Headshock Pressurising

martin.k440

I've changed the headshock on my F700 a few years ago for a Fatty 70 off another bike (from 1998) but have never bothered to sort out the shock. I am now looking at pressurising the thing, as it should be an air shock, but have been struggling to locate the valve. There is an aluminium cap located just above the wheel, but it seems to be stuck fast - am I just being a dunce or is there an obvious solution.

Does anyone know or have experience about the old fattys, if so, please can they help