Rear End Noise/hum

I recently installed a -1 counter sprocket on my 05 F4i.  Now when I ride i hear a weird humming coming from the rear end/tire.  Any ideas as to what it could be?  Maybe the chains too tight?  I don't think its the tire being bald because I just had it put on maybe 1000-1500 miles ago.  Also now when I tighten my chain the chain adjuster on the left side doesn't seem to hold.  My chain becomes loose after a few miles of riding.  I don't think the chain would stretch that much during the initial phase but i could be wrong. Any help would be appreciated.  Thanks in advance

the chain will stretch the first week or 2 of riding. after that it'll level out. the whine you hear could be from a misaligned rear or too tight of a chain.
double check your tension and torque rear to 69 ft. lbs.

Sounds good.  Thanks Tahoe

also...when you first get a chain...it does have a different tune to it...

Yeah I thought the sound of the chain was a little different than the old one.  I think I isolated the hum to not the rear tire but instead the new counter sprocket.  I realized that when I took the stock sprocket off there were rubber bushings on each side of the sprocket.  On the new JT sprocket there wasn't these but instead just metal lips on each side.  Is this normal?  I think maybe the hum is actually air being circulated around the sprocket since the new one doesn't have the rubber bushings.  Is this possible?

Actually I heard that the aftermarket sprockets will be quite loud compared to a stock one...You can tell by dropping the stock sprocket on the concrete and dropping the aftermarket one also.  Not a far drop though just a small one....You can noticeably tell a difference in the noise.