I had the same noise (exactly). Here is what I found to be the cause. It was the inner roller bearing of my clutch. It is dead easy to fix and was about $25.00 for the bearing and a buck or two for bearing grease.
Here is how I did mine...by the way, my Burgman 400 is a 2004, but the clutch is similar if not the same in this area. Remove the CVT side cover, then remove the retaining nut on the Variator, remove the outer face. This enables you to remove the drive belt. Next remove the nut holding he clutch to the shaft. Once this is done, slide the entire clutch assembly off its shaft. The inner roller bearing on the clutch is viseable and can be removed quite easily with a hammer (mallet if you will) and a long drift pin, driver, or similar. I personally used a 12" extension from my socket set and a mallet. You insert the driver through the shaft hole from the outside of the clutch so it contacts the inner bearing surface. A few well aimed blows and the bearing will come right out. Grease a new bearing, inspect the bearing seat inside the clutch, clean it and install the new bearing. I have a "C" press, but it can be carefully tapped in. Once it is fully seated, install the clutch, belt and outer Variator face and spin your rear tire. The noise should be gone.
I hope this helps..
