RE: Burned out motor.........Why?
You need to understand that at any particular voltage the size of the prop determines what the motor will try to draw... the battery is just supplying what the motor wants... I reckon that 11x7 was causing that 1250Kv motor to draw a LOT more than it is designed for!
I have not tested your particular motor but a Turnigy C3530-1100 (~1075Kv) drew over 21A with an 11x7 and got very hot very fast. A higher Kv motor like yours will draw even more. A Turnigy SK 3530 (~1275Kv) I tested was drawing over 20A with just a 9x5... I'd say an 11x7 might have caused it to draw 30A+. Despite their optimistic specs those Turnigy 3530-size motors are probably no good for more than 225-250W.
Can you give me a link to your motor... I can't find a 3530-1250 anywhere (1100, 1400, 1700 yes... but not 1250Kv).