Regulators on a permanent Magnet Alternator do not regulate the output from the alternator, they apply additional load to ground to keep the generated voltage from exceeding 14.6 to 15 volts.
The regulator is a SCR (a switchable diode) controlled by a Zener Diode. A zener diode is a diode with a specific, higher than usual forward voltage (14.6 to 15V).
The reality is the Zener isn't really at that forward voltage, but is tricked with some resistors into working at that voltage. When the DC volts from the rectifier hit about 14.6 volts, the zener diode starts activating the SCR and allows it to gradually short the rectifier output to ground. Since the SCR is controllable, it isn't a dead short, but more like adding additional lights to the bike. This causes the voltage from the rectifier to drop, maintaining the 14.6 volts.
this all assumes a properly functioning diode, resistors and SCR. If they start to fail, they can fail open circuit (then too much voltage output, shorted ( then no output,) or somewhere in between).
When you have all the alternator coils engaged, but don't have the lights on, you generate high voltage, causing the regulator to ground more current then usual, usually shortening the life of it from excess current and heat.
This is why you should not jump a motorcycle with a permanent magnet alternator from a car. If the regulator on the bike is working at a lower voltage, the running car alternator can supply enough current to overheat and kill the regulator quite quickly.
A 2 phase regulator should work, but you will have an empty wire, as the output should only go to one pair of inputs on the regulator.
The popular replacement in the $25 range, is the Kohler Regulater for their small engines, which also use a single phase, permanent magnet alternator. A google search will fing you all sorts of articles on it.
The alternator on the small Honda twin and others, are really sized just enough for the stock lighting, and a little extra to charge the battery. Extra lights or accessories will overwhelm the system, and your battery will slowly (or quickly) go dead. The CB350 has a 110 Watt alternator, the CB360 has a 130 watt alternator. The Ignition system is in the 40-50 watt range, the headlight 35 watt, the battery needs about 10-15 watts to charge. And the rest of the little lights (gauges) another 5 to 10 watts. Doesn't leave anything for even one extra light, without cutting into the battery charge current.
