I just brought a x525 frame with KK 2.1 board. After ARMED the KK board the front two motors are not responding bt the rear are working great. bt when i'm trying to connect the ESC directly to the receiver the motors are working great. Their is no problem in the motor. But after connecting to KK board the front motors are not working . Please help me 

increasing throttle make any movements?

your kk 2.1 board is faulty. try another board and try   

I hv just checked the ESC and motor and KK board and found tht after increasing throttle another motor is working but the last motors ESC are getting too hot with in 20-30 second and that motor still dosnt working and now it also not directly working with Rx   .. so i checked the motor with another ESC and that time its running smoothly so now i think that ESC is faulty.

have  you  select a motor mode .. x or + mode for quad ?