Strange whirr from my 400ex. Normal?

My 2005 400ex makes a bit of a whining noise, almost exactly like in this video I found on youtube. Suggestions as to what it is? It goes away after riding for 10 minutes or so. But definitely follows the revving of the bike, and happens in both neutral and while riding. Not sure if this is normal or a problem since this is my first 400ex. It’s 100% stock, and even though it’s a 2005, has less than 10 hours on it.…5h5ohw&index=1