Odd noise

[jamesh]

Just got a 2005 a few weeks ago.

Now that it's warmed up and I've actually been riding it I've noticed an odd hum to the engine -- it kind of ramps up and down, but doesn't really seem connected to the revs...

Here's a video clip where you can hear it, its quite audible. Notice when I rev the engine a bit higher it seems to go away, then when I stop, it comes back!

Is it something to do with the carbs/air filter?



Thanks!