Many thanks Steve.
The jets are all pretty close to ideal, I intend to go to a rolling rd later to get them spot on, but having spoken with southern carbs I'm sure they are close enough to not be the problem. i got the carbs second hand, but had them ultrasonic cleaned, then fitted new gaskets, and new float valves. There are no resriction for the air. The weird thing is its just one barrel. I've double checked the float levels, and fitted a filter king, the pressure is below 3lb psi. Funny after a good clean, when i went back into the carbs I did find sediment in the bottom of the float chamber. It has a cold start, but Im sure those are firmly closed. Maybe take the carbs off again and blow everything through with an airline. Now the sun is out it would be nice to have it running! Thanks again.
Maybe i will switch the jets over and see if the problem moves, incase one of the jets has been messed with...
clive.