Just finished a rebuild on the B400 and I am having what appears to by gyro issues. I have not changed anything on the Tx since my last flight, just replaced the boom, rotors and rebuilt the head. Now when I throttle up before it takes off, if I give it right or left rudder it spins constantly in a circle on the ground and does not stop until i spoil down a bit. Any ideas?

Which direction is the heli spinning?
Does it always spin in the same direction?
When I rebuilt another heli, I had inverted the tail rotor servo by mistake effectively reversing the HH gyro.

It mainly does it to the left. The nose goes left. I tried with the servo setting either way and it does it in the reverse direction then.

Do you get full pitch on the tail blades? Is your belt tight enough?

Nick

With throttle hold on... do you get full travel with your tail servo?

With Gyro Sens set to 50, where is your servo horn in relationship to the tail boom? What position is your tail rotor pitch level relative to the tail boom?

Did you change out the tail servo? If so, flip the switch on the gyro from nor to rev.

Right on the money JP. I changed the tail servo a while ago and it flew fine. Not sure why it was a problem now, but it flew ok. Felt a little different after the rebuild, I am sure some things are still off.

The tail likes to wander away, if I give it one click of right rudder, it holds fine. Not sure if that is ok.

May want to check if the tail rotor is spinning in the correct direction. It is easy to reverse the twist on the tail drive belt and the tail rotor spins backwards.