As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT EXPERIENCED A PARTIAL POWER FAILURE ALONG WITH A SUDDEN VIBRATION. DURING THE SUBSEQUENT INSPECTION, THE ACCELERATOR PUMP DISCHARGE CHECK VALVE IN THE CARBURETOR WAS FOUND TO HAVE BACKED OUT OF ITS CHAMBER. RECOMMEND REDESIGNING ALL THE CHECK-VALVES AND JETS IN THE CARBURETOR TO INCORPORATE A PERMANENT NYLON THREAD LOCK IN THE THREADS.