I'm terribly sorry, my bad. Yes, they are the CVK's. These are "constant velocity" carbs, right? That goes back to my initial premise that the slides don't move when the engine is not running. The throttle cable actuates the butterfly shafts, and only when running, does the air flow/vacuum actuate the slides, correct? So my sticking middle carb when it's not running must be related to the shaft/fittings or perhaps the butterfly, and not the slide(s), which goes back to your initial assessment that its a loose screw on the shaft. I'll check it out some more when I take the tank off to sync them.
Thanks!
