Pale Rider
Legendary Member
Haw do you get valve cores out then? This is new information to me.
Put the slotted end of the dust cap key into the valve and turn anti-clockwise.
You will feel it 'seat' onto the top of the valve core.
Straightforward enough, although if you do it too quick the valve core will be ejected with the escaping air and you may not find it again.