I had the same problem with me Rebel X, what I did is to screw the rear velocity adjuster all the way in, push it in, and then the screw came a little less tight and push it all the way out and *puff* all the internals all over the place
you can put some oil too in the screw too, it will help. I had to use my dremel to sand a little the little inner curve that the plug has, now I have no prob. dissambling it. Don't worry I went to the same thing having no idea how to take it appart. It's incredible that I had more troubles learning to dissamble my rebel than I did with my timmy
thankx to twich for the guide.
That's a picture of the spare kit at countypaintball.com. You can download the manual *.pdf manual at http://www.32degrees.com/html/manuals.asp.
Try changing the o-rings of the valve. I think the PT X doesn't have a "cupseal" but a washer instead, sorry for that.