Abstract: An improved intake air heating device of internal combustion engine for motorcycles, having a compact and durable construction and adapted to heat the intake air to be fed to the engine by the heat derived from the exhaust gas. The device has an intake system leading to an intake port of the engine, an air cleaner connected to the intake system, an exhaust system connected to an exhaust port of the engine, an air heater disposed to surround a part of the exhaust system, and a heated air conduit providing a communication between the air cleaner and the air heater. The heated air conduit is arranged within the transverse breadth of the engine.

Abstract: Controlled amounts of relatively rich mixture and relatively lean mixture are supplied separately to a combustion chamber of an internal combustion engine. The position of the intake valves, exhaust valve and spark plug are such that the rich mixture tends to remain near the spark plug during the compression stroke of the engine and does not disperse throughout the lean mixture. At the time of ignition enriched mixture near the spark plug ignites readily and the flame propagates into and through the lean mixture which fills the remainder of the combustion chamber. Several constructions are disclosed to achieve the desired mixture ratios for various operating conditions of the engine.

Abstract: Herein disclosed is an exhaust gas recirculation system for an internal combustion engine, in which system communication is provided between an exhaust passage and an intake passage by way of an exhaust gas recirculation passage so that the exhaust gas in the exhaust passage is partially recirculated into the intake passage by the intake vacuum prevailing in the intake passage.

Abstract: An exhaust gas cleaning system for an internal combustion engine having an exhaust system leading to an exhaust port of an engine body. The exhaust gas cleaning system comprises a TWC catalyst disposed in the exhaust system for simultaneously cleaning HC, CO and NO.sub.X in exhaust gas flowing through the exhaust system. A secondary-air supply passage is connected to the exhaust system on the upstream side of the TWC catalyst and coupled to the atmosphere.

Abstract: A structure for facilitating the starting and warming of an internal combustion engine provided with a carburetor in its intake passage. A side passage which is separate from the intake passage by-passes a throttle valve in the carburetor is connected to the intake passage. A fuel nozzle capable of injecting fuel into the side passage and a control valve adapted to open and close the side passage are also provided. A heating chamber is formed in the side passage on the downstream side of the control valve. A heating element adapted to heat a gaseous mixture generated in the side passage to turn the gaseous mixture into a combustible gaseous mixture is accommodated in the heating chamber. The structure may further include a heat insulating member inserted between the heating chamber and carburetor and/or intake passage. Further, the structure may include a secondary air passage, a fuel injection unit for injecting fuel into the heating chamber and a catalytic converter in the heating chamber.

Abstract: A tubular inlet for a fuel tank includes a transverse baffle having an opening sized to receive a fuel nozzle of a determined diameter, and apertures located laterally of said opening and which permit viewing of the tank interior when a nozzle is inserted into the said opening, the structure optionally including a movable shutter which is resilient biased to a position in which it closes said opening, the shutter being movable by said nozzle against said bias.

Abstract: A catalytic converter having two spaced catalyst elements is positioned between a front muffler and a rear muffler. Chrome plating of the mufflers does not adversely affect performance of the catalyst elements because welding of the mufflers to opposite ends of the catalytic converter is accomplished after the chrome plating step. Masking of the joinder areas before plating avoids blow holes at the welds, and silver paint is later applied to the areas which were masked. The catalytic converter is constructed by simultaneously pushing the two catalyst elements and flanged sleeves into opposite ends of the catalyst casing, using tapered guide rings and flanged pusher bars to squeeze peripheral cushions into place within the catalyst casing and around each of the catalyst elements. Welding electrodes are employed in combination with the flanged pusher bars to spot weld the catalyst casing to the flanged sleeves.

Abstract: A catalytic converter effective to prevent damage or breakage of a catalytic element for improved durability. A catalytic element is housed in a casing and a pair of first and second end members are fitted into the opposite end portions of the casing so as to support the opposite end portions of the catalytic element via first and second end cushions. The first and second end cushions have, when in a free state, a rectangular cross section and inner diameters gradually increasing toward the catalytic element. The first and second cushions are compressed, when the catalytic converter is assembled, by the first and second end members to be fitted and held at their respective inner end portions between the inner circumferential surface of the casing and the outer circumferential surfaces of opposite end portions of the catalytic element.

Abstract: A motorcycle comprising a frame on which are mounted a fuel tank, a seat, front and rear wheels, and a multi-cylinder internal combustion engine disposed in a space defined by the fuel tank, seat and wheels. The engine has a plurality of exhaust ports open at the front of the engine connected to an exhaust system. An exhaust gas cleaning system is provided for the multi-cylinder internal combustion engine and comprises a reed valve assembly on the engine operating in response to pulsating exhaust pressure in the engine for selectively connecting an upstream secondary air passage connected to an inlet port of the reed valve assembly and a plurality of downstream secondary air passages of substantially equal length connected between outlet ports of the reed valve assembly and corresponding exhaust ports of the engine.

Abstract: A device for improving combustion efficiency of mixture in a four cycle internal combustion engine is disclosed in which burnt gas is introduced, upon the intake stroke, into a combustion chamber from an exhaust passage to generate a swirl whereby fresh mixture supplied from an intake port to the combustion chamber is disturbed to form a strong swirl. To this end, the valve opening periods of intake and exhaust valves are partially overlapped with each other and a swirl generating guide wall is formed around an exhaust port and extends inwardly from the combustion chamber wall so that a part of burnt gas flows back, upon the intake stroke, into the combustion chamber through the exhaust port unclosed by the exhaust valve to impinge against the guide wall thereby to generate a swirl. A portion of the exhaust passage leading to the exhaust port may extend in a direction offset from the center of the combustion chamber so as to promote the generation of a swirl.

Abstract: An exhaust system for an engine of a motorcycle is disclosed having catalytic and silencing mufflers arranged in adjacent side-by-side series flow relationship, the catalytic muffler extending rearwardly of the motorcycle, and, adjacent its rear end, being interconnected with the silencing muffler, the silencing muffler including plural expansion chambers which are interconnected in flow reversal relationship for gases to be exhausted rearwardly of the motorcycle.

Abstract: A high power output internal combustion piston engine is provided with two intake ports and one exhaust port for each combustion chamber. Flow through each port is controlled by a valve, the exhaust valve being positioned on one side of the combustion chamber and the two intake valves on the other side. A spark plug communicates with the combustion chamber on the same side as the exhaust valve, and near one of the intake valves. An air-fuel mixture is supplied to each of the intake ports through first and second throttle valves. Means including a lost-motion connection coordinates the movements of the throttle valves.

Abstract: An internal combustion piston engine drives a rotary supercharger of the positive displacement substantially continuous flow type, the supercharger turning in proportion to the engine speed. A power control valve is positioned upstream from the supercharger for controlling the flow of air-fuel mixture to said supercharger. Objectionable fluctuations in speed of the engine when idling are minimized by a secondary valve operatively positioned between the supercharger and a valved intake passage leading to the combustion chamber of the engine. The operation of the secondary valve and the power control valve are coordinated so that the secondary valve remains in idle position when the engine is idling but remains in open position during all other engine operating conditions.