beat one's gums(to waste time talking a great deal without results: I'm tired of beating my gums about this over and over. You're just beating your gums. VLZ_58)
talk a big game(to say things that make people believe that one can do something or that something is true about oneself even though it is not true. They talk a good game, but they're not really ready for the championship. VLZ_58)