How is it that the R1150GS is and air cooled engine and the R1100R is oil cooled? What is the actual difference between the two engines? Can the R1100R be turned into air cooled? They look exactly the same, though that doesn't mean they are. Any thoughts about the differences between these two bikes? P.S. I looked up the specs and it is an air/oil cooled engine but I don't see the oil cooler.