Hate it when that happens. Next time you need one made adjustable drop me a line. I've got a lathe and ain't afeerd to use it.The regulator with the cast-zinc piece is destroyed, visible in the photos above, and another below. The bottom broke out of it when I tried to make it "adjustable".
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I wrecked another one, different style, also trying to make it "adjustable".
In the end, I stretched the spring, and put a washer or three on the spring seat to jack the pressure up a bit. Not adjustable, but pressure increased.