There was a time in San Francisco, long distant now, when life was communal and good. Shopkeepers were as likely to be out back toking a doobie as tending to their stores. If you needed some help -- bike repair work, say -- a shopkeeper might perform it expertly, then ask nothing more than a cold beer in return. Those days are mostly gone now, but at the Bike Hut, a chicken coop-size cabin next to the Giants' ballpark, proprietor Victor Vesey keeps alive a bygone era of laid-back, idealistic, share-and-share-alike San Francisco. The Bike Hut is run as a nonprofit cooperative, with a prominent sideline of training kids in bike repair. But Vesey offers plenty for the casual shopper, too: Boxes of donated used parts and clothing invariably contain treasures unavailable elsewhere. A recent visit turned up a pair of cycling shoes, $200 when new, for $10, and a $60 crankset for $20. Vesey's an expert mechanic, having served as City College's bicycle maintenance and repair instructor, and he's likely to charge less than other shops do, if he charges at all. And with the service and repairs, be prepared to get an earful of idealistic soliloquy on how Vesey plans to change the world with bicycles. Just like in the old days.