Greg, this is an answer to your later question, "Determining Power Source for DC Gear Motor?"

I'm hoping you'll merge that question into this question.

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Let's start with the battery. 90 V is high enough to be dangerous. You can run the motor with a lower voltage, but with two side effects-- the top speed will decrease, and the torque will drop. I'd start with a few lantern batteries connected in a series string (+-+-+-) and turning it on and off by hand with a wire.

If you can tell us a little more about your DC speed controller, we might be able to help with that too. (For example: What does it look like? Where did you get it? Are there any words written on it?)