Page 34 of the 3.0 manual states:
To increase maximum speed:
1. Press and hold the plus (+) and minus (-) buttons on the control
pad simultaneously until the screen says “P1”.
2. Press the button on the control pad to cycle through the settings.
3. Go to setting “P08” and change this value from 32 to 100.
NOTE: This setting represents the top speed in kilometers per hour.
For Class 2 performance, this speed setting must not exceed 20
mph (32 km/h). For Class 3 performance, this setting will be set
at 100, indicating the bike has been completely unlocked to enable
speeds of up to 28mph. Please note: The maximum achievable
top speed will vary by tire inflation pressure, road conditions, total
payload, battery charge level and other factors.
4. Press and hold the plus (+) and the minus (-) buttons on the
control pad to exit Settings Menu.
5. Power bicycle OFF by holding the button to save the settings.