How Do Lawn Mower Engines Work

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An engine is required for the mowers to move their blade. 

Most lawnmowers employ a variation of Briggs & Stratton’s lightweight aluminum blade, which was created specifically for lawnmowers.

These engines work on the same principles as automotive engines, and at times, they fail when the key components for combustion, air, fuel, and a spark, are not balanced appropriately.

However, it’s easier to maintain your lawnmower operating if you understand how the engine works, which will also help you in repairing your mower by yourself. Now let’s find out how.

how does engine work in lawn mower

How Does a Lawn Mower Engine Work?

The explosive interaction between the spark and the gasoline powers engines. And Fire, (which requires oxygen, fuel, and a spark to be kept alive) is the center of this combustion.

Oxygen: Fire requires oxygen, which is also known as air. Water really puts out flames by depriving them of oxygen. However, this does not work with grease fires since the grease will float to the surface of the water.

Fuel: It is required to keep the fire going. To put it another way, you’ll need something to burn, for instance, just like wood meant for a campfire, Gasoline is burned in tiny engines.

Spark: The spark is what ignites the flame. Consider igniting a charcoal barbecue with a match. In an engine,  a spark plug is used.

After you’ve produced combustion, you’ll need to figure out how to use it. To keep it confined, a cast iron or aluminum cylinder is built to block around it. Then energy is directed towards something useful, such as spinning a lawnmower blade.

How is Heat Energy Converted Into Mechanical Energy?

Combustion generates heat energy, but heat alone is insufficient to move something. The energy from combustion is transferred to practical use through a sequence of mechanical elements in engines.

The procedure begins with the piston. 

A piston is a metal component that sits within the cylinder of an engine.

A connecting rod connects the piston to the crankshaft. The crankshaft is placed at the bottom of the engine and is responsible for rotating the blades or wheels of the equipment you’re operating.

When combustion occurs in the engine, the piston is forced down the cylinder, rotating the crankshaft and turning the mower blades.

None of these mechanical pieces could move adequately without sufficient oil lubrication. An oil slinger is used to lubricate the different engine elements of many small engines.

That is why it is crucial to refresh your engine oil on a regular basis.

 working of Lawn mower engine

Working of a 4-Stroke Engine

Nowadays, a 4-stroke engine is used in Mowers. Let us understand how does a 4-stroke engine works.

The engine cycle is divided into four phases that explain the piston’s movement inside the cylinder:

Phase 1:Intake

Air and fuel are supplied into the combustion chamber at the engine cylinder block during the intake stage.

A carburetor mounted to the engine block mixes air and fuel in the proper amounts in classic engines. Electronic injection (EFI) of gasoline into the combustion chamber has replaced the carburetor in many newer engines. Therefore it is important to clean the carburetor of lawnmower regularly for smooth functioning of the lawn mower.

Phase 2: Compression

The fuel mixture must be compressed in order to optimize combustion power. The more compact it is, the warmer and so more explosive it becomes.

As it advances up the engine cylinder, the piston compresses the fuel mixture.

Phase 3: Power

Combustion takes place during the power stage. The piston has compressed the fuel mixture and made it to the top of the cylinder at this moment.

To ignite the combination, all that is required is an electrical spark delivered by the spark plug. 

The piston is forced down by the explosion, resulting in the mechanical energy described before (Pre-ignition or knocking occurs if the mixture explodes before being fully compressed and will damage the engine).

Phase 4: Exhaust

Engine combustion produces exhaust that must be expelled, much as a bonfire does. During the exhaust stage, this happens. The intake stage restarts the engine cycle after the exhaust is emitted.


You now have a rudimentary understanding of how a tiny lawnmower engine works, which will come in handy if your engine breaks down.

Do you think the engine of a lawnmower is interchangeable? Yes or No! Check out the article to find your answer.

The problem can be found by looking at the symptoms you’ve seen in your engine and taking the appropriate steps. Also, with proper maintenance, you can avoid engine problems.

About Tom Reynolds

My name is Tom Reynolds, and I like lawn mowing. When I was a kid, I used to help my dad in cutting grass using a reel mower, now, I have my own 6 different lawn mowers. Keeping my lawn healthy and beautiful gives me satisfaction, and I still enjoy working in my lawn.