[JoeFishNC]

looks like the vent valve for the drive.

 

[JoeFishNC]

I put this on mine, that is why I recognized it..

Final Drive Breather Relocation Kit, BMW R1250GS / ADV & R1200GS / ADV, 2008-on (Oil & Water Cooled)

Water crossings can be the most exciting part of an off-road adventure on your R1200GS or GSA. Unfortunately with the liquid cooled R1200GS, the final drive can sustain some damage from being submerged. With the Touratech vent relocation

touratech-usa.com