As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) PILOT REPORTED THE MAIN ROTOR RPM TO BE FLUCTUATING WITH POWER CHANGES. RPM TESTER INSTALLED AND CONFIRMED RPM DROP TO APPROX 370 RPM, THEN RETURNED TO 380. SLIGHT POWER REDUCTION RPM WOULD INCREASE TO 395-400 RPM, THEN RETURN TO 380-385 RPM. FCU REPLACED.