The upper-middleweight naked bike segment, which currently has entrants from the likes of BMW, Aprilia and Ducati, is about to get an good ol' injection of Japanese know-how as Yamaha readies its upcoming new FZ8 for production. Yamaha apparently sees room for a machine that splits the difference between the smaller FZ6 (and FZ6R) and the full FZ1 naked literbike.As far as we're aware,