Yes, it's spring loaded. Controllable by the fingers of the average adult. Turn the cap counter clock wise until it nears the end of the threads. C-a-r-e-f-u-l-l-y turn to release the spring tension. The cap will shoot up a short distance from the fork top...maybe two inches.
Off is not a big issue. Be carefull threading the cap back on. Getting the cap started back on under spring tension can be tricky. Stripping the threads is not uncommon, and will get you the KLRforum Primitive Pete Award complete with custom Avatar.
This is not a good place to store things. May I ask what you are going in after?
Well,,long story short.I replaced right side fork after a F-250 hit it at 35 MPH,,so the new has oil,,I loosened the drain screw a bit,,and it started to drip reddish oil,,very much like automatic trans fluid for FORD vehicles,,,not sure if thats what it really is, but it looks like it ,,,so I loosened the original,,[left side] drain screw to see what the oil looked like in that fork,,and the oil was almost black in color,,,,NOT GOOD!!! So I want to drain oil out of old [original] fork and replace with new. So the info you gave is a big help because I've never taken the caps off before ,,and I did start to loosen one of the cap cover bolts and as it backed out,,it felt like there was something "pushing" from below,,and I thought" I bet theres a spring under there just waiting to surprise me". So I stopped ,,screwed it back on,,,and thought I should post something to get some info on it.And the kawi service manual says nothing about the spring pressure under the cap.Also it says to compress fork completely,,and check level. How do you compress the fork all the way and check without having 4 arms? Those Japanise are very clever,,indeed! Is there a level [ MM] that you can check without compressing the forks? And what type of oil can be used in the fork,,manual just says 10w20,,didnt say fork oil or what,,not sure. And what are the "top pinch bolts" the cap,,or the air bleeder screw valve? Maybe the fork clamp bolts??