Abstract: A charge pipe passage includes: a first engine-side pipe passage part which extends vertically; a second engine-side pipe passage part which is connected to a lower end of the first engine-side pipe passage part on one side in the vehicle widthwise direction and extends from one side to the other side in the vehicle widthwise direction above the engine body; and a third engine-side pipe passage part which is communicably connected to the second engine-side pipe passage part on the other side in the vehicle widthwise direction and is connected to the engine body, and at least a part of the charge pipe passage between a frame-side support part and an engine-side support part is formed of an elastic tube.

Abstract: A charge pipe passage includes a first tank-side pipe passage part which is connected to an upper surface of a fuel tank, and a second tank-side pipe passage part which is connected with the first tank-side pipe passage part and extends toward the other side of the fuel tank from one side of the fuel tank in the vehicle widthwise direction on an end portion thereof on a fuel tank side, and the first and second tank-side pipe passage parts, are fixed to the upper surface of the fuel tank.

Abstract: Disclosed is a cooling air intake structure for a V-belt drive continuously variable transmission, which is disposed beside the rear wheel of a small vehicle and which does not permit muddy water and dust to enter therein. A cooling air inlet through which cooling air is taken in is formed at a position beside a transmission case and above a cooling fan side opening formed in the transmission case opposite to a drive pulley. A cooling air passage extending from the cooling air inlet to the side opening is formed so as to surround the side opening. Cooling air taken in through the cooling air inlet is guided so as to flow upward first and then flows downward along a U-shaped cooling air passage to the side opening of the transmission case beside the cooling fan.

Abstract: A charge pipe passage includes a second pipe passage part which is connected to a fuel tank by way of a first pipe passage part and extends toward the other side from one side in the vehicle widthwise direction, and a third pipe passage part which is communicably connected with the second pipe passage part on the other side in the vehicle widthwise direction and has a highest part arranged at a highest position of the charge pipe passage at an intermediate position thereof. A first check valve is interposed on the third pipe passage part downstream of the highest part, an atmospheric air introducing pipe passage is connected to the third pipe passage part upstream of the first check valve, and a second check valve is interposed on the atmospheric air introducing pipe passage at a position higher than the highest part.

Abstract: Disclosed is a radiator cooling structure for cooling a radiator of a water-cooled power unit mounted on a small vehicle and disposed on a laterally outer side of the small vehicle, which radiator cooling structure improves the efficiency of cooling an internal combustion engine by using a head wind. The radiator is provided with a radiator cover having a louver for guiding cooling air to the radiator. The louver is formed such that a rear part thereof is more protruded laterally outward than a front part thereof. The louver of the radiator cover has parallel slats tilting forward, and a lower body cover is provided with a cooling air intake opening capable of guiding a head wind toward the louver positioned obliquely above and rearward of the cooling air intake opening.

Abstract: A saddle-type vehicle is provided with: a seat on which a driver sits; a fuel tank positioned in front of the seat; an engine positioned below the fuel tank and having a crankcase and a cylinder projecting upward from a front of the crankcase; and a fuel vapor passage that is connected to the fuel tank and emits evaporated fuel in the fuel tank to an outside of the fuel tank. At least a part of the fuel vapor passage passes behind the cylinder. The fuel vapor passage is connected to the crankcase mat a portion in a rear side of the cylinder and opens toward oil in the engine.

Abstract: A saddle-type vehicle is provided with: a seat on which a driver sits; a fuel tank positioned in front of the seat; an engine positioned below the fuel tank and having a crankcase and a cylinder projecting upward from a front of the crankcase; and a fuel vapor passage that is connected to the fuel tank and emits evaporated fuel in the fuel tank to an outside of the fuel tank. At least a part of the fuel vapor passage passes behind the cylinder. The fuel vapor passage is connected to the crankcase at a portion in a rear side of the cylinder and opens toward oil in the engine.

