i have heard a few references to the noise our bikes make... sewing machine... valve adjustment (if im not mistaken) from my memory is been the biggest response to this. i my self have not heard this till yesterday on my way into work. first thought was hmmmm i have gathered a few miles maybe its time... on my way home i heard it again. later down the road my fuel light came on and, well time to stop and get gas. i thought well hell i will go ahead and drop mid grade fuel in... so i did. coisodince? maybe but the noise quit. i didn't hear it the last 25 miles home, i did a few highway miles and a few back roads, even thru down town Flint with many lights to deal with. Just wondering if anyone who has heard this noise has upped their octain intake and found same thing?