In a valve train of an internal combustion engine, an input sprocket mounting portion is provided on one end of an exhaust camshaft, and a valve operating cam portion is formed on the other end of the camshaft. A decompression shaft of a decompression device is inserted in a decompression shaft hole, which is formed from the input sprocket mounting portion toward the valve operating cam portion. The decompression shaft hole is formed at a position offset from an axis of the camshaft. A camshaft inner oil passage is formed in the camshaft to extend from one end toward the other end of the camshaft in parallel arrangement to the decompression shaft hole to supply lubricant from the bearing journal portion to the bearing journal portion. The above arrangement makes it possible to supply a sufficient amount of lubricant oil to slide portions of the valve train of a saddle riding vehicle.

A bearing supporting an end of a layshaft in an internal combustion engine is lubricated by injection of oil through a flange that mounts the layshaft on the engine. A pressure responsive flow control valve controls delivery of oil through the flange to the bearing. A backflow prevention adapter prevents backflow of oil to the engine's oil pump.

A bearing supporting an end of a layshaft in an internal combustion engine is lubricated by injection of oil through a flange that mounts the layshaft on the engine. A pressure responsive flow control valve controls delivery of oil through the flange to the bearing. A backflow prevention adapter prevents back flow of oil to the engine's oil pump.

An oil passageway structure for internal combustion engines includes a cylinder head having an inter-bearing wall fluid communication oil passage for providing fluid communication between a plurality of bearing walls to allow oil to flow therebetween. The cylinder head further includes a bearing wall oil passage branched from the inter-bearing wall fluid communication oil passage to supply oil to a bearing surfaces of at least one of the bearing walls. The inter-bearing wall fluid communication oil passage is defined in one of facing side walls. The bearing wall oil passageway is defined in at least one of the bearing walls. The oil passageway structure is thus made up of a reduced number of parts, can be assembled with a reduced number of man-hours, can lead to productivity growth, and is inexpensive to manufacture.

An oil supply path passes through members separate from a cylinder head (4) to supply a lubricant to bearings (73, 74) of camshaft journals. The oil supply path includes an oil supply passage (66) for the camshaft above the camshaft (19, 20), a connection passage (64) for the camshaft between the oil supply passage for the camshaft and an internal passage (61, 62) in the cylinder head (4), and branch oil passages (68) for the camshaft journals. Each branch oil passage branches off from the oil supply passage for the camshaft, and is connected to one of the bearings (73, 74) from above. Each of the branch passages includes a throttle (168) with a smaller cross-sectional flow area than the oil supply passage for the camshaft.

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 control device controls an internal combustion engine including: an elastic wave sensor arranged and configured to output a signal responsive to the strength of an acoustic emission wave produced at a sliding portion; and a variable oil pump. The control device is configured to execute an oil pressure control such that the oil pressure approaches a target oil pressure according to an engine operating condition. This oil pressure control includes a first pressure-increase processing executed where an AE correlation value correlated with the strength or occurrence frequency of the acoustic emission wave detected by the elastic wave sensor is greater than a first threshold value. The first pressure-increase processing increases the target oil pressure associated with a first engine operating condition present when the AE correlation value becomes greater than the first threshold value, as compared to when the AE correlation value is not greater than that.

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 camshaft has a lubricating oil passage formed along the longitudinal axis of the same, a cam communicating oil hole is radially formed from the lubricating oil passage to an outer peripheral surface of the camshaft at the same axial position as an engine valve. Cam lubrication holes are radially formed from the inside to cam surfaces of cam lobes formed around a cam carrier fitted around the camshaft. One of the cam lubrication holes of the cam lobes shifted to a position for operating the valve communicates with the cam communicating oil hole of the camshaft to supply lubricant oil.

A continuous variable valve timing apparatus may include a camshaft, a cam device on which a cam is formed respectively and of which the camshaft is inserted thereto, wherein a relative phase angle with respect to the camshaft is variable, an inside bracket configured to transmit rotation of the camshaft to the cam device, a lifter in which the inside bracket is rotatably inserted therein and on which a cylinder opening and a shaft opening are formed thereon, a control shaft parallel to the camshaft and to which a control rod, inserted into the shaft opening, is eccentrically formed, a control cylinder on which a control rod opening where the control rod is inserted therein is formed and inserted into the cylinder opening, a guide portion guiding movement of the lifter and a controller selectively rotating the control shaft, wherein the lifter may move.