Did the 18,000 miles service on my 2011 GS Adventure today. Bike was purchased new December 29th 2011. Look at the differences in color between the two valve covers: the normal colored one is the right cylinder, the dark one is the left. 2000 miles ago the dealer replaced a leaking cam chain tensioner seal on the left side. Makes me go "hmmmmmm........". Also, the forward valve cover fastener can be completely backed out of the cover because the rubber grommet under the integral bolt washer comes out of the valve cover. Maybe a little thermal expansion? So, what would cause this? Did the left cyclinder run way hot? Any tips are much appreciated. I take some comfort in the fact that the bike is still under warranty, but I do hope this isn't something serious. By the way, the thing has been running like a champ!