I used to try to get sixth gear alot on my old bike but haven't had that problem with the Nightster. I usually hit 4th about 50 and 5th about 60. Unless I am on it hard and then that all jumps up 5 to 10 mph.
I dont pay to much attention to speed gears and such I mostly go be feel and sound but I dont always wind it up ..............oh ya thatmystery6th gear is there someplace I just know it is ! it has to be ! dont it ???
According tothe 03 Sportster Owner's Manual (pg 87), shifting from 3rd to 4th at 35mph is recommended. Tends to chug a little too much for me and I usually run it up to 40 (I really miss the tach!).