91 nighthawk vaccum to petcock issue

[91 cb750 knighthawk]

PLEASE Help, I have a 91 cb750 nighthawk not getting any fuel, I replaced the petcock to find out that that is not my issue. It’s the smaller vacuum line that look like goes into the engine. I am not getting any suction to the Petcock is not pushing fuel thru to the carb. Please if anyone can provide guidance. I know this sounds like a common knowledge issue but this is my first motorcycle! Thanks