Lever-mechanism motor or pump

A lever-mechanism machine, comprising a cylinder, a rotary piston equipped with an eccentrically set shaft set in bearing in a cylinder block, an operating-medium inlet port, an outlet port, and a lever piston, which is mounted in bearings on a lever shaft and which is in essentially tight contact with the rotary piston, so that the cylinder forms an essentially cylindrical first chamber for the rotary piston and a partially cylindrical second chamber for the lever piston that moves backwards and forwards, wherein the lever piston is mounted in bearings at one end of the shaft which is essentially parallel to the eccentrically set shaft and that the lever piston is in essentially tight contact with the surface of the rotary piston, and wherein the lever piston and inlet port are oriented so that an operating medium passing through the inlet port urges the lever piston against the rotary piston whereby the lever piston pushes the rotary piston simultaneously with the operating medium and characterized in that it is euuipped with a spring that presses the lever piston against the rotary piston or the bearings.