the reason you can't go without a battery is because this bike uses a rotor that is a spinning electromagnet. There are many honda twins that did, in fact, have a rotor that is a spinning permanent magnet, and those bikes will generate current with no battery. But even those are not enough to easily make spark at kick start speeds. A capacitor would be necessary in that situation.
I'm sure there are people who have retrofit permanent magnet rotors to the SOHC4. If this is something you really want to do, it's not impossible, but possibly just above your pay grade , so-to-speak