Oddest thing. I was just looking the bike over and happened to see that the top right engine mount bolt was dangling out of it's hole! I had torqued and shimmed the mounts last winter so I'm not sure why this came loose. The nut was gone but I found a spare locking nut and torqued the loose bolt and checked the others while I was at it. It's amazing that the bolt didn't go the way of the nut. Lately I'd been thinking that the bike was sure running smoother than it ever had. Now I know why!