I'd suspect you made it either way too rich or lean - if you're talking about the plastic knob on the left side. Why were you monkeying around with it anyway?
If you can get the bike started, you might try holding the throttle and reving it up around 2-3k rpms. Once the bike is somewhat warm just start turning the knob and letting off the throttle to see where it's idling. (Make sure your choke is off for this part.)
If the bike dies, you can turn the knob to increase the idle speed. Start it up, let go of the throttle, and see where the idle is.
Or if the bike continues to idle above 1K, (i.e., when you let go of the throttle, the bike continues to idle 2-3k rpms), just screw the knob back down to an acceptable 1k idle. . .
The online manual can tell you how to turn the knob to increase or decrease idle. I can't remember it offhand.
Of course if you messed with the small brass air idle screws on the sides of the carbs, you can just screw them all the way in, then out 2.5-3 turns as a starting point.
If you messed with the bolt head/screw slot thing that sits at the very bottom between the carbs, do a search for "balancing carbs" and for how to make yourself a $5 carb balancing tool out of clear vinyl tubing, excess oil, and a stick.
Let us know what's up.
MF Battery, Iridium Plugs, RR relocated, Voltmeter, 170/80/15 Kenda Kruz rear tire, DIY Samsonite hard bags, DIY shaved seat with Beaded seat pad ('cause that's how I roll) and the dreaded STATOR CHANGE.
Shining Black Bess '86 VN750, retired for parts after a fried stator and being knocked (kee-runch) in her parking spot.