Abstract: A saddle-ridden vehicle includes: an engine and an air cleaner case that are supported to a body frame and respectively arranged in front and rear sides of the vehicle; a rear cushion arranged between the engine and the air cleaner case, the rear cushion being coupled to the body frame; and a connecting tube that extends forward from the air cleaner case and is coupled to the engine. The connecting tube upwardly bypasses an upper end of the rear cushion so as to be curvedly arranged under an occupant seat. The connecting tube defines a breather-gas return chamber between an inner wall and an upper-side outer wall of the connecting tube, the breather-gas return chamber being communicated with an internal space of the air cleaner case and receiving breather gas from the engine, the inner wall being integrated with the upper-side outer wall.

Abstract: A saddle-ridden vehicle includes: an engine and an air cleaner case that are supported to a body frame and respectively arranged in front and rear sides of the vehicle; a rear cushion arranged between the engine and the air cleaner case, the rear cushion being coupled to the body frame; and a connecting tube that extends forward from the air cleaner case and is coupled to the engine. The connecting tube upwardly bypasses an upper end of the rear cushion so as to be curvedly arranged under an occupant seat. The connecting tube defines a breather-gas return chamber between an inner wall and an upper-side outer wall of the connecting tube, the breather-gas return chamber being communicated with an internal space of the air cleaner case and receiving breather gas from the engine, the inner wall being integrated with the upper-side outer wall.

Abstract: An air/oil-cooled internal combustion engine capable of increasing accuracy in detection of the temperature of the air/oil-cooled internal combustion engine by a temperature sensor and carrying out the warm-up operation after the start-up of the air/oil-cooled internal combustion engine favorably. The air/oil-cooled internal combustion engine includes cooling fins that are provided on the circumferences of a cylinder block and a cylinder head; and a cooling passage that is provided in a combustion chamber upper wall covering a combustion chamber of the cylinder head and is used for cooling the combustion chamber upper wall with lubrication oil. The air/oil-cooled internal combustion engine has a temperature sensor configured to detect the temperature of the air/oil-cooled internal combustion engine by detecting the temperature of oil. The temperature sensor faces a cooling oil outlet portion of the cooling passage.

Abstract: An air/oil-cooled internal combustion engine capable of increasing accuracy in detection of the temperature of the air/oil-cooled internal combustion engine by a temperature sensor and carrying out the warm-up operation after the start-up of the air/oil-cooled internal combustion engine favorably. The air/oil-cooled internal combustion engine includes cooling fins that are provided on the circumferences of a cylinder block and a cylinder head; and a cooling passage that is provided in a combustion chamber upper wall covering a combustion chamber of the cylinder head and is used for cooling the combustion chamber upper wall with lubrication oil. The air/oil-cooled internal combustion engine has a temperature sensor configured to detect the temperature of the air/oil-cooled internal combustion engine by detecting the temperature of oil. The temperature sensor faces a cooling oil outlet portion of the cooling passage.