Ok ive been flying my corona 120 for a little while now learning how to hover pretty good. I bought the Carbon fiber flybar and man i got it on was unbalanced fixed it yesturday then it flew great. I hovered like i never have before. But today I went to go fly it and the Tail kept swinging left. Thought maybe something was wrong with the gyro but my gain hasnt been changed ever. I have it at 75. Then my heli kept flying forward really fast on its own. Is that called hunting? but anyways. now my tail boom goes up and down like its unbalanced. Can anyone help me out here. did I do something wrong or is something wrong with my heli? It wasnt acting like this yesturday which is strange. Thanks to anyone who replies.

Did you change the CG somehow? Trims? Start there... also make sure you've got the z-links setup the same on both sides.

Hunting is when the tail wags because they gyro gain is too high.

Good luck.

Follow KLRico's advice, in addition if the CG is correct, make sure the swashplate is square to the main shaft and there isn't any free play in the linkages. The tail swinging to the left can be caused by many things. If you are using a HH gyro, make sure all rudder trims and centering on the Tx are set to zero. Again check for slop in the linkages or in the Spider eyelet and collar. Electronic HH gyros suffer from temperature drift. If I take my Corona from in the house (70 degrees) to outside (50 degrees) and try to fly immediately, the tail always drifts left. As far as the tail bouncing goes, sounds like something is out of balance, blade tracking is out or a bent MR shaft. Hope this helps.

bouncing tail boom can mean unbalanced tail rotor

That's what I was thinking!

A bouncing TR could also mean a bent main shaft. You may want ot take it out and roll it on a piece of flat glass like a table.

Also check the linkage going to the TR. It should be very easy to push back & forth. (ie., no binding.)

BTW: check your linkages on each side of the rotorhead. They should be the same length.

Ok I have a gy240 gyro. which i believe is a HH. Ill have to check everything you guys said 2 of the pins in the tailroter were sticking out a bit so I pushed them back in. It seemed to help a little bit. there is no vibration in the tail like up and down when its still on the ground when i first power up there is. then when I increase the throttle right before take off it stops. then when it gets in the air it starts again. How do you balance the tail rotor? I looked in the manual but didnt see anything.
The trim is fine I corrected it. At low head speeds the entire frame shakes side to side like the main shaft is bent. Ill have to take it off and see if you guys have anymore advice feel free to post thanks.

Try to cg and balance your blades.

Well thanks for all your help everyone. the balancing problem is fixed. i brought the gears closer together. from the tail rotor gear to the main shaft gear that spins the direct drive. now there is no vibration in the tail anymore. but still pulls to the left. the tail does. I guess trimming needs to be done now. I woudl have just now but the low battery alarm went off on my transmitter so i better not risk it. If anyone has anymore advice to help with anything im all ears. thanks for all your help.

Oh what is cg im sorry im truely really new at helis. still learning everything. thanks again

http://www.dream-models.com/eco/Blade_balancing.html

hmmm
thanks for showing me that site its going to become very useful