An electrical motor rotor being balanced using the belt drive on a Precibalance Dynamic Balancing Machine. Precibalance supplies balancing machines for motor rotors from few hundred grams to many tons weight capacity. The built in ISO tolerance calculator enables easy calculation of the desired tolerance of balancing as per ISO standards. The remote angle electronic protractor using a rotary encoder enables easy identification of the unbalance location even on the belt drive for a quick and easy correction. Standard features such as the place-weights program enable precise calculation of correction masses at predetermined location such as corrections by rivets and washers greatly reducing guesswork in the balancing operation. The precise balancing results enables balancing of rotors to low residual unbalance levels delivering low vibration levels in the assembled motor.