Kawasaki Prairie 360 KVF-360 Factory service manual, Page 66Get this manual
3-18 FUEL SYSTEM Carburetor
Check that the vacuum piston moves smoothly in the carburetor bodyThe surface of the piston must not be excessively wornIf the vacuum piston does not move smoothly, or if it is very loose in the carburetor body, replace both the body and the vacuum piston.