ENGINE

An upwardly protruding cylinder block (30) is formed in a front portion of a crankcase (28) for supporting a crankshaft (26) of an engine (E). A cylinder head (32) is connected with an upper portion of the cylinder block (30), and a combustion chamber (71) of an internal combustion engine is formed within the cylinder block (30) and the cylinder head (32). A knocking sensor (80) for detecting the occurrence of knocking in the engine (E) is fitted to a left side end surface (30) of the cylinder block (30).