Hey Steve, Somethings obviously not right, most gs´s sore pass 50mph in 3rd-4th, depending on conditions; hills, weight, the actually mass of the person riding on it. Maybe your speedos busted, it wont seem like your going much faster than 50mph if your concentrating on what the speedos reading. also i would check the brake pads and disks to see if they´re rubbing. Fuel intake, either adjust the carb or see if the actual fuel tap is clogged (Mine does quite regulary). Airflow, check the air filter to see if it blocked. Or maybe it might just be restricted to 50mph, which is stupid because that just isnt fast enough! Sorry if im no help, cant really think of that much to go wrong, keep us updated =]