In a 4-stroke engine the piston completes four separate strokes during two revolutions of the engine’s crankshaft.

How does it work?

The four strokes of the cycle are intake, compression, power, and exhaust. Each stroke corresponds to one full stroke of the piston, meaning that the complete cycle takes two revolutions of the crankshaft to complete.

A complete cycle works as follows:

The piston moves down from the top of the cylinder to the bottom, forcing a mixture of air and fuel into the cylinder. The intake valves then close.

With intake and exhaust valves closed, the piston moves back up to the top of the cylinder. This compresses the air/fuel mixture in the combustion chamber of the cylinder head.

The spark plug fires to ignite the compressed fuel. As the fuel burns it expands and forces the piston back down.

At the bottom of the power stroke the exhaust valve opens. The upward stroke then pushes exhausted fuel through the valve and out of the cylinder before the cycle is repeated.

Looking after your 4-stroke engine

To keep your engine running smoothly, it’s important to use a quality 4-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.
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