Here's a strange one for you.
Anybody ever experience a medium pitched howling noise when coasting down from say 40 mph? I've tried applying the brakes to see if it affects it, but it doesn't. I've even tried disengaging the clutch and popping it into neutral but no change. I've got the feeling it has something to do with the drive belt but the dealer claims it's o.k.. I did notice it only does it after a fairly long ride. In fact it won't do it at all till I ride for 30 minutes.
Any takers on this one? By the way, it's an '08 1200R but I doubt that'll make any difference.

 

harmonic reverbrations through sheet metal or engine cases.

My friends kawasaki vulcan does it on a nearly empty tank at 40 mph in 3rd gear always, the noise mutes if you hold something against the tank.

obviously its not normal but i would check EVERY mount and fastener, tank mount fender mounts. also engine cases, check your oil levels. my sportster does it when im low on tranny oil, and make sure your tires are not rubbing anything.

get up to speed and turn off the engine and coast, if the noise persists its not inside the motor, if it stops then look at motor mounts and something wrong inside.

hope some of this helps

 

This was my 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 3000 trouble free miles on so far this year. Last 8 or 10 times I rode, total of about 1800 miles or so, my 06 1200-C with a total of about 8000 miles on the bike. I started to notice this just as I let out the clutch in first gear and the bike starts to move at normal take off speeds and is completely in gear, at about 10 mph, the noise only last about 2 seconds it makes kind of a high pitched moaning noise with a kind of hollow sound to it, as soon as I speed up it starts to fade away. I can just hear it a little in second gear at low rpm. 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. If I take off very slow it don't do it at all.. About 1000 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 today and redid the clutch adjustment, and feer play, 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. 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...

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Now I have over 4500 trouble free miles on and the noise is still with my bike every time I take off. My bike runs great and I have no problems with it.
I know the noise my bike makes is different from yours but I think we both may have some kind of harmonic vibration noise. Make sure you do look over the drive belt because I can see that doing it on yours. I hope you dont have to spend all the time like I have this summer looking for your noise. Good luck...

 

Check the rear wheel alignment.If your belt was recently adjusted, during a service,the wheel could be out a fraction of an inch. This could cause the belt to rub the pulley and make noise.

 

Primary too tight? they do get tighter as they warm up so maybe it just takes that long for it to get fully up to temp. I would loosen that off a bit and take it for a ride.