See this thread on xs11.com for more details.

http://www.xs11.com/forum/showthread.php?p=364572#post364572

One of my carbs had a butterfly valve that would not close all the way. This was causing the bike to idle at 2k rpm which was a problem.

Turns out I had installed a thin plastic washer on the wrong side of the carb when reinstalling the butterfly valve. This happened when I replaced the butterfly valve shaft seals. Once I relocated the thin plastic washer to the other side of the carb, the valve closed at expected and could not be pulled out of alignment even when the throttle was full open.

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Smll Med Lrg only the #2 carb had an issue with the valve	Smll Med Lrg shows the gap around the valve, this was enough to prevent the bike from idling	Smll Med Lrg	Smll Med Lrg washer on wrong side, needs to be relocated to the opposite side
Smll Med Lrg	Smll Med Lrg	Smll Med Lrg	Smll Med Lrg
Smll Med Lrg slight gap visible where thin plastic washer had been, now its on the other side.