How a motorcycle works

How a motorcycle works – FI Racing's guide

Understand the basics of how a motorcycle works. Whether you're a new rider or looking to maintain your bike, this guide will help you understand how a bike works. A motorcycle can't move without three things: fuel, air, and spark. Together, they create the engine's power source—the explosion that turns the rear wheel.

Engine Operation – Two-Stroke vs. Four-Stroke

The engine is the heart of the bike. A two-stroke engine (2T) is light, simple and efficient – especially in mopeds and enduros. A four-stroke (4T) engine offers more torque and a longer service life.

Basic principle:

-Fuel + air → compression → spark → explosion → movement

-This rotation is transferred to the crankshaft, which moves the wheel via chains.


1 - Air and gasoline mix


It all starts when oxygen comes in with the intake air and a carburetor (e.g. PWK) mixes the right amount of gasoline with it. This mixture is called the air-fuel mixture.

If the mixture is too lean (too much air), the engine may run hot. If the mixture is too rich (too much gasoline), the engine may choke or smoke.

2 - The mixture enters the cylinder


The piston moves downwards and sucks the mixture into the engine. When the piston rises up, it compresses the mixture.

3 - The spark ignites the mixture

Once the mixture is compressed, the spark plug provides a spark. The mixture explodes, creating enormous pressure that quickly pushes the piston down.

This movement is the "explosion phase" of the engine – it provides power.

4 - The crankshaft converts motion into rotation


The piston's motion is transferred to the crankshaft, which rotates after each explosion.

The crankshaft ultimately rotates the chain, which transfers power to the rear wheel.

5 - The rear wheel spins and the bike moves


The chain connects the engine and the rear wheel. When the crankshaft rotates → the chain rotates → the rear sprocket rotates → the rear wheel moves forward.