[Bob Hancock]

Dana, this is a California evaporative emissions canister. Europe doesn't have them but BMW puts them on all US bikes to be able to make them all the same. The idea is to catch vapors from the gas tank, not raw gas. If you over-fill your tank you can get raw gas into the canister and then that can cause a problem when the solenoid has the throttle bodies purge vapors from the charcoal in the canister. If you search the forum you will find how some of us drilled the necks of our tanks on the R11S to squeeze in that last bit of fuel.
So....I just remove it. On most bikes it sticks out there and is ugly (especially on the Ducati). The R12S comes with it tucked up front near the front shock which makes it almost impossible to adjust preload. I see very little use for it, but if your state has an inspection protocol that requires it or if you have concerns about the gas evaporation and what that may do to the environment, then you might want to keep it.