Ed,


'Egging out can be due to wear patterns... But it could also be a result of actual elongation of the 'yoke', whether it is at the top-end, or at the bottom-end of the rod, or both.

Excessive loading of the con-rod, from the piston repeatedly being pulled down, out of a seize at TDC (a very cold and rich break-in in a tight ABC type engine), will do that. Over-revving a four-stroke engine can also eventually cause that (unless floating valve-piston contact occurs before...), but this will take much, much longer.

Egging out due to wear is more likely to be due to excessive compression loading of the con-rod, like when running the engine for long periods on the verge of detonation; especially with a grossly exaggerated prop size.

...Or, as was suggested, spinning the engine with an electric starter, when it is 'nearly' hydro-locked...
That will wear down the near-sides of both bushings.