There is no white in oem wiring (based on '00 wiring. The schiz in the manual doesn't list a white, either. Shouldn't be different for a '97) That is prolly coming from your acerbis. Did on my UFO, anyway. It was ALL white!
Yellow is from the lighting coil (under magneto). Goes to the switch.
Red is FROM the switch to the rest of the system...the front light, taillight and regulator (through another connector).
The white is probably part of the acerbis, either 'to' or 'from'..doesn't matter which.
So, one of the whites (if there are two..just look at the connectors on the headlight shell) would likely be connected to red from the switch, the other would go to ground.
You MUST keep the regulator in the circuit!! So..the RED wire heading off to the rear of the bike from the switch MUST be connected. If you (just) connect the red to the headlight, ground the other side and 'test' it, you'll blow your lamps.
ALWAYS have the red to the regulator plugged in!
If you don't have a manual, do yourself a favor...get one! ;)