QBS -
Hey brother - hope this turns out to be minor. Great info by all (esp Supervision and Waltm).
The RR is supposed to put out about 14.5 volts when charging. Certainly.... 15 would be ok. 16 I think is pushing it and probably means something wrong. Remember... the stator is outputing 50 volts AC !! So.... this is not hugely bad but not quite right either.
There are 2 wires on some Vision RR not on others. The Yellow and Brown wire.
The yellow wire is NOT used at all.
The Brown wire as discussed above is to provide a low amp +12 reference wire for the RR. ANotherwords, it tells the RR what your battery charge is. It drives the RR.
SO.... the brown wire needs to be a good connection to the +12 side of the battery.
Now... I agree with Waltm this should NOT be hot-wired direct to the +12. Yes, does work but then the bike is always ON.
SO..... where's the Brown wire? WHere's Waldo ?!?
Here are the diagrams from Lucky I split so your can see them better.


What I would do:
As per Supervision I would connect a wire directly between the Brown RR wire and the +12 post battery. Run the bike and see what happens? Does this make a difference? If not.... then my guess this is NOT the problem. Oh Well.
If it does make a difference then:
- I would run a new wire between the RR and where is should be connected in the bike.
I HAVE NOT GONE OUT TO THE GARAGE TO DO THIS..... but the diagrams above show me that from the key ignition switch there is a connector with a red/blue/brown wire. This is where the brown wire is. So I would splice into the brown wire just after it leaves the ignition. HOW HARD IS IT TO GET TO THAT? I don't know off top of my head. Probably a pain in the ass. But there it is. That's what you'd want to do.
Let me know if that doesn't help.
Cheers !