After working at it for a few hours, I finally decided the walk-behind mower's carburetor just never was going to work right. Going online to find a parts-layout diagram, I not only found the graphic I wanted but also learned that for very little expense I could simply replace the balky carburetor with a new one! I ordered one from Monster Scooter Parts and had it within about three days. A couple hours work had the mower cleaned, repaired, and starting on the first pull every time.