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What is a Four Stroke Engine?


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What is a Four Stroke Engine?

02 Jul, 21

Shailza Singh

Riders usually love their bikes and some of them are really attached to the beauty of the bike. But did you ever ponder if the aesthetics of the bike enhance its beauty, an engine inside is the heart of the bike. 

Many a time when we see an advertisement or go to a bike showroom, we are told that the bike is equipped with a four-stroke engine. 

Let's discuss today what exactly is a four-stroke engine.

All the engines of the world can be classified into two categories. 

  1. Internal Combustion Engines.
  2. External Combustion Engines.


No other category discovered until now. Simply combustion means fire, hence the Internal Combustion Engines (Also known as IC Engines) are those where the event of fire or burning takes place inside the engine. Similarly, in External Combustion Engines, the event of fire or burning takes place outside of the engine.


Simple till now.


Now IC Engines can be further divided into some categories

  1. Rocket Engines
  2. Jet Engines
  3. Piston Engines

EC Engines -

  1. Steam Engine.


We don't get deeper and keep it simple with our subject. So let's see 'What is a Piston Engine'.


Simply it is an engine that has a Piston. 

And this piston moves up & down inside a cylinder (Engineers tell it a reciprocating action :-) )


Interestingly, these types of engines can work in 2 ways. 

  • 2 Stroke cycle
  • 4 Stroke cycle

The 2 Stroke engine simply gets the power within 2 strokes of the piston. So it how it works

First Stroke ( Piston Moves Down to Up) - Valves are closed. The fuel & Air mixture is already inside the cylinder. The piston moves out burnt gases first, then compresses the fuel and air mixture. Our spark Plug comes into action and gives a spark into already compressed gases mixed with fuel. 

Burning takes place and gases expand tremendously and the piston. 

Now the power is generated and transferred via the piston to the crankshaft to the gearbox. The piston at the same time creates suction and moves in the air and fuel mix inside.

These kinds of engines were earlier used in bikes. They are now obsolete and not used because of the wastage of unburnt fuel which escapes with exhaust gases.


The Four Stroke engine solves this and divides each cycle into a single stroke. Here are they


  1. Suction Stroke
  2. Compression Stroke
  3. Power Stroke
  4. Exhaust Stroke

As you can see, there is no wastage of fuel in 4 stroke engines and these engines give a better mileage to the biker hence cost less to the pockets. 


With advanced technologies day by day being incorporated in 4 Stroke Engines, we can see Fuel Injection systems being implemented in high-end bikes. With engineering inventing every day a new way on roads, We may also see the " SuperCharger" coming soon to give tremendous power to our bikes at a low cost very soon.



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