The extra ball is from inside the mainshaft it keeps the peace between the fixed clutchs rod and the short rod that is pushed by the clutch lever in the housing.
The mess(mainshaft) with the big spring will come all apart I have the pictures posted all you got to do is look I have the assembly all apart on one of the posts.( I went and found it)
Here is the assembly apart the only part thats on the small inner shaft is the spring retainer and the retainers pin this is the shaft that you are trying to get at to clean the threads on. The washer looking thing above the flower nut will unscrew and release the spring so you can take it all apart see the ball between the two shafts that is where it lives. The pressure on the spring will be all the way released I think? as you unscrew the washer looking thing that has what looks like 4 machined slots in it. does that make it as clear as mud? all the stuff below the spring in this picture is inside the mainshaft except for the retainer that's on the small shaft that you are going to clean the threads on.