MG Car Repair: 1978 MGB GT- wont start properly., head gasket, mgbgt

Question
I bought a 1978 mgb gt about 6 months ago and have been trying to tackle the engine problem since. I have added a new fuel pump as the car didnt have one. I have also done some minor things to the engine such as adding a new head gasket to block and cleaning and grinding the valves. On close inspection the engine block and cylinder head seem fine no cracks and the valves when installed do not leak petrol etc. I have also done some work on the carbs cleaning them and installing new seals, float and fuel needle. again they seem fine. After putting all together and testing the car didnt start first off but when it did it was very rough and wouldnt keep started below 2000+ rpm. the engine when started and the choke pulled out stays at very high rpm about 5000 and wont go much lower without cutting out. if I do push the choke in it loses rpm and then when it gets low around 1-2000 it cuts out. ive checked the choke and throttle cable etc they are not stuck. I have also checked valve clearance on rocker and timing etc. When at high rpm it isnt constistant its like high rpm,slightly lower,high rpm, slightly lower. The engine does not tick over properly. Im just wondering what it could be I must also add that I think there is a problem with the electrics as the plugs spark sometimes and then sometimes not. Could this be the problem. would really like to know the problem. Thanks, Tyler.

Answer
Hi Tyler.  Your MGBGT has twin SU carbs type HIF.  It sounds to me that you do not have a fuel supply to the main jets.  These carbs have a totally separate enrichment device supplied via the choke spindle which only works with the choke pulled out.  I think the engine is trying to run on the fuel from the choke spindle alone.

Strip and rebuild the carbs again, paying special attention to the float levels.  These should be bent until they will hang upside down with a gap of less than 1mm when you place a ruler across the flat surface where the float has a dip in the middle.  

I could send you a diagram, but copyright forbids it.  Send me a private query with your e-mail address and I could send you the diagram outside of this system.