The small scooters lend themselves well to hacking because they're so simple. (To those who don't understand 'hacking' ... this is one of those multidimensional words with multiple meanings, not all of whom refer to computer crime.)
To demonstrate hacked up small scooters I'll use these pages to show what I did with my Vego 600sx. The Vego scooters were American made and designed from the 2003-5 time period, but the company went out of business around the time cheap Chinese scooters started coming to the U.S. in large quantities. There were two models with the 600sx being the larger. Stock it has a motor rated for 24 volts 500 watts. It used two non-standard sized batteries so one issue you'll see is that the batteries will have worn out and you'll be unable to find a replacement. Over on electricrider.com they suggest you can use a pair of 12v 10ah batteries to replace each of the two Vego-supplied batteries. An alternate solution is to gut the original Vego and do as below.
The stock system is pretty nice and includes brakes which automatically inhibit the controller, a key switch, etc. In my case the Vego 600sx I received was just a bare frame and I had no choice but to start it from scratch. If I'd received a stock Vego I might have left it stock.
VERY VERY IMPORTANT IMPORTANT: The Vego 600sx had a flaw in its frame at the place the steering column is welded to the main frame. A crack can form there resulting in the frame breaking. If yours has a crack it's a simple matter to take it to a welding shop and get a patch welded over the crack.
NOTE: The following tutorial information is incomplete and is a work-in-progress.