Weber 40 IDF's running rich

[901chassis]

Okay...I admit that I am one of those people who spends alot of time here looking at posts, but never seems to have any reason to post...until now.

My 1969 912 has been running progressively richer over the past few weeks. The problem turned out to have a simple (and free)fix, but I thought I would share this in case one of you experiences the same symptoms.

Someone in this car's history had removed the top 'cap' from the carb body-perhaps to adjust float level, etc.-and neglected to retorque the 5 M5 screws that secure the cover to the carb body (two of them were actually wobbling in their threads they were so loose)! Over time, these screws loosened enough to open a gap wide enough to draw air between the cover and carb body. Ordinarily, I would have expected a lean condition from such a leak, but I think that-in this case-the airflow was pushing/pulling the floats down, allowing a constant fuel flow regardless of the fuel level in the bowl. (To illustrate just how rich it has been running, I got 8 mpg on my last tank)!

Anyway, I tightened the screws, replaced the filter assembly, and she purrs like a kitten now...without the diesel-like black cloud at the tail pipe!