YS Engine YSF9129 piston wrist pin for F91AC piston assembly  [YSF9129]

Piston wrist pin for F91AC

This wrist pin is an RC-scale replacement component intended for use with the YS F91AC piston assembly. It functions as the pivot between the piston and the connecting rod inside small nitro engine cylinders, and is supplied as a single part to restore proper piston articulation when the original pin shows wear or scoring.

For maintenance and tuning, the wrist pin's condition affects piston movement and sealing consistency. Inspect the pin bore and piston walls for wear during routine engine servicing, and replace the pin if there is visible scoring, ovality, or excessive play. Proper fit and straightness are important to maintain piston alignment and reliable combustion behavior in RC nitro engines.

Installation requires disassembly of the engine's top end to access the piston and connecting rod. When reinstalling, ensure clean mating surfaces and correct orientation of any retaining clips or circlips used by the engine design, and perform a careful run-in after reassembly to confirm smooth operation.