As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER DEPARTING, LEVELED OFF AT 1500 MSL, ENGINE TEMPERATURE APPROXIMATELY 600 DEGREES, ROTOR & ENGINE IN GREEN RANGE. HEARD A LOUD BANG FOLLOWED BY AN IMMEDIATE SHUTTER AND RT YAW. LOWERED COLLECTIVE IMMEDIATELY AND TURNED BACK TOWARD DEPARTURE, REGAINED ALTITUDE TO 1500 MSL. AT A LOWER POWER SETTING, DID THE SAME ACTION 2 MORE TIMES. MADE A NORMAL LANDING WITHOUT ANY DAMAGE TO AIRCRAFT. MX TROUBLESHOOTING PROBLEM.