The headset is smooth as new not stiff at all.It's disassembled like a standard threadless (a-head) stem, but the bearings are usually sat within the frame head tube.
Just take note of the order of dust caps and spacers when taking it apart to check the bearings.
Are you experiencing play in the headset, does it feel "notchy" or stiff on turning?
Could it be something trapped in the frame causing this noise....?
Still trying to figure out how to dissemble it