Problem solved ..... however, I'm still not sure what caused the oil leak. Maybe the original O-ring did get pinched, as several of you suggested, but there was no evidence of that. Nevertheless, I replaced the O-ring and slapped everything back together. I'm happy to report that, after 60 miles of riding, the bottom of my engine is clean and dry. Thanks very much to everyone who responded to my post with suggestions. The US RE Community is fantastic.