I recently bought an ´81 650 C. The front of the cyclinder heat fins are getting oiled/greased, and my left shin get´s an oil bath whenever I ride. Are these bikes kown to leak oil from the head gasket or cam cover? I´ve pulled the tank and can tell execlty where´s itcomming from, and want to know if I should plan on an overhaul or a gasket swap on the cam cover....