[artdutra04]

If you saw "steam" coming off of them, it may be too late.

CIM Motors will smoke and/or die, although they don't always release magic smoke. Once they pass this point of no return, they will continue to function to a certain degree: they'll still spin, but they will be very inefficient at making mechanical motion and VERY efficient as a space heater. So much so, that as soon as you apply power to them under a moderate load, within ten seconds they will be too hot to touch.

As for your application, do you have any pictures of this set up? Did you leave the Fisher Price transmissions on the robot and add a CIM motor in addition to that*? What is the gear ratio between the CIM motor and the output sprocket where it interfaces with the output of the FP?

* If you did this, and the output from the addition of the CIM motor gear ratio is not almost exactly (within a few percent) the output rpm of the Fisher Price transmission, the CIM motor will be back driving the FP. This will waste a huge amount of mechanical power, and would likely lead to an overheating issue.