Two-stroke cycle engine

A two-stroke cycle engine using a preceding air-layer for scavenging and having a scavenger passage connected to a branching scavenger passage opened to a scavenging port and a connecting passage linking the air and fuel passages so that negative pressure in the air passage forces the fuel-air mixture in the fuel passage into the air passage. The engine also has a removable guide with a surface forming a curved smooth channel which is attachable to the scavenger passage in the crankcase from the mounting surface, and forms a portion of the scavenger passage with the curved channel. The blow-up angle of the scavenger passage varies along the circumference of the cylinder, and the crankcase is configured such that the front and rear portions are separated by a block, and a scavenger passage is provided inside both said front and rear portions of the crankcase and cylinder. Two parallel air passages extend from the air cleaner, the first connected to the air passage, and the second connected to the air inlet of the carburetor to provide air for the fuel passage, and a choke valve on the air cleaner is provided to open and close the first and second air passages.