My MINI-Z suddenly slows down and stops though steering is working

Most likely the safety protection circuit (poly switch) attached to the motor has cut off the current because of high load. Please try the following:

  1. Remove the motor and check if the wheels and drive train are spinning freely. Note: do not touch the motor or poly switch while they are hot.
  2. Use a smaller pinion gear or a larger spur gear to reduce the load.