Abstract: A tensioner acting on and allowing an endless transmission belt, stretched between a driving wheel and driven wheels supported on the body of an internal combustion engine, to run under a constant tension, wherein an oscillating lever supports a tension pulley pressed against a loosening side of the transmission belt and has a base end pivoted on the engine body, and an automatic adjuster connected to a tip end of the lever is supported on a case for a hydraulic pump of the engine. A spacer is interposed between contact portions of the oscillating lever and the engine body, and an outlet of the pump and an oil port of the adjuster are directly communicated. An adjusting screw is provided on the tip end of the oscillating lever and is operatively connected to the upper end of a plunger of the automatic adjuster.

Abstract: A crankshaft supporting structure in a multicylinder internal combustion engine has a cylinder block made of a light alloy and including a cylinder housing and a crankcase having a plurality of spaced journal walls. A plurality of spaced bearing caps made of an iron alloy are coupled respectively to the journal walls. A crankshaft is rotatably supported in bearing holes defined by the journal walls and the bearing caps. A bridge made of a light alloy extends across the bearing caps and is coupled to the bearing caps. The bearing caps and the bridge are fastened together to the journal walls by connecting bolts disposed one on each side of the crankshaft. The bridge has a main portion defining a main gallery extending longitudinally therethrough and a plurality of legs coupled to the bearing caps, respectively. The bearing caps and the legs jointly define branch oil passages communicating with the main gallery and the bearing holes.

Abstract: A cylinder block structure of a light alloy for use in a multicylinder internal combustion engine includes a cylinder-defining portion having a plurality of cylinder bores with a water jacket defined in surrounding relation to the cylinder bores, and a crankcase-defining portion integrally formed with the cylinder-defining portion and having a plurality of integral journal walls spaced in the direction in which the cylinder bores are arranged. Concavities are defined in opposite sides of the cylinder- and crankcase-defining portions between the adjacent cylinder bores, the concavities lying between the water jacket and journal walls. A plurality of reinforcing rib systems project from the opposite sides of the cylinder block and each rib system surrounds one of the concavities. The concavities reduce the amount of molten metal to be poured in casting the cylinder block structure, for thereby preventing casting defects such as cavities from being produced in the cylinder block.

Abstract: A lubricating oil passage arrangement for a water-cooled internal combustion engine with a cylinder block having a plurality of cylinder bores and a water jacket surrounding the cylinder bores. The cylinder block includes a side wall and a bulging portion projecting laterally outwardly from the side wall for defining a lubricating oil passage adjacent to the water jacket. Lubricating oil flowing through the lubricating oil passage is effectively cooled by the cooling water in the water jacket.

Abstract: A closed-deck cylinder block of a light alloy such as an aluminum alloy for use in a water-cooled internal combustion engine includes a cylinder-defining portion having a plurality of cylinder bores defined therein, and a crankcase-defining portion integral with the cylinder-defining portion. The cylinder-defining portion includes a water jacket extending substantially the entire length of each of the cylinder bores and defined by an inner side wall, and outer side wall spaced therefrom, and a bottom wall interconnecting the inner and outer side walls. The bottom wall has a wall thickness substantially equal to at least one of the wall thicknesses of the inner and outer side walls. The wall thicknesses of the inner and outer side walls are substantially equal to each other.

Abstract: A cylinder block and head assembly for use in an internal combustion engine includes a closed-deck cylinder block having a deck and a water jacket, a cylinder head mounted on the deck and having a water jacket, and a gasket interposed between the cylinder block and the cylinder head. Communication passages are defined in the cylinder block, the cylinder head, and the gasket and provide communication between the water jackets in the cylinder block and the cylinder head. Recesses are defined adjacent to the communication passages and between the cylinder block and the cylinder head for increasing the pressure on the surfaces of the gasket between the cylinder block and the cylinder head through a reduction in the area of contact between the gasket surfaces and the cylinder block and head. In alternate embodiments the gasket or the cylinder block has holes providing communication between the recesses and the communication passages.

Abstract: A blow-by gas processing arrangement for an internal combustion engine includes a cylinder block having a chamber for collecting a blow-by gas, a blow-by gas passage communicating with the chamber, and a plurality of spaced journal walls for supporting a crankshaft. A relatively large oil mist separating passage is defined in the cylinder block and extends into one of the journal walls, the oil mist separating passage communicating with the blow-by gas passage for preliminarily separating an oil mist from the blow-by gas supplied from the chamber. The blow-by gas processing device also includes an oil separator communicating with the oil mist separating passage for separating an oil mist from the blow-by gas supplied from the oil mist separating passage, a PCV valve connected to the oil separator, and an intake manifold connected to the PCV valve.

Abstract: A tensioner device for applying a predetermined tension force to a transmission belt extended between a driving wheel and a driven wheel supported on the body of an internal combustion engine, including a hydraulic automatic adjuster which comprises a plunger case fitted in a cylinder bore through a seal member and a plunger slidably and axially movably fitted in the plunger case, open edges of the plunger case and plunger being sealed from outside by means of a flexible boot. An extra feed oil chamber formed within the plunger is in communication with a feed oil source by means of a closed oil path through a feed oil port and in communication with an oil reservoir by means of another closed oil path through an oil discharge port provided in a spaced relation from the feed oil port.

