I have the Hobby zone super cub and now i when I fly it i can throttle it up to about 75% and then the engine quits. I have changed the battery on it and on the transmitter and it still does weird stuff. Got any suggestions?

Possibly the esc is cutting out at that amp level.

I second that motion.  I had a brushless setup one time, and changed prop pich, diameter.  Every time I would throttle past 60% the esc would overheat and cut out.  Did you chang anything on it, and did it do this from the start?