Details
Twin Chamber Damping Rod Seals must be perfect. If the cartridge is low on oil upon disassembly this seal may be leaking (check the Damping Rod Seal and Reservoir Piston O-ring as well). Also check the shaft itself for wear and replace as necessary.
Note: early Showas with 12mm damping rods have an extremely sharp edge at the thread relief. This must be carefully deburred with a file before disassembly.