I doubt that I have the definitive answer, given the electrical experts in our group; however an ask.com search turned up several references to riders who were rewinding their own coils. A big part of the rewind is choosing the right wire guage: thinner wire gives you more windings, but it would provided higher resistance.
This post from the
Motorbikebanter.com Forum seems to indicate that the results might not justify the effort:
"One can always use fewer turns of heavier wire to get more current, but
that will require more rpm's to achieve usable voltage at idle. It's a
fundamental tradeoff of stator design. When comparing stators it's
important to look at volts, amps _and_ the rpm required to make them.
It's easy to turn a 30 amp stator into a 60 amp stator _if_ you're
willing to spin the rotor twice as fast."
That said, I'd put effort into increasing alternator output if I knew I'd get some solid improvement.
