The accelerator check valve is put there to stop siphoning out of that circuit at cruising speeds, I found out about them the hard way back in the early 1960s on a Rochester 4GC carb on a 1957 Chevy 283 motor, it was my bosses car and he ask me to rebuild it. He ran the gas station in SO CA that I was working at.
It was my first carb. to take apart and dip it in carb cleaner that he bought and I put back together, I didn't see the check ball fall out and couldn't tell were the new one in the kit was suppose to go so I left it out
He ended up taking it to a local professional shop that fixed it for him. I ask that guy later what was wrong with it and what it took to fix it but he wouldn't tell me
That was along time ago, good luck on fixing all the issues you may have