Every motorcycle engine must have 3 things to run:
- A combustable mixture, or fuel.
- Compression. When the pistons move, air needs to be compressed in the cylinders.
- Spark. As compression pulls fuel into the combustion chamber, something needs to ignite the mixture.
A motorcycle engine runs as these 3 things (fuel, compression, spark) happen in a continuous cycle.
The fuel mixture is pulled into the cylinder under compression, it’s ignited by the spark at the right moment, and it’s expelled from the cylinder through the exhaust.
To make sure your bike is doing these things properly:
- Ensure the carbs are clean and properly synced.
- Adjust your valves.
- Align the camshaft.
- Time your ignition.
How 4-Stroke Motorcycle Engines Work
The intake valves open as the piston is on the down stroke and the fuel/air mixture is pulled into the engine’s cylinder. The intake valve closes as the piston comes back up and the mixture is compressed and ignited. The piston is pushed down as a result, the exhaust valves open and the burnt gasses are blown out of the engine as the piston returns and the cycle continues.