I picked up the new belt yesterday - installed it this morning and let 'er go. Now that's how a tiller is supposed to work. Tightened up the clutch a tad and the old tractor and I took a full bite of the soil - worked it up pretty well.
And then I found buried treasure.
I had already dug up half of an old walkway of largish flat stones. Most of them were slightly buried and when I started digging and prying, the 6-inches showing turned out to be 24-inches of buried rock.
I didn't see any more rocks and assumed (wrongly as it turns out) that the rest had been moved or disposed of by previous owners/tenants. No so.
The new and improved tiller action bounced rather wildly (throwing me and the tractor several feet) when it ran over rocks in what is going to be a garden area.
Now I know where the rocks are and a half hour of digging and prying left me with this rather motley assemblage of rocks of the pathway persuasion. They'll go into the pile for future consideration and building projects.