As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) A STUDENT PILOT NOTICED THAT THE ENGINE WOULD NOT RUN WHEN THE RT MAGNETO WAS SELECTED. MAINT WAS CALLED AND THE RT MAGNETO WAS REMOVED FROM THE ENGINE AND DISSASSEMBLED. THE ROTOR WAS FOUND SHEARED AT THE CAM ROTOR SLOT. (TC NR 20070703002)