Abstract: To provide a two cycle combustion engine utilizing a connecting structure of a shape that can be formed inexpensively with a simple process to enable the efficiency of cooling of the cylinder block to be maintained at a high level and, also, that can firmly connect the cylinder block with the crankcase with fastening forces exerted by the fastening bolts, the two cycle combustion engine includes a crankcase 2 including first and second crank casings 2A and 2B that are split in a direction conforming to a crank axis C for operatively supporting a crankshaft 11, and a cylinder block 1 having a cylinder bore 1a defined therein and fixedly mounted atop the crankcase 2 by means of a plurality of fastening members 38 and 39 fitted in a direction upwardly from a crankcase-side.

Abstract: To provide a two cycle combustion engine utilizing a connecting structure of a shape that can be formed inexpensively with a simple process to enable the efficiency of cooling of the cylinder block to be maintained at a high level and, also, that can firmly connect the cylinder block with the crankcase with fastening forces exerted by the fastening bolts, the two cycle combustion engine includes a crankcase 2 including first and second crank casings 2A and 2B that are split in a direction conforming to a crank axis C for operatively supporting a crankshaft 11, and a cylinder block 1 having a cylinder bore 1a defined therein and fixedly mounted atop the crankcase 2 by means of a plurality of fastening members 38 and 39 fitted in a direction upwardly from a crankcase-side.

Abstract: It is an object of the invention to provide an air scavenging two-stroke cycle engine capable of smoothly supplying fuel-air mixture into a combustion chamber, reducing the number of parts to thereby reduce cost, and suppressing the blow-by of the fuel-air mixture. An air scavenging two-stroke cycle engine that introduces fuel-air mixture Introduced into a crank case, through an intake port into a combustion chamber from a first scavenging port, comprising: an air passage; a communicating passage; and a second scavenging port, wherein the second scavenging port is formed in a cylinder such that it is disposed above the intake port and has an upper end higher than an upper end of the first scavenging port, the air passage is connected to the second scavenging port for introducing air through a check valve, and a portion of the air passage that is situated downstream from the check valve communicates with an inside of the crank case through the communicating passage.