Abstract: An intake port for a 4-cycle engine includes an intake port base integrally formed with a cylinder head, and an intake port forming member that forms an intake port together with the intake port base. The area of the cross section of the intake port orthogonal to a centerline of the intake port is substantially uniform from an open intake side thereof toward a combustion chamber. The angle made by the centerline of the intake port and an intake valve shaft is larger than 90° from a viewpoint of the intake valve. Thereby, the 4-cycle engine can output high power with the intake port shape, as formed with above mentioned configuration, that reduces intake resistance and that uses simple design molds. More specifically, the engine can reliably prevent condensed fuel from remaining in the intake port to avoid incomplete combustion of gas.

Abstract: A portable 4-cycle engine with a configuration which allows cooling air to flow in the direction of the crankshaft relative to a cylinder head on a cylinder, and a portable machine equipped with this engine, are provided, respectively. In such an engine, the cylinder is separated from the cylinder head including a combustion chamber formed at the cylinder side therein. The engine further comprises a valve train area formed in the cylinder head at the downwind side of the cooling air, and a plurality of vertical fins protruding upward from the cylinder head and extending in the direction of the crankshaft. The valve train area and the plurality of vertical fins are all integrally formed with the cylinder head, so that the cylinder head can be made thinner and lighter with high rigidity to enable the portable machine to become smaller, lighter, and more powerful.