Mine ended up being the exhaust baffle. Wasn't till the bolt fell out completely did I figure it out. Quite baffling [ ha ha]

 

Have you replaced the inner primary bearing? there were a lot of problems with them in 06

 

Just had the same problem, squeaking with rapping the throttle, low speed, or sometimes idle. Mine was the top motor mounts on the left side also. Drove me nuts, tightened everything on the bike, then thought
I had it with the horn, but it was the left side mounts. Hope this helps someone.

 

My belt chirps once in awhile, been keeping an eye on it.

 

Had a squeak from a loose clamp on the heat shields on the exhaust pipes.

 

Mine was the gas cap , I thought the noise was coming from the front mount area but nope , just the gas cap

 

Wow! 4 year old thread! Still, good info here. Things to look for.

Anyone figure out what causes the front brake noise? Someone described it the other day as a "strange electrical buzzing". I tend to agree. Kinda sounds like a tattoo gun running out of juice as the front brake is applied and the bike slows.

 

Sounds like a wheel bearing to me.

 

I have seen a few people mention the drive belt as a cause of the mystery squeak. I am curious how a cog belt causes a squeak? It is not like a fan belt on a car, if it is spinning free, the belt is toast.

 

the metal on metal chirp try checking front fender my fender is riveted and the rivets are loose and makes same sound you are sayin i get the belt squeek sometimes but i have 2 ride 3 miles of gravel 2 get 2 pavement and the dust makes the belt squeek