Well if made in the 70's isn't old than I'm a spring chicken..:thumbsup: What i call real mini bikes are made no later then say mid 70's Yours was made somewhere between 1965 to 1970.. Here is some info on yours.
You can buy a Owners Guide on minidoodle for $7
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MTD minibike owners guide $7.00 usd [/FONT]
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This is the owners guide for the minibike models 640-200, 640-250, 640-520 and 640-550. It includs the the parts list and parts diagram.[/FONT]
MTD-COLUMBIA INFO
MTD MINIBIKE