E-tec whining noise

[ahlangle]

2010 evinude Etec 250 runs great but lately has been making a high pitched screaming noise when running. Noise isn't constant, just every minute or so for a few seconds.
Sounds kind of like a loose washer spinning on a bolt.
No paricular rpm or speed makes it so it, but usually when running 3500+.
Removed cowling and everything looks great.
No problems with it, but the noise makes me think there may be eventually.
Any ideas?

Thanks guys.