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Four Storke Motorcycle Engine
- Oct 20, 2017 -

Four stroke engine,the piston should be fired once every four times. Namely:

1. intake: at this point, the inlet valve opens, the piston down, 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 up, the mixture is compressed.

3. combustion: when the mixer is compressed to the minimum, the spark plug ignites and ignites the mixture. The pressure generated by the combustion pushes the piston downward and drives the crankshaft to rotate.

4. exhaust: when the piston goes down to the lowest point, the exhaust valve opens, the exhaust gas is discharged, the piston continues to go up and the surplus exhaust gas is discharged.

Motorcycle knowledge -- Engine chapter


The 4 journeys are carried out separately, so the work is reliable, efficient and stable. High speed range from low speed to high speed

Reduce the backflow loss of gas channeling and low fuel consumption.

Low speed running smoothly, lubricated by lubrication system, not easy to overheat.

• volumetric efficiency, average effective pressure.

• heat load is smaller than two stroke engine. Large displacement, can be designed into high-power engines.


Valve complex, many parts, maintenance difficulties

• large mechanical noise

• because the crankshaft rotates 2 times fire 1 time, the balance of rotation is unstable

Classification according to valve mechanism

According to the valve mechanism, the engine can be divided into lateral camshaft and top camshaft, also called CG machine and CB machine.

CG series top rod machine - side camshaft (OHV) engine

In 1899, the French bichet in order to improve the speed and power of engine, launched the first side camshaft mechanism (OHV). The cam shaft is installed on the lower side of the cylinder, the push rod rocker arm longer to push through the downward pressure on the valve rocker; valve can be arranged on the cylinder head, the optimization is hemispherical or wedge that the combustion chamber, so as to improve the compression ratio of the engine and the heat efficiency, achieve high speed and high power objective.