A kit servomotor consists of an electromotor and a rotary encoder. The electromotor has a motor stator (3, 8) and a rotor (1), which is positioned in unsupported fashion in the motor stator. The motor stator (3, 8) and the rotor (1) can be installed on the output end. The rotor (1) is designed as a hollow shaft, at least on its end opposite the end used for installation. The rotary encoder is attached to the electromotor on the end opposite the installation end and has a stator unit (4) and an encoder shaft (5). The stator unit (4) is connected to the motor stator (3, 8). The encoder shaft 5 is connected to the rotor (1) using a coupling that is isogonal with respect to the angle of rotation, but elastic in the radial and axial directions. At its motor end, which is coaxial to the hollow shaft of the rotor (1), the encoder shaft (5) has an outer diameter that is smaller than the inner diameter of the hollow shaft. The coupling is axially flat in design and bridges the annular gap between the outer diameter of the encoder shaft (5) and the inner diameter of the hollow shaft of the rotor (1).