Originally Posted by Charles Wahl

Do try to identify (rings, knurling, text; see Sutherland's above) the thread of the fixed cup before starting with heavy-duty tools -- Motobécanes were sold using both French (right-hand thread) and Swiss (left-hand) and maybe even English, though that might be Peugeot. Definitely both French and Swiss. If you've removed spindle and left cup, and cleaned the BB reasonably, you may be able to identify threading with a bright light. Photo might help too.

And if using the bench vise, double-check the direction you're turning before really leaning into it.