I'll agree that most bikes don't NEED a rejet if a street baffle slipon is installed. But, most carbureted bikes sold in the US, and the CA models are usually worse, since around 1980 or so could benefit from a rejet when stock. The jetting is set up to pass EPA tests and most bikes will have a lean spot at 55-65 in top gear since this is where they are tested on a rolling dyno by the guvment. The 'Hawk is one of the few bikes with carbs that is universally accepted as being jetted well as it comes stock. It also suffers the least from having slipons installed. Anyone who's ridden a Kawasaki ZX10 or 11 or any model with this basic engine, Councours, Eliminator, etc., from 1986 until the ZX12 can tell you about their lean spot. These were nasty! Surging, bucking and coughing at steady throttle and slowing when the throttle was slowly opened from a cruise. Every bike I've ridden that fits in this group acted this way and most magazine testers agree. Hell, I know someone with a Mazda pickup that has this problem. It was the last year before they went with fuel injection on their trucks.