TWO-CYCLE INTERNAL COMBUSTION ENGINE

PROBLEM TO BE SOLVED: To provide an air-preceding two-cycle internal combustion engine in which gaseous mixture is prevented from being mixed in air previously introduced into a combustion chamber during scavenging so that stratified scavenging can be carried out more completely. SOLUTION: The two-cycle internal combustion engine is provided with single or plural pairs of schnurle scavenging passages 31, 31, 32, 32 which are so located symmetrically with respect to a longitudinal section F-F which divides an exhaust hole 34 in two parts, as to connect the combustion chamber 15 and a crankcase 18 with each other, in such a manner that the air is introduced into the scavenging passages and that the gaseous mixture is introduced into the crankcase. In the descending stroke of a piston 20, scavenging ports 31a, 32a provided at the downstream ends of the scavenging passages are opened after the exhaust hole is opened, thereby introducing the air into the combustion chamber through the scavenging passages prior to the gaseous mixture. The single or plural pairs of scavenging passages include throttle portions 31e, 32e formed adjacently to the end portions of the scavenging passages on the side of the crankcase.