This won't be a timing problem.....you have done the obvious things like replacing plugs and leads etc. (Although I would be inclined to swap the plugs around). Therefore the problem seems to be fuel. Twin choke webers are in fact two carburettors in one unit, and mighty fine they are too - however it does seem that the choke that feeds number 2 cylinder isn't passing any fuel so a blocked jet has to be the main cause. I suppose the inlet manifold gasket hasn't blown?
John
March 2008