Small Engines (Lawn Mowers, etc.): Half moon, briggs stratton, vertical shaft

Question
I have a walk behind briggs & stratton 4.5HP  mower that seems to have jumped timing. Does this mower have halfmoon slot in the vertical shaft and if so how can I replace it.

                     Wyatt, thank you

Answer
WYATT, I AM NOT SURE WHAT YOU ARE ASKING.  IF YOU ARE ASKING ABOUT THE KEY IN THE FLYWHEEL I AM SURE IT DOES HAVE ONE.  TO REPLACE IT REQUIRES PULLING THE FLYWHEEL REMOVING BOTH PIECES OF THE SHEARED KEY ALIGNING WITH THE FLYWHEEL AGAIN AND REINSTALLING.

GEORGE