40SF Wrist Pin - OS25406000 for O.S. Engine  [OS25406000]

Installation notes for wrist pin replacement

The O.S. Engine OS25406000 piston pin is supplied as a replacement wrist pin for 40SF series RC glow engines, fastening the piston to the conrod assembly. It is intended to remove slack where a worn piston-to-rod interface causes play.

During installation confirm pin orientation, seat the retaining clips or circlips fully in their grooves, and verify the piston moves freely within the sleeve before final assembly. Because the pin controls piston alignment and compression consistency, careful fitment supports better idle stability during tuning.

When overhauling a 40SF engine inspect the piston bore, pin journal, and clip seats for signs of wear or scoring and renew affected parts as a set to maintain correct running tolerances. Routine checks reduce the chance of drifting carburetor settings between sessions.