Reciprocating engine of a spark ignition type

摘要

A spark ignition type reciprocating engine of a natural intake system with an ignition plug arranged to face a combustion chamber defined and delimited by a piston inserted into a cylinder so as to move in a reciprocating way, which has: a bore size of the cylinder ranging from approximately 45 mm to 67 mm; a volume of a single chamber of the cylinder ranging from approximately 110 cc to 340 cc; a ratio of a stroke of the piston to the bore size of the cylinder being larger than 1; and a compression ratio of the engine being 11 or larger.