I agree with the problem being with your regulator, I had 2 sleds with 2 different problems, my 500xc had dim lights, and my son's 440xcr was blowing headlights left and right. I solved both problems by accident, I pulled the regulator, noticed the aluminum grounding tab was very oxidized, wire brushed it clean and shiny, also the wire connectors that went to the mounting bolt, and my 500 had bright lights again. Decided to try it with the 440, and after a good cleaning, no more blown lamps all season, so I'm assuming both problems were due to a bad ground, if a good cleaning does not solve it, just bolt in a new or used regulator, make sure all connections are as clean as possible.
2000 Indy 500 XC, Fox shocks up front, M10 trail in back. '99 440 XCR for my son. 96 XCR 600 SP tripple pipe, 862 miles on it !! (until it snows....then look out, odometer !!)