As above. I've opened the reel in order to check it and to install a Smooth Drag Washer set. Have an issue on removing Main gear which I believe is addressed somewhere on this site. Main issue is that I cannot find where a Micro size interior screw came from (did I mention it was very small). My eyesight is not the best and any parts blowup online defies me. Any help would be appreciated.
there is a little spring loaded click button that sits under the main gear. any chance that your screw is not actually threaded, but just super small? it's key #2122.
http://schematics.mikesreelrepair.com/albums/shimano/Shimano_CTE400.pdf
Those reels take some time. I bet its the tiny click pin. I dont know what caused them to put it way down in the reel. It fits into a spring. Don't lose it ;D