Re: dismantling Marzocchi Bomber Z2 damper unit - help needed
Am rebuilding some 2001 atoms at the moment. On mine I can simply hold the large nut in one hand, and turn the threaded rod anticlockwise until it passes completely out through the large nut. It is quite fine threaded so at first there is a sense of it not unthreading. If you turn the threaded rod clockwise too far i think it drops off the thread inside the large nut and feels like it just continually turns as you describe. Perhaps the rubber is holding the threaded rod off from picking up the internal thread of the large nut. Try pushing down on the threaded rod as you turn it anticlockwise, so as to 'pick up' the internal thread of the large nut.
Just one other comment - should be no real need for force or spanners, since this rod/nut arrangement is what you adjust by hand anyway once the shocks are built. There are no 'stops' on the rod or large nut to jam up against. The large nut is shaped to stop it turning when housed inside the outer retaining plug.