Internal combustion engine

This application is based on Japanese Application No. 2000-173971, filed Jun. 9, 2000, the entire contents of which is hereby expressly incorporated by reference. A four-cycle engine includes a cylinder block defining a cylinder bore. A piston is reciprocally disposed within the cylinder bore. A cylinder head member closes an end of the cylinder bore to define a combustion chamber together with the cylinder bore and the piston. The cylinder head member defines an inner passage having a first end communicating with the combustion chamber and a second end terminating at an outer surface of the cylinder head. A valve assembly having a valve section and an actuateable section is provided. The valve section is selectively placed at an open position and a closed position to connect and disconnect the inner passage with the combustion chamber, respectively. The actuateable section is formed oppositely from the valve section. A valve actuation mechanism is arranged to actuate the actuateable section to move the valve section between the open position and the closed position. The cylinder head member further defines a guide opening through which the actuateable section is slideably disposed. An external conduit defines an outer passage communicating with the inner passage. The external conduit depends from an end portion of the cylinder head member. The cylinder head member still further defines a recessed portion between the guide opening and the second end of the inner passage.