Check the belleville washer/spring washer configuration. The misconfiguration of these washers in most lever drag reels after service is the main reason for loosing freespool. This means going deep into the reel again with most the parts coming off so it is often the last place people look.
It's hard to tell by looking at the schematic but to me it looks like the belleville's, part numbers 609 goes like this ()() and 609-1 on the other side of the spool's main shaft is the same ()(). That's where I'd start.
Edit. Here is a link to the 80W schematic.
http://schematics.mikesreelrepair.com/albums/okuma/MK80W2.pdf