Z1 1973 carb sync

I have been trying to bench sync the 4 carb slides. Number 4 is locked and I have found that by turning any of the other 3 adjusting screw it moves ALL the slides. Can anyone advise on how to stop this,so that I can adjust them individually. Thanks.

I have the later Z1B carbs, so not sure if this will work, but here is what I do.

First, adjust the fully open position for the throttle slides. They should stop when fully above the venturi in the carb throat.

Back off the idle adjust screw so that it does not touch it's contact plate.

Completely unscrew all four of the synch screws. (In your case you may not be able to do this with #4.) Begin screwing each synch screw back in just to the point where they make contact with the adjuster linkage. (the ball that the synch screw pushes down) You should be able to feel when the bottom of the synch screw makes contact with the linkage.) Do not over adjust them.

At this point they should be roughly mid way to fully screwed in and the throttle slides should be fully down. Check to ensure the idle adjust screw is not touching its contact plate. Begin adjusting each synch screw to bring its slide up to the proper height.

I may be wrong on the early Z1 Piston slider carb sync but on the modern buttelfly throttle carbs you have a master carb (non adjustable) and slave carbs (adjustable).
AFAIK all later (four carbs) Z1B, KZ900/1000 Piston slider carb are adjustable on the top linkage.