The compression stroke is one of the four strokes that occur in a four-stroke internal combustion engine, including those found in most motorcycle engines. The four strokes are:
Intake stroke: The intake valve opens, allowing the air-fuel mixture to enter the combustion chamber as the piston moves downward.
Compression stroke: Once the intake stroke is complete, both the intake and exhaust valves are closed. The piston moves upward, compressing the air-fuel mixture in the combustion chamber. This compression increases the pressure and temperature of the mixture, preparing it for combustion.
Power (combustion) stroke: At the top of the compression stroke, when the piston is near the top of its travel, the spark plug ignites the compressed air-fuel mixture. The resulting combustion creates a rapid expansion of gases, driving the piston downward with force. This downward motion of the piston is what generates power.
Exhaust stroke: After the power stroke, the exhaust valve opens, and the piston moves upward once again, pushing the burnt gases out of the combustion chamber and into the exhaust system. This process prepares the engine for the next intake stroke.
It's important to note that each of these strokes occurs in a specific sequence and is synchronized with the engine's rotation. The crankshaft, connecting rod, and piston work together to convert the reciprocating motion of the piston into rotational motion, which ultimately drives the motorcycle's wheels.