[DrKnow65]

In your picture it looks like I'm seeing the bottom of the carb? If that is the case then the part that fell out is likely the mixture screw. It would have been a fine thread with a tapered point and a spring which keeps it's position once set. From your description you are running the motor very rich. You could try backing the screw out a bit and see if it gets better (or likley worse). If you are very handy with a dremel and a drill you could fabricate the taper on the end of the screw and use a nut to lock in the position. You'd want about a 20 degree taper and the setting would be roughly 1-1/4 turns from fully seated.