Mystery - Strong Fuel Smell

I would suspect the fuel tank vapours expanding in the warm garage and exiting the tank, as suggested. If it hasnt been said yet, one more safety related item. Get rid of the plastic fuel filter. Plastic and glass filters can crack or rupture......you get the picture. Steel canister filters only! And yes, the chrome mesh / foam air cleaner is a underhood fire waiting to happen if you have a backfire through the carb. I have been there.