DeathGrip, The following link has some good information that you might find helpful including a dealer that still services Benjamin Air Guns.
Benjamin Franklin Air Rifle
Benjamin Air Rifle Links
Serial number information from crossman.com
http://www.crosman.com/site/date_manufactured_benjamin
Benjamin Franklin repair parts, and rebuild kits
Bryan and Associates Crosman
Most Benjamin models require the Benjamin tool to open and close the valve, $12.95
Most Benjamin kits are $28.75. All kits contain valve and pump parts that should be replaced
to insure service and effect, plus, a parts drawing, sample oiler and step by step work sheet.
The correct model number id needed to supply the correct kit.