I'm sure you guy's have seen this. But this is a 250 watt Synchgo super monkey fitted with a throttle and as you can see the it cruises way above the restricted 15.5 mph. Ive got a Carrera e bike and that cuts out at about 16.5 mph in highest speed mode and i find it will only go to about 17 -...
If you want greater distance then swap battery for a higher ah, but 16ah is pretty good. And i notice that the 750 watt motor has even smaller battery at 14ah. Maybe you could give us a distance sometime, flat out and see how far you can get.
The 250 watt bikes use a 36 volt battery and the 750 watt a 48 volt battery. So completely different. Ive read that you could swap to a 500 watt motor, but not sure how the controller would take that