Abstract: A deflector comprising a U-shaped embossed part is provided on the top surface of the loop scavenging type two-cycle engine in such a direction that the opening of the U-shaped boss is on the side of the exhaust port of the cylinder, and a combustion chamber is shaped such that the U-shaped deflector of the piston is fitted therein and is placed in the cylinder head opposite the said top surface of the piston. When the piston rises and the deflector is fitted inside the combustion chamber of the cylinder head, there is formed a squish zone between the outside area of the deflector at the top surface of the piston and the cylinder head for pressing the air-fuel mixture into the combustion chamber, to thereby decrease the emission of unburned gas containing harmful hydrocarbons and the improve the combustion efficiency for higher output.