Hi HondaMan & Grouop
The "hot wire" as a check to see if bypassing the regulator gets the alternator going is a valid diagnostic tool. I was under the impression that You were saying that some of the regulators out there were running full voltage to the field coil all the time. Then shunting the excess output to ground. Maybe you can explain "Kawasaki-like shunt regulated system" in more detail.
I brought up the CB750 to show that Honda could have done this correctly but choose not to. That extra 75 watts more or less makes a world of difference.
TomC in Ohio
Well, keep in mind that this bike was designed in 1968 and 1969: at the time, this WAS the state of the art. Kawasaki introduced the shunt style regulator in the 1975 KZ1000 bikes. Honda had the highest-output alternators on bikes, back then!
The shunt-style regulators divide the 3 alternator windings into two different types. The field coil is run at 100% current all the time. One of the alternator windings is run at 100% output all the time, directly thru the rectifer to the battery. The other 2 windings are connected back to the next winding in the rotation sequence by way of an SCR. This device is triggered (or not) on each power peak by the voltage sensing circuit that is monitoring the battery voltage: as the voltage rises, the SCR is triggered earlier and earlier to shunt that coil's output into the next coil of the alternator, where it becomes heat instead of power. Thus, 2/3 of the alternator's output can become heat after the battery is fully charged. Most of the bikes that are set up this way also have the lights on all the time to help burn off the extra current instead of just making it heat. The alternators where this method is used must also have superior wire insulation and are usually NOT oil-bath type, so as to not catch the oil on fire in an electrical short situation. Honda's first version of this method was in the ill-fated CX500/650 twin series, and we all know how reliable those didn't turn out to be...
This was done in response to the DOT laws in the U.S, circa 1972, that suddenly required all motorcycles have their headlights on. I think this law was struck down from the federal level, back to the individual states, in the mid 1980s again. The KZ1000 became popular as a police bike because it had this high-output shunt system (the Police Special had even more power) to run radios and other lights, too, which actually cools off the alternators in those applications (since less shunt current is sent back to the alternator). The CB750 fell out of police use primarily over this issue. Only the CB750A addressed it, in both the civilian and police versions, by adding the higher-current field coil to boost the CB750 standard alternator: it still used the conventional regulator to prevent engine fires from overheated windings.