In considering of safety, all civibikes models come with default speed limit which might be lower than regulated.  In order to adjust the speed limit to CLASS II and CLASS III, and make sure all your controller settings are good, please see following step:

For Rebel & Predator

• Power on the display by holding M button for 2 sec;
• Hold + and - buttons at the same time to enter setting interface;
• Press + or - button to choose between different settings, and M button to enter. Now enter "Set LS"
• Press + or - button to change speed to 32 km/h ( 20mph)
• Press M button to confirm
• A step furthermore: Change "Set WD" to 23(Rebel) or 28(Predator) so that you can get accurate current speed. And press M button to confirm.
• If you found the unit is not Miles but KMH, change the Unit to Miles in the same setting menu.
• To get access to further deep settings, hold + and - buttons for 2 sec again. Explore as many functions as you can.
• Hold M button for 2 sec to confirm all settings and back to main interface.

For Cheetah

• Power on the display by holding M button for 2 sec;
• Hold SET button for 2 sec to enter setting interface;
• Press + or - button to choose between different settings, and SET button to enter. 
• Now choose Speed Limit and press + or - button to change it to 32 (20 mph) or 45(28 mph). Be noted you must wear helmet and older than 16 yrs old. See more requirements Here
• Change Wheel Size to 28 to get accurate current speed.
• Change Unit in the same menu. You can choose Miles or Kilometer as you like.
• Now choose Save & Exit
• You are ready to enjoy the full power of Cheetah!