Black smoke is fuel, way too rich. The carburetor is flooding, probably from a piece of trash under the needle valve. A leaky float that is partly filled with fuel will also cause flooding. The engine is probably difficult to keep running at idle, right? Blue smoke is oil, and white smoke is coolant. You probably need to give the carburetor a good cleanout, and install a good-quality inline fuel filter between the fuel pump and the carburetor.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!