Abstract: Disclosed is a cooling air intake structure for a V-belt drive continuously variable transmission, which is disposed beside the rear wheel of a small vehicle and which does not permit muddy water and dust to enter therein. A cooling air inlet through which cooling air is taken in is formed at a position beside a transmission case and above a cooling fan side opening formed in the transmission case opposite to a drive pulley. A cooling air passage extending from the cooling air inlet to the side opening is formed so as to surround the side opening. Cooling air taken in through the cooling air inlet is guided so as to flow upward first and then flows downward along a U-shaped cooling air passage to the side opening of the transmission case beside the cooling fan.

Abstract: A water pump attachment structure of a water-cooled internal combustion engine is provided to facilitate the maintenance of a valve train. A water pump attachment structure of a water-cooled internal combustion engine includes a semicircular cut-away surface of a water pump holder opposed to a semicircular surface of a cylinder head to form a water pump support circular hole. Screw members are passed through respective screw through-holes of the cylinder head and threadedly engaged with internal thread holes of the water pump holder. Thus, the water pump holder is fastened to the cylinder head. A water pump is fitted into and secured to the water pump support circular hole. A cylinder head cover is attached to the cylinder head by allowing their mating surfaces to conform with each other with the water pump holder liquid-tightly sandwiched therebetween.

Abstract: A charge pipe passage includes a first tank-side pipe passage part which is connected to an upper surface of a fuel tank, and a second tank-side pipe passage part which is connected with the first tank-side pipe passage part and extends toward the other side of the fuel tank from one side of the fuel tank in the vehicle widthwise direction on an end portion thereof on a fuel tank side, and the first and second tank-side pipe passage parts, are fixed to the upper surface of the fuel tank.

Abstract: A charge pipe passage includes: a first engine-side pipe passage part which extends vertically; a second engine-side pipe passage part which is connected to a lower end of the first engine-side pipe passage part on one side in the vehicle widthwise direction and extends from one side to the other side in the vehicle widthwise direction above the engine body; and a third engine-side pipe passage part which is communicably connected to the second engine-side pipe passage part on the other side in the vehicle widthwise direction and is connected to the engine body, and at least a part of the charge pipe passage between a frame-side support part and an engine-side support part is formed of an elastic tube.

Abstract: A charge pipe passage includes a second pipe passage part which is connected to a fuel tank by way of a first pipe passage part and extends toward the other side from one side in the vehicle widthwise direction, and a third pipe passage part which is communicably connected with the second pipe passage part on the other side in the vehicle widthwise direction and has a highest part arranged at a highest position of the charge pipe passage at an intermediate position thereof. A first check valve is interposed on the third pipe passage part downstream of the highest part, an atmospheric air introducing pipe passage is connected to the third pipe passage part upstream of the first check valve, and a second check valve is interposed on the atmospheric air introducing pipe passage at a position higher than the highest part.

Abstract: Disclosed is a radiator cooling structure for cooling a radiator of a water-cooled power unit mounted on a small vehicle and disposed on a laterally outer side of the small vehicle, which radiator cooling structure improves the efficiency of cooling an internal combustion engine by using a head wind. The radiator is provided with a radiator cover having a louver for guiding cooling air to the radiator. The louver is formed such that a rear part thereof is more protruded laterally outward than a front part thereof. The louver of the radiator cover has parallel slats tilting forward, and a lower body cover is provided with a cooling air intake opening capable of guiding a head wind toward the louver positioned obliquely above and rearward of the cooling air intake opening.

Abstract: A secondary air supply system in which individual members may be arranged to be disposed on substantially the same straight line in an engine, whereby connection path lengths are reduced and the attachment thereof is facilitated. The secondary air supply system may be provided between an air cleaner and attached to an engine and an exhaust port of the engine. The secondary air supply system has a secondary air control valve, a lead valve and secondary air supply paths which connect the air cleaner, the secondary air control valve and the lead valve together and supply air to the exhaust port from the air cleaner. The air cleaner, the secondary air control valve and the lead valve may be arranged to be disposed on substantially the same straight line when viewed from the side.

