Abstract: To reduce the cost of an ignition plug tube by making it of a cylindrical member and to provide a simple structure having only a small number of parts for mounting the ignition plug tube. A mounting structure of an ignition plug tube that is made of a cylindrical member includes a sealing member made of a soft member fitted to a cylinder head cover. The sealing member is interposed between the cylinder head cover and the ignition plug tube. The ignition plug tube is fixed and supported between an ignition plug plughole formed in a cylinder head of an internal combustion engine and the cylinder head cover.

Abstract: The lubrication structure of an engine is provided with a crankcase having a crank chamber that houses a crankshaft. A first oil reservoir is in communication with the crank chamber and is formed adjacent a bottom of the crank chamber. A second oil reservoir is in communication with the first oil reservoir and is formed adjacent the side of and on the bottom of the first oil reservoir. A reed valve extends diagonally from the bottom of the first oil reservoir toward the top of the second oil reservoir in an opening where the first oil reservoir and the second oil reservoir communicate with the crankcase. The reed valve includes a valve element that opens and closes according to the variation of pressure in the crank chamber. The valve element of the reed valve is arranged on the side of the second oil reservoir.

Abstract: To reduce the cost of an ignition plug tube by making it of a cylindrical member and to provide a simple structure having only a small number of parts for mounting the ignition plug tube. A mounting structure of an ignition plug tube that is made of a cylindrical member includes a sealing member made of a soft member fitted to a cylinder head cover. The sealing member is interposed between the cylinder head cover and the ignition plug tube. The ignition plug tube is fixed and supported between an ignition plug plughole formed in a cylinder head of an internal combustion engine and the cylinder head cover.

Abstract: The lubrication structure of an engine is provided with a crankcase having a crank chamber that houses a crankshaft. A first oil reservoir is in communication with the crank chamber and is formed adjacent a bottom of the crank chamber. A second oil reservoir is in communication with the first oil reservoir and is formed adjacent the side of and on the bottom of the first oil reservoir. A reed valve extends diagonally from the bottom of the first oil reservoir toward the top of the second oil reservoir in an opening where the first oil reservoir and the second oil reservoir communicate with the crankcase. The reed valve includes a valve element that opens and closes according to the variation of pressure in the crank chamber. The valve element of the reed valve is arranged on the side of the second oil reservoir.

Abstract: A power unit has a power case which includes a crankcase portion integrally formed with a transmission case portion. The crankcase portion forms a crankcase in which the crankshaft of a 4-cycle internal combustion engine is received. The transmission case portion forms a transmission case in which a wet type multiple disc friction clutch for transmitting the torque of the crankshaft is received. A partition wall makes the crankcase independent of the transmission case, and thus separates the lubrication system of the internal combustion engine from the lubrication system of the friction clutch. The lubrication structure of the present invention can improve the durability of the friction clutch and make the friction clutch compact, and secure good connection performance of the friction clutch by separating the lubrication system of an internal combustion engine from the lubrication system of friction clutch.

Abstract: A power unit has a power case which includes a crankcase portion integrally formed with a transmission case portion. The crankcase portion forms a crankcase in which the crankshaft of a 4-cycle internal combustion engine is received. The transmission case portion forms a transmission case in which a wet type multiple disc friction clutch for transmitting the torque of the crankshaft is received. A partition wall makes the crankcase independent of the transmission case, and thus separates the lubrication system of the internal combustion engine from the lubrication system of the friction clutch. The lubrication structure of the present invention can improve the durability of the friction clutch and make the friction clutch compact, and secure good connection performance of the friction clutch by separating the lubrication system of an internal combustion engine from the lubrication system of friction clutch.