Briggs And Stratton 19r6 Why Is My Briggs And Stratton Keep Poping Black Soot Out The Exhaust And The Mower Is Very Vibraty?

Why is my briggs and stratton keep poping black soot out the exhaust and the mower is very vibraty? - briggs and stratton 19r6

I have is some Briggs & Stratton gasoline stabilizer in the fuel and that when he little clouds of black smoke at full every few seconds show started when the engine with the hope that someone may experience one help me