Abstract: A valve operating system for internal combustion engines comprises a free cam follower which is disposed between first and second drive cam followers operatively connected to engine valves and which is capable of becoming free relative to the engine valves, first and second guide holes respectively provided in the first and second drive cam followers with their axes corresponding to each other. The guide holes is opened to the free cam follower. A double open-ended guide hole is provided in the free cam follower in correspondence to the axes of the first and second guide holes. A first change-over pin is axially slidably received in the first guide hole and adapted to be fitted into the guide hole, and a second change-over pin is axially slidably received in said guide hole with one end thereof abutting against the first change-over pin, and is adapted to be fitted into said second guide hole.

Abstract: A drive cam follower operatively connected to an engine valve and a free cam follower capable of becoming free relative to the engine valve are adjacently disposed and adapted to impart in mutually different modes of operation in response to said engine valve rotation of a cam shaft. A connection change-over mechanism is provided between the cam followers and is capable of changing-over the interconnection and disconnection thereof, and resilient biasing means is provided between the free cam follower and the engine body for resiliently urging the free cam follower toward the cam shaft. The resilient biasing means comprises an urging piston slidably received in the engine body for abutment against the free cam follower, and a spring arrangement interposed between the urging piston and the engine body to resiliently bias the urging piston in a direction to abut against the free cam follower.

Abstract: An SOHC type internal combustion engine wherein in a wall portion projectingly formed on a cylinder head and supporting a cam shaft is provided a bearing hole which supports a journal of the cam shaft having a larger diameter than the rotational path of the tip of a cam lobe, and an ignition plug insertion hole is provided continuous to an ignition plug mounting hole which is provided in the cylinder head and opens into the combustion chamber and wherein a protecting cylinder provided with the ignition plug insertion hole is integrally formed with the cam shaft receiving wall.

Abstract: In a valve actuating device of four-cycle internal combustion engine, a valve actuating cam shaft for driving an opening and closing valve via a rocker arm is carried on a cam holder block, an adjusting bolt is held on the cam holder block so as to be adjustable relative to its position to the latter and the rocker arm is supported on a pivot portion integral with the adjusting bolt for rocking motion. Valve clearance between the rocker arm and the opening and closing valve is adjusted by displacing the position of adjusting bolt relative to the cam holder block.

Abstract: An SOHC type internal combustion engine having a cam shaft for opening and closing intake and exhaust valves via rocker arms, the cam shaft being held between a cam shaft receiving wall of a cylinder head and a cam shaft holder which is secured to the cam shaft receiving wall, wherein a hole for allowing insertion of an ignition plug into a plug mounting hole is formed in the cam shaft receiving wall and opens to the surface of the wall against which a cam shaft holder abuts, and a hole for guiding a high power cord for an ignition plug is formed between the mutually abutting surfaces of the cam shaft receiving wall and the cam shaft holder.

Abstract: A spark plug cap apparatus for an internal combustion engine having relatively deep and generally vertical spark plug receiving bores. The upper end of the bore is provided with an annular protrusion. A resilient head cover has a bent flange for extending over and sealably engaging the annular protrusion. The head cover has a downwardly extending seal lip for engaging the inside of the bore. A pipe is molded to the head cover and extends downwardly to engage the top of the spark plug. The spark wire extends through the head cover and pipe. A vent hole is provided in the head cover.