When we talk about the performance of motorcycles, we must talk about motorcycle engines. This is because people can always feel the vibration, heat and exhaust sound of the engine when riding a motorcycle.

On motorcycles, a very common engine is a piston reciprocating internal combustion engine.

Engines can be divided into two-stroke and four-stroke according to the stroke. At present, four-stroke engines are widely used. So, let's focus on the four-stroke.

Four-stroke engine, that is, the cylinder ignites once every four reciprocating movements of the piston. They are:

1. Intake: At this time, the intake valve opens, the piston moves downward, and the mixture of gasoline and air is sucked into the cylinder.

2. Compression: At this time, the intake valve and exhaust valve are closed at the same time, the piston moves upward, and the mixture is compressed.

3. Combustion: When the mixer is compressed to a small level, the spark plug jumps and ignites the mixture. The pressure generated during the combustion process continuously pushes the piston downward and drives the entire crankshaft to rotate.

4. Exhaust: When the piston drops to a specific point, the exhaust valve opens and the exhaust gas is discharged. The piston continues to discharge excess exhaust gas upward.

Advantages:

1. Each of the four strokes is performed independently, and the operation is reliable, efficient and stable. The speed range from low speed to high speed is large.

2. Reduce the loss of blowby gas reflux and the fuel consumption rate is low.

3. Smooth operation at low speed, relying on lubrication system lubrication, not easy to overheat.

4. High volumetric efficiency and high average effective pressure.

5. The heat load is smaller than that of a two-stroke engine. The displacement is large and can be designed as a high-power engine.

Disadvantages:

1. The valve timing mechanism is complex, with many parts and difficult maintenance.

2. High mechanical noise

3. The rotation balance is unstable because the crankshaft explodes once every 2 revolutions.