YS Engine YSF9129 Wrist Pin — Replacement for F91AC Piston Assembly  [YSF9129]

Replacement wrist pin for piston-to-rod connection

Specifically intended for use with the YS F91AC piston assembly, this wrist pin restores the pivot point between the piston and connecting rod in compact nitro cylinders. It is supplied singly to replace pins that have developed scoring or wear marks.

The wrist pin plays a key role in piston travel and the consistency of ring sealing. During engine servicing inspect the pin bore and piston walls for wear, ovality, or looseness. Replace the pin if any of these faults are present to protect piston alignment and engine reliability.

Accessing the pin requires top-end disassembly of the engine to remove the piston and connecting rod. When reassembling, make sure mating surfaces are clean, clips are correctly seated, and carry out a careful break-in to confirm smooth movement and proper sealing.