Abstract: The crankshaft of an engine is supported by bearing caps mounted on journal walls of a cylinder block and a bridge interconnects the bearing caps. Oil passages in each bearing cap lead from the bridge to each crankshaft journal bearing at a laterally offset location rather than on the cylinder axis. A longitudinal main gallery in the bridge supplies oil to the passages and is laterally offset even further to that side. A supply passage in the bridge and one bearing cap at one extreme lateral side supplies oil from a pressurized oil supply passage in the cylinder block to that supply passage in the bearing cap.

Abstract: A simplified intake/exhaust valve assembly for an internal combustion engine which has a change-over operation of operative and inoperative state of the intake/exhaust valve is provided.

Abstract: An intake/exhaust valve assembly of an internal combustion engine, comprising a reciprocating valve movable into and out of the combustion chamber, a cam driven for rotation by the crankshaft, a cam follower intervening between the cam and the reciprocating valve, a control plunger slidable between first and second axial positions in a main axial bore and defining a pressure-acting chamber in the main axial bore, the control plunger being formed with a passageway open at one end to the pressure-acting chamber and at the other end through the peripheral wall of the plunger, the plunger being operative and inoperative to bear the force transmitted from the cam through the cam follower when the control plunger is in the first and second axial positions, respectively, a check valve providing one-way communication from the passageway in the plunger to the pressure-acting chamber, a fluid discharge chamber open to the pressure-acting chamber, a fluid outlet passageway communicable with the fluid discharge chamber,

Abstract: A power transmission for a two-wheeled vehicle includes a variable-diameter drive pulley mechanism (2) mounted on a drive shaft (1) connected to an engine (E), a variable-diameter driven pulley mechanism (22) mounted on a driven shaft (18) operatively coupled with a driven wheel (W), and a clutch (36) mounted coaxially on the driven shaft (18) and operatively connected to the driven pulley mechanism (22). The drive and driven pulley mechanisms (2,22) are interconnected by a V-belt (7). The drive and driven pulley mechanisms (2,22) have axially movable members (5,24) located on opposite sides of the V-belt (7) adjacent to the engine (E) and the clutch (36) to allow parallel displacement of the V-belt (7) during the changing of the diameters of the pulley mechanisms (2,22), to prevent belt twisting or distortion and to prevent the belt (7) and pulley mechanisms (2,22) from being loaded while the vehicle is moved around with the engine (E) turned off.

Abstract: A front wheel suspension assembly for a motorcycle includes parallel telescoping forks of the hydraulic shock absorber type which straddle the wheel and which are inclined in a forward direction. The bending moment imposed on the telescoping parts by this inclination is partly or fully opposed by a counter bending moment imposed by one or more springs positioned rearward of a vertical plane containing the wheel axis and below a bottom bridge joining the front fork tubes. The purpose is to reduce the frictional resistance between telescoping forks in their axial sliding motion. The springs apply the compensating bending moment between the telescoping parts.

Abstract: A power transmission for a two-wheeled vehicle includes a variable-diameter drive pulley mechanism (2) mounted on a drive shaft (1) connected to an engine (E), a variable-diameter driven pulley mechanism (22) mounted on a driven shaft (18) operatively coupled with a driven wheel (W), and a clutch (36) mounted coaxially on the driven shaft (18) and operatively connected to the driven pulley mechanism (22). The drive and driven pulley mechanisms (2,22) are interconnected by a V-belt (7). The drive and driven pulley mechanisms (2,22) have axially movable members (5,24) located on opposite sides of the V-belt (7) adjacent to the engine (E) and the clutch (36) to allow parallel displacement of the V-belt (7) during the changing of the diameters of the pulley mechanisms (2,22), to prevent belt twisting or distortion and to prevent the belt (7) and pulley mechanisms (2,22) from being loaded while the vehicle is moved around with the engine (E) turned off.

Abstract: A silencer for an internal combustion engine includes a main silencer having an axially movable tubular member located therein which is movable from a first position in which it constitutes an extension of an inlet to the main silencer and a second position in which it is spaced from the inlet for exhaust gases entering the silencer, thus permitting the exhaust gases to flow directly into the main silencer.

Abstract: A front wheel suspension assembly for a motorcycle includes parallel telescoping forks of the hydraulic shock absorber type which straddle the wheel and which are inclined in a forward direction. The bending moment imposed on the telescoping parts by this inclination is partly or fully opposed by a counter bending moment imposed by one or more springs positioned rearward of a vertical plane containing the wheel axis and below a bottom bridge joining the front fork tubes. The purpose is to reduce the frictional resistance between telescoping forks in their axial sliding motion. The springs apply the compensating bending moment between the telescoping parts, or between the lower telescoping fork parts and the frame of the motorcycle.

Abstract: A hydraulic shock absorber of the type having a cylinder and a piston with axial passages therethrough. The piston is mounted to slide within the cylinder. Valve plates having orifices therethrough are provided to control flow through the axial passages of the piston. Certain of the valve plates are situated to operate together with a variable effective orifice on the downstream side of the axial passages and to act with a fixed effective orifice as check valve plates when the flow is reversed. The composite valve thus defined offers a smooth and properly sloping velocity-resistance curve. The shock absorber also includes a foot valve assembly controlling flow between the interior of the cylinder and an annular oil reservoir outside the cylinder. The foot valve assembly may have two check valves for controlling flow through two sets of foot valve passages or it may employ a check valve spring which changes from a "V" shape to a flat shape to cover orifices in a check valve plate.