I recently bought an older 250 Yamaha bike, pretty old but in pretty good shape. Runs good, just need to replace tires before long. I understood it was a 72 or a 73 model but I am trying to be sure and see if the engine is same as frame as far as accuracy. the frame has RT1-186654 on it and engine has DT1F-35654. I see references to both RT1 and DT1 bikes so I am doubtful of the engine being original. Any help as far as year or either or both as well as confirmation of typed appreciated!