An engine is described having a crankcase, a liner and a head assembly. The crankcase is split along a plane defining a two part crankcase, where fluid passages are passing through only one of the crankcase portions, so as to not require crossing the split line. A connecting rod also includes a tapered end, and the piston has a complementary carrier receiving the connecting rod.

In an internal combustion engine for a saddle riding vehicle, in which a gear transmission and a shift drum of a shift change device is stored in a crankcase, the gear transmission having a plurality of transmission shafts parallel to a crankshaft extending in a vehicle width direction, a single pump shaft common to first and second oil pumps is rotatably supported by the crankcase. First oil pump rotors of the first oil pump are disposed at a mating face of a pair of left and right crankcase half bodies. A second oil pump rotor of the second oil pump is disposed between a pump gear and the first oil pump and at a side surface, on a side opposite to the mating face, of one crankcase half body out of the pair of left and right crankcase half bodies, the pump gear being arranged in the pump shaft.

An engine includes a crankcase in which a crank chamber that houses a crankshaft is formed, a cylinder block that is attached to the crankcase, and a cylinder that is formed with a sliding surface with respect to a piston. The crankcase includes a partition wall that forms the crank chamber. A lower end of the cylinder protrudes into the crank chamber from a lower end of the cylinder block, and a communicating hole that connects inside and outside of the cylinder is formed on a side surface of the cylinder as viewed in an axial direction of the crankshaft. The partition wall is formed with an opening that is communicated with the communicating hole.

An engine includes a crankcase in which a crank chamber that houses a crankshaft is formed, a cylinder block that is attached to the crankcase, and a cylinder that is formed with a sliding surface with respect to a piston. The crankcase includes a partition wall that forms the crank chamber. A lower end of the cylinder protrudes into the crank chamber from a lower end of the cylinder block, and a communicating hole that connects inside and outside of the cylinder is formed on a side surface of the cylinder as viewed in an axial direction of the crankshaft. The partition wall is formed with an opening that is communicated with the communicating hole.

An engine is described having a crankcase, a liner and a head assembly. The crankcase is split along a plane defining a two part crankcase, where fluid passages are passing through only one of the crankcase portions, so as to not require crossing the split line. A connecting rod also includes a tapered end, and the piston has a complementary carrier receiving the connecting rod.

An engine is described having a crankcase, a liner and a head assembly. The crankcase is split along a plane defining a two part crankcase, where fluid passages are passing through only one of the crankcase portions, so as to not require crossing the split line. A connecting rod also includes a tapered end, and the piston has a complementary carrier receiving the connecting rod.

A small air-cooled internal combustion engine includes an aluminum engine block including a cylinder extending along a longitudinal cylinder axis and a block mounting surface, a piston configured to reciprocate within the cylinder, a crankshaft coupled to the piston and configured to rotate about a crankshaft axis in response to reciprocation of the piston, and an aluminum crankcase cover including a cover mounting surface. The block mounting surface contacts the cover mounting surface. The block mounting surface and the cover mounting surface are both positioned at an angle to the crankshaft axis and the angle is not 90 degrees.

In an internal combustion engine for a saddle riding vehicle, in which a gear transmission and a shift drum of a shift change device is stored in a crankcase, the gear transmission having a plurality of transmission shafts parallel to a crankshaft extending in a vehicle width direction, a single pump shaft common to first and second oil pumps is rotatably supported by the crankcase. First oil pump rotors of the first oil pump are disposed at a mating face of a pair of left and right crankcase half bodies. A second oil pump rotor of the second oil pump is disposed between a pump gear and the first oil pump and at a side surface, on a side opposite to the mating face, of one crankcase half body out of the pair of left and right crankcase half bodies, the pump gear being arranged in the pump shaft.

A cylinder block for an engine includes a first composite portion having a first surface adjacent to a first recess, a second composite portion having a second surface adjacent to a second recess, and a cylinder liner received by the first and second recesses and positioned between the first and second portions. The first surface is adapted to mate with the second surface along a plane extending through the cylinder liner.