Replacement Wrist Pin for 40SF Series OS25406000 by O.S. Engine  [OS25406000]

O.S. ENGINES PISTON PIN FOR 40SF SERIES
Price:
£4.16
Brand:
O.S. Engine
Model:
OS25406000
Condition:
Brand New
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Fitment and service guidance

The O.S. Engine OS25406000 piston pin is intended as a direct wrist pin replacement for 40SF series RC glow engines, locking the piston to the conrod and correcting excessive piston-to-rod clearance. It is supplied to restore internal fit where wear has developed.

Ensure correct pin orientation and fully seat retaining clips or circlips before completing assembly, then verify unobstructed piston movement within the sleeve. The pin's function is internal alignment and compression stability, which supports consistent running behavior after servicing.

When overhauling a 40SF engine inspect the piston, the wrist pin bore, and clip grooves for wear or deformation; replace any damaged items together to maintain original tolerances. Scheduled inspections help keep carburetion and tuning adjustments steady over time.

How do I check for wrist pin wear on a 40SF?

Check for lateral movement at the piston-rod joint, visible scoring on the pin or bore, and any looseness of the clip seats. Any of these signs indicate the OS25406000 should be fitted.

What components should be replaced together with the pin?

It is best practice to replace worn pistons, clips, and the wrist pin as a set to preserve running tolerances and avoid repeat wear that can upset tuning.

How often should I inspect the wrist pin area?

Inspect during any engine strip or rebuild and at regular service intervals; early detection of wear prevents poor compression repeatability and helps retain tuning consistency.

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