I have a 1.6S with the CVH engine, it has been laid up for about 18 months and the engine tries to die when the accelerato is pressed but it then revs freely. there is a thing oin the carb which senses that the acceperator has been pressed by a change in the inlet manifold vacuum, and its supposed to make the mixture richer for a short period (only very short, a second or so).
I think my problem is due to hardening of the vacuum hoses, as I have cleaned up the mecahnical bits on the carb.
I think most carbs have some kind of way that prevents the mixture being too weak the instant you press the accelerator.
there are many other possibilities, sorry I canot help more.