I've got an old Huscavana chain saw which for sentimental reasons I want to get working. The problem is though everything functions when I pull the engine the fuel goes back down the pipe! The carb has been rebuilt byTillitson and all new seals have been fitted. Now I have used a pice of non Huscu fuel pipe, so I'm wondering A is the fuel pipe to big a bore, though it fits the carb intake, or B Does the fuel tank need to be sealed tight, if so could air leacking in at the tank /pipe gasket cause the problem? Your's Clueless.l