Abstract: In an internal combustion engine including a driving-sprocket cam chain guide 70 for guiding a cam chain 47 along a driving sprocket 45, as viewed in a crankshaft axial direction, a guide body 71 of the driving-sprocket cam chain guide 70 extends beyond a winding termination point P of the cam chain 47 on the driving sprocket 45 to a position adjacent to a chain moving surface 51c of a cam chain tensioner 51, on which the cam chain 47 slides. The engine provides a cam-chain dropout preventing function to the cam chain guide, thus reducing load on the cam chain tensioner and improving durability of the tensioner lifter.

Abstract: In an internal combustion engine including a driving-sprocket cam chain guide 70 for guiding a cam chain 47 along a driving sprocket 45, as viewed in a crankshaft axial direction, a guide body 71 of the driving-sprocket cam chain guide 70 extends beyond a winding termination point P of the cam chain 47 on the driving sprocket 45 to a position adjacent to a chain moving surface 51c of a cam chain tensioner 51, on which the cam chain 47 slides. The engine provides a cam-chain dropout preventing function to the cam chain guide, thus reducing load on the cam chain tensioner and improving durability of the tensioner lifter.

Abstract: A ball valve includes a valve hole provided in an engine body to communicate with an inner end portion of a breather hole and is open in the engine body. A valve seat is formed on an inner surface of the engine body to coaxially surround the valve hole. A guide sleeve is in coaxially communication with the valve hole and the valve seat and is secured to the engine body at one end portion. A metallic valve element, formed to be ball-like with a predetermined weight is received to be rollable in the guide sleeve for enabling the closing of the valve hole and to be prevented from falling off the other end of the guide sleeve, is provided in the engine body so that the valve hole is placed within a moving range of oil in the engine body depending on the inclination of the engine body.

Abstract: A ball valve includes a valve hole provided in an engine body to communicate with an inner end portion of a breather hole and is open in the engine body. A valve seat is formed on an inner surface of the engine body to coaxially surround the valve hole. A guide sleeve is in coaxially communication with the valve hole and the valve seat and is secured to the engine body at one end portion. A metallic valve element, formed to be ball-like with a predetermined weight is received to be rollable in the guide sleeve for enabling the closing of the valve hole and to be prevented from falling off the other end of the guide sleeve, is provided in the engine body so that the valve hole is placed within a moving range of oil in the engine body depending on the inclination of the engine body.

Abstract: An engine body includes a crankcase with a crank chamber therein, a cylinder block attached to the crankcase, and a breather passage which selectively permits fluid communication between the crank chamber and an area outside of the crank chamber. The engine body includes a one-way valve between the crank chamber and the breather passage, which allows a one-way flow of gases from the crank chamber to the breather passage. The one-way valve is pressure-operated and is operatively attached to a side wall of the engine body proximate a cylinder sleeve. The one-way valve may be mounted in a mounting window in a side wall of the crankcase, and a timing chamber may function as the breather passage. In an illustrative embodiment, the one-way valve includes a base plate having a valve hole formed therein, and a flexible reed valve plate with one end affixed to the base plate.

Abstract: An engine body includes a crankcase with a crank chamber therein, a cylinder block attached to the crankcase, and a breather passage which selectively permits fluid communication between the crank chamber and an area outside of the crank chamber. The engine body includes a one-way valve between the crank chamber and the breather passage, which allows a one-way flow of gases from the crank chamber to the breather passage. The one-way valve is pressure-operated and is operatively attached to a side wall of the engine body proximate a cylinder sleeve. The one-way valve may be mounted in a mounting window in a side wall of the crankcase, and a timing chamber may function as the breather passage. In an illustrative embodiment, the one-way valve includes a base plate having a valve hole formed therein, and a flexible reed valve plate with one end affixed to the base plate.

Abstract: A motorcycle engine includes a crankcase housing a crankshaft, and a transmission unit therein, a cylinder block disposed above the crankcase, a cylinder head disposed above the cylinder block, and an intake system arranged behind the cylinder head, and a knock sensor arranged on an upper surface of the crankcase. The knock sensor is arranged behind the cylinder head, and disposed between the intake system and the cylinder block, such that the knock sensor does not restrict arrangement of additional functional parts of the engine on an upper surface of the crankcase. The knock sensor is substantially surrounded and protected by the intake system, the cylinder head, the cylinder block and the crankcase.

Abstract: A motorcycle engine includes a crankcase housing a crankshaft, and a transmission unit therein, a cylinder block disposed above the crankcase, a cylinder head disposed above the cylinder block, and an intake system arranged behind the cylinder head, and a knock sensor arranged on an upper surface of the crankcase. The knock sensor is arranged behind the cylinder head, and disposed between the intake system and the cylinder block, such that the knock sensor does not restrict arrangement of additional functional parts of the engine on an upper surface of the crankcase. The knock sensor is substantially surrounded and protected by the intake system, the cylinder head, the cylinder block and the crankcase.