Shifter clunk after flushing clutch fluid

[Thombar]

1993 gl1500 sat 20 yrs 14k miles. Was careful to not let fluid level get too low in reservoir while flushing system allowing air. Bled after and put vacuum pump on bleed screw, no air. Shifts fine just hard clunk. Clutch not totally disengaging, Slave weak? Could the clutch cylinder on handle bar be weak needing disassembly and cleaning?