I ride a '95 Stumpjumper M2 with the old Specialized FSX carbon/ti air-oil fork. After nearly 20 years of service, one leg's air needle valves has failed. I can deal with it, but it makes accurate pressure setting a real chore.
Last night, I tore open one of the top caps (to replace a suspect O-ring, but took the opportunity to see how the needle valve was constructed), and took a few photos:
Needle Valve rubber element:
Now, from what I can see, that rubber element is "unobtanium". I intend to try to make a replacement by moulding an RTV sealant cylinder, with a small pilot hole cast to about 80-90% of its depth (this mirrors the stock piece's design), and I'll use a razor blade to cut the valve flaps in the closed end. Jam it up into the adjuster cap, and see if it works.
Anyone else here attempt this? Did it work? What material did you use? I'd appreciate any thoughts or advice on offer. This FSX WILL ride on!