Racerone I have an update for you. Took spark plugs out and I think I am getting somewhere finally! If you look at pics, the plugs on the right are from cylinders 3 & 4 (I have my finger pointing out for cylinder 1 and with 3 next to it and then 2 and 4 in the other pic). So, the plugs on the right are from the problematic bottom carby that I replaced the float valve, seat, washer, pin and float and cleaned out the 4 side screws and jets on the float bowl. It is obviously running a lot richer and fouling bottom cylinder plugs. Why is that so? Any suggestions on where to go from now please? Cheers