Yerbuddy

I have a 2004 Gas Gas TXT280 Pro. I am having problems with the clutch not disengaging fully. I have tried "tuning" the friction discs (cleaning excess resin from between the patches) and sanding the metal plates. I even installed a brand new Gas Gas factory clutch pack and saw no difference. The clutch pack measures within specs and the basket shows no galling or damage. I also tried pushing DOT 4 backwards through the slave cylinder with a syringe, but was unable to get fluid out the other end. What am I missing here?