fuel line

Hello, I recently bought a 1977 cb750 k7, however, the fuel lines weren't connected. It looks like the carburetors have two inlets on top, but I can't find which one connects to the fuel tank or if both have to be connected. Could anyone point out what each inlet is used for?

Hey all, Been searching for a while and I simply can't find any documentation or labeling about something I'm looking to identify on my fuel tank and was hoping you all could help me out. Long story short, I recently bought a '75 CB750F which has a '78 CB750K fuel tank mated to it. Everything...

79 CB750F. There is a little white plastic (looks like an inline filter) from the vacuum fuel tank cutout switch to the carbs inlet port. It has a directional arrow impressed on it for flow, but it doesn't look like it is doing anything. I blew air through it in both directions. If it is a check...