Gears are need to transmit and transform the power from the motor to the wheels. You can find suppliers by googling for “electric scooter sprocket”. Common gear/sprocket tooth profiles:

#25 Sprockets are the most common type of sprocket used on electric scooters, electric bicycles, electric pocket bikes and small electric go karts.

#35 Sprockets are the most common type of sprocket used on mopeds, mini bikes and full size go karts.

8mm Sprockets are the most common type of sprocket used on pocket bikes.

Bicycle Sprockets are used on standard pedal bicycles and electric bicycles, and typically correspond to ANSI #40N (narrow) chain size.

Useful References:

• http://www.smex.net.au/Reference/Ratios02.php Determining the required gear ratio or maximum speed is not always intuitive. Many factors have to be taken into account. This page is particularly useful for electric or motor-driven locomotives w/javascript calculator.
• http://www.electricscooterparts.com/bicyclesprockets.html