I've had an ebike now for about 2 weeks, and I'd like to take a minute to share some info for those out there who (like me) know next to nothing about ebikes.
There are brushed and brushless motors, do not(like me) buy a brushed motor kit from a guy on the back of a truck. It is not 1000W, and will not work for more than a day. An easy way to tell the difference is to count the wires going to the motor. 2=brushed more than 2=brushless.
3 large square batteries does not a ni-cad make. That is lead acid. Let the words lead and acid dissuade you from them. They are heavy and don't go that far on a charge, especially used. At the very least don't think they are ni-cad because the guy in the truck says so.
Ebikes are like cars. I can't take my 2000 pound car, put another 2000 pounds on it and expect it to climb a 25% grade. likewise, a motor designed for a 100 pound kid will not haul a 6'4", 240 pound man up that hill either. Both car and bike will break and leave you very sad.
Find out what a torque arm is and get one. Hell, get two. When you apply power, it is better for the wheel to turn then the axle.
Use caution. Always think before connecting electronics. I can now tell you that if you plug the battery into the power OUTPUT(where you should plug in the motor) of a controller, you will cause a fire and burn the crap out of yourself. Also, might be a good idea to use separate connector types for this sort of thing.
The magnets inside a strong motor are STRONG. Anything you put between magnet and metal will be crushed by said STRONG magnet. Don't let this be your(previously burned) fingers. Also, holding the magnets in your hand can erase all your credit cards in your pocket!
Hopefully this information will keep someone from sitting at home with a crushed, burnt hand with no bike to get to the doctor and a demagnetized wallet.
-Aaronski
I hope that was based on theory, not the school of hard knocks.
Also, just because the charger plug is the same as your computer's chassis plug, do not plug 110 volts into the scooter (this really happened, but not to me).