Got it jacked up and undid a bunch of clevis-type pin things, retaining arms and a cable or two – and un-wound the belt.
Secured by two big heavy rubber wheel-chocks and pointing uphill (slightly).
The underneath looked pretty clean since I had washed it out and swept away a bunch of debris.
But the deck was a gunk-hole and I had to scrape away a lot of hardened green-crud.
One of the pulley’s was a bit bent and we straightened it out. The blades were as round as a rubber hose and nicked all over.
I wandered up to my neighbor’s house (who was working on his deck with a helper) and he came down to have a look. We un-bolted the baldes and he took them in hand and applied them to his grinding wheel to sharpen them up.
With his helper (Tom, who was a close friend of the previous owner here) we pounded on it a bit and got it all straightened out and re-assembled, and now the blades turn and don’t drop-off the belt, or visa-versa.