kz550 buttoned back up and won't idle

You may want to try disconnecting the throttle cable at the carbs just to be positive the cable isn't hanging up a bit. OR if you have the both a push and pull cable like the KZ650s if you turn the throttle closed tight can you see if the throttle cable pulley is going all the way closed? Ed

If not caused by the things mentioned by 650ed, the inability to idle down low enough might result from failing to have the idle thumb screw in mid-position during the bench synch.

Good Luck!

Definitely enough slack in the throttle return. Which is the idle thumb screw? The large one in the center?

I have been trying to find a base setting for the fast idle screw that raises and lowers the slides together. The bike is hard to start cold (at least the 2 days I've tried) but runs very well when warmed up. So far the central idle screw is out of the equation.

I followed the book procedure when I had the carbs off but there may have been some confusion on my part. I don't know if we're using the same terms or referring to the same carbs.