Original post

I did a search but could not find one just like this. I'm not new to Sportsters, so I know about the noises they make. I have about 3500 trouble free miles on so far this year. For about the last 2400 miles or so, my 06 1200-C with a total of about 8500 miles on the bike. I started to notice this just after I let out the clutch in first gear and the bike starts to move at normal take off speeds and is completely in gear, around 10 or 15 mph it makes kind of a high pitched moaning noise with a kind of hollow sound to it, last for about 2 seconds as soon as I speed up it starts to fade away. I can just hear it a little in second gear at low rpm sometimes, It don't seem to do it when downshifting. I have no slippage, and no other odd noises, for a Sportster. Shifts in to gear just fine, just this high hollow moaning sound. Other then this I love the bike. If I take off really slow it don't do it at all.. About 1500 miles back I adjusted the chain and the clutch and the clutch play. I think I did it right. Just to make sure I went out and redid the clutch adjustment, and feer play, about 1000 miles ago,still doing it. Then I loosened up the chain a little and that didn't help. So I put that back to spec. so I don't think thats the problem. My old 1200 didn't make this noise and my Brothers 2000 1200 and a guy I know with a 03 1200 dont do it ether. One last thing when I go over any kind of road that makes the bike vib, I think I can hear the noise just a little. I have spent a lot of time trying to find something loose on the bike but I cant. I cant tell for sure where it's coming from, kind of sounds like it's more from the front and a bit to the right, but it's just to hard to tell. Could this just be a new or normal Sportster noise for the 04 and up I haven't noticed befor ?...
Thanks for any advice you guys may have... In time and with help from you guys I cald this a harmonic vibration...

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UP-DATE

"THE NOISE IS GONE"
I cant believe it, I fixed it today. I had to take off the rear pipe to get the rear wheel off to get new tires, the nuts that hold the pipe to the motor was loose, I got them off with my fingers. Today I got the new tires on and tightened the pipe to the motor. As soon as I took off I could tell the noise was gone. I put on 35 miles and I'm so happy that noise is gone. Now My bike is really fun to ride... Thanks to all of you for your advice...
Gary.