I searched this forum and on line and could not find much information on rebuilding regulators. My regulator is a North American Dispense System (NADS) Model # 70012. This company is no longer in business but was bought out by Tapright and they no longer make this regulator or parts for it. The problem I had, was CO2 was leaking out of the blow off hole near the adjustment screw.
When I took it apart, every thing looked OK as far as I know. I ordered a replacement diaphragm and the valve under the diaphragm (rebuild kit) for a Tapright system, It looked different than mine but was told by the salesman that it would work. When I received it, it looked like it was build a lot better than the original. I replaced the parts and what do you know it still leaked.
After trying everything I could think of, I did my last ditch effort. I took the spring behind the valve and stretched it out a little (not sure why that did not come in a rebuild kit) and put it all back together. Opened the valve and no leaks. Closed the valve and left it pressurized for 3 days and it did not move. All that, and it was a weak spring.
Hope this helps someone get their beer back on tap.