OK, here we go. This is not a joke, but I know the responses will make me laugh. My problem is the tank bag phenomenon. The clear plastic on top seems to generate a yellow/green fungal growth (?) overnight. Clean it thoroughly with plastic cleaner and it "regrows". Tried different cleaning agents, and nothing works. Strange. When it is wiped off with a white tee shirt or white towel, the color is clearly visible on the towel. So it must be something! The 2016 GS is kept in a garage where there is no moisture present. The tank bag is a BMW part-- the smaller of the two bags available. When it is cleaned, the plastic is very clear. This is not going to kill me or anything like that, but I'm somewhat like Sherlock Holmes. I love a good mystery. But other than that, the bike is perfect. Much more so with the Wilbers shocks!