[Spridgets] Two perfect cylinders?

[Michael Rowe]

All right all you mystery lovers.  My "new" engine starts perfectly and runs easily - on two cylinders, 3 and 4.  Cylinders 1 and 2 are flooded out and will not fire.  At one point, cylinder 2 was firing enough to make the plug sooty.  Cylinder 1 was always wet with gas.  Pretty much everything is either new or cleaned and checked.  Electronic ignition, new wires, rotor, cap, coil plugs.  Spark to all cylinders confirmed by inline checker.  Compression mid 170's on 1, 2, and 4, mid 160's on 3 (which is firing).  The same problem occurred with two different sets of carbs.  

Here's the fun part.  When the carbs were set at 12 flats down, plugging the front carb caused a large increase in speed.  Plugging the back carb caused instant death.  I leaned the front carb pretty much all the way to the top because cylinders 1 and 2 were flooding.  In that condition, I covered the intake with my hand and absolutely nothing happened, as though there were no airflow through the front carb at all.  The vacuum felt very weak compared to the rear carb.  There does not appear to be anything wrong with the butterfly.  No evidence of leaking by an ether test at the gaskets, etc.  Later, I even stuck my finger in the manifold to see if there were a mouse nest or something.

I am a complete newbie, but my mechanic/tutor has 30 years experience with MGB's.  We are baffled.  

Michael Rowe
'74 Midget
Long Island, NY