Did you set your throttle endpoints? If not one motor could be racing to full power while the others are still spinning up. Take the props off, put the Yaw POT to zero, turn the Tx on, put the throttle to full, power up the tricopter, wait for the start beep, a battery beep, then two beeps, then put the throttle to zero and power off the tricopter. Put the Yaw POT back to 50% or whatever and power on. With the props still off, slowly power up and make sure you hear all the motors spinning up at once.
Also what controller board and firmware are you running? I've seen this behavior with a reversed roll gryo.
The KK V1.6 firmware out of the box should not need any reversing with the motor rotation as follows: front left CW, right right CCW, rear CCW.
Another thing to check is that the controller board itself is mounted with the arrow facing forward, and that you have the motors plugged into M1,2,3 correctly. If the roll axis / arrow on the board is pointing forward, with the props off spin up the motors to 1/4 throttle. Then move the right stick left, down, right, up. You should hear the motors correspond with left:right motor spins faster, down:front two motors spin faster, right:left motor spins faster, up:rear motor spins faster. If that's not working right, switch out the M1,2,3 connections to correct it. If this is working right, check your gyros, with the props off and the throttle at 1/2, when you dip the left boom down, the right motor should slow down. Do this for each direction and check to make sure the behavior is the same. Front dipped, rear slows down etc.
Hope this helps.