I loosened the one bolt and clamp that holds the speedo gear in the NP231 (mechanical, 1990), but can't get it out. Should it just yank out, or is there a hidden retaining ring, set screw, etc that I am missing? I tried to wedge a screw driver under it, feels like its hung up on something.

 

O-ring is dry and probably just stuck. Try prying a little with a screwdriver should come out