I can only speak of my bike...a '14. It really helps to put the year down when speaking of the bikes in general. What you described is completely normal for '14 and above. It happened to me too and when I asked the pros, they all said this is normal. I noticed a change in the tone of the engine after about 2k miles. Very quiet at first, then a little rattly. The pre '14's I've heard are even worse with the rattly noise.