As long as you are idling around 1500-2000 rpm, the lights should be steady, most common problem is a bad ground on the aluminum tab on the voltage regulator to the frame. Take it off, polish it shiny with a wire brush, make sure the mounting bolt is clean, and the frame hole isnt all rusty. I usually replace the bolt with a stainless steel one, then use a lock washer to really bite into the tab and the frame mount metal. That usuall fixes the problem, unless your reg is starting to die. If cleaning does not help, try swapping in a new reg and see what happens.
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 !!)