The air leaks are simple to fix. Remove the carb and clean the part that sticks into the engine. Clean the hole where the carb goes. I would use a carb cleaner such as Gumout orn whatever brand you get. Go to an auto store and get some black silicone. Permatex is the usual brand available. Do not let the salesman talk you into the red stuff. It does not seal nearly as well as the black. Put a light coating on the carb base and reinstall it. Let it sit 24 hours and you are done. Do the same for the backplate. Do not forget to reinstall any gaskets and "O" rings. This should solve any air leakages.

Mark Shuman