Abstract: A dosaging pump driving mechanism for converting the rotary motion of a driving wheel into the oscillatory motion of a piston connecting rod, which is connected at right-angles to the axle of the driving wheel, by a radially moveable eccentric. The stroke of the connecting rod adjustable by an adjustment device, which acts upon the radially movable eccentric to change its eccentricity and has a shaft, which can be moved in the axial direction of the driving wheel and of the eccentric by an adjusting-spindle. The shaft defines a slot at an incline to the shaft axis, in which a sliding member is linearly displaced in radial direction together with the eccentric.