Carb Running Rich

[gbhrps]

Gentlemen,
The 55 was put on the road 2 years ago after a 30 year sleep. It runs well but is is running rich. It starts easily and blows moderate black smoke out the tailpipes until warmed up, but still leaves the pipes sooty and black, even after an afternoon of highway cruising. The carb was cleaned up, but not rebuilt, and appears to be operating fine, although I think rich. A competent mechanic has set the idle and mixture on both sides. This hasn't cured the problem. I have been led to believe from a different source that the automatic choke may be set to the rich side of the spectrum, should be set back, and that the 3/8 inch "heat tube?" (from the manifold to the carb, near the automatic choke) may be plugged. Any thoughts would be appreciated.

[gbhrps]

A total rebuild of the carb has been done, and though not on the road yet due to winter weather here, I can see no black smoke at idle or at startup. The carb rebuilder says that the floats were set too high.