your engine not to run efficiently, thus emitting white smoke.

You can fix the excess oil problem by draining oil from your lawnmower and idly running the engine until the white smoke clears. Check the lawnmower manual to locate the oil drain valve on your lawn mower.

Solution 3: Clean or Replace the Carburetor

You can troubleshoot problems with your carburetor by checking the oil level and looking for a gas smell when the engine runs. The first step is checking the oil level and identifying if it is overfull. The second step is getting close to the engine exhaust and trying to see if you can smell gas. Chances are you have a faulty carburetor if the oil level is overfull, and you can smell gas on your engine.

Your first option for fixing a faulty carburetor is replacing it with a new one, or you could opt to clean your carburetor instead. Ensure you also change the oil after cleaning the carburetor because faulty carburetors leak gas into the oil, causing the oil to be thin and less efficient. Cleaning/replacing the carburetor works if oil blocks the gas feed jet and causes your lawnmower to emit white smoke before choking and killing the engine.

Solution 4: Replace the Head Gasket

You can troubleshoot if your engine requires a head gasket replacement by keenly listening to the engine when running. Faulty head gaskets cause oil leaks and high crankcase pressure, thus causing the engine to “puff” while running. The only fix to a failing head gasket is to replace it with a new one before changing the oil and running the engine to clear any oil leakages in the system.

Solution 5: Rebuild the Engine

You can rebuild the engine if it contains worn-out cylinders/rings. You are likely experiencing faulty cylinders/rings if you can hear the engine misfire while the engine is running. One of the options for fixing faulty cylinders/rings is rebuilding the engine. However, purchasing a new lawnmower engine is more efficient because it is inexpensive, takes less time, and offers a guarantee. Ensure you compare the price of a new lawnmower engine and a new lawnmower to make a more informed choice.

Conclusion

It is also possible on rare occasions that the cause of white smoke on your lawn mower could result from filling the gasoline tank with oil. It may sound absurd, but it happens more often than you think. You can fix the problem by draining the gas tank before filling it with gasoline.

Ensure you run the lawnmower afterward for about 5 minutes to ensure the oil clears from the engine. You can perform the above fixes if you have the right tools and the patience to see the work through. Seek help from a professional mechanic if you require assistance or lack the time to complete the work yourself.