O.K., this ones kind of weird. I have an '08 XL1200R and for about the last six hundred miles or so I've had a strange humming/howling sound whenever I decelerate. It starts at about forty mph and stops at about 20. It almost sounds like the drone of drum brakes but very subdued (quite) and the pitch doesn't change with speed.
The dealer can't find it. I had the 1,000 mile service done about 200 miles after the noise started and nothings changed. For what it's worth the dealer replaced a defective rim at the the service, it was pitting like crazy, so I know they had to adjust the belt. I really thought it was the belt but wouldn't the pitch change with speed? The noise only occurs when I decelerate, as soon as I apply any amount of throttle the noise stops. Popping the bike in neutral or pulling in the clutch has no affect. I've checked everything I can think of. I kind of wish my arms were 2 foot longer so I could push and pull on things while I'm riding. The noise seems to come from down low on the bike. From somewhere behind the engine/trans.
Hey, as long as I'm asking for help, what's the best way to align the rear wheel? I'm used to metrics which have graduated marking in the swing arm so you can make sure the wheel is true.
As always, thanks for the help.
I hope everyone had a great Thanksgiving!

 

First off, congrats on your scoot, second, go out and get a shop manual, that thing is worth it weight in gold. The noise you describe does indeed sound like a belt. Maybe an alignment issue, Look at the side of the belt for wear marks, the belt idealy should be in the middle of the pullies. Like I said, get a shop manual and go over your scooter yourself, that way you know it was looked at.

 

the belt would be the logical place to start. Is pretty strange though

 

Agree with Zimbob. Try scrubbing the belt real good with soap and water. I have had this problem with the FXRP and after giving the belt a good cleaning, the noise goes away.

 

Using a tape-style ruler, measure the axle from the pivot shaft (unless there is a small hole on each side of the swing arm like my '01 inwhich case a piece of wire bent to an "L"-shape with an o-ring on it is used to gauge): measurements should be within 1/32" and the belt deflection should be 5/16-3/8" with 10 lbs of force applied using belt deflection gauge. Also check primary chain tension at small inspection window for 3/8-1/2" play at it's tighest point found by rotating by hand a raised rear wheel in 4th gear.

 

I just talked to a friend today who has a street bob that was making the same sound. some how his belt was miss aligned. after he fixed the alignment he said the sound went away.

 

I would start with an adjustment of the belt. The belt may put off a frequency that causes something else to vibrate that you hear. Fiberglass body cars many times have a "drone" vibration in the body that is caused by the exhaust that is not excessively loud, you may have a similiar situation coming from the belt.
My opinion on adjusting the belt is to lift the rear wheel off the ground, I use a wedge jack for this, loosen the axle and adjust the right axle tensioner for the correct belt tension. Then adjust the left axle tensioner so the belt runs in the center of the pulley while you manually rotate the rear wheel foward. Don't get all hung up on trying to determine precisely where the rear wheel is pointed. If all things were perfect, the rear wheel would be perfectly straight, but the bike is a bunch of welded up pieces of steel that can be less than perfect and if the wheel in off to the right or left slightly, it won't bother anything, get the belt tracking in the center of the rear pulley and that will be close enough. Tighted the axle and check the belt tension and tracking position again, adjust again if necessary. Tightening the axle may slightly change the tension or track of the belt. Good luck