are you been able to determine if it's behind the primary or in the tranny ? can you hear it on the right side of the bike? it sounds to me like the 5-6 shifting dog rings is hitting it's gear.

 

To me it sounds closer to the prim side.

 

Have you tried pulling your clutch in and move the bike to see if the sound changes or goes away? That would give you an idea if the clutch has anything to do with it or not.

 

I would almost bet money its tranny output shaft bearing.
Plastic caged bearings and they sound funky when they start to come apart.
Look for lotsa fuzz when you drain tranny. Also get muddy fuzz in trap door where clutch cable goes in.
Get it early enough and rest of tranny may be ok...

 

Any ideas as to what can cause this? Bike only has 19,900 miles on it.

 

Dont take my word for it. This is just my own opinion but i think recommended belt tension is on the tight side and that particular bearing (which is not up to the task) takes the brunt of it.
Factory belt tension feels great when cold but warm that sucker up and i defy you to move it a tenth of an inch. Thats alot of tension!
I personally run mine a little looser than spec and everything seems alright so far.

 

Its not that dingy platic belt gaurd flapping on the belt somewhere

 

Don't forget that you just had a pretty good ride and may have picked up some trash/oil/etc. and the belt can make that sucking click sound as it crosses the teeth of the sprocket--which means the noise is not constant- as in your audio. Telling you about the powder was NOT a joke--besides, it don't cost nothin to find out

 

Did you ever find the problem

 

Been too busy with work and kids to start on it, hoping to free up some time later this week. Will keep you posted.