The bubbles are not likely coming from the carb, more likely coming from the lines from your fuel tank. Replace them - its hard to "see or check" if there is anything wrong with the lines unless its a big hole. You don't want those bubbles - it acts like leaning out your engine. Could cause engine to quit when you don't expect. It makes it harder to tune properly. I have had the exact problem. You might also try putting on a small plastic strap around the fuel tank ends.