Abstract: A water pump attachment structure of a water-cooled internal combustion engine is provided to facilitate the maintenance of a valve train. A water pump attachment structure of a water-cooled internal combustion engine includes a semicircular cut-away surface of a water pump holder opposed to a semicircular surface of a cylinder head to form a water pump support circular hole. Screw members are passed through respective screw through-holes of the cylinder head and threadedly engaged with internal thread holes of the water pump holder. Thus, the water pump holder is fastened to the cylinder head. A water pump is fitted into and secured to the water pump support circular hole. A cylinder head cover is attached to the cylinder head by allowing their mating surfaces to conform with each other with the water pump holder liquid-tightly sandwiched therebetween.

Abstract: To suppress the overall length of a camshaft including the length of a decompression device provided in an engine and also to suppress an increase in number of parts of the decompression device, an engine includes a decompression device having a decompression weight pivotably supported through a pivot shaft to a camshaft and adapted to be rotated at a predetermined angle by a centrifugal force generated during the rotation of the camshaft. A weight accommodating portion for pivotably accommodating the decompression weight is formed between the opposite end portions of the camshaft. The outer diameter of the decompression device mounted to the camshaft is smaller than that of a ball bearing. The decompression weight is directly engaged with one end of a decompression camshaft to thereby rotate the decompression camshaft.

Abstract: A water circulation structure of a cylinder block having a compact layout of piping connecting an engine body and a radiator. A water-cooled internal combustion engine is provided with an engine body including a cylinder block and a cylinder head and a radiator. The radiator is disposed to be separated, in a prescribed direction, i.e. in a rightward direction, from the engine body. A cooling water outlet portion is open to a cylinder head water jacket and is provided in the end portion of the cylinder head. The cooling water outlet portion being connected with an inlet pipe for leading the cooling water flowing out of a cylinder block water jacket into the cylinder head water jacket to the radiator. The cooling water outlet portion is disposed to the right closer to the radiator than a chain chamber.

Abstract: A water circulation structure of a cylinder block having a compact layout of piping connecting an engine body and a radiator. A water-cooled internal combustion engine is provided with an engine body including a cylinder block and a cylinder head and a radiator. The radiator is disposed to be separated, in a prescribed direction, i.e. in a rightward direction, from the engine body. A cooling water outlet portion is open to a cylinder head water jacket and is provided in the end portion of the cylinder head. The cooling water outlet portion being connected with an inlet pipe for leading the cooling water flowing out of a cylinder block water jacket into the cylinder head water jacket to the radiator. The cooling water outlet portion is disposed to the right closer to the radiator than a chain chamber.

Abstract: To suppress the overall length of a camshaft including the length of a decompression device provided in an engine and also to suppress an increase in number of parts of the decompression device, an engine includes a decompression device having a decompression weight pivotably supported through a pivot shaft to a camshaft and adapted to be rotated at a predetermined angle by a centrifugal force generated during the rotation of the camshaft. A weight accommodating portion for pivotably accommodating the decompression weight is formed between the opposite end portions of the camshaft. The outer diameter of the decompression device mounted to the camshaft is smaller than that of a ball bearing. The decompression weight is directly engaged with one end of a decompression camshaft to thereby rotate the decompression camshaft.

Abstract: A secondary air supply system in which individual members may be arranged to be disposed on substantially the same straight line in an engine, whereby connection path lengths are reduced and the attachment thereof is facilitated. The secondary air supply system may be provided between an air cleaner and attached to an engine and an exhaust port of the engine. The secondary air supply system has a secondary air control valve, a lead valve and secondary air supply paths which connect the air cleaner, the secondary air control valve and the lead valve together and supply air to the exhaust port from the air cleaner. The air cleaner, the secondary air control valve and the lead valve may be arranged to be disposed on substantially the same straight line when viewed from the side.