[Tom Line]

I will hazard a guess without having all the information that you are running WAY too high a gear ratio.

I helped another team set up a shooter to shoot from mid court with 6 inch wheels and 2 banebots 775 (13000 rpm free speed). Their gear ratio once we did the math is around 2.5:1.

FP's run around 18000 rpm. Which means to run the same setup, you should be running around 6:1 or 7:1. You've overheating because you're on the wrong side of the motor curve, and are stalling the motors.

Fisher price are incredible motors, as long as you run them at high speed so their fan can cool them off a bit. That means a high gear ratio.

Cims are bulletproof and can be abused. FP's take a bit more math and finesse.