Those brass screw on type weigh enough to cause problems. Not a good choice. You need ones that have the correct fitment size and are permanently mounted like traditional straight valve stems; preferably made of aluminum.
I believe the hole size on your rim is 11 mm, but you should veify that. Check one of the online parts fiches to confirm (http://www.maxbmwmotorcycles.com/fiche/PartsFiche.aspx). Once you are sure of the size you can then search online for 90 degree aluminum valve stems in the correct size.