Cylinder head of a four-cycle engine

Claim 1

A cylinder head assembly for an internal combustion engine, comprising an elongate cylinder head arrangement having upper and lower surfaces and a central plane which extends in the elongate direction in substantially perpendicular relationship to the lower surface, a plurality of combustion chamber openings opening inwardly into the cylinder head arrangement from the lower surface in spaced relationship generally along the central plane, an inlet passage formed in said cylinder head arrangement and communicating with a respective said combustion chamber opening and having a poppet-type inlet valve movably associated therewith, the inlet valve having a stem projecting upwardly toward the upper surface, an exhaust passage formed in said cylinder head arrangement and communicating with a respective said combustion chamber opening and having a poppet-type exhaust valve movably associated therewith, said exhaust valve having a stem projecting upwardly of the cylinder head arrangement, said inlet and exhaust valves having upper ends disposed in sidewardly offset relationship on opposite sides of said central plane, an elongate cam shaft disposed adjacent the upper surface of said cylinder head arrangement and rotatably supported thereon, said cam shaft extending generally parallel with but being sidewardly offset to one side of said central plane, first and second cams secured to and rotatable with said cam shaft, an elongate rocker support shaft disposed adjacent the upper surface of said cylinder head arrangement and supported thereon, said rocker support shaft extending generally parallel with said cam shaft and being disposed sidewardly between said cam shaft and said central plane, a single-arm rocker mounted adjacent one end thereof to said rocker support shaft and engaged at the other end thereof with the upper end of one of said intake and exhaust valves, said first cam being maintained in sliding engagement with said single-arm rocker at a location between the ends thereof, a double-arm rocker mounted at an intermediate part thereof to said rocker support shaft and having a first arm which projects outwardly from said rocker support shaft and adjacent its free end is engaged with said second cam, said double-arm rocker having a second arm which projects outwardly from said rocker support shaft and adjacent its free end is engaged with the upper end of the other of said intake and exhaust valves, a spark plug hole extending downwardly from the upper surface through said cylinder head arrangement for communication with a respective combustion chamber opening, and a spark plug mounted adjacent the lower end of said hole for communication with the combustion chamber opening.