A drive unit is situated between a first wheel axle and a second wheel axle and has an internal-combustion engine with a crankshaft system including a horizontally oriented crankshaft, which crankshaft acts upon a continuously variable transmission system which drives wheels of the first wheel axle and of the second wheel axle. The crankshaft is caused to rotate by at least one piston of the engine. The crankshaft interacts with a first set of V-pulleys of the transmission system, which first set of V-pulleys, by way of a first drive shaft, is connected with a first differential of the first wheel axle. The first set of V-pulleys, by way of an endless member, is in an operative connection with a set of V-pulleys which, with the interposition of a second drive shaft, influences a second differential of the second wheel axle.

An internal combustion engine includes a reduction gear including: at one end thereof, a small-diameter gear in mesh with a one-way clutch gear; and at an opposite end thereof, a large-diameter gear in mesh with a drive gear of a starter motor. The starter motor has a driveshaft disposed below a rotation axis of the reduction gear and within a width of the large-diameter gear as viewed in an axial direction. Accordingly, in the internal combustion engine, it is possible to efficiently dispose components in a reentrant space formed between a crankcase and a cylinder block.

A camshaft housing includes two longitudinal frame bars and lateral frame bars. The longitudinal frame bars extend in the axial direction of a camshaft. The lateral frame bars extend between the longitudinal frame bars. A bearing portion is arranged in each of the lateral frame bars to rotationally support the camshaft. Each lateral frame bar has a bolt hole to receive a bolt that is inserted through the bolt hole to fix the camshaft housing to a cylinder head body. The bolt hole extends through the lateral frame bar and is arranged on the outer side of the bearing portion in the longitudinal direction of the lateral frame bar. Each longitudinal frame bar has a vibration reducing portion. The cross-sectional area of the longitudinal frame bar gradually changes in the longitudinal direction of the longitudinal frame bar.

An internal combustion engine optimizing small-size arrangement of the valve drive mechanism, considering that the exhaust valve diameter is smaller than the intake valve diameter. Intake and exhaust valves are in a radial arrangement, intake and exhaust cam surfaces are inclined relative to intake and exhaust cam axes, intake and exhaust rocker arm support members are inclined correspondingly in the same way and disposed between an intake camshaft and an exhaust camshaft. Pivotal support base portions of intake rocker arms and pivotal support base portions of exhaust rocker arms are disposed such that the distances thereof from a joining surface joining a cylinder head and a cylinder body are different.

A camshaft module includes: a head cover in which a camshaft is seated; a cylinder head with an upper portion coupled to a lower portion of the head cover, and in which a plurality of cam followers, operated according to a rotation of the camshaft, are formed on the upper portion; and a gasket sealing between the head cover and the cylinder head. The gasket has a plurality of cam holes formed therein. The cam followers penetrate through the cam holes. The gasket has supporting parts formed to protrude so as to prevent a falling of the cam followers around the cam holes.

Provided is a V engine which uses common cylinder heads, and permits favorable arrangement of oil passages so as to accommodate various oil regulating features that are required to operate valve property varying mechanisms. Each end of each cylinder head is formed with a plurality of distribution oil passages opening out at an upper surface of the cylinder head for supplying oil pressure from a main gallery to a valve actuating mechanism. A pair of oil passage connecting members internally defining mutually different connecting oil passages are attached to the upper surfaces of the corresponding end parts of the respective cylinder heads.

A drive unit is situated between a first wheel axle and a second wheel axle and has an internal-combustion engine with a crankshaft system including a horizontally oriented crankshaft, which crankshaft acts upon a continuously variable transmission system which drives wheels of the first wheel axle and of the second wheel axle. The crankshaft is caused to rotate by at least one piston of the engine. The crankshaft interacts with a first set of V-pulleys of the transmission system, which first set of V-pulleys, by way of a first drive shaft, is connected with a first differential of the first wheel axle. The first set of V-pulleys, by way of an endless member, is in an operative connection with a set of V-pulleys which, with the interposition of a second drive shaft, influences a second differential of the second wheel axle.

A camshaft module includes: a head cover in which a camshaft is seated; a cylinder head with an upper portion coupled to a lower portion of the head cover, and in which a plurality of cam followers, operated according to a rotation of the camshaft, are formed on the upper portion; and a gasket sealing between the head cover and the cylinder head. The gasket has a plurality of cam holes formed therein. The cam followers penetrate through the cam holes. The gasket has supporting parts formed to protrude so as to prevent a falling of the cam followers around the cam holes.

An internal combustion engine includes a throttle valve assembly having a main passage and an idle air passage. The main passage is in fluid communication with the intake valve, air being intermittently input into a combustion space through the main passage based on position of an intake valve. The idle air passage is integrally formed in the throttle valve body, and is controlled by a motor to selectively introduce air into the main passage downstream of the throttle plate. For a cylinder hole diameter in the range from 70 mm to 74 mm, both the intake valve angle defined between the intake valve axis and the cylinder axis and the exhaust valve angle defined between the exhaust valve axis and the cylinder axis are in the range from 11 degrees to 15 degrees.

An internal combustion engine includes a throttle valve assembly having a main passage and an idle air passage. The main passage is in fluid communication with the intake valve, air being intermittently input into a combustion space through the main passage based on position of an intake valve. The idle air passage is integrally formed in the throttle valve body, and is controlled by a motor to selectively introduce air into the main passage downstream of the throttle plate. For a cylinder hole diameter in the range from 70 mm to 74 mm, both the intake valve angle defined between the intake valve axis and the cylinder axis and the exhaust valve angle defined between the exhaust valve axis and the cylinder axis are in the range from 11 degrees to 15 degrees.