I have a rusted rear derailleur cable. The bike is a 1987 Trek 400 but the drivetrain is a new Ultegra rear derailleur operated by an indexed Dura Ace bar-end shifter.
This is my rain/winter bike, so it will see water and road salt this time of year. I had my lbs install Jagwire a year ago. The install is pictured below. The cable runs over a guide that is below the BB, then runs into the chainstay.
I would like to find the best way to install the cable, It seems to be rusted within the chainstay.