I am in the process of attempting to restore a 1987 Honda 250 Big Red and a 1986 Honda 250SX. I did not realize that the gas caps on the tanks were different circumferences. They are the same circumference on the inside 7 1/4 inches, but the outside circumference is different. One cap is 12 3/4 inches and the other is 12 inches outside circumference. Both caps fit both machines, but I would like to keep them as close to original as possible so I was hoping someone might know which cap goes with which machine.