Hi! I have a Compy300 (a Blade CP/Esky CP2 sized EP heli with belt driven tail) and have been flying it for about a month now without any problem. A few days ago though, it started spinning to the left even with full right rudder. There is very little tail authority with right rudder but enough thrust with left rudder.

I have checked/adjusted the tail pitch and there is more tail blade pitch w/ right rudder. I made the belt tension tight/loose. No bindings in the tail drivetrain. The tail pitch slider travels the entire length of the tail shaft. Tail blade leading edge correct. Tail belt pulley not worn out. Problem still exist.

If I hold the heli in my hand, throttle it up and eyeball the tail from behind, I can see that the pitch slider move towards the boom (uses the entire left side of the shaft w/ full right rudder) and can see the blade pitch. It just doesn't generate enough thrust to move the nose to the right. I can also tell by the sound of the main blades/motor that it loses more headspeed with right rudder. If I hover it, at low throttle, right rudder puts the nose to the right but at throttle just before the skids gets light the heli spins to the left even w/ full right rudder.

The Compy 300's main blades rotates clockwise and the tail blades counterclockwise. Can anyone please help. Thanks!

I recently removed the main blades. Held the Compy in my hands, applied full right rudder and there is enough thrust to point the nose to the right (same with left rudder). With the blades removed, left and right rudder is functioning normally/properly (but I surely can't fly it w/o the blades)

What could be wrong?