Well, you don't have to remove the airbox on a ZR800 (500 should be the same) to change the clip pos. on the jet needle. You said needle jet but you must have ment jet needle. You will need a 2.0 or 2.5mm (i can't remember which) allen wrench to loosen the bolt holding the retaing clip. Move the clip to one side but do not remove the bolt. If you are alone you can put a hose clamp on the throttle lever to hold the slids all the way open for easier acsess. Don't forget to remove the hose clamp !!!!