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What is a Two-Stroke Engine and Why it Had to be Killed?

Karl Benz was the first to get the two-stroke engine registered into the books (Patent) back in 1879. For you to know, Karl Benz is the same person who started the brand ‘Mercedes-Benz’. Nearly a decade ago, two-stroke motorcycles were the prime choice of motorcycle lovers. Yamaha RX-100, Yezdi and more, were the old cool.

But what changed? What was so special about these 2-stroke engines? these engine’s signature characteristics, power being one of them, made them popular. A 2-stroke engine is more powerful than it’s the 4-stroke counterpart with the same displacement. The powerful 2-stroke motors also produce a distinctive sound that one can only associate with this type of engine.

Yamaha RX 100 | Forgotten Bikes In India
Yamaha RX 100 | Forgotten Bikes In India | 2-Stroke Motorcycle

So, now the question comes, why was it necessary to kill the 2 stroke motor?

The answer to this question lies in the working of a 2-stroke engine. So without wasting further time, let’s see how this gem engine works.

2-Stroke Engine | Working

2-Stroke Engine
2-Stroke Engine | Image Source: (1)

Unlike a 4 stroke engine, that has 4 cycles, in which only one stroke produces power, the two-stroke is quite the opposite. This type of motor produces power in every 2nd stroke, hence drastically increasing the power output of the engine. But what are the strokes of a 2 stroke engine?

  1. Up-Stroke
  2. Down-Stroke

How is The 2-Stroke Engine Different?

The basic parts are the same as in the 4-stroke engine like the Piston, combustion chamber and spark plug, but the difference lies in the charge delivery into the engine. (Air-Fuel Mixture).

  • For starters, a 2-stroke engine does not have valves, instead, ports do the job. The piston’s movement open or close the ports.
  • Unlike any engine, this has a transfer port that transfers the fresh charge from the crankcase to the combustion chamber.
  • Though the motor has a piston it is slightly different from conventional ones. The piston head has a hump.

More on that later in the article. So, without further wasting time, this is how a 2-stroke engine works.

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Upstroke | Image Source: (1)

The secret lies in the details. In an upstroke, the piston is moving from BDC (Bottom Dead Centre) to TDC (Top Dead Centre).

  • In this movement, the piston is compressing the charge in the combustion chamber. Side by side, the exhaust gasses are also expelled from the exhaust port.
  • This is where the Hump on the piston head comes handy, as it further pushes the gases towards the exhaust port.
  • Alongside, due to the piston’s upward movement, the inlet port opens letting fresh charge into the crankcase.

Hence, compression and suction stroke occurs simultaneously.

Down Stroke
Down Stroke | Image Source: (1)
This is the stroke where the piston moves from TDC to the BDC.
  • First things first, it is the combustion that forces the piston to move from top to bottom.
  • Alongside that, when the piston is moving towards the bottom, the exhaust port opens hence allowing the exhaust gases to escape.
  • Simultaneously the inlet port is closed and due to the vacuum, the fresh charge in the crankcase enters the combustion chamber to be combusted through the transfer port.

Now, the cycle repeats itself and in just two strokes the power is generated. In other words, every downward movement is because of the power stroke. A 2-Stroke engine is more powerful, it is fun to drive and it sounds better. So, why is it that we don’t see it now?

Why 2-Stroke is no More?

New Delhi Odd-Even Scheme Extended To Privately Owned CNG Vehicles
Delhi Pollution

The only reason for this motor not existing anymore is ‘POLLUTION’.

  • A 2-stroke engine relies on the fuel and oil (2T-oil) mixture for lubrication and the air-fuel charge is what that combusts in the combustion chamber.
  • The lubricating oil also combusts with the charge hence producing thick white smoke. This smoke is very prominent and adversely affects the environment.
  • Not just that, after the combustion some unburnt gases also contaminate the environment.
  • In the end, the manufacturers were not able to reduce the emission to comply with then-new norms (India 2000).

Still, some petrol heads have a 2-stroke motorcycle or scooter parked in their garages. Surely this motor was a gem motor. You have to drive it before you believe it. The sheer power was just remarkable.

Also Read: What Is Engine Redlining And Does It Hurt Your Engine?


Informative Read: The “By-Wire” System Explained (Drive, Brake, Steer, Shift, Throttle)

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Utkarsh Bhardwaj
Utkarsh Bhardwaj
Technical Content Strategist at GoMechanic | Big Time Petrolhead with the passion for building cars and driving those beauties.


  1. Be Specific About automobile world, because two stroke engine is still popular and advancing in Marine World


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