Personally, I'd check the basics first, all the fluids, oil pressure, ect. To make sure your engine and trans are healthy. Just listening to the video Ito sounds like it's coming from the primary but I can't really tell.

 

That don't sound right...

Some questions..... Does it go away at higher revs or just not as easily heard?
Still squeaks in gear?
Any metal bits on your primary or oil pan drain plugs?

Is it predominately heard on the left or right side? Sometimes the Air intake can whistle/fart like that but that sounds like metal on metal to me.

 

 

Its a long shot but when its doing that put you hand on the tank and make sure its not a loose mount etc.

 

Something is squeaking and it's more likely outside the engine rather tan inside. A 17 year old bike with 8k miles has spent a lot of time sitting. check for loose exhaust mounts and most any other nut or bolt you can find. That fact that it's worse at idle when the engine shakes the most and quiets as the RPM's are increased suggests to me that something is loose, corroded or dried out rubber in a foot peg, shifter linkage, or even the horn mount has a rubber bushing that could be squeaking. Start it cold and push/pull on anything that moves.

Good luck

 

 

Sounds like lifters to me. They make some serious squealing noise when they fail and start wiping instead of rolling on the cams.

 

listening again, it could be the top stabilizer mount has come loose. Motor vibes smooth out as you rev up so it won't vibrate as much and the sound seems to disappear. As others have mentioned check front and rear engine mounts as well.