Here are a couple of quick observations:
1) Your ignition module will draw substantially more current at high rpm that at idle. Perhaps the cause of the voltage drop.
2) I am surprised that you get 14 volts at idle. I no longer have mine to measure on, but in my memory, charging on both my bikes did not do much below 3000 rpm.
3) The total power available from the charging system, according to the manual, is about 400 watts. I replaced my filament supplementary running lights with LED ones, as my generating system could not support the entire load I had on it, and the battery would actually discharge, even when running 5K or more RPM, with the auxiliary lights on. With the lower current but much brighter LEDs, this problem went away.
4) It is not easy to measure the current to/from the battery. One needs a high current, low value resistor in series with the battery, and a voltmeter across it that measures in millivolts. I never bothered to rig up such a measuring system.
5) I relocated my regulator/rectifier, using an aftermarket unit with MOSFET instead of bipolar transistors, to the frame on the right side of the bike, just behind the side cover. Gets it out of the high heat from the engine, and into the slipstream. I posted some temperature measurements I made of the case of the R/R at the new location. The only place where it was not clearly superior to the original mount under the battery box was parked at idle in direct sunlight for an extended period.
6) From your video, and with no additional load connected, it would appear that your system is not giving you the advertised 400 watts -- or your ignition system is drawing substantially more current than standard. I did not hear any misfiring, so if you have not modified it, it is probably OK.
7) I concur that a stator problem is rare. It is possible, but not likely, that if the rotor got very hot at some point (and I mean VERY hot -- like smoking the oil) the magnetic strength could be compromised and you would not get the full output even with a good stator.
Finally, if you are coming to the reunion at Greg's place, let me know. I will bring some test gear and we can sniff around a bit. Might dope it out.
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