I think reversing the air would not be very effective in cooling the headers as most of the incoming air will come from around the engine. When the fans run the 'right' way, they discharge directly onto the headers. Again, all this is just thought and opinion- someone would have to do a real test to find out.
Yes, reversing DC permanent magnet motors is just a matter of reversing polarity.
The fans draw something like 10 amps and can run continuously, as they often do in hot climates, without ever using all available power from the battery. There is about 300 watts and a bit more excess power put out by the alternator; the fans could be more than three times more powerful than they are without overtaxing the alternator. This assumes the two main uses of large amounts of power are NOT being used when the fans are being fed all this power: that heated clothing is not being used (duh) and that large, auxiliary lights are not being used (not likely when stopped in traffic).
Output control of the fans is relatively easy also- Pulse Width Modulation (PWM) is an easy, very efficient way to control the speed of DC motors and works very well. One can buy a 15 amp PWM controller for $30 or so. Of course this comes with a manual control but it could be adapted to external, automatic control fairly easily.
Brian
Reading what you said, I agree that just part-time reversal on full blast won't cut it, but it might if the fans stay on but at a lower speed while not actually needed (while at the stop). This might help to keep air moving across the headers. I mean, it might be designed for air to move back, but air moving forward is still likely to cool all the same stuff.
I also agree that the bike needs to be "virtually" stopped- even a few MPH would greatly fight the airflow. But I also think that there would need to be a circuit that would quickly kill the concept and revert back into normal mode if the bike calls for cooling during the "reversed" mode. I think that would certainly make the mod "safe" (as long as there are no real issues with the exhaust system).
I do think it is a mod worth investigating. But I am concerned that at idle, will the alternator be able to keep up with the fans on for long periods (with other full electric load- headlights, running lights, accessories)? We don't want to EVER dip into battery reserve, of course. And is it even possible to run the stock fans at different speeds (that other possibility I am thinking about)? And most DC motors can be reversed by simply changing the direction of the current- is that true with the C14's fans?
Heat when stopped is my primary annoyance when it comes to the C14. I suspect most people agree that addressing it would be something very welcome.