A 2-stroke engine achieves all the elements of the 4-stroke engine in just two strokes. With fewer parts they tend to be lighter, simpler and less expensive to manufacture than 4-stroke engines.

How does it work?

A 2-stroke engine uses both the crankcase and cylinder to turn fuel to power in just two strokes. To make this possible, the sparkplug fires once every revolution (as opposed to once every other revolution in a 4-stroke engine).

A complete cycle works as follows:

Intake
The upward stroke of the piston creates a vacuum that draws a mixture of fuel and air into the crankcase.

Crankcase compression
During the downward stroke, the fuel/air mixture is compressed in the crankcase.

Transfer/Exhaust
Towards the end of the downward stroke, the piston exposes the intake port. The compressed fuel/air mixture then rushes into the main cylinder to fill it with a fresh charge of fuel and expel the exhaust gases.

Compression
The piston rises and compresses the fuel/air mixture.

Power
At the top of the stroke, the spark plug fires and ignites the fuel. The burning fuel expands and drives the piston back down to repeat the cycle.

Looking after your 2-stroke engine

To keep your engine running smoothly, it’s important to use a quality 2-stroke motorcycle oil. The right oil won’t just help clean the engine and minimise friction and heat – it will give you better mileage. Find out how Shell Advance oil can help keep your engine in great condition. 

Content courtesy of howstuffworks.com, and animatedengines.com