Do what yauler said and take the clutch apart and inspect it piece by piece. I'm still not 100% convinced that's your prob, but you got the cover off, may as well go through everything. Far as checking the clutch engagement/disengagement, you should be able to depress the bearing with something to make it disengage. I've never had to do it, but that is how the clutchs works to begin with. Did you ever get a manual or download the one from here? It has the installation instructions for the clutch release mech in the cover. Since you got the bike used and have already moved the arm on the shaft X # of times, it may behoove you to make sure it is assymbled correctly, using the manual as reference.