I had a similar problem with the shaft leaking. This was on the "Ford" 2 BBL and it to drove me nuts in trying to find out what the problem was. Although the carb did not have that many miles on it (less than 80,000), it was more like the how many years it was on the car (32 years). I guess it plume wore out just sitting on the car. The way I discovered it was by using some WD 40 in and around the linkage. The second I sprayed the linkage, the car almost died. And yes, it was running a little bit lean. Just a thought and my remedy was to trashed the carb and find something a little more to my liking.