I had the same feeling on my Deuce. I realize it's not the same bike as yours, but it turned out my problem was the rear tire (stock Dunlop) was worn flat in the center from riding mostly hiways. You couldn't really see it, but if you ran your hand across the tire from one sidewall to the other, you could feel a slight 'shoulder' in the rubber. When the bike leaned over in a turn, it would ride over the 'shoulder' to the rounded section just above the sidewall. I found it hard to believe, but when I put a new tire on the problem went away.
I actually had an old timer indy tell me that he used to glue coarse sandpaper to a 2x4, put the bike on a lift, start the engine, and sand the 'shoulder' off.