PURPOSE: To reduce the occurrence of unevenness in a scavenging timing and an exhaust time by a method wherein a cylinder block is divided at a division surface from the upper end in a piston slide direction of the cylinder block to the lower end thereof and the port of each of a cylinder sleeve and the cylinder block is machined.

CONSTITUTION: A cylinder 10 is formed in a cylindrical shape and assembled with a cylinder sleeve 12 and a cylinder block 14, where a piston is slid over an inner peripheral surface 12a. Main scavenging ports 16MR and 16mR, auxiliary exhaust ports 16SR and 16sR, and a main exhaust port 8M and an auxiliary exhaust port 18SR are respectively caused to correspond to each other. In the above constitution, the cylinder block 14 is divided into right and left half bodies 14R and 14L at a cut surface extending from an upper end in the slide direction of a piston to a lower end. Each port of the whole or a part of the cylinder 10 is formed with high precision through a machining work. This constitution reduces the occurrence of unevenness in scavenging and exhaust timings and performs exchange of only the cylinder sleeve 12.