Honda Lawn Boy?

I am a diehard two stroker to the end but my brother is giving me his Lawn Boy Honda motor push n go trans with bagger. He claims it runs rough after he cleaned the carb and is puffing black smoke.No he did not want a Duraforce he went out and bought a Toro What it the issue with mixing gas and oil? I will say this two stroke Lawn Boy is the way to go and once you know your way around them they are kinda fun to work on.