Paoli Fuel Taps leak down shaft when open to flow.

[insanity]

Hi All,
Hope all are well.

These nice petcocks seal when closed, fuel runs into the carb when wound open, but also leak down the shaft
and drip from the knob onto the engine.
I cant see how to dismantle them further is there a replaceable shaft seal that has failed ?

Thanks Chaps
kind regards
Loopy