Actuall there is a passage under there and it's not sealed completely. When you spray carb cleaner in the right hole yhr spray will come out at the welch plug........
Some techs consider it a vent area......
Thanks again, ALSO I have a strange thing going on. I fired the mower up today and it ran great, in fact it's running way faster rpm than ever in it's history. Actually it's sounds about like the rpm of my newer briggs push mower but this old one has never ran that fast. Anyhow the kicker is I cannot idle the mower down now.
I got to looking at the governor-throttle spring to see if I got it back on correctly and it looks the same as I remember but it's been a few days. It has a side mount throttle lever (on the carb filter housing) that simply slides toward back of mower for fast and to the front of mower for slow. But now I have no slow, just runs wide open in both positions ?? Kinda concerned bout that. Edit add ( Looking at the pick what do you think? )
(Oops jpeg balked after first load, never would load again. After trying to load the jpeg From Computer button, the screen just sat there forever on the loading files. I finally gave up and closed it out. Not sure what's going on with that. I will try in another reply below.