Unfortunately, you cannot change the speed limit per pedal-assist mode however, you can increase the max number of pedal-assist levels which will reduce lower assist levels.
In order to do so; when the bike is off, please press and hold the power button until the settings menu comes up after the Ariel Rider logo.
The passcode for the advanced settings is 2020.
From there select pedal-assist mode and increase that to 9, please.
Please do not change any of the other parameters as it may result in wrong reading information and giving faulty speed/battery data on the screen.