Thanks for keeping us up to date, blackriverfish. We hear very little about OHV Tecumsehs (as you may have gathered from all the uncertainty about whether the emulsifier was screwed or pressed in), so this thread will be useful to other people in the future.
It appears that the tube simply became fouled over time, and the previous owner did not know how to clean it so he bodged the mixture screw instead. Of course now you know how to clean and maintain it in a civilised way, like any other carburetor. I'll be interested in your comments on how pleasing an engine it is to use, once you finish the carburetor overhaul.
