have 136 that started smoking an died.Wouldn't start. Fuel coming out exhaust.Took apart found impulse tube split.Ordered tube an intake boot.Looked at piston thru exhaust an took apart.Not bad cleaned up piston an jug.Put back together.upon getting tube an boot replaced fuel line the tube an intake boot.Started right up ran for a while started smoking again.Fuel is properly mixed.Shut off an excess fuel from carb an exhaust. Emptyed fuel tank an removed carb when disconnected fuel line fuel stil pushed out as if pressure in tank is there suppose to be pressure in tank? Any ideas would be appreciated