I have a new to me 31 year old CR500 that is missing the stock bottom chain roller. There is a small tab on the base of the frame with a drilled and tapped hole for a screw and supposedly a roller. Issue is I cannot find a good enough image of what it is supposed to look like and from what I can tell there really isn't enough room in that spot for anything larger than 3/4 dia. Is this maybe some kind of spring loaded mechanism instead of just a roller on a bolt? I can see another small hole closer to the frame for what might be the end of a spring.