Abstract: A drive device for coolant pumps having a pump shaft, a boss having a bore in which the pump shaft is rotatably disposed and a driven gear made from synthetic resin to transmit the rotational power from the crankshaft to the impeller to move the coolant into circulation through the coolant jacket for engine cooling, is disclosed which comprises a pin, fixedly implanted in radial pattern in the circumference of the pump shaft, a couple of radially extending grooves outwardly from the center of the driven gear bore in that side of the driven gear facing the impeller to receive therein fittingly the pin, respectively, and a washer mounted about the pump shaft between the front end face of the bore and the pin so as to prevent the pump shaft from falling off from its bore. When the driven gear is driven by the crankshaft, the pin closely fitted in the grooves transmits the torque to the pump shaft, without any slip.

Abstract: A cooling system for V-type engine comprises rows of left and right cylinders arranged in V-type and having coolant jackets, respectively. A coolant pump having a pump shaft parallel to a crankshaft is arranged with a V-bank and at a place away from each cylinder in an axial direction of said crankshaft, and coolant jacket inlets are provided on the side of the coolant pump of each cylinder. Alternately, the coolant jacket inlets of the cylinders are opened respectively at one end face in the direction of the crankshaft of a crankcase-forming member, and a distributing exit passage is defined by joint faces of said crankcase-forming member, a pump casing and a pump casing cover respectively.

Abstract: A compression release device for side-valve and overhead-valve internal combustion engines is disclosed, which takes advantages of the difference in thermal expansion of different materials to control the valve opening depending on the condition of ambient temperature. A first material of comparatively higher linear expansion coefficient is used for the cylinders and cylinder head, while a second material of comparatively lower expansion coefficient for the push rods and tappets for either or both of the intake and exhaust valves, with the valve or valves being set to take a valve lift enough to cause the valve, upon compression stroke, to remain properly slightly open at cold start to ease crankshaft rotation, while stay fully shut, as a result of the cylinders and cylinder head having undergone a greater degree of thermal expansion than the push rods and tappets, when the engine gets warmed up.

Abstract: A liquid-cooled engine of the vertical shaft type has a row of left and right side cylinders arranged in a V-shape as viewed from the above. The cooling water jackets of the left and right side cylinders are connected to each other at the highest ends of the cooling water jackets at the sides of cylinder heads of the cylinders through a communicating passage, a thermostat chamber is provided at the highest end of the cooling water jacket of one of the cylinder heads which is located lower than the other cylinder head, the communicating passage being connected at its one end to the thermostat chamber.

Abstract: An engine balancing system for a single-cylinder engine including a single primary balancer and a counterbalancer for reducing rotational vibration, wherein the single primary balancer has an axis of rotation disposed parallel to a crank shaft of the engine and is driven at the same velocity as the crank shaft in a direction opposite to the direction of rotation of the crank shaft. A cylinder of the engine has a center line which deviates from the center axis of the crank shaft and is displaced toward the single primary balancer.