This paper develops a theoretical model to describe the operation of harmonic side-drive micromotors. The model is based on a detailed analysis of the electrostatic and friction forces acting on the bearing and bushing contacts. In particular, the model accounts for sliding and rolling of the rotor on the bearing, and sliding of the rotor on the bushing. Using the model, the rotor transient can be predicted for a step voltage excitation of a given stator pole. The shape of this step transient is affected by the excitation voltage magnitude, and the friction parameters for the bearing and the bushing. The model is used to fit data from experimental measurements of rotor motion to determine the bearing and bushing frictional parameters.