burning out motors

i think im going to leave the gearing the same and check temps like every three minutes, this is weird i didnt seem to have problems before with the 9xl...is there a limit to the amount of time i shoud run? or is it all dependant on temps

although i had never done successive speed runs before, could it be that the large pinion is only causing heat issues only at high speed, because ive done general bashing in the dirt and stuff at lower speeds for a while (mostly staying in first gear)

and would changing the timing on the mm do anything? its set at default now, i think its "normal"