A quick search revealed that this is the process for programming your speedo.
Speed Control Programming
NOTE
: While in the programming mode, no power is
applied to the motor.
1. Turn on the transmitter’s power switch. (Be sure the transmitter
batteries are fully charged).
2. Turn the ESC switch on.
3. Press and release the setup button. The red and green LEDs
will light.
4. Move the throttle to the full throttle position and press the
programming button. The green LED will remain lit and the red
LED will go out. (If the ESC does not sense throttle movement
in 3 seconds by the transmitter, it will exit the programming
mode and you will have to begin again.)
5. Now move the throttle to full reverse and press the
programming button. The red LED will glow and the green
LED will go out.
6. Return the throttle stick to neutral and press the programming
button. The green LED will glow and the red LED will go out,
indicating programming is complete.
During normal operation, the green LED indicates neutral and the
red LED indicates full forward and full reverse.
If you are still having problems, let me know which transmitter you have and I'm sure we can work out how to reverse one of the channels.