the lehner 1930 and bk9918 esc

[captain harlock]

I just received the 1930/5 motor, but now I have a problem. When I use 7 cells with the motor it runs nice and cool, but at 12 or 13,2 volts the motor makes a very strange sound and it coggs to the point that it sometimes feel like the speed cont.(9918) cant deliver enough power, it seems as if the controller is about to shutt down. I really have no Idea what's going on. The 9918 works with the help of a 4cell receiver pack and I have took out the black jumper near the red one to disable the BEC system, May be it could be the problem, but may be not. If you say that I'm using too much cells then I dont really think so because there are som people who used 12 cells with such motor without having such problem. Monster Mike, I seek your help.:W: