Checking for proper operation:
Take off the plastic cover (3 screws). Grab the actuator lever with pliers or small crescent wrench and unscrew the top nut (clockwise). Then with your hand see that the actuator rod (shaft that was covered by the plastic cover) can freely move in and out (about 1 inch). If not then there is binding and it needs to be dissasembled and cleaned. To check that the valves aren't broken or their gear teeth stripped, take off the exhaust pipe and look inside the cylinder. To the left and right of the main exhaust port look and see that the valves are moving (opening and closing the port) as you move the actuator rod in and out. If all seems OK then put all back together except for the plastic cover. Start up the bike and blip the throttle so that the revs sometimes (for a split second) exceed 6000 rpm. Check that the actuator rod is moved out by the system for each moment when the revs are high. If there was no difficulty previously when you moved the rod in and out by hand and the rod isn't moving out with high revs then probably a small part (listed as LEVER-COMP,GOVERNOR SHAFT part # 13236-1190 for my '89 KDX200) inside the cases is broke off by someone who before did not keep the actuator lever from moving when removing or installing the top nut. You can look for part numbers at http://www.buykawasaki.com/site/home/
The right side case needs to be taken off by a mechanic since it involves removing the clutch also.