Hello, there were two problems with mine. The first was the carb which I changed for a new one and the second thing was that there was a restriction in the petrol fuel line. Check there are no kinks in it and that it is only one pipe not two fixed together with a smaller pipe in the middle which was the problem I had. Once that was done, problem solved. It may also be carburetta 'ICE', basically in cold weather if the carb gets too cold from the cold air coming in through the radiator and fan then it can effect it in the same way. So if it is getting very very cold where you live may be worth trying a radiator muff. To test this theory block the radiator/partially block by putting some cardboard between the rad and front grille. Mine hasn't had this problem but it hasn't got too cold here, may of -2/-3 whilst I've driven it.
Hope this helps!
Hope this helps!