What happened
The FAA’s narrative, in sentence case. The FAA writes it in capitals and removes private details.
(-23) Pilot stated after flying for 25 minutes and at an altitude of 950' feet MSL the aircraft lost power. The tachometer dropped from 2,400 RPM to 1,000 RPM. A landing was initially attempted at a nearby grass airstrip but it was in use by a departing aircraft. The aircraft continued to lose altitude and impacted terrain in a wooded area. After the aircraft was recovered from the scene, subsequent investigation showed that the left cylinder intake valve would not open as the engine was hand cycled through. The intake valve would not open because the mechanical pushrod lifter was out of adjustment. The lifter adjustment jam nut was loose and had allowed the lifter adjustment to bottom out. The improperly adjusted filter would not allow proper travel of the pushrod and rocker arm. The rocker arm could not compress/open the intake valve.
As the FAA filed it
(-23) PILOT STATED AFTER FLYING FOR 25 MINUTES AND AT AN ALTITUDE OF 950' FEET MSL THE AIRCRAFT LOST POWER. THE TACHOMETER DROPPED FROM 2,400 RPM TO 1,000 RPM. A LANDING WAS INITIALLY ATTEMPTED AT A NEARBY GRASS AIRSTRIP BUT IT WAS IN USE BY A DEPARTING AIRCRAFT. THE AIRCRAFT CONTINUED TO LOSE ALTITUDE AND IMPACTED TERRAIN IN A WOODED AREA. AFTER THE AIRCRAFT WAS RECOVERED FROM THE SCENE, SUBSEQUENT INVESTIGATION SHOWED THAT THE LEFT CYLINDER INTAKE VALVE WOULD NOT OPEN AS THE ENGINE WAS HAND CYCLED THROUGH. THE INTAKE VALVE WOULD NOT OPEN BECAUSE THE MECHANICAL PUSHROD LIFTER WAS OUT OF ADJUSTMENT. THE LIFTER ADJUSTMENT JAM NUT WAS LOOSE AND HAD ALLOWED THE LIFTER ADJUSTMENT TO BOTTOM OUT. THE IMPROPERLY ADJUSTED FILTER WOULD NOT ALLOW PROPER TRAVEL OF THE PUSHROD AND ROCKER ARM. THE ROCKER ARM COULD NOT COMPRESS/OPEN THE INTAKE VALVE.
NTSB investigation
The NTSB’s investigation of this event, with its probable cause and findings. Matched to this report by N-number and date.