I had almost the same problem and had a cooked generator. See the pic.
I replaced it with a rick o gsxr conversion and it been the best. I would imagine the 30 min it take to remove the gen cover to inspect it would be worth your time.

I doub a charging system that can produce more than 14 volts at 5000 rpm, when loaded by 2 x 130W highbeam bulbs, is "cooked".

If the battery voltage measurement results posted are accurate, energy storage appears to be the problem although the over wattage bulbs would give even a good battery a headache.

What are the battery voltage results with the correct wattage bulbs and a good battery?

I'd like to know where the 90/130s came from, and how the hell they didn't melt the wiring and switchgear.

90/130 bulbs exits and can be fitted with mods, and I have already questioned how the lowbeam switchgear could survive but we can only work with the info provided by the owners.

I had the same problem on an old vfr when one of the three yellow wires from the ? Alternater plug on the rhs melted and came loose. Charged fine at 5000rpm, but discharged at idle...

It charged at more than 14 volts at 5000 rpm with headlights on highbeam with 2 x 90/130 watt bulbs?

Malc wrote:I'd like to know where the 90/130s came from, and how the hell they didn't melt the wiring and switchgear.

Well whoever did that is probably the same owner who hacked away at the bulb holder to force it in. I now require one of the bulb pins to hold it in place, as it was just being kept in by the rubber casing and the plug. Don't suppose anyone knows where I can get one of those pins?

magg wrote:90/130 bulbs exits and can be fitted with mods, and I have already questioned how the lowbeam switchgear could survive but we can only work with the info provided by the owners.

My low beam switch was surprisingly working. It only completely stopped working when the new bulbs went in.

Alas, if I knew the first thing about bikes and/or electrics, I would have solved this quickly and not needed to make a thread. I now know for the future! Thank you all for your help.