Id di some experimentation and reading. Unlike yours, mine clogged closed. It was a combination of dirt/carbon in the valve itself and a clogged teeny, tiny screen.
I took it out and flushed it with carb cleaner, blew through it both ways, and put it back. It worked, but I knew this was only temporary. So, to bulk up the teeny, tiny valve, i added a length of gas line on the input side, cut it, and spliced in a $1.43 lawnmower fuel filter. Now i have a Giant, Gonzo pre filter and nary a problem.
Since yours is open, i presume it too is stuck, and the sticking might well be gunk arriving there. Same fix might work. Not $400, not $200, $1.43.
Have at it.
Grant
Grant
gee-lenahan-at-gee-mail-dot-com