A crankshaft bearing assembly is for a reciprocating fluid-machine. The crankshaft bearing assembly comprises a shaft having a co-rotating first eccentric surrounded by a second eccentric. The second eccentric is adjustable around the first eccentric, and the second eccentric is surrounded by a bearing and a crankshaft bearing housing. The second eccentric is connected, by means of a coupling, to a shaft sleeve concentrically rotatable around the shaft. The coupling comprises a carrier which co-rotates with the shaft sleeve. The carrier, at a radial distance from the center axis of the shaft, is provided with a slide bolt projecting into a groove in a slide casing, the slide casing being fixedly connected to the second eccentric.