Last August I had a similar situation, although I hadn't recently been into the clutch. I rebuilt/replaced both the master cylinder and slave before finding I had a broke one of the rivets that hold the inner drum to the outer. When I first pulled the cover I could not see it but, as soon as I rotated the assembly it became obvious is was out of whack.
Jimbo. 1800c, Drag Bars, Drag Pipes, Chrome Wheels, 31T Ring Gear, BadX Extreme Seat, SOTMC Shocks, 200 Rear Tire, Elimination of all Non-essentials, Kingdom of Kicks.