How motorcycles work

Take the working principle of a four-stroke engine and a two-stroke engine as an example:

Four-stroke engines are widely used. Four-stroke engines mean that the cylinder fires once every four reciprocating movements of the piston. The specific working principle is as follows:

1. Intake: At this time, the intake valve opens, the piston descends, 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 goes up, and the mixture is compressed.

3. Combustion: When the mixer is compressed to a minimum, the spark plug flashes and ignites the mixture, and the pressure generated by the combustion pushes the piston down and drives the crankshaft to rotate.

4. Exhaust: When the piston descends to the lowest point, the exhaust valve opens, the exhaust gas is discharged, and the piston continues to ascend to discharge the excess exhaust gas.

The working principle of a two-stroke engine As the name implies, a two-stroke engine is that the piston moves up and down for two strokes, and the spark plug ignites once. The intake process of a two-stroke engine is completely different from that of a four-stroke engine. A two-stroke engine undergoes two compressions. On a two-stroke engine, the mixture first flows into the crankcase and then into the cylinder. To be precise, it should flow into the combustion chamber. , The mixture of the four-stroke engine flows directly into the cylinder, the crankcase of the four-stroke engine is used to store oil, and the crankcase of the two-stroke engine cannot store the oil because the crankcase is used to store the mixture, so the oil for the two-stroke engine cannot be used. Recycled combustion oil.

The working process of the two-stroke engine is as follows:

1. The piston moves upward and the mixture flows into the crankcase.

2. The piston goes down to push the mixed air pressure into the combustion chamber to complete the first compression.

3. After the mixture reaches the cylinder, the piston goes up to close the intake and exhaust ports. When the piston compresses the gas to the minimum volume (this is the second compression), the spark plug ignites.

4. The pressure of combustion pushes the piston down. When the piston descends to a certain position, the exhaust port opens first, the exhaust gas is discharged and then the intake port opens, and the new mixture enters the cylinder to squeeze out the remaining exhaust gas.

At the same speed, because the two-stroke engine burns one more time than the four-stroke engine, the power is large, and the two-stroke engine is much lighter than the four-stroke engine of the same displacement, so the two-stroke engine has an overwhelming advantage in racing. , but since the intake and exhaust of the two-stroke engine are carried out at the same time, when the engine speed is low, because the exhaust port is opened for too long, a part of the fresh mixture will be discharged from the exhaust port together with the exhaust gas, so The power is not high at the bottom speed. The new two-stroke engine has added some components to improve this problem, such as YAMAHA's YPVS, HONDA's ATAC SUZUKID's SAEC. A two-stroke engine wears out much faster than a four-stroke engine due to the carbon deposits from the combustion oil and the intake and exhaust holes opened in the cylinder walls.