The other option here is, keep running it just like you are, maybe not so long at one time, don't run the battery down quite so far, it's not good for lipo. If the motor is still working, so what, sometime you will kill that motor, then just get another one, they are fairly cheap. Your combo of gearing and where you run is what's making all the heat, but so what if it's working and nothing is melting or burning, have fun with it, that's what it's for! Maybe you could get a clip on haetsink for the motor of some kind....