i would try a new tail motor if you are still running the stock motor. Also, there is a mount that you can get to either use two stock tail motors,(helps keep them from burning up), or a direct drive motor. I might not be a bad thing to check the pitch of your main blades aslo. If the pitch is excessivly high, the tail rotor won't be able to compensate for the tourque generated by the main rotor head.