Hi Bill
Bloody electrics eh?
You could try a look at the universal single phase reg/rec here
http://www.sparxelectrical.com/acatalog/SPARX_Regulator_Rectifiers.htmlThey have a linked wiring diagram which is pretty straightforward. Price is 30 quid plus vat. My only note of caution would be that it might be too chunky to fit under the tailpiece. Their comment on resistive sparkplug caps is interesting.
Before you go too far though, have you had a good look at the earthing of the "16V" one. If the earth (and it's earthed through the body of the unit from memory) is bad, I think the unit will work, only at a higher voltage range, just like you describe. I made a point of running an extra earth strap from the mounting bolt of the reg/rec to the frame of the bike on mine. The problem could equally well be internal though.
Best of luck with it.
