Abstract: A cylinder head in which any valve guide can be press-fitted in the cylinder head with a substantially uniform press fit force based upon the cylinder head in which at least one valve guide out of a plurality of valve guides for respectively guiding intake and exhaust poppet valves of an OHC four-stroke internal combustion engine are provided with valve lifters so that the valve guide can slide in a direction in which each valve that is opened or closed is fitted differently in the depth of a fitted part.

Abstract: To provide a high performance four-stroke internal combustion engine wherein an increase in a side of a cylinder head is prevented and a valve resting mechanism is provided for a valve lifter. In a four-stroke internal combustion engine with a valve resting mechanism includes a valve lifter having a valve resting mechanism interposed between a valve motion cam and a stem of a poppet valve and a valve lifter spring is provided for biasing the valve lifter in a direction in which the valve lifter is normally held in contact with the valve motion cam. A slide pin holder is pressed against the valve lifter by a spring force of the valve lifter spring that is provided on the valve lifter while a shim portion having a predetermined thickness for controlling a relative positional relationship with the valve lifter is formed integrally with a valve lifter top wall.

Abstract: A valve resting mechanism, for use with an internal combustion engine, which is capable of facilitating assembly of a valve lifter in the valve device. A valve device having a valve resting mechanism used for an internal combustion engine is configured such that a valve lifter having a lost motion mechanism is interposed between a cam and a stem of a poppet valve; the valve lifter is usually biased by a lifter spring in the direction in which the valve lifter is engaged with the cam; and a peripheral groove is provided for introducing hydraulic pressure for driving the lost motion mechanism is formed in an inner peripheral surface of a valve lifter hole for slidably guiding the valve lifter. In this valve device, the valve lifter, the lifter spring, and the peripheral groove are formed in such a manner that a lower end A of the valve lifter is positioned under a lower end of the peripheral groove in a state in which the lifter spring is freely extended.

Abstract: A valve system for an engine including a valve resting mechanism provided between an engine valve and a valve lifter supported by a cylinder head. The valve resting mechanism can place the engine valve into a resting state. The valve resting mechanism has a pin holder which includes a sliding hole having an axis perpendicular to the axis of a valve lifter, and an insertion hole for allowing a valve stem to pass therethrough. The pin holder is slidably fitted in the valve lifter. A slide pin is slidably fitted in the sliding hole, with a hydraulic force and a spring force applied to both ends of the slide pin. A containing hole is coaxially connectable to the insertion hole, and a rotation stopping means for stopping axial rotation of the slide pin is provided between the pin holder and the slide pin.

Abstract: To provide an engine with a valve resting function for resting at least one of a plurality of intake valves when the engine is in a specific operational region, which is capable of preventing the flow-in of the remaining fuel in a combustion chamber when the rested intake valve is switched to be opened/closed, thereby preventing the reduction in engine output and the increase in unburned hydrocarbon. A communication passage is provided in a cylinder head for enabling a fuel-air mixture to flow from an intake passage corresponding to an intake valve in a resting state to an intake passage corresponding to an intake valve in a resting state, when said engine is in a specific operational region.

Abstract: To provide a multi-cylinder engine for a motorcycle, in which at least one of a plurality of engine valves provided in a cylinder head for each of combustion chambers corresponding to a plurality of cylinder bores arranged in the width direction of a body frame can be rested in a specific operational region by a hydraulic valve resting mechanism. A hydraulic control valve is provided for controlling the hydraulic pressure of working oil supplied to the valve resting mechanism and is mounted on the cylinder head. The length of the multi-cylinder engine along the width direction of the body frame is made as short as possible although the hydraulic control valve is mounted in the cylinder head. A hydraulic control valve is mounted on a side surface of a cylinder head to which a plurality of intake ports are opened along the longitudinal direction of a body frame.

Abstract: A valve system for an engine including a valve resting mechanism provided between an engine valve and a valve lifter supported by a cylinder head. The valve resting mechanism can place the engine valve into a resting state. The valve resting mechanism has a pin holder which includes a sliding hole having an axis perpendicular to the axis of a valve lifter, and an insertion hole for allowing a valve stem to pass therethrough. The pin holder is slidably fitted in the valve lifter. A slide pin is slidably fitted in the sliding hole, with a hydraulic force and a spring force applied to both ends of the slide pin. A containing hole is coaxially connectable to the insertion hole, and a rotation stopping means for stopping axial rotation of the slide pin is provided between the pin holder and the slide pin.

Abstract: A valve system for an engine including a valve resting mechanism provided between an engine valve and a valve lifter supported by a cylinder head. The valve resting mechanism can place the engine valve into a resting state. The valve resting mechanism has a pin holder which includes a sliding hole having an axis perpendicular to the axis of a valve lifter, and an insertion hole for allowing a valve stem to pass therethrough. The pin holder is slidably fitted in the valve lifter. A slide pin is slidably fitted in the sliding hole, with a hydraulic force and a spring force applied to both ends of the slide pin. A containing hole is coaxially connectable to the insertion hole, and a rotation stopping means for stopping axial rotation of the slide pin is provided between the pin holder and the slide pin.

