It is the rotor on the Kawaton of my brother. The Kimtabs have a 6 bolt pattern same as the early CB750. I'm researching as much as I can about the bike. I've spoken to the guy who made the pipes. He thinks he did those around 1980. Bike has a tag last dated 1976. Bike was ridden away when the pipes were made. The PO was killed on Mulholland on another bike while making a U turn and got hit by a car.