The HPI coil seems like it was only designed to power a brake light for daytime riding.
The HPI rotor is a 2 pole design, and the stock rotor has 4 poles.
The gaps have to be as small as possible between the core on the HPI lighting coil, and the rest of the core that wraps around the stator. You know magnets pull harder when they're closer together.
I wonder if there's a way to wind a coil halfway around the circular core on the HPI coil.
There has to be a better way. What does the little red box at the top do? It's a coil to power the CDI, and a hall effect sensor, right? How is the curve achieved? Is this done in the red box in the stator, or the little square external one?
<a href="http://s36.photobucket.com/albums/e20/novakarl/Puch%20HPI%20Parts/?action=view¤t=RotorStatorPoles.jpg" target="_blank"><img src="http://i36.photobucket.com/albums/e20/novakarl/Puch%20HPI%20Parts/RotorStatorPoles.jpg" border="0" alt="Coil and stator poles"></a>