Big cloud of smoke? If blue or white it means oil is burning.. If BLACK as you say it is excess gasoline. Might be the carb float or carb needle and seat has went away causing extreme flooding of the engine. So much so that it cannot digest the gasoline in liquid form.
TaKE THE AIR CLEANER OFF HOLD THE THROTTLE WIDE OPEN AND CRANK IT.. damn caps key.. carefylly looking into the carb for liquid while cranking.. also looking for liquid on the manifold.. Please don't be stupid and hold your face over the carb as a possible backfire will cause injury!!!
Big Jim <img src="/forums/images/graemlins/pfft.gif" alt="" />