Gen Power

First try and add an ammeter in series with controller circuit. Measure voltage as it drops and current as you accelerate. This way you can get an idea of power that is really needed. I thought of using my Honda 650 watt generator but the power to weight ratio kills. Something I tried was use an inverter and a big Gel Cell battery 12 volt and a 60.00 volt power supply to my XM-3000. No current draw sitting and 20 Amperes going fast. I got to Maynard and swapped out Gel Cell and went home again. Forty miles round trip with one real charge for a few minutes well 15 at the most is fine with me. My 5 Ever green hang around 65 and 69 charging and used to drop to 55 driving so 60 volt was a good choice for me.
My XM-3000 draws 55 amperes at flat out speeds and I try to keep it down to the 25 to 45 at most.
So all I can say is measure everything to see what power you need or can use. Keep an eye on generator for it can possibly over charge your pack unless you have a good regulator.
A two stroke generator has a better power to weight ratio but all that smelly oil and gas mixture and noise? My Honda is a four stroke and is heavy so inverter power was a better choice for me plus I always leave batteries charged at friends house and here. As the batteries start to die the voltage sags fast. Less of a sag starting out. I plan on doing that with my VX-1 too. It has a 125 volt pack and most inverter make 145.00 volts rectified. So dead on the monies perfect for charging NiMH pack to 145 to 150 volts. But I'll wait on any and all express warranties to expire. All I need is five to seven bars of battery for range. Keep us informed of you plans and if it works out if you go Generator Set route.