Abstract: An air-fuel mixture intake apparatus for internal combustion engines includes a two-barrel carburetor having a primary venturi for supplying an air-fuel mixture into a combustion chamber under all loads and a secondary venturi for supplying an air-fuel mixture into the combustion chamber under medium and high loads. The primary venturi is of a fixed cross section and the secondary venturi is of a variable cross section. A vacuum-operated actuator controls operation of a secondary throttle valve in response to a vacuum developed in the primary venturi and subsequently in the secondary venturi. The secondary throttle valve is interlinked with a primary throttle valve by a linkage mechanism such that the secondary throttle valve is allowed to open when the primary throttle valve opens to a predetermined degree with the maximum opening of the secondary throttle valve being variably controlled by the opening of the primary throttle valve after the latter has opened beyond the predetermined degree.

Abstract: An internal combustion engine equipped with a sub-suction path to produce a swirl of suction in the combustion chamber, characterized in that there are two inlets to the sub-suction path, one of the inlets opening into the atmosphere side after bypassing the throttle valve of the carburetor to the venturi and the other being operable by the throttle valve of the carburetor and opening in the duct of the carburetor so that it can be closed by the throttle valve at idling. In this arrangement of the engine, the fuel consumption can be saved; a misfiring can be prevented; an untimely or delayed injection of fuel from the main fuel nozzle in low to high load operation can be averted; and a stable combustion can be assured in medium load operation in which a particularly heavy EGR takes place.

Abstract: An internal combustion engine, which is equipped with a sub-suction path for generating a swirl of the suction gas in the combustion chamber in addition to a main suction path to be opened or closed by a suction valve. The sub-suction path is equipped at its inlet side paths with two fuel supply device-line and atmosphere-line paths, the former of which is opened into the draft passage of a fuel supply device and between the air metering portion of said fuel supply device and a throttle valve downstream of the air metering portion and the latter of which is vented to the atmosphere while bypassing said air metering portion and said throttle valve. With the aforementioned atmosphere-line path, moreover, there is connected a vacuum-operated valve which is made operable in accordance with the vacuum prevailing downstream of said throttle valve.

Abstract: An intake manifold for an internal combustion engine having a plurality of cylinders is composed of a primary intake manifold assembly including a plurality of primary branch pipes extending from a two-barrel carburetor to the cylinders, respectively, and a secondary intake manifold assembly including a plurality of secondary branch pipes extending from the two-barrel carburetor to the cylinders, respectively. The primary and secondary branch pipes are joined together immediately upstream of intake ports opening into the combustion chambers. The primary and secondary branch pipes are dimensioned to meet the relationship of (n-1)S.sub.1 .ltoreq.S.sub.2 where S.sub.1 is the cross-sectional area of each of said primary branch pipes, S.sub.2 is the cross-sectional area of each of said secondary branch pipes, and n is the number of said cylinders.

Abstract: An accelerator pump supplies additional fuel into a primary intake passage when a primary throttle valve is opened. A vacuum-operated actuator is responsive to a vacuum developed in a manifold passage upon cranking for actuating an accelerator pump plunger to discharge extra fuel into the primary intake passage. When the engine which is cold is to be started, such an additional supply of fuel assists the engine in getting started quickly. When the engine which is hot is to be restarted, the actuation of the accelerator pump clears away fuel vapor from the accelerator pump and a fuel feed passage connected therewith, thus readying the accelerator pump for normal operation. The primary throttle valve is operatively connected to the accelerator pump through a plate cam having a cam edge which is profiled such that the amount of extra fuel as supplied by the accelerator pump is proportional to opening of the primary throttle valve.

Abstract: An intake passage structure for an internal combustion engine includes a primary air-fuel mixture passage disposed remotely from a water jacket located below a secondary air-fuel mixture passage. A secondary slow fuel supply passage extends from a float chamber adjacent to the primary air-fuel mixture passage so that fuel in the secondary slow fuel supply passage will be cooled by an air-fuel mixture flowing through the primary air-fuel mixture passage, thereby preventing vapor lock from occuring in the secondary slow fuel supply passage. The primary air-fuel mixture passage is composed of a common passageway, a distribution slot and branch slots for supplying an air-fuel mixture to engine cylinders. The distribution and branch slots are closed by a cylinder head. Any liquid fuel in the distribution and branch slots are vaporized with heat from the cylinder head.

Abstract: A suction system for an internal combustion engine which is equipped with a sub-suction path provided separately from a main suction path for generating a swirl of the gases in a combustion chamber during the suction stroke. The amount of the air to be supplied via the sub-suction path to the combustion chamber is less than 40% preferably from 10 to 40%, more preferably from 20 to 30% of the total amount of the air to be supplied to the combustion chamber. Alternatively the effective area of the sub-suction path at its outlet end is 0.2 to 3.0% of that of the main suction path.

Abstract: An air-fuel mixture intake construction for an internal combustion engine comprises a primary intake system for supplying an air-fuel mixture under a full range of engine loads, a secondary intake system for supplying an air-fuel mixture under medium and high engine loads, and an induction passage having one end opening into a secondary intake passage immediately upstream of a secondary throttle valve disposed therein, and the other end opening immediately upstream of an intake valve for a combustion chamber. The open end of the induction passage in the secondary intake passage is spaced inwardly from an inner wall surface of the secondary intake passage to prevent fuel in liquid form from flowing into the induction passage from the secondary intake passage.

