Hi Martin ! Not sure it's anything to worry about. Mine has always ground some at higher rpms. I think it's because the engine has very little flywheel effect. If your a little leisurely on the up shift, the engine speed drops below the speed of the next gear and they don't mate smoothly. I asked about it early on when I had the dealer in Kalamazoo load the tors tune for me. After the test ride he said mine shifted better than some of them he had ridden. I noticed mine shifts lousy with Castrol synthetic but much better with Mobile one.