unjonharley wrote:Will the volts go up with more speed??
Yes, but you probably don't want to go much faster than 25% over the maximum speed the motor was designed to run at. I'd wager that if it's a 12-volt motor, you'll probably get 12 volts as a generator until you're in the 3x range above the original maximum RPM.
Some "universal AC/DC" motors work as generators. Some electric lawnmowers I've seen use a 150V DC motor with a bridge rectifier (the Black-and-Decker ones that short out the motor to stall it when you let go of the trigger), and they work as generators. I also found a junked 120VAC electric string trimmer and when I ran the motor on my drill press, I could get it to produce usable power above 12 volts -- enough that it seemed plausible to use that as a generator. In general, if a motor "cogs" (snaps to angular positions) it has magnets which makes it a candidate for a generator.