Abstract: A two cycle interal combustion engine constituting of upper exhaust ports and a lower exhaust port provided on the upper and the lower of the level of the upper edge of scavenging ports, respectively, and having only the upper exhaust ports connected to a cleaning device. As a result of that, exhaust gas containing large amounts of hazardous components is mainly discharged from the upper exhaust ports and, because the exhaust gas can be cleaned concentratively, the decontamination efficiency of exhaust gas is good.

Abstract: A decompressor for an internal combustion engine having a decompressor valve mounted on a cylinder and a decompressor actuating lever slidably supported by guide members. A proximal end of the decompressor actuating lever is connected to a driving pawl member and a distal end of the same is closely disposed to and cooperated with a valve rod of the decompressor valve.

Abstract: A portable work machine equipped with an internal combustion engine. A starting pressure reducing device is mounted on a cylinder of the engine for reducing, at starting of the engine, pressure within a combustion chamber defined in the cylinder. A hole is formed at a portion of an engine cover which is within reach of a finger of a hand holding a handle, and is closed by a flexible cap. An actuating portion of the starting pressure reducing device is disposed inside the cap.

Abstract: A centrifugal clutch is disclosed in which a clutch boss rotatably supported to a drive side fixture has in its center an axial center hole. A clutch drum shaft has an inner end portion having an outer diameter somewhat smaller than an inner diameter of the center hole of the clutch boss. The inner end portion of the clutch drum shaft is arranged in the center hole of the clutch boss with a clearance. The driven side fixture and the drive side fixture are adjustable in relative position to each other.

Abstract: An internal combustion engine provided with an air cleaner and a muffler respectively on both sides of the crankshaft of the engine body and with a fuel tank below them wherein the air cleaner and the muffler are formed to be vertically extended respectively at the lower ends thereof along both sides of the engine body, the fuel tank is formed to be substantially like T made integrally of a barrel part and a head part inflated out on both sides in front of the barrel part, the barrel part is fitted in a space made by the air cleaner and the muffler below the engine body and both side parts of the head are arranged respectively in front of the lower parts of the air cleaner and the muffler.

Abstract: A separated lubrication type two-cycle internal combustion engine system having: a lubricating oil pump capable of discharging lubricating oil at a rate higher than the rate at which an internal combustion engine needs to be lubricated, the lubricating oil pump being disposed in the vicinity of one of projecting ends of a crankshaft and having an inlet communicating with a lubricating oil tank and a pair of outlets one of which communicates with the interior of the internal combustion engine and the other of which communicates with the lubricating oil tank; and a drive member disposed at the one of the projecting ends of the crankshaft to drive the lubricating oil pump by the torque of the engine.

Abstract: A vibration damper comprising; a main body which is formed from an elastic material into a substantially cubic overall form; and fixtures which are attached to each of two surfaces of the main body which are adjacent each other.

Abstract: A vibration damper includes a hollow cylindrical member which is formed of an elastic material and to one end of which a fixture is secured a plug-like member which is formed of an elastic material, which has a flanged head portion with another fixture secured thereto, a neck portion to be inserted into the cylindrical member and which is disposed away from the cylindrical member in the axial direction such as to form spaces and an elastic connecting member for integrally connecting the cylindrical member and the plug-like member.

Abstract: A reed valve includes a main reed member and an auxiliary reed member which is overlaid on the outside surface of the main reed valve. The auxiliary reed member has a smaller length than that of the main reed member. The width of the auxiliary reed member is gradually decreased from its fixed end to its free end.

Abstract: A crankshaft assembly including a pair of crankshafts and an intermediate crank arm, wherein a through opening is formed in a crank web of each of the crankshafts to extend axially of the respective crankshaft. In assembling the part, one crankpin of the intermediate crank arm is force fitted in an opening formed in a crank arm of the one crankshaft and a jig having a columnar portion is inserted in the through opening formed in the one crankshaft to support the one crankpin, thereby providing a crankshaft sub-assembly. When another crankpin of the intermediate crank arm is force fitted in an opening formed in a crank arm of the other crankshaft, the pressure applied to the crankpin is borne by the jig, so that the other crankshaft can be accurately secured to the intermediate crank arm.

Abstract: A suction device suitable for use with a two-cylinder internal combustion engine including a second suction port formed at a wall of at least one of the pair of cylinders in a position in which it is opened and closed by a piston in the cylinder, and a second conduit allowing the second suction port to communicate with a carburetor therethrough.

Abstract: A reed valve includes a reed member fixed to a valve body and a stopper member which is fixed at one end thereof to the valve body together with the reed member. The stopper member is constituted by a flat plate-shaped member which is curved outwardly from the one end to its free end, and a lump member which is secured to the surface of the flat plate-shaped member on the side thereof which is remote from the reed member. The lump member has a shape which is substantially coincident with the shape of a space which is formed on the downstream side of the reed valve and does not virtually take part in the flow of intake. The lump member is disposed within the space.

Abstract: Disclosed in an exhaust muffler for internal combustion engine such as opposed twin cylinder 2-cycle internal combustion engine of simultaneous ignition type for driving a chain saw. The muffler is connected at a plurality of points thereof to portions of the engine such as cylinders, characterized by comprising a corrugation S for absorbing thermal distortion provided in at least one side wall of the part of the muffler between adjacent portions at which the muffler is connected to the engine.