My experience with these diaphragms, if original and 40 to 50 years old, is that they may not leak but are so stiff and hard that they do not likely work. Kits can be found or there are rebuilders out there. And these days you will want a diaphragm good for modern fuels.
Not as good but cheaper, I'm thinking.Ken, I would agree. New rubber seal and diaphragm to last another 50 years hopefully. I've got one of these FRB-11's on my Super and the adjustable banjo bolt fittings are nice for fitting. I wonder why they stopped making these and went with the fixed ones?