Abstract: A four-cycle engine is provided which is suitable for use in a vehicle or an apparatus such as a small jet boat to be operated on the premise that it often overturns, and which is simple in structure. An oil pan 22 is disposed below the bottom of a crankcase 13, the spaces in the components are communicated with each other via a communicating hole 27 which is formed in the bottom of the crankcase 13, and a cylindrical peripheral wall 26 which is downwardly extending from the bottom of the crankcase 13 toward the oil pan 22 is formed around the communicating hole 27 and is spacially separated from the side wall of the oil pan 22 by a distance.

Abstract: A four-cycle engine is provided which is suitable for use in a vehicle or an apparatus such as a small jet boat to be operated on the premise that it often overturns, and which is simple in structure. An oil pan 22 is disposed below the bottom of a crankcase 13, the spaces in the components are communicated with each other via a communicating hole 27 which is formed in the bottom of the crankcase 13, and a cylindrical peripheral wall 26 which is downwardly extending from the bottom of the crankcase 13 toward the oil pan 22 is formed around the communicating hole 27 and is spacially separated from the side wall of the oil pan 22 by a distance.

Abstract: A down-drafting constant vacuum pressure type diaphragm carburettor includes a carburettor body with an induction passage, a throttle valve, a Venturi portion variable of open area. A vacuum actuated valve is arranged at upstream side of the throttle valve across the induction passage and extending in horizontal direction from one side to the other side, and controls an open area of a Venturi portion depending upon a vacuum pressure generated in the Venturi portion. A jet needle is mounted on the vacuum actuated valve. A fuel control system including a diaphragm arranged between a recessed portion of the carburettor body and a cover covering for defining a regulator chamber at the side of the recessed portion and an atmospheric pressure chamber at the side of the cover, and a valve seat. The diaphragm is arranged at lower side of a longitudinal axis of the jet needle.

Abstract: A spark plug cap includes a metal connection member for electrically connecting a spark plug to a high-voltage cord and a tubular rubber body fitted on an end of the high-voltage cord and on an insulating portion of the spark plug to seal the end and the insulating portion. A core member is mounted within the rubber body surrounding the metal connection member, and the core member has a through hole. The through hole places a space, formed between the spark plug and the rubber body, in communication with a contact surface between the core member and the rubber body. Even if the rigidity of the rubber body is increased, this construction eliminates the possibility that the plug cap will be lifted or displaced relative to the spark plug by air compressed within the plug cap when the plug cap is attached to the spark plug.

Abstract: A spark plug cap includes a metal connection member for electrically connecting a spark plug to a high-voltage cord and a tubular rubber body fitted on an end of the high-voltage cord and on an insulating portion of the spark plug to seal the end and the insulating portion. A core member is mounted within the rubber body surrounding the metal connection member, and the core member has a through hole. The through hole places a space, formed between the spark plug and the rubber body, in communication with a contact surface between the core member and the rubber body. Even if the rigidity of the rubber body is increased, this construction eliminates the possibility that the plug cap will be lifted or displaced relative to the spark plug by air compressed within the plug cap when the plug cap is attached to the spark plug.

Abstract: A spark plug cap includes a metal connection member for electrically connecting a spark plug to a high-voltage cord and a tubular rubber body fitted on an end of the high-voltage cord and on an insulating portion of the spark plug to seal the end and the insulating portion. A core member is mounted within the rubber body surrounding the metal connection member, and the core member has a through hole. The through hole places a space, formed between the spark plug and the rubber body, in communication with a contact surface between the core member and the rubber body. Even if the rigidity of the rubber body is increased, this construction eliminates the possibility that the plug cap will be lifted or displaced relative to the spark plug by air compressed within the plug cap when the plug cap is attached to the spark plug.

Abstract: An engine exhaust system for a small watercraft. The engine is fixed to a hull through a damper, while an expansion chamber is fixed directly to the hull. An exhaust port of the engine and an inlet of expansion chamber are connected by an exhaust pipe, and the inlet of expansion chamber and an outlet of exhaust pipe are connected by a fitting with thermal durability and flexibility. In the case where the expansion chamber is followed by a muffler, at least a latter half of the expansion chamber is inserted into the muffler.

Abstract: The present invention relates to a pipe fitting device which connects pipes that flow a high temperature fluid such as engine exhaust gas. The device includes a first cylindrical block, a second cylindrical block and a follower ring disposed between a ring portion of the first cylindrical block and an edge member of an opening of a second cylindrical block. A spring pushes the follower ring to the second cylindrical block side. Flexible connection sleeves connect the flanges of the first cylindrical block and the second cylindrical block and through holes are drilled into the first and second cylindrical blocks.