lsi mini late model help with xcelorin

[tdog1006]

I have a losi mini late model with a Xcelorin brushless system part number losb9560 i am running a 1600 mhz battery but it wants to surge. When you first take off it is fine but then it starts to surge. if you let out of the throttle and it stops but will start again. i can put the stock motor in and it doesn't do it. Any idea's what could be causing this? Also if you run at half throttle it doesn't do it