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What Does A Four Stroke Engine Mean?


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What Does A Four Stroke Engine Mean?

07 Mar, 17

Shailza Singh

Welcome guys. We often hear that this bike is powered by –CC four Stroke engine. But do we know exactly what does a four stroke engine is? Let’s dive into the details and find out more about this stroke thing.

All automobile engines can be divided in two categories – Spark Ignition Engine and Compression Ignition Engine. All Spark Ignition Engines are essentially consuming petrol as fuel and Compression Ignition Engines consumes diesel as the fuel. Spark Ignition Engines can further be divided in two categories – 2 stroke and four stroke engines.



All modern bikes are using four stroke engines as their powering device. The reason behind that is a good mileage and clean environment. So let’s understand what a four stroke engine is –

A four stroke engine is made of following essential components –

  1. A cylinder
  2. A piston
  3. Two valves (One inlet and another exhaust)
  4. Cylinder head
  5. A spark plug
  6. A carburetor
  7. A crank shaft and connection rod
  8. A cam shaft to control the sequence of valve operation.

There are more systems connected to an engine such as accessory gear box, transmission system and cooling system etc. Superbikes may have more advanced components such as Supercharges and fuel injectors.

The piston reciprocates within cylinder within its highest possible point and lowest possible point which is named as TDC (Top Dead Centre) and BDC (Bottom Dead Centre). The diameter of the cylinder is termed as ‘Bore’. Let’s see how strokes are helpful for engine to function and produce power for our loved motorcycle.

  1. INDUCTION STROKE – The Piston travels from TDC to BDC and sucks air fuel mixture provided by carburetor. In this stroke Inlet Valve remains open and allows air fuel mixture come inside. So by the time piston reaches BDC, the cylinder is filled with highly inflammable Air Fuel mixture ready to be ignited.
  2. COMPRESSION STROKE – The piston now travels from BDC to TDC and compresses the air fuel mixture to make it more powerful and more inflammable. Both of the valves remain closed in this position.
  3. POWER STROKE – This is the only stroke that produces power and hence called power stroke. The valves remain closed and exactly after the completion of compression stroke, the spark plugs give spark. The air and fuel mixture is lit and explosion of gases pushes the piston downwards towards BDC.
  4. EXHAUST STROKE – Our last stroke that is alone responsible for cleaning the engine. The exhaust valve remains open. Piston travels from BDC to TDC and the burnt gases are pushed out from the engine. The cycle continues and our engine continues to produce power for our motorcycles.

The connecting rod and crank shaft transmits the power from piston to the accessory gearbox. The complete system is working in sync so that nothing mismatches to create nuisance within the engine.





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