Are you sealing the carburetor to the intake manifold with something or just relying on the metal to metal and the clamp to seal it? Use a good gasoline compatible sealer on the intake and the slots in the carb throat to seal against air leaks and to help hold the carb tight. Some suggest a silicone gasket sealer but most of them are not gasoline resistant and will deteriorate over time. I like Seal-All even though it makes disassembly a little harder. It seals and stands up to gas.
Tom
Red label Loctite is a great product but has no place on a motorized bicycle. It is nearly impossible to loosen a fastener unless heat is applied which can usually cause more damage than what can happen with a loose bolt/nut. If you want/need a thread locking compound use the blue label product, never the red. Especially on a steel to aluminum assembly.I put a piece of heat shrink tubing on,heat it up and then put on carb and use blue or red locktite on bolt and nut. No problems after 400 miles