I am interested in the resultant effects of this topic. Occasionally, and particularly when it is hot, there is the smell of petrol when the bike (2001 XT600E 4PT) is ridden in a spirited fashion, i.e. lots of acceleration/deceleration. Friends following me have remarked on it and once or twice I have smelled petrol after stopping following a good run. It happens infrequently and there have been no other signs/symptoms, e.g. no carb overflow, float height appears OK etc. The bike runs faultlessly with no fuelling issues. I guess it is one of the quirks of this particular type of carb which should be savoured, as long as it doesn't get worse, or course.
I remember my Dad telling me of one of his bikes, an old Panther, which used to weep fuel and which went up in flames one day whilst he was sitting astride it talking to his brother. Jerry Lee Lewis's "Great Balls of Fire" springs to mind!