I have a K8 600 with a -1 front sproket & speedohealer. At 65 in 6th ill be tacking 6500.
Its kinda weird...as long as im in 6th gear I can tell the speed im going just from looking at the tack. It holds true 40-100mph. I havent tested it beyond that. Im guessing if it does hold true all the way to redline then i guess my top speed would be 160mph.