Do you have a windscreen? I mention this because you will get quite a bit of sound "directed" at you from the windscreen and a lot of it will be reflective in nature. It will make it harder to determine the actual source. I had a "rattly, tinny" noise that I found was coming from the radiator screen. Once I was able to determine that, and knew what it was, I adjusted things and got it quieter. It hasn't gone away but I know what it is now and know I don't have to worry about that particular noise.