Hi forum members, I had purchased a quad kit from Quadkopters about 4 months ago and just found time to build it for mini project at college.
My setup is kk2.1,TBS discovery clone frame,5200 mAh orange lipo,sunny sky 2212 980kv motor and turnigy props(I broke the DJI clone props 1045 when testing it outside) ,I use CT6B as TX.

I calibrated each ESC individually and also did all of them at once,it gets armed like a charm,I callibrated using spirit level and also the gyro bubble stands at origin in the axis ,all the motor direction and propeller directions have been triple checked,all the motors start at once and there is no issue with it,I have set the trims to 0 too,since I'm a newbie and  I have no idea about pgain limit and stuff.the quad keeps flipping on one side.the kk runs stevie 1.9s firmware.would be great if someone could help me with it,and if from Chennai,I'd love to personally meet you and get to know things!thank you forum heroes! Have a great day.

If all props and motor direction are correct, Then check motor outputs. Its a common mistake to connect motors to wrong outputs.

Regards Ashim.

I had this problem too.
if your quad flips check these things.
1) turn on your quad and do all calibrations at once.
2)make sure you have connected all the escs in the flight controller correctly. because even your motors are spinning in the right direction this can make your quad flip.

and one question does it have gps?

If you use an accelerometer, is it calibrated?

Is the motor numbering correct as per your firmware?

@samjoseph123 since you are saying you have checked the props and motors orientation then you might want to check if you have loaded the correct motor layout in your KK2.1.5 board.
Make sure you are on X layout if your are flying a X quad and check the motors and ESC connection according to the display and this should solve your problem!!
Safe Flying!!

check the gyro direction ...it might be the issue

go to mixer editor and check if the roll values or not in -ve ...if they are change them to positive