1975 Z1 900 carburetor slides hanging

Just checking to see if there is anything I can do to cure a problem with a slide or slides hanging on my 75 Z1 900.  Bike runs great, idles great, but if i ease in and out of the throttle slowly, the idle will hang at about 2000rpm.  If i snap the throttle, it idles back to normal speed.  I've done all the normal non-carb checks - timing, compression, etc...  Took the carbs off today and a couple of the slides were a little sticky in the bore and would hold the linkage up.  I cleaned up the bores with 1500 grit and they became smooth and free.  The linkage is all smooth and free.  bench synched.  The thottle linkage now closes fine, but in order to get the idle down after slow roll in/out of the throttle, i have to push down the slide linkage by hand.

Any ideas or are these carbs junk?  This is the 2nd set of carbs i've had for the bike.  The first set had bad bowl leaks and were pig rich at idle no matter what i changed.  Thinking about seeing if i can find a set of modern carbs that will work on this bike.  It is a stock 75 Z1B.

Thanks - Scott.

Over richness at idle would have most likely been the choke plungers.
Hanging idle as you describe is probably too little slack on the throttle cables.

No, there is slack.  The cable shaft closes to the idle stop screw, it seems to be the slides hanging up right at the end of their travel in the bores.

Sounds like you need to adjust the heights down on the individual slide adjusters.