The float bowl gaskets on the Classic Concours (1986 through 2006) are very robust, but they have been known to dry out and become brittle over time. If you're "going in" to the carbs, do yourself a favor and get a set of these to have at the ready ahead of time. Nothing is quite as frustrating as not having everything you need on hand for the job, or having to go back and do it again. Consider this cheap insurance!
These are genuine OEM, Kawasaki part number 92055-1222, known officially as "RING-O, FLOAT CHAMBER".
The price shown is for a full set of four.