Abstract: An overhead-camshaft internal combustion engine having an outer wall of a crankcase provided adjacent a crankshaft, with a spiral-surfaced opening through which the crankshaft is passed. The outer crankcase wall is integrally provided with a loop guide engaging recess formed thereon. The loop guide engaging recess supports a base end portion of a loop guide for guiding an endless chain. A loop-retaining member for preventing the timing endless chain from dropping is arranged at a position on the lower side of a loop drive sprocket integrally formed at an end portion of the crankshaft.

Abstract: A breather structure for internal combustion engine, the structure making a breather chamber smaller and thus making an internal combustion engine as a whole smaller. A breather chamber and a small chamber are formed. The breather chamber includes a first side face cover. The first side face cover is joined to a case to cover a first one of the right and left side faces of the case. Inside the first side face cover, an auxiliary apparatus chamber is formed. The auxiliary apparatus chamber houses a clutch mechanism connecting or disconnecting the power transmission route. Additionally, formed inside a housing are an external communication port communicating to the outside of the housing, and the small chamber communicating to a crank chamber and to the auxiliary apparatus chamber. Moreover, the auxiliary apparatus chamber communicates to the breather chamber.

Abstract: An overhead-camshaft internal combustion engine having an outer wall of a crankcase provided adjacent a crankshaft, with a spiral-surfaced opening through which the crankshaft is passed. The outer crankcase wall is integrally provided with a loop guide engaging recess formed thereon. The loop guide engaging recess supports a base end portion of a loop guide for guiding an endless chain. A loop-retaining member for preventing the timing endless chain from dropping is arranged at a position on the lower side of a loop drive sprocket integrally formed at an end portion of the crankshaft.

Abstract: A breather structure for internal combustion engine, the structure making a breather chamber smaller and thus making an internal combustion engine as a whole smaller. A breather chamber and a small chamber are formed. The breather chamber includes a first side face cover. The first side face cover is joined to a case to cover a first one of the right and left side faces of the case. Inside the first side face cover, an auxiliary apparatus chamber is formed. The auxiliary apparatus chamber houses a clutch mechanism connecting or disconnecting the power transmission route. Additionally, formed inside a housing are an external communication port communicating to the outside of the housing, and the small chamber communicating to a crank chamber and to the auxiliary apparatus chamber. Moreover, the auxiliary apparatus chamber communicates to the breather chamber.

Abstract: A lubricating system for a vehicle transmission is provided by which the transmission is effectively lubricated, without increasing the number of component parts. The transmission includes an input shaft, an intermediate shaft and an output shaft, each of which are contained in the inside of a power unit case. The intermediate shaft has with an axially extending oil passage that establishes communication between both opposed ends of the intermediate shaft such that one end of the intermediate shaft permits communication between the axial oil passage and a first oil passage formed in a first case half, and a second end of the intermediate shaft permits communication between the axial oil passage and a second oil passage formed in a second case half. The intermediate shaft also includes radial oil passages extending radially outward from the axial oil passage and opening in an outer peripheral surface thereof.

Abstract: A valve pause mechanism of a four-stroke internal combustion engine includes a valve pause mechanism. A valve lifter fitted between a valve cam and a valve stem of a poppet valve is always pressed in a direction in which the valve lifter contacts the valve cam with a lifter spring. However, a slide pin is fitted into a slide pin holder fitted in the valve lifter so that a slide pin can slide in a direction perpendicular to the valve stem. A stem working face in contact with the valve stem of the poppet valve and a stem through hole that the valve stem pierces are both adjacently formed in the slide pin and a slide pin driving mechanism. The slide pin driving mechanism selectively makes the stem working face and the stem through hole face the valve stem by moving the slide pin. A side of the slide pin at the back of the stem working face is chamfered across the stem through hole.

Abstract: A valve pause mechanism of a four-stroke internal combustion engine includes a valve pause mechanism. A valve lifter fitted between a valve cam and a valve stem of a poppet valve is always pressed in a direction in which the valve lifter contacts the valve cam with a lifter spring. However, a slide pin is fitted into a slide pin holder fitted in the valve lifter so that a slide pin can slide in a direction perpendicular to the valve stem. A stem working face in contact with the valve stem of the poppet valve and a stem through hole that the valve stem pierces are both adjacently formed in the slide pin and a slide pin driving mechanism. The slide pin driving mechanism selectively makes the stem working face and the stem through hole face the valve stem by moving the slide pin. A side of the slide pin at the back of the stem working face is chamfered across the stem through hole.