Abstract: An intake port structure for an internal combustion engine having a primary intake passage defined in a cylinder head for supplying an air-fuel mixture into a combustion chamber in a full range of loads, and a secondary intake passage defined in the cylinder head for supplying an air-fuel mixture into the combustion chamber under relatively high load conditions. The primary intake passage has a first outlet port opening into the secondary intake passage immediately upstream of the valve face of an intake valve. The secondary intake passage has a second outlet port opening into the combustion chamber through the valve face. A wall projects sidewardly into the secondary intake passage adjacent to the second outlet port for deflecting an air-fuel mixture flowing from the secondary intake passage into the combustion chamber to form a swirl of air-fuel mixture in the combustion chamber.

Abstract: Internal combustion engine constituted such that two inlets are provided to a sub-suction path which is provided separately from the main suction path and serves to inject gas such as air or air-fuel mixture at high velocity in the peripheral direction of a combustion chamber at the suction stroke; one of said inlets is located upstream of the throttle valve, the other located in the air path of the carburetor at a position where the throttle valve can be shut in time of idling, wherein the effective opening area of the throttle valve can be enlarged through appropriate number and form of the inlets to be shut by the throttle valve and the downstream side inlet of the two inlets is set to be within the range of an angle, i.e., the downstream side inlet is located within the range of 60.degree.-120.degree.

Abstract: Disclosed are suspension devices for motorcycles, in which the rear wheel is rotatively supported by rear ends of right and left side swing arms front ends of which are pivotally connected to rear low-portion of the vehicle frame, one end of a link lever pivotally supported at its center portion by rear upper-portion of the frame is pivotally connected to the swing arms via a rod member at each side of the rear wheel and other end of said link lever is pivotally connected to upper end of a spring member, and lower end of said spring member is pivotally connected to a position of each swing arm.

Abstract: A duplex carburetor for an internal combustion engine has a primary barrel having a primary venturi for supplying an air-fuel mixture to an intake manifold under a full range of engine loads and a secondary barrel having a secondary venturi for supplying an air-fuel mixture to the manifold under higher engine loads. The primary venturi has a cross section which ranges from 20% to 30% of that of the secondary venturi. The secondary barrel has a flattened cross-sectional shape such as of a segment of a circle of an ellipse, and is located adjacent to the primary barrel. The intake manifold is of a duplex construction having primary and secondary common passages connected to the primary and secondary barrels, respectively, of the carburetor. The secondary passage of the manifold has a flattened cross-sectional shape such as of a segment of a circle or an ellipse, and is positioned adjacent to the primary passage.

Abstract: An intake passage construction for an internal combustion engine has a primary intake passage for supplying an air-fuel mixture when the engine operates under a full range of loads and a secondary intake passage for supplying an air-fuel mixture when the engine operates under relatively high loads. A secondary slow fuel passage has a pair of fuel supply ports opening into the secondary intake passage, and a fuel drain passageway extends from one of the fuel supply ports and has a fuel discharge port opening into the primary intake passage. Ambient air can be introduced into the fuel drain passageway in response to a vacuum developed in the primary intake passage so that fuel can be drained from the secondary slow fuel passage to prevent vapor lock therein. The fuel discharge port of the fuel drain passageway may open into an induction pipe.

Abstract: A throttle valve is opened upon engine cranking through a predetermined angle by a vacuum-operated valve in response to a vacuum signal supplied thereto from a vacuum pickup port positioned downstream of the throttle valve, for assisting the engine in getting started quickly and stably. A directional control valve is actuated upon engine cranking to allow the vacuum signal to be fed to the vacuum-operated valve. The vacuum pickup port communicates with the vacuum-operated valve through vacuum passages having thermosensitive valves one openable when the engine is kept below a preset temperature and the other openable when the engine temperature is above the preset level. A pressure delay means may be connected between the vacuum pickup port and the vacuum-operated valve to delay closing of the latter after the engine cranking.

Abstract: An internal combustion engine having a plurality of main suction paths adapted to respectively communication with a single combustion chamber are so provided that they can be opened or closed by different suction valves and in which a plurality of sub-suction paths provided separately of the main suction paths are pointed directing to the single combustion chamber so that the gases injected therefrom during the suction stroke may be swirled in an identical circumferential direction within said identical combustion chamber.

Abstract: An internal combustion engine is described in which the shape and construction of the gas outlet end portion of a sub-suction path is made operative to inject a gas such as air, an air-fuel mixture or exhaust gas circumferentially into the combustion chamber during the suction stroke. The gas outlet end portion has a reduced diameter and an injection nozzle which has a length greater than its internal diameter. Moreover, the gas outlet end portion is constructed of a pipe member which is rotatably and adjustably fitted into the insertion hole of a cylinder head and which is so shaped that the open direction of the outlet end thereof can be changed when it is rotationally adjusted.

Abstract: An internal combustion engine has a primary intake passage including a primary throttle valve for supplying engine cylingers with an air-fuel mixture under a full range of loads, a secondary intake passage including a secondary throttle valve for supplying the engine cylinders with an air-fuel mixture under high loads, and an exhaust-gas recirculation passage including an exhaust-gas recirculation valve for introducing an exhaust gas into the primary intake passage. Vacuums at the primary and secondary throttle valves are utilized to control the exhaust-gas recirculation valve. A distributor for producing ignition sparks is also controlled by the vacuums at the primary and secondary throttle valves for ignition timing. The engine also includes a first mechanism for retarding ignition sparks and a second mechanism for promoting engine idling.

Abstract: The present invention relates to a four-cycle internal combustion engine in which a strong swirl can be generated within the combustion chamber through the directionality of the mixed gas supplied from the main suction path and the injection of a gas from the sub-suction path, and a heavier EGR than before can be carried out without detracting the engine performance, and NOx generation can be substantially reduced by EGR alone. In time of idling when a heavy EGR is needless, the gas injection from the sub-suction path is controlled to prevent a misfiring.