That sounds as if your Pulsa-Jet carburetor had been fitted with a service fix to overcome the effects of a bowed carburetor body or fuel tank top, which unless dealt with, causes extremely rich mixture in that model of carburetor. It would have been a small roll pin dropped into a hole in the fuel tank top right near the center. It would have had a small transparent Teflon washer around it, maybe about 6 mm diameter - difficult to see, and if lost, impossible to find. The purpose of the roll pin was to hold the washer in place. If you can't find the transparent Teflon washer, the roll pin is no use to you.
The Briggs part number for the kit is 391413. They are commonly sold in ten-packs. Here is a picture of what they look like:
http://www.equipatron.com/briggs-stratton-4184-10-to-pack-of-391413-overhaul-kit.htmlI suggest you check whether the tank top or carburetor bottom is bowed a couple of thousandths of an inch in the center.
