Whilst I was working on the 2009 Uly after I removed the control cable, I noticed the cam on top of the servo motor under the tank cover wasn't in the right place.
Long story short, I removed the unit, opened the case and found that the "half-gear" has opened-out and no longer limits the travel of the main cam/cable.
Photo here - at the top left - the black gear has a tab (visible at 3 o'clock sitting above the edge of the half-gear underneath) which should rest behind the tab at 11 o'clock on the half-gear.
Another angle - see where the tab has worn and moved out from the black gear.
Found a temporary fix on BuellXB.com http://www.badweatherbikers.com/buell/m ... 41661.html
The fix - drill and screw in a grub screw. Make sure it is far enough in or it hits the pillar on the upper case (DAMHIK).
All working again but I've sourced a replacement motor - tip from BuellXB.com https://www.buellxb.com/forum/showthrea ... e+actuator
which will need a bit of fettling but is a replacement for the factory unit (S1038.2AAA). Dorman 911-912 is used on Fords and Lincolns. Bought off Amazon US for $64 shipped to US - a friend is bringing back for me!
TBH I think the gear failed due to my hamfistedness, trying to remove the cable. I will unscrew the whole assembly from the airbox next time, so I don't manually rotate the cam too far (and break it again....)