Patent ID: 6895909

Claim:
A two-cycle combustion engine which comprises: a cylinder block having a two-staged cylinder bore defined therein, said two-staged cylinder bore having a reduced diameter bore portion and a large diameter bore portion; a two-staged piston having a reduced diameter piston portion and a large diameter piston portion and drivingly accommodated within the two-staged cylinder bore; an annular auxiliary chamber defined between the large diameter bore portion of the two-staged cylinder bore and the reduced diameter piston portion of the two-staged piston; an air passage for introducing air into a crank chamber; an air-fuel mixture passage for introducing the air-fuel mixture into the auxiliary chamber; a scavenge air passage for supplying the air within the crank chamber into a combustion chamber; an injection passage for injecting the air-fuel mixture within the auxiliary chamber into the combustion chamber from an inner peripheral surface of the cylinder block in a direction oriented substantially diagonally upwardly; a first check valve for selectively opening or closing the air passage; a second check valve for selectively opening or closing the air-fuel mixture passage; and a third check valve for selectively opening or closing the injection passage, wherein the injection passage includes an iniection port opening into the cylinder bore and positioned at a level higher than an exhaust port opening into the cylinder bore.