Fuel problem :/

Hello
Greetings from Switzerland.
I have now almost completely restored my Valiant (/6 170cui), unfortunately I still have a problem with the fuel system.
When I operate the starter it takes ages until the engine starts, or it doesn't start at all.
When I pour gasoline into the carburetor (Carter BBS), it runs until the gasoline is used up.
The fuel pump is new, so is the line from the pump to the carburetor.
When I disconnect the line from the carburetor and operate the starter, gasoline comes out.

I suspect that the carburetor is not letting in the gasoline. Is it possible to adjust somewhere how much fuel flows into the carburetor? But the fuel filter is usually not really filled with a lot of gasoline.
In my opinion it must be something with the carburetor. The pump is new and gasoline is coming out, even if not toooo much.