I'm having a strange problem. My final belt drive whines or squeals when decelerating or downshifting.

When the clutch is pulled in it goes away. I can't seem to figure out why.

Could the belt be too tight or too loose? Or maybe the rear wheel is out of alignment?

Its a 1999 Night Train 23k miles. Stock belt and pulleys.

 

While the tension and alignment are really important and should be checked, you may find the problem is simple wear. the front of each tooth is normally wearing at a slightly faster rate the rear of the tooth. Checkthe belt by loosening it off, see if the tooth can move back and forth in the sprocket, there should be virtually no play.
Riding in dry dusty conditions or wet can accelerate the wear, of course along with hard launches. You could also look for a dirt buildup in the sprockets teeth. FWIW Fastrider124

 

Take a small squeeze bottle of Johnson baby talcum powder and give the inside belt area about 4-5 light puffs of it while you pull fwd. Then check it out If you still here the whine. If it's gone it truly is the belt. A brand new Harley belt comes with a dry lubricant on it that goes away shortly but is replaced with a little road dusk,brake dust and rubber dust that keeps the belt quite. If you keep the bike real clean especially with a water hose the belt will be so clean it squeaks. If that is the case at least you know it's not a problem. Squeaky clean is good. I prefer mine or least pretty much it stays dirty. With a Softail there is enough alignment tolerance to the swing arm bearings that truly you align the rear sprocket to the drive sprocket so as the belt tracks with a slight gap on one side and light friction on the other side on the inside lip face of the rear pulley. it pulley does not show any wear on the side belt is up against that is all you can expect in alignment on a Softail with the solid mounted engine. Remember on a Softail sine it only has two wheels and there is no caster or camber adjustment, alignment of the rear is to the fixed engine. You align the handle bars to align bike. Also always use a gage and lay across saddle to get at least part of your weight on saddle to set tension at mid range unless you have someone set on seat. That belt and pulleys are big bucks. Do not trust the twice belt , push till it gets tight and such. My belt has 40K and still looks pretty good. However the hard chrome just went thru on the back pulley and the cogs look rippled from wear. Not sure how long it's going to last like that. Harley says to replace it all then. Interesting that the part man said he has never seen one do that. I drive a grooved concrete interstate that has a lot of sand flying around that ground it off I think

 

Thanks for the tips. The belt and the sprockets/pulleys have no signs of wear. I am new to the whole belt drive thing(my first belt drive bike).

I think that it may be what RIPSAW said. The belt may be too clean. I just picked the bike up from a dealer and it was soooo damn clean you could eat off it.

I've put about 70 miles on it so far and the sound seems to be getting quieter. Maybe its just my imagination.

One thing I forgot to mention. The original owner had the rear end lowered. I'm not sure exactly how this is done on a Softail.

Could that be a potential cause of the noisy belt?

 

No. Mine has the SE rear shock/spring shock setup. Interestingly to lower a Softail require a longer shock/spring. It drives the wheel up into the fender lowering the bike. You loose wheel travel and I set mine soft and now it bottoms out easily and it's a pain to go under their and crank up the spring tension. Of course a minor belt adjustment is required but very little. I serious doubt a Harley mechanic loads a Softail to set tension. Most Harley do not even call to load them but a softail is a little different setup since the engine and suspension are separate.