Abstract: An internal combustion engine with valve rest mechanisms. Exhaust secondary air is introduced at an exhaust port in a stable manner regardless of the resting, opening and closing operations of exhaust valves. Certain exhaust valves in the internal combustion engine are equipped with valve rest mechanisms. Exhaust valves that are not equipped with valve rest mechanisms located on neighboring cylinders are located on neighboring sides of their respective cylinders.

Abstract: In an engine valve drive control device, a cam lobe is removably engaged with a cam shaft of a valve actuating line of an engine. The cam lobe is rotated, when engaged, together with the cam shaft to drive a valve. Free rotation of the disengaged cam lobe is halted by a cam rotation halting device to leave the valve inactive. The cam lobe is made axially slidable in the axial direction with respect to the cam shaft, and the engagement/disengagement of the cam lobe with/from the cam shaft are switched according to the sliding motion of the cam lobe.

Abstract: A four-stroke cycle internal-combustion engine having two large- and small-diameter intake valves and two large- and small-diameter exhaust valves in one cylinder and mounted with a valve-operating mechanism on either of the intake valve side and the exhaust valve side. Each valve-operating mechanism comprises a first valve-operating cam of a narrow total valve-opening angle and a low lift, a second valve-operating cam of a wide total valve-opening angle and a high lift, a rocker arm for the small-diameter valve in direct engagement with the first valve-operating cam, a rocker arm for the large-diameter valve, and a connecting means capable of simultaneously operatively connecting the second valve-operating cam with the rocker arm for the small-diameter valve and the rocker arm for the large-diameter valve. In each cylinder at least three spark plugs are mounted. The combustion chamber is formed high on one side and low on the other side.

Abstract: The present invention provides methods to take advantage of the exhaust gas pulses in an exhaust system of a multi-cylinder internal combustion engine to increase the volumetric efficiency over the complete operating range of the engine. It solves the problems of other systems which are only able to gain a beneficial effect from the exhaust gas pulses over a limited range of the engine operating speeds, by providing a means of varying the exhaust pipe lengths, combinations, and cross-sectional area of the exhaust passages of the multi-cylinder internal combustion engine. By this means it provides an exhaust system in which the exhaust gas pulse frequencies can be varied over the entire operating range of the engine to obtain desirable pulse frequencies matching the cylinder exhaust timing for efficient extraction of the exhaust gases, improvement in volumetric efficiency and a higher maximum engine speed.

Abstract: An intake system for an internal combustion engine includes a variable length intake tract having a moveable intake pipe which selectively abuts a fixed intake pipe. During high speed operation, the moveable intake pipe is separated from the fixed intake pipe to provide a relatively short intake pipe length while in low speed operation, the moveable intake pipe abuts the fixed intake pipe so that a longer intake tract is formed. The influence of positive pressure waves on the air/fuel ratio during low speed operation is reduced by air flow resistance control means which increases the resistance of the intake system during low speed operation. This may be accomplished by use of an induction housing having a high speed chamber receiving the outlet of the fixed intake pipe and a low speed chamber receiving the outlet of the intake system when in the low speed intake mode, the low speed chamber having an intake opening having a higher air flow resistance than that of the opening of the high speed chamber.

Abstract: The present invention relates to an intake device for an internal combustion engine mounted on motorcycles or other various vehicles. The intake device comprises an air flow resistance adjusting mechanism for adjusting the air flow resistance in an intake passage in linkage with a variable intake pipe length mechanism to provide an excellent optimum air/fuel ratio over the entire speed range of the internal combustion engine. The variable intake pipe length mehcanism comprises a stationary intake pipe connected to a carburetor, a guide pipe separated from the stationary intake pipe, and a movable intake pipe slidably mounted on the guide pipe so tat the movable intake pipe is capable of coming in contact with or being spaced from the stationary intake pipe in response to the engine revolving speed. The movable intake pipe is connected to the stationary intake pipe below the predetermined engine speed and separated from it above the predetermined engine speed.

Abstract: A valve operating device for internal combustion engine which includes a cam shaft rotated by a crankshaft and a rocker arm which follows the cam of the cam shaft to open and close an intake or exhaust valve of the engine. Oil-pressure-operated control is provided for suspending the operation of the intake or exhaust valve according to the operating conditions of the engine. For this purpose, a cam shaft passage is formed in an oil pressure supplying passage which extends from an oil pressure source through an oil passage in the rocker shaft to the control mechanism in such a manner that the cam shaft passage extends through one end portion of the cam shaft. A changeover valve for opening and closing the cam shaft passage is provided at the one end portion of the cam shaft.