mark, l am not talking about the kx450. mark l raced a kx 250 76, then got the rear end modified to 74 spec`s, and raced the bike in pre75., the engine are the same, tanks are the same, wheel are the same. what l and trying to say is, pre 75 vintage needs pre78 bikes racing at our meetings, l will say it again, pre 75 meetings needs to have the pre78 bikes in the programs.