Understanding how your lawnmower works can be the first step to diagnosing a problem should it occur. Remember that eSpares stocks a huge selection of lawnmower spare parts and accessories.
The Four-Stroke Engine Cycle:
Inside the cylinder of a petrol engine, the cycle begins with the piston moving down and drawing a mixture of air and fuel into the combustion chamber through the intake valve. This is called either the intake stroke or induction stroke.
The piston then begins to move upwards, the intake valve closes and the air/fuel mixture is compressed. This stage is called the compression stroke.
When the piston is nearly at the top of its travel, the combustion stroke or power stroke starts. The spark plug fires and ignites the air/fuel mixture, which expands and forces the piston down at high speed.
The last stage is the exhaust stroke. Here the momentum of the engine forces the piston back up and the exhaust valve opens allowing the spent fuel gases to escape.