What I don't understand is that why d does the tail motor oscillate on its own. I am not getting that locked in feeling as the flite test guy says.i guess the kk board tries to over compensate even small changes.as per flite test I have changed the mpu settings to a rate of 500 instead of the default 2000 for the gyro.

Did you change the rudder value from 100 to -100 in the channel setting. Try it with both the changes.

I had the same problem but when I did both the changes the problem just disappeared!

Thanks I will try that tomorrow n let you know. Thanks again.

1. the servo is directly connected to yaw setup. try with the servo on downside of the boom and a pushrod in between. this will reduce the problem a bit.
2. are the yaw setup snug fit and yet smooth enough not to bind the servo?
3. go for either a standard servo or a 9g metal gear servo.
4. you still havent replied my earlier question. have you tried taking it above the ground a bit. it is normal for tricopters to show this defect on ground.