I think I read in one of your threads that the mixer is a CA100.
There is a diaphragm in the top of the CA100 that lifts a fuel valve.
It is possible that the backfire concussion has ripped the diaphragm making it inactive.
CA100s also have 4 small screws that attach the fuel valve to the diaphragm backer plate. I have seen these screws loosen and fall out. When that happens, the effect of intake vacuum will be reduced and if there was little vacuum to begin with, the diaphragm may not work at all.
If a screw has come out, it will be loose between the diaphragm and the top cover plate. So be sure to hold the cover plate over a table or other surface if you pry the diaphragm loose from the cover.