You can never do anything for that kind of power for $500. That 70000W (70Kw) Gabriel's go kart, has Zilla 1000amps controller that $2000+ and lithium batteries that $3000+ and you still need a charger. The motor you can pick them up from $50 at any forklift junk and still have to another few buck to do a few trick on the motor.
I have spent a few buck on mine and still have to spend plenty more, remember I'm doing mine for around 125000W (125 Kw). My motor is 8 inch diameter and Gabriel's motor is 6.7 inch diameter.
For $500 you do something just to play around and do around 20 to 30 mp/h.
Albano
That ZK1 is rated at 2k amps lol O_O
I'd reckon a couple grand just in the controller... too bad I'm cheap.