I have a brand new NOS carb. I also have a fresh rebuilt carb. I also have a good condition older carb. I also have a really old pretty worn out carb.

They all do exactly the same thing - and I have no idea why. The power cuts out for a split second when you get past half way on the pedal. This is when the second throttle opens. If you slowly depress the pedal through the transition to the second barrel it will hesitate slightly at the same point but wont cut out completely.

I have a theory that when that second barrel opens quickly the vacuume in the manifold drops and the mix leans out momentarliy - but I still don't know what to do about it.

I have a fresh A14, brand NEW carb and this is the last thing I expected!

Does anyone know what causes this?