My W.A.G. is that your throttle cables are binding and the "click" you're hearing is the carb slamming closed.
Further, (since it's the internet, and my W.A.G. is worth zackly what you payed fer it), that you mis-routed the cables when you re-installed the tank after the valve adjustment, or just routed them the way they were when you took it off, which was wrong.
That, and your idle speed was never right, and your throttle cables have slack in them. I'll also bet that your throttle works really swell if you just sit in the driveway with the front wheel turned all the way to the right (left, on '01 or later bikes) except it won't idle.
If i'm wrong you win all my Barry Manilow records.