Abstract: An intake system construction for an internal combustion engine includes a combustion chamber formed with upper and lower extremities thereof defined by a lower wall of a cylinder head and a top wall of a piston, an intake open end formed in the lower wall in opposition to the combustion chamber on one side of a reference plane which contains a central axis of the cylinder, an intake port formed in communication with the combustion chamber via the intake open end and extending upwardly from the intake open end so that a vertical swirl of inducted air is formed in the combustion chamber, an intake valve having a head portion for opening or closing the intake open end and a stem portion extending from the head portion to an upstream side of the intake port through the cylinder head, and a straightening member arranged in the intake port on a downstream side of the stem portion so that an inducted air flow is straightened on the downstream side of the stem portion.

Abstract: An intake system construction according to the present invention for an internal combustion engine is provided with a combustion chamber formed with upper and lower extremities thereof defined by a cylinder head and a piston, an intake open end arranged for being opened or closed by an intake valve, an exhaust open end arranged for being opened or closed by an exhaust valve, an intake port formed extending upwardly from the intake open end so that a vertical swirl of inducted air is formed in the combustion chamber, and an exhaust port for discharging combustion gas from the combustion chamber. The intake port is formed wider in one of halves thereof located adjacent a reference plane, which contains a central axis of a cylinder, than in the other half thereof located remote from the reference plane.

Abstract: An intake system construction according to the present invention for an internal combustion engine is provided with a combustion chamber formed with upper and lower extremities thereof defined by a cylinder head and a piston, an intake open end arranged for being opened or closed by an intake valve, an exhaust open end arranged for being opened or closed by an exhaust valve, an intake port formed extending upwardly from the intake open end so that a vertical swirl of inducted air is formed in the combustion chamber, and an exhaust port for discharging combustion gas from the combustion chamber. The intake port is formed wider in one of halves thereof located adjacent a reference plane, which contains a central axis of a cylinder, than in the other half thereof located remote from the reference plane.