How a 2 stroke motorbike engine works

All thrash and blue smoke baby 🙂

A Very Basic 2 Stroke Engine

Please note – the diagram below represents a very simple version of a 2 stroke motorcycle engine, in reality, they are a little bit more complicated!

Engine Terminology…

Stroke: Either the up or down movement of the piston from the top to the bottom or bottom to top of the cylinder (So the piston going from the bottom of the cylinder to the top would be 1 stroke, from the top back to the bottom would be another stroke)

Induction: As the piston travels down the cylinder head, it ‘sucks’ the fuel/air mixture into the cylinder. This is known as ‘Induction’.

Compression: As the piston travels up to the top of the cylinder head, it ‘compresses’ the fuel/air mixture from the carburetor in the top of the cylinder head, making the fuel/air mix ready for igniting by the spark plug. This is known as ‘Compression’.

Ignition: When the spark plug ignites the compressed fuel/air mixture, sometimes referred to as the power stroke.

Exhaust: As the piston returns back to the top of the cylinder head after the fuel/air mix has been ignited, the piston pushes the burnt ‘exhaust’ gases out of the cylinder and through the exhaust system.

Transfer Port: The port (or passageway) in a 2 stroke engine that transfers the fuel/air mixture from the bottom of the engine to the top of the cylinder

The 2 stroke Cycle…

We have simplified this explanation as much as possible so some of the ‘correct’ terms have been replaced. There are many more factors which enable an engine to run, such as fuel/air ratios, ignition timing and shaped piston heads (extensively used in 2 stroke engines) but the explanation below outlines the basic differences between 2 and 4 stroke engine operation.