Get The App From Play Store!

Skip to main content
  • Over 4 million customers served

    Part assist UK call centre

  • Over 299,000 Reviews!

    Rated 4.7/5

  • 15 million parts delivered

    Fast UK Delivery

How a Four-Stroke Engine Works

A great way of better diagnosing a fault with your lawn mower is to better understand and increase your knowledge of the machine. With eSpares stocking a large selection of lawnmower spare parts, when a fault occurs - and you have identified that fault - you won’t need to worry about those hefty repair fees, as we might just have what you need.

Here we have highlighted the four steps that a four-stroke engine takes to begin the combustion cycle.

Intake Stroke

Intake Stroke

Inside your petrol engine's cylinder, the cycle begins with the piston moving down and drawing a mixture of air and fuel; this gets taken into the combustion chamber through the intake valve. This process is the intake stroke or induction stoke.

Compression Stroke

The compression stroke is a slightly different process, when the piston begins to move upwards, the intake valve closes and the air and fuel mixture is compressed.

Combustion Stroke

A combustion stroke is when the piston is nearly at the top of its travel and the combustion or power stroke will begin. The spark plug will then fire and the air and fuel mixture will ignite, this expands and forces the piston down at high speed.

Combustion Stroke


Exhaust Stroke

The final stage is called the exhaust stroke, at this point the momentum of the engine forces the pistons back up and the exhaust valve opens. This allows the spent fuel gases to escape.

Understanding how your appliance works can greatly improve your chances of correctly diagnosing any faults, and with the assistance of our vast catalogue of spares you can hopefully continue to use your trusted mower time and time again!

Print Article Print this article