How Do I Clean A Carburetor On A New Briggs & Stratton Generator That I Let Set Up Too Long And It Won't Start?

Pull the bowl and the nut/jet from the bottom of the bowl. Clean out all the debris out and flush with carburetor cleaner. Make sure you have fresh gas in the tank. This should do it if it isn't to bad. You may need to pulled the whole carb off and clean it all but I would try it this way first.