My 1988 Kawasaki KX80 is reving up loud and it wont cut off but the throttle is not stuck.

With the engine turned off, open and close the throttle let go of the twistgrip as the slide decends to the bottom of the carb, you should here a cosmetic clang as the slide hits the bottom of the carb, make sure you have lots of free play in the addjuster on the cable at the carb end,undo the idle screw all the way allowing the slide to travel further down now start the engine and check if the engine still races if the engine stops when you let loose the twist grip, slowly addjust the idle screw till the correct tickover is obtained, if this does not correct the problem, remove the slide from the carb noteing the cutaway in the bottom of the slide, this must face to the rear away from the engine, forward facing would cause the engine to race as the cutout is to let air in to the rear, when facing front it will let exsess fuel in