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That looks like a CT811B9 speed controller to me. Here is a link to The CT811B9 wiring directions: http://www.electricscooterparts.com/hookup/SPD-CT811B9.htm

On your controller the battery gauge most likely shares a ground wire with the throttle so it has one less wire than the CT811B9.

To determine which controller connectors go to which components the wires will need to be tracked back to which part they go to. If any wires are lost then they will need to be replaced to rewire the scooter.

If you want to replace the old controller then any new controller could be used as long as it has the same specifications and functions. I can tell from looking at your attached photos that the scooter has a 350 Watt motor and 24 Volt controller, so just about any 24 Volt 350 Watt controller could be used to replace it.

 That type of problem is usually caused by the speed controller however it could also be the throttle. I would disconnect the throttle from the controller and see if the motor still runs at full speed. If the motor runs at full speed with the throttle disconnected then the speed controller is faulty, and if the motor stops running at full speed with the throttle disconnected then the throttle is the problem.

For more information on troubleshooting this type of problem I recommend visiting our troubleshooting guide at this link: http://www.electricscooterparts.com/troubleshootingmotorrunsconstantly.html