RE: Walkera #60b - Tail Rotor Problem??? Not sure whats happening!!
The first things i would look for is any loose locking screws around the tail drive gears and to make sure they are not slipping on there shafts in any way, i would also be checking the one way bearing on the main drive gears, also check that the drive belt is not to loose and jumping teeth/slipping, i dont have a 60B but most tail drive problems are of similar origin, and the above is a good place to start looking. If you increase head speed it will increase tail speed also, but it will also increase the amount of tail rotor force required to compensate for torque generated by main blade pitch. You could try more head speed with less +ve pitch, this would require less tail compensation.
Hope this help you out.
Cheers guru