I had this nut come loose on my 01, and the leaking.
You could take the tension off the belt and see if you get any slop in that bearing, I had none.
There should be a splined washer under the nut with a tab bent up to hold the nut tight once it has been torqued.
Check that you have that washer and its in good shape, or replace it.
get a 36mm socket, Loctite, and tighten it back up, bend the tab.
Mine has not leaked a drop in the last 25K miles.
Smell the oil leaking, its 90W transfer grease.
Good Luck and Ride On