A lubricating structure for a four-stroke engine includes a first oil groove and a second oil groove. The engine includes a crankcase, a cylinder, a cylinder head and an oil pan. The crankcase makes up a crank chamber. The cylinder head is equipped with a valve chamber housing valve driving mechanism. The oil pan is provided on a bottom of the crank chamber. The first oil groove leads mist of the lubricating oil in the crank chamber to the valve chamber by communicating the crank chamber and the valve chamber with each other. The second oil groove leads surplus lubricating oil in the valve chamber to the oil pan in the crank chamber by communicating a lower part of the valve chamber with a neighborhood of the oil pan in the crank chamber. The first oil groove is set smaller in flow path cross-sectional area than the second oil groove.

An axis line of a cylinder and a cylinder head of a four-stroke engine is disposed inclining to one side in a lateral direction with respect to a center line extending in a front-rear direction of the outboard motor from a top view, and a fuel tank is disposed on a side portion of the cylinder and the cylinder head in another side in the lateral direction with respect to the center line.

The present disclosure provides an engine with an oil supply system including a cam carrier in which a camshaft support hole is formed and in which an oil supply hole is formed to the camshaft support hole; a camshaft in which a camshaft oil line is formed, in which an inlet supplying oil from the cam carrier oil supply hole is formed and in which a first camshaft bifurcated line is formed; first and second cam portions on which cams are formed, of which the camshaft is inserted thereto, of which relative phase angles with respect to the camshaft are variable, disposed corresponding to a first and a second cylinders, and the first and second cam portions in which a cam portion oil line in fluid communication with first camshaft bifurcated line is formed.

A cam chain tensioner device of an internal combustion engine includes a cam chain tensioner, and a tensioner lifter pressing the cam chain tensioner to a cam chain. The tensioner lifter is mounted on an inclined upper surface of the cylinder head. The cylinder head has therein a valve train oil supply passage supplying oil from an oil pump to the valve train camshafts, and a tensioner lifter oil supply passage supplying oil to the tensioner lifter. The valve gear oil supply passage has a branching portion where the tensioner lifter oil supply passage branches. The branching portion is at a position higher than the tensioner lifter, and communicates with the tensioner lifter disposed at a position lower than the branching portion. It is thus possible to prevent fluttering of the cam chain and to reduce noise generated by the cam chain at the time of restart of the engine after it is stopped.

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.

An axis line of a cylinder and a cylinder head of a four-stroke engine is disposed inclining to one side in a lateral direction with respect to a center line extending in a front-rear direction of the outboard motor from a top view, and a fuel tank is disposed on a side portion of the cylinder and the cylinder head in another side in the lateral direction with respect to the center line.

An outboard marine engine comprises a vertically aligned bank of piston-cylinders; a camshaft that operates a plurality of valves for controlling flow of air with respect to the vertically aligned bank of piston-cylinders, the camshaft vertically extending between a lower camshaft end and an upper camshaft end; and a cam lobe at the upper camshaft end. Rotation of the camshaft causes the cam lobe to cam open an uppermost valve in the plurality of valves. A lubricant circuit extends through the camshaft and has a lubricant outlet located at the upper camshaft end. The lubricant outlet is configured to disperse lubricant onto the uppermost valve, which is located above an uppermost cam bearing bulkhead for the upper camshaft end.

An object of the present invention is to simplify portions of an oil supply passage which portions are formed at a cylinder block. An oil supply device according to the present invention includes a cylinder block, an oil pan, an oil pump, and an oil filter. Wall portions of the oil pan are coupled to wall portions of the cylinder block. An oil filter is attached to the oil pan. An upstream oil supply passage through which the oil filtrated by the oil filter flows is formed at the oil pan. A downstream oil supply passage including a main gallery extending in a cylinder column direction is formed at the cylinder block. A first communication passage through which the main gallery and the upstream oil supply passage communicate with each other is formed at the wall portion of the cylinder block and the wall portion of the oil pan.

A lubricating structure for a four-stroke engine includes a first oil groove and a second oil groove. The engine includes a crankcase, a cylinder, a cylinder head and an oil pan. The crankcase makes up a crank chamber. The cylinder head is equipped with a valve chamber housing valve driving mechanism. The oil pan is provided on a bottom of the crank chamber. The first oil groove leads mist of the lubricating oil in the crank chamber to the valve chamber by communicating the crank chamber and the valve chamber with each other. The second oil groove leads surplus lubricating oil in the valve chamber to the oil pan in the crank chamber by communicating a lower part of the valve chamber with a neighborhood of the oil pan in the crank chamber. The first oil groove is set smaller in flow path cross-sectional area than the second oil groove.

The present disclosure provides an engine with an oil supply system including a cam carrier in which a camshaft support hole is formed and in which an oil supply hole is formed to the camshaft support hole; a camshaft in which a camshaft oil line is formed, in which an inlet supplying oil from the cam carrier oil supply hole is formed and in which a first camshaft bifurcated line is formed; first and second cam portions on which cams are formed, of which the camshaft is inserted thereto, of which relative phase angles with respect to the camshaft are variable, disposed corresponding to a first and a second cylinders, and the first and second cam portions in which a cam portion oil line in fluid communication with first camshaft bifurcated line is formed.