As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING ENGINE RUNUP THE PILOT NOTICED A 250 RPM DROP DURING MAG CHECK AT 2000 RPM. THE ENGINE WAS ALSO RUNNING VERY ROUGH ON THIS ONE MAG. MAG INSPECTION REVEALED THAT THE ROTOR SHAFT WAS CRACKED IN TWO AT THE BASE OF THE SLOT IN THE SHAFT.