Couldn`t tell you, I removed them intact (to reinstall if I sell or trade the trike) and tossed them into a box when I installed aftermarket units.
This is purely a guess, but given that HD does not even mention "air adjustment", I woudl bet there is a simply cable mechanism inside that tube, that twists a cable "in" or "out" to turn an adjustment wheel inside each shock. Notice thta it takes a LOT of turns to move from one numbered setting to the next, but turning the **** is relatively easy. That's because this kind of system craetes lots of favorable leverage by having a very small gear on the end of each shock's cable, and a much larger gear that each cable roatates on each shock.
Yesterday, 10:18 PM
