PURPOSE: To obtain good loop scavenging by forming mask wall extending toward a combustion chamber from the internal wall surface of a cylinder head, between intake and exhaust valves, and allowing an opening port between the periphery of the intake valve at the exhaust valve 7 side and the valve seat to close during the period of full opening of the intake valve by these mask walls.
CONSTITUTION: A projected part 5 is formed toward a combustion chamber 4 on the internal wall surface 3a of a cylinder head 3 while it is extended along the entire diameter line on the internal wall surface 3a of the cylinder head 3. The projected part 5 is formed in triangular section with a ridge 5a on the bottom thereof, and a pair of intake valves 6 are positioned at one side of the projected part 5 and a pair of exhaust valves 7 are positioned at the other side thereof. A mask wall 10 is formed for each intake valve 6 to cover the opening port between the periphery of the intake valve 6 positioned at the exhaust valve 7 side and a valve seat 9. The opening ports can be closed, by these mask walls 10, during the period of full opening of the intake valve 6, and thus good loop scavenging can be maintained.
NAKAMURA NORIHIKO
KANAMARU MASANOBU
EINAGA HIDEO
NOGUCHI HIROSHI
NOMURA KENICHI
UMEHANA TOYOICHI
KOBAYASHI TATSUO
ITO TOSHIO
ITO KAZUHIRO
NAKAE KOICHI
