Hello
BMW Motorrad recommends SAE 5W-40, API SL / JASO MA2, Additives(e.g. molybdenum-based) are not permissible
because they can attack coated components of the engine,
There is no other viscosity discribed, so I think it's your choice to test the separating of the clutch, gear box noises when switching gears
and all the diverences for the engine with this "thick oil".