Two-stroke engine

A two-stroke engine comprising:

• a cylinder having an inner surface defining a bore;
• a piston reciprocating in the bore of the cylinder;
• a cylinder chamber partitioned by the inner surface of the cylinder and the piston;
• a crank chamber located under the piston;
• an air-fuel mixture intake port causing air-fuel mixture to flow into the crank chamber;
• a scavenging port provided in the inner surface of the cylinder for causing the air-fuel mixture in the crank chamber to flow into the cylinder chamber through a scavenging passage;
• and
• an exhaust port provided in the inner surface of the cylinder for exhausting combustion gas in the cylinder chamber;
• the piston having a communication passage opening to the crank chamber;
• and
• an air intake port provided in the inner surface of the cylinder for causing air to flow into the communication passage;
• wherein the communication passage opens on the outer surface of the piston so that after the outer surface of the piston moving from the bottom dead center toward the top dead center closes the scavenging port so as not to communicate with the cylinder chamber, the communication passage communicates with the air intake port and the scavenging port, whereby, an air flowing via the air intake port into the communication passage and the original air-fuel mixture in the communication passage together form a diluted air-fuel mixture which is more diluted than the original air-fuel mixture, and the diluted air-fuel mixture flows via the scavenging port into the scavenging passage, and
• wherein when the outer surface of the piston moving from the top dead center toward the bottom dead center causes the exhaust port and the scavenging port to open to the cylinder chamber, the combustion gas is exhausted by means of the diluted air-fuel mixture.