The FL engine has an air bleed carb.  Thus the idle is controlled by the air bleed port or hole.  There is but one screw to open/close the hole.  Opening the hole leads to a leaner operation (more air less fuel mixture), closing the hole leads to a richer operation (more fuel and less air ratio).  Ideally, it should be set half way open (or half way closed - your choice of words).  Only a small variation from side to side can be achieved.  Alternatively, boring out the hole so that it is larger can also have an effect.  Juat set it for a good idle and leave it alone.

I would not worry about the smoke, probably a good sign in that oil is going through the combustion process.  The Castor in the blend will typically not repeat not be burned and thus results in visible smoke.

Sounds to me as if your engine is running just fine.

Chip