Re: How do you detect air leaks?
Loosen the carb retaining bolt and slide off the carb. Clean the manifold neck and inside the carb where it slides on with carb cleaner, brake cleaner, even alcohol. It just needs to be dry and clean. Smear on a coat of RTV silicone to the manifold neck and slide carb back on over it and tighten bolt. Let it cure for a while and see if it still has an air leak.
The primer will always leak some.