So after facing major issue with my quad earlier, there are these 2 issue i cant seem to get over with.

1> when i bring the quad down , it starts to wobble slowly , not much but its not entirely stable either.

2> The YAW, I've trimmed it and still the they yaw is biased towards the left sie ( moves clockwise ).

Any help here ?

Otherwise its fine. and the PI values i am using now surprisingly, sow the same reaction it used to earlier when i had kept the values at default ( 2500 ones )

Anyways, please let me know here...

Helicopters have the same problem. It's known as the vortex ring effect.
http://en.wikipedia.org/wiki/Vortex_ring

this is caused due to the aircraft passing thorugh it's own propwash. the easiest solution to this is to reduce altitude while moving instead of just coming down vertically.
Heavy aircraft suffer less due to the lower kv motors and the increase in weight.

as for the yaw, check if any of your motors are tilted.... for trimming yaw, dont use the transmitter controls. trim it on the board directly.

hope this helps

wow ! that did help thanks a lot

BTW,, i have the KK2.1, so where do i go to trim the Yaw ?