Interesting problem. Without actually seeing it, here is my suggestion.
It involves using the actual threads and nut on the post to "jack" the post out of the sleeve. (In my 86 H17 every nut or bolt I have had to remove has needed some thoughtful coaxing - so my mind is in this mode.)
Stack a few greased washers (as thrust washers) against the cross bar. Then jack the rod out with the nut. While trying to jack the post out, it will rotate. So, create a "bolt head" to grab onto with a 2nd wrench; using two nuts tightly counter-rotat to lock at the post-end. To jack - apply a wrench to one of these "bolt head" nuts to stop rotation, and another wrench to the jacking nut to actually jack the rod, drawing it out of the sleeve.
I am sure you will have to tweak this approach; stacking washers etc... to achieve proper spacing etc.. but this method sounds reasonable to me.