boy alot of this is going around, i had the exact same problem on my sons 98 xcr440.replaced the voltage regulator,and it was good to go.When you replace it,it doesnt hurt to clean up the ground on it,and use dielectric grease on the connections.
*98 XC600 and some RMK add ons
*98 XCR440 and some SKS add ons
*Some old 70s Chappral Firebird with a 1 lunger Fuji,15mph downhill on ice with a 14 mph tailwind,AND ITS FOR SALE FOR SALE!!!
*new edition to the fam.83 Polaris Star 250.givin it some TLC for the lil guys to ride