Abstract: A fuel injection type two-cycle engine for motorcycles. A fuel injection valve for injecting fuel into an air intake passageway at a predetermined timing is disposed on the upstream side of a reed valve in the air intake passageway communicating with an interior of the engine via the reed valve, with the injection port thereof directed towards the reed valve. An air intake pipe forming the air intake passageway extends nearly in the vertical direction from the upper surface of a crank case at an middle position between a crank shaft extending in the widthwise direction of the vehicle body and a transmission shaft separated from the crank shaft in the back and forth direction and extending in the widthwise direction of the vehicle body, and a fuel injection valve protrudes from this air intake pipe in the back and forth direction.

Abstract: A power transmission system for vehicles comprising a driving member connected to a crankshaft of an engine and a driven member connected to a driving wheel, the driving and driven members being connected together via a one-way clutch, a friction clutch and a direct-coupling clutch, which are disposed parallel to one another. The one-way clutch is adapted to transmit power only from the driving member to the driven member. The friction clutch is adapted to frictionally connect the driving and driven members together when it receives a rotary torque at not more than a predetermined level whereas it is slipped when the rotary torque has exceeded a predetermined level. The direct-coupling clutch is normally maintained in a connected state but it is put in a disconnected state when the speed of revolution of the engine has exceeded a predetermined level.

Abstract: A power transmission system for vehicles comprising a driving member connected to an engine crankshaft, and a driven member connected to a driving wheel, the driving and driven members being connected with each other via a one-way clutch and a friction clutch which are disposed in parallel to each other. The one-way clutch is in a connected state when a forward load is applied to the engine, and in a disconnected state when a back load is applied to the engine. The friction clutch is operated to slip when it receives a torque greater than a predetermined value.

Abstract: A piston ring for use with an oblong piston and cylinder has a gap at one end. A resilient corrugated expander is positioned behind the piston ring and within the piston ring groove in the piston. The expander also has a gap and the two gaps are adjacent each other and in close alignment.

Abstract: A piston ring for an oblong piston reciprocating in an oblong cylinder has side portions which merge at one end with a relatively long convex portion. Each side portion also merges with a relatively short convex end portion, respectively. The short convex end portions define a gap between them. Upon installation of the piston ring into a groove on the piston and within the wall of the oblong cylinder, the width of the gap is substantially reduced, thereby to stress the side portions and cause them to reduce pressure variations between the piston ring and the cylinder wall around the periphery of the piston ring. The oblong piston and cylinder may have straight side walls merging with arcuate end walls, or may be substantially elliptical in cross section.