Different controller, additional batteries, change the sprocket.

 

If you just want it to go over 30 mph an easy way to do it is put a razor
mx500 twist grip(4 wire)twist grip and a 100 amp speed controller you can buy the parts off of Houston rasor(for the twist grip) and the controller off of eBay get 3 12 volt 12 amp batteries and put a 36 volt 1000 watt motor and hardwire a 10 cell (12 volt) rc car battery and you should go over 30 mph,because I did. You can also change the sprocket 2 eather get more acceleration or top speed.If you keep getting tired off the ride time and you ride it in the day more then you ride it at night you can buy solar pannels from a cheap solar car kit and use those to help recharge it while your riding.