hi ive just done a head gasket and new cylinder head on a nova 1.2 g reg with carburetta it all went back together fine with a reconditioned head now when I start it it only runs if you have the choke on or if you keep the throttle open, but when you let it idle it cuts out straight away ive tested the spark and its fine the fuel pump is working well and also compression tested it, all 4 cylinders came back 150psi does anyone have any ideas?