MG Car Repair: flooding cylinder 1&2, piston rings, fresh oil

Question
Hi, My MGB 1972 18V series has a problem with loading clyinders 1 and 2. The engine runs rough and backfires with black and blue smoke. I just had the head redone and and not able to get the engine to run properly. Cylinder 2 plug is very wet and #1 is loaded with black.  Everything has been replaced including needle and seats. The carbs are rebuilt. I do notice that the problem is most previlent when the fuel pump is constantly running. By this I meam that the pump sometimes stops pumping when the ignition is turned on as it should when it reaches pressure. The problem seems to be when the pump continues running when the ignition is turned on and does not stop as it does"nt seem to reach pressure. It would appear that the float in the #1 carbs is sticking. I don't believe it is. The floats are new as is the needle and seat. I set the floats a -1mm as per data. Could the float on # 1 carb be set to high. Can the float be lowered to allow less fuel into the bowl or does it matter regarding the float? There is no fuel running out of the carbs that I can see. I do know that the engine runs fine when the pump is functioning properly.What other problems could the #1 carb have other than float problems.I also noticed that an extreme amount of gas has gone through the engine since I have started trying to get it running.  Thanks in advance. Al

Answer
Hi Al.  I presume you have the later HIF type SU carburetters.  There is a shaft inside the carb that rotates when you pull the choke cable.  This shaft has an O-ring seal, and your symptoms are all consistent with a failed O-ring on the front carburetter choke spindle.

By the way, the front carburetter has been flooding the front 2 cylinders with fuel and some of this fuel will have run past the piston rings and into the sump.  Check the oil level on the dipstick.  If the oil smells of petrol (gas) or the level on the dipstick is too high, then you MUST drain the contaminated oil and refill with fresh oil.  Otherwise you run the risk of major damage to the crankshaft bearings and the cylinder bores due to lack of lubrication.