A small air-cooled internal combustion engine includes an aluminum cylinder block at least partially defining an aluminum cylinder bore, an aluminum cylinder head attached to the aluminum cylinder block, and an aluminum push rod tube separate from and press fit between the aluminum cylinder block and the aluminum cylinder head. The aluminum push rod tube includes a cylinder block end portion, a cylinder head end portion, and a main body extending between the cylinder block end portion and the cylinder head end portion.

A crankcase for a reciprocating piston engine, in particular of a motor vehicle, includes at least first one wall region that has a greater wall thickness than at least one second wall region of the crankcase that adjoins the first wall region. The crankcase is produced from an aluminum alloy and by at least mainly laminar die casting and is heat-treated completely or heat-treated completely and additionally locally or heat-treated only locally.

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.

A cover of an internal combustion engine includes a cover body to be mounted to a crankcase of the internal combustion engine. The cover body includes a through hole, a protruding part, and a plurality of first recessed grooves. The through hole is to support a shaft rotatably. The protruding part is provided above the through hole in an upward direction of the internal combustion engine and protrudes toward an inside of the cover body facing the crankcase. The protruding part includes a first upper part and a first lower part in the upward direction on an inner surface of the protruding part facing the crankcase. The plurality of first recessed grooves extend radially from the through hole so as to connect the upper part and the lower part of the protruding part.

An engine assembly includes an air-cooled engine and an external oil reservoir. The engine includes a vertically-oriented crankshaft a crankcase cover having a front portion and a rear portion, wherein the front portion of the crankcase cover and the cylinder head are located forward of a vertical plane that includes the crankshaft axis, a return pump housing formed in the exterior of the crankcase cover, a return pump positioned in the return pump housing, and a return pump inlet formed through the crankcase cover, wherein the return pump inlet is located in the front portion of the crankcase cover and the return pump inlet is located closer to the camshaft than to the crankshaft. The external oil reservoir includes an oil tank and an oil filter assembly.

An engine assembly includes an engine, an external oil reservoir, a supply pump, and a return pump. The engine includes an oil gallery configured to distribute oil and a crankcase chamber. The external oil reservoir includes an oil tank defining an oil chamber and an oil filter assembly including a housing at least partially defining a filter chamber, and a filter positioned within the filter chamber. The supply pump is in fluid communication with the oil chamber and the oil gallery and the supply pump is configured to draw oil from the oil chamber and provide pressurized oil to the oil gallery. The return pump in fluid communication with the crankcase chamber and the filter chamber and the return pump is configured to draw oil from the crankcase chamber and provide pressurized oil to the filter chamber.

A small air-cooled internal combustion engine includes an aluminum cylinder block and an aluminum cylinder head welded to the aluminum cylinder block.

A small air-cooled internal combustion engine includes an aluminum cylinder block, an aluminum cylinder head welded to the aluminum cylinder block, and a weld securing the aluminum cylinder block to the aluminum cylinder head, wherein a joint having a first length is formed between the aluminum cylinder block and the aluminum cylinder head and wherein the weld extends for a second length that is at least 25% of the first length.

A two-stroke engine has a cylinder with a combustion chamber formed therein. The combustion chamber is delimited by a piston. The cylinder has a base on which extends a partition plane whereat the cylinder is separated from a crankcase. The combustion chamber is, in at least one piston position, connected via at least one transfer channel to the crankcase interior. The transfer channel passes from the cylinder into the crankcase at at least one opening. A side wall of the transfer channel has, in the cylinder, a first region wherein the wall encloses an angle of 90 with the cylinder longitudinal axis. Between the first region and the opening as viewed in the cylinder circumferential direction is arranged a second wall region. The second region has a spacing, measured parallel to the cylinder longitudinal axis, to the partition plane. The spacing is greater than the spacing in the first region.

A small air-cooled internal combustion engine includes an aluminum cylinder block, an aluminum cylinder head welded to the aluminum cylinder block, and a weld securing the aluminum cylinder block to the aluminum cylinder head, wherein a joint having a first length is formed between the aluminum cylinder block and the aluminum cylinder head and wherein the weld extends for a second length that is at least 25% of the first length.