Piston valve type layered scavenging 2-cycle engine

A piston valve type layered scavenging 2-cycle engine comprising:

• a scavenging port (61) which is open to a cylinder chamber (56) of a cylinder (52) mounted on an upper surface of a crank case (51) forming a crank chamber (57) in an inner side thereof, and sucking a pilot air taken from an external portion so as to scavenge;
• and
• a scavenging flow passage which is provided in an outer side rather than a side wall surface of the cylinder, and communicates the scavenging port and the crank chamber,
• wherein said scavenging flow passage (70) is constituted by a first scavenging passage (71) which is provided in an outer side of a side wall surface of said cylinder so as to be substantially in parallel to an axis of the cylinder, and a second scavenging flow passage (72) which is provided on an upper surface (58) of said crank case opposing to the first scavenging passage so as to be expanded in a substantially perpendicular direction to the first scavenging passage and has an opening portion (73) communicated with said crank chamber in a terminal portion, and
• wherein the opening portion and the second scavenging passage are formed by a recess portion (64) which is provided on the upper surface of said crank case, a cylinder base surface (66) of said cylinder which is brought into contact with the upper surface of the crank case, a cylinder skirt portion (67) in a lower portion of a side surface of the cylinder, and a cylinder skirt extended portion (68) which is extended so as to make a portion opposing to the second scavenging passage in the cylinder skirt portion close to or in contact with a bottom surface portion (65) of the recess portion.