This invention has two main embodiments. An opposed piston 2-stroke axial engine and a 4-stroke axial engine. The opposed piston two stroke also offers an option of a novel cylinder deactivation design. Both, two stroke and four stroke engines share novel systems for coupling piston reciprocation to shaft rotation, piston and piston ring lubricant distribution, and provision for reacting out piston side load with minimum mechanical friction

The present invention relates to a two strokes per cycle Scotch Yoke engine that completes four power strokes per revolution per pair of pistons/cylinders by using both sides of each piston as a combustion chamber. This doubles the power to weight ratio over previous scotch yoke engines and quadruples the power to weight ratio over conventional 4 stroke cycle engines. The present invention is capable of operating in and withstanding the forces of either deflagration (subsonic) and pulse detonation (supersonic) cycles, and is capable of homogeneous charge compression ignition. The present invention can also be an internal/external combustion gas/steam hybrid. The present invention can operate under constant volume or constant pressure cycles as well as most thermal cycles of operation (EG the Otto and Diesel cycle). The present invention works best when using a modified Humphrey cycle to achieve homogeneous charge compression ignition pulse detonation engine using constant volume combustion.

The present invention relates to a two strokes per cycle Scotch Yoke engine that completes four power strokes per revolution per pair of pistons/cylinders by using both sides of each piston as a combustion chamber. This doubles the power to weight ratio over previous scotch yoke engines and quadruples the power to weight ratio over conventional 4 stroke cycle engines. The present invention is capable of operating in and withstanding the forces of either deflagration (subsonic) and pulse detonation (supersonic) cycles, and is capable of homogeneous charge compression ignition. The present invention can also be an internal/external combustion gas/steam hybrid. The present invention can operate under constant volume or constant pressure cycles as well as most thermal cycles of operation (EG the Otto and Diesel cycle). The present invention works best when using a modified Humphrey cycle to achieve homogeneous charge compression ignition pulse detonation engine using constant volume combustion.

A pump shaft support structure includes: a crankcase body which rotatably supports a crankshaft of an engine; a pump shaft which interlockingly rotates with the crankshaft; a crankcase cover which covers the crankcase body; a pump cover which is coupled to the crankcase cover to define a pump chamber therebetween; and a pump rotor which is disposed in the pump chamber and engages with the pump shaft. The pump shaft includes: a supported section which is rotatably supported by the pump cover on the other side of the pump chamber from the crankcase cover; and an insertion section adjoining the supported section in an axial direction. The pump cover has a through bore which passes the insertion section of the pump shaft therethrough. The insertion section of the pump shaft has a diameter smaller than that of the supported section.

A method of operating a fan for an air-cooled internal combustion engine includes starting the air-cooled internal combustion engine, operating the fan in a first operating mode in which the fan rotates in a first direction, and operating the fan in a second operating mode in which the fan rotates in a second direction.

A baffle for a thermal transfer device can include a body having a multiple first apertures that traverse therethrough, where each first aperture has a first outer perimeter that includes a first base shape and at least one first protrusion extending from the first base shape. Each of the first apertures is configured to receive a tube. The first base shape of each first aperture has a first shape and a first size that is configured to be substantially the same as the first shape and the first size of an end of a tube.

An outboard motor to be attached to a hull of a marine vessel that reduces an amount of oil in blow-by gas reaching a breather chamber includes an internal combustion engine including a cylinder block including at least one cylinder. The cylinder block includes two blow-by gas flow paths to guide blow-by gas from a crank chamber to a breather chamber, and the internal combustion engine is oriented such that a crankshaft extends along a direction perpendicular or substantially perpendicular to a bottom of the hull when the marine vessel is sailing.

A pump shaft support structure includes: a crankcase body which rotatably supports a crankshaft of an engine; a pump shaft which interlockingly rotates with the crankshaft; a crankcase cover which covers the crankcase body; a pump cover which is coupled to the crankcase cover to define a pump chamber therebetween; and a pump rotor which is disposed in the pump chamber and engages with the pump shaft. The pump shaft includes: a supported section which is rotatably supported by the pump cover on the other side of the pump chamber from the crankcase cover; and an insertion section adjoining the supported section in an axial direction. The pump cover has a through bore which passes the insertion section of the pump shaft therethrough. The insertion section of the pump shaft has a diameter smaller than that of the supported section.

An air-cooled internal combustion engine including a crankshaft rotating about a crankshaft axis, a first cylinder having a first cylinder head, a second cylinder having a second cylinder head, and a blower assembly. The blower assembly includes a blower housing, a first fan, and a second fan. The first fan is positioned proximate the first cylinder and the second fan is positioned proximate the second cylinder. The first fan and the second fan are each received within the blower housing.

An engine assembly includes a small air-cooled engine and a dry sump lubrication system including an external oil reservoir, wherein the dry sump lubrication system has an overall oil capacity that provides at least five hundred hours of engine oil life.