Thanks guys,
I have ordered some 16OD x14ID x2mm o-rings. They should show up later today. I think the 2mm thickness will compress and seal the flange.
Phil, I have read your posts on the rebuild of the valve. I'm sure it is the best way to get a reliable valve. This is the first time I have shut the valve since I got the bike and I hope to not have to use it much, otherwise it will most likely necessitate your repair.
Regarding the o-ring, do you think a dressing with some kind of sealer is adviseable?
The ones I ordered are, Buna-N - Standard Nitrile Butadiene Rubber.