Ok I now see its a different ser-up then the Hirobo which uses two motors on the main rotor system - well if it has a tail rotor it has to have a gyro to stabilize it, so it could be either the gyro which is built into the reciever board and more than likely not replaceable or the tail rotor motor.

Is there a trim for the tail rotor on the trans - if so does it make any difference when you move it?