It's what we thought as well, but what is confusing is that it was used daily without issue, until one morning it simply started doing this. There was no gradual degeneration in performance in the slightest to make us think a gasket or diaphragm or valves had slowly gone bad or out of whack. Why we thought maybe something got yanked. Or when I saw the broken old hose I assumed it was some sort of vacuum issue, so I just replaced all the hoses. But it seems that's not a thing. Again, it starts fine, and unless you're flooring the gas, it simply dies out, which certainly smells more like a fuel thing.

But yes, we started with replacing the regulator/solenoid, with no effect.

I will try the carb mixture screw. I'm not sure what the secondary regulator is. Seems impossible to find any kind of shop or service manual for that thing, which I find a little surprising.

We having a running photo album of a random assortment of reference pics as we go along if you're curious to see the setup.

Thanks for the input.

https://photos.app.goo.gl/bkVJrhbLpyKcR8v46