Two-stroke internal combustion engine

A two-stroke internal combustion engine comprising:

• a crank chamber (22) formed by a cylinder block (12) and a crankcase (20) attached to the cylinder block;
• an air-fuel mixture suction opening (25) in communication with the crank chamber for admitting air-fuel mixture to the crank chamber;
• an exhaust port (28) formed on the cylinder block;
• upper and lower scavenging passages (27, 27) formed at an interior wall of the cylinder block in a longitudinal direction of the cylinder block and symmetrical with respect to a lateral cross section (F) through the exhaust port, with the lower scavenging passage having lesser cross section as compared with the upper scavenging passage;
• and
• a flow restricting portion (40) disposed on an inner peripheral surface (22a) of the crank chamber for restricting liquid fuel flow from the crank chamber into the lower scavenging passage.