That would probably be to low a km for dampers but next time you change the rear tire have it checked out anyway! My 2002 VTX R had over 100k km when I had to change mine. They were pretty worn and falling apart by that time.
I'll take a stab at this and suggest you might hear the brake pads running over the holes in the rotors. I've heard something like that at low speeds. Try a little brake pressure while running and see if it stops. That may be it.