You will need a special small and long wrench socket size 14mm to remove the spark plugs of your BMW DOHC engine (article number 682062). In addition to the wrench socket you will need an extension (article number 880039) and the correct 3/8inch ratchet wrench (article number 821557).
BMW R1200GS 2010-2012
BMW R1200GS Adventure 2010-2013
For DOHC engines!