What Causes a Two Stroke Engine to Smoke

Mowers powered by two-stroke engines are among the most ubiquitous in use across the globe. They are simple to maintain and don't require a lot of money, but they have a propensity to develop small leaks every once in a while. When there are leaks, smoke will result, and before you know it, you'll be dragging a smoky mower around the yard.

Mowers powered by two-stroke engines are among the most ubiquitous in use across the globe. They are simple to maintain and don't require a lot of money, but they have a propensity to develop small leaks every once in a while. When there are leaks, smoke will result, and before you know it, you'll be dragging a smoky mower around the yard.

When a two-stroke engine begins to smoke, the problem could be the result of oil that is burning, clogged air filters, damaged head gaskets, or piston rings that have failed. Nevertheless, brand-new lawnmowers frequently have excess lubrication that needs to be burned off; this is the likely cause of any smoke that you may observe.

You'll learn the following information about what causes a two-stroke engine to smoke as you read through this article:

  • There are a variety of causes and potential solutions that will put an end to the engine smoking.

  • How to deal with a smoking lawn mower so that you don't have to buy a new one

  • Ways to avoid creating smoke in your engine with these preventative measures

Pro Tip: Old or incorrect engine oil can ruin a mower in a matter of minutes. In fact, the vast majority of mowers end up getting tossed before their time. Check out the best two-stroke engine oil on Amazon.com to keep your mower alive and thriving for a long time to come.

Why Does My Mower’s Two Stroke Engine Smoke?

A two-stroke engine mower can emit blue or white smoke during mowing. Here are some of the reasons why this may happen:

Oil spills on the engine


If you've just recently changed the oil in your mower, it's possible that it will let off some white or blue smoke. It's possible that your vehicle's engine has experienced an oil leak because of this.

When you tip your mower over for cleaning or maintenance, you run the risk of oil spills similar to the ones that occurred when you mowed on a sloppy area with a slope greater than fifteen degrees.

The burning of oil is the most common cause of white smoke coming from a two-stroke engine, as pointed out by the Garden Tools Expert.


Clogged air filters


In order for combustion to take place in the combustion chamber of a two-stroke engine mower, there must be sufficient air present. Air filters that are dirty or clogged with debris restrict airflow, which in turn results in an inefficient combustion process. Smoke can be white or black depending on the color of the unburned fuel that is present in the combustion chamber.


Adding too much oil to gas


During operation, there will be a great deal of friction in an engine that has a low oil level because there will be insufficient lubrication. In the event that excessive oil is added, some of it will make its way into the cylinder, where it will catch fire alongside the fuel. Because of this, the exhaust will be spewing out an excessive amount of smoke.

Additionally, excess engine oil will be expelled through the exhaust muffler. The typical air-to-fuel ratio for a two-stroke lawn mower falls somewhere between 50 and 40 to 1. Even though the extra oil won't be harmful to the engine, you'll need to switch fuel if you want to get rid of the smoke.


It’s a new mower


The first time a mower is used, there is a possibility that it will produce white smoke because the manufacturer may have left oil residues. You need to give the lawnmower some time to run in order to remedy this situation.

It is expected that once the engine of the mower has burned off the residual oil, the smoke will stop.

Is your lawn mower, on the other hand, making more noise than it should be?


Damaged or leaking head gasket


According to Hunker, the head gasket functions as a seal that prevents unwanted air from entering the engine. The gasket can be located in the part of the engine where the cylinder is connected to the rest of the machine.

White smoke is produced continuously by a faulty or leaking head gasket, and this smoke does not disappear even after the engine has been run. Even if there is a slight breach in the head gasket, the cylinder that is responsible for sucking oil from the crankcase will typically contain a high number of compressions.

White smoke is produced as a result of the oil starting to burn as it is introduced into the cylinder. If you keep running the engine, more oil will be sucked into the cylinder, which will cause the amount of smoke to continue to increase.

There is a possibility that you will hear the sound of air being blown as a result of the leaking gasket and loss of compression, which is causing the mower to produce less power than usual.

It is possible that the oil flow that is flooding into the cylinder will eventually cause it to stop running or even prevent it from starting.


Failed piston rings


If your lawnmower uses a lot of oil, emits white smoke, and has very little to no power while running, this could indicate that the piston rings in your mower are worn out and need to be replaced. This is most commonly observed in older, worn out lawnmowers or mowers that have not been properly maintained.

As repairing the mower is a very involved process, this is the cause of white smoke that is the most problematic. The amount of oil in the engine is controlled by the piston rings, which also supply the piston with a very small amount of oil so that it can move smoothly inside the cylinder.

In addition to this, they drain any excess oil from the combustion chamber and recirculate it throughout the engine block. The following are some of the factors that can lead to damaged piston rings:

The piston rings are susceptible to damage if they are not adequately lubricated, which can be caused by dirty engine oil or a lack of timely oil changes.

Dust that makes its way into the combustion chamber through air filters that have become worn out can cause damage to the piston rings.

The documentary How Stuff Works enlightens us to the fact that oil seepage in two-stroke engines is not all that unusual.



How to Fix a Smokey Two-Stroke Engine

● Restart the mower


If there has been an oil spill in your engine, you can make the problem easier to fix by restarting your mower. This will ensure that the oil that has been spilled is burned off. Especially if you turn your mower upside down on a regular basis for cleaning and maintenance, it is highly recommended that you consult the owner's manual to learn the most effective way to minimize the possibility of oil leaks.


● Check for overfill and drain excess oil


White or blue smoke could also be caused by an oil reservoir that is too full. Find out exactly how much engine oil your lawnmower needs by consulting the user manual that came with it. Doing so will help you avoid accidentally overfilling the tank.

When you have finished adding engine oil to your mower, check the oil level using the dipstick that is located on the reservoir. Check the amount of oil to ensure it is at the recommended level, which is indicated on the stick. If you have put in more than what is required, you will need to drain the engine's oil and then re-fill it to the correct level.


● Replace a damaged head gasket


Since it is not possible to repair a damaged or leaking head gasket, the only option is to replace it. It is possible to acquire a high-quality head gasket at a cost that is reasonable. Head gaskets are not prohibitively expensive.

It is not an easy task to repair worn or damaged piston rings because doing so requires a full engine rebuild, which in turn requires the engine to be opened up in its entirety.

If the piston rings in your lawnmower are damaged, then there is a good chance that the head cylinder will also show signs of wear and tear, and it will also need to be replaced.

Because the process of repairing something requires a great deal of expertise, the job is best left to a trained professional. However, because a repaired engine does not typically function in the same manner as a brand-new one, it is recommended that a new engine be purchased.



How Do You Prevent It from Happening?


Upkeep is essential if you want to stay smoke-free while operating your mower. It is our hope that the following advice will assist you in staying smoke-free:

  • Make sure that you regularly replace old and soiled oil with fresh oil that has not been used before.

  • Make sure that you check the air filters for dirt and clean them if any is found. This will prevent the air filters from becoming clogged, which will prevent sufficient air from entering the combustion chamber.

  • Always make sure that you use the dipstick to check the amount of engine oil that is required before you overfill your engine.




Are you sick of having to move a smoke-belching lawn mower around? It is important that you get to the source of the problem as quickly as possible, regardless of whether the oil is leaking due to a broken head gasket or the head gasket itself is broken.

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