Motobecanes are notorious for their electrical demons and fuel delivery issues. The OEM gurtner carb can be very problematic. One thing you can do to improve its fuel delivery shortcomings, is swap out the gurtner carb with a Dellorto. But then you also have to change the intake (I think).
If you have to have one, get one that is already in A1 running shape. Buying a project Moby would be a major mistake in my opinion. All you’ll do is inherit someone else’s problem child.(edited)