New here. Ran across a vintage 4hp sears mini bike by accident and bought if for cheap. A little love later and she's running great. My boy has a blast with it. Found the exact same bike and model at a flea market a few days later. More of a project, missing back wheel and not original motor, but perfect match including color, both original blue. Looks very "70s" to me. How can I better date these machines and what kind of value do they have? Where can I get parts? Thanks for any help, great site.