Ok it's probably not the transmission/clutch then, how about the stator/Gene, i'd whip off the cover and have a look in there for any signs. Make sure you order up a new gasket or have the ability to make one, before you do. Also if you haven't already http://www.zx-9r.net/phpBB2/index.php i used to have a C2, and that place a mine of info and experience.