Piston pin clip SYM Ø15mm (1 pc)

This aftermarket piston pin clip set is manufactured for the SYM Symphony 125I ST 125cc engine, compatible with 2017-2020 model years and cross-referenced to OEM number 94601-15000. These seemingly insignificant components play a critical safety role, preventing the wrist pin from migrating laterally out of the piston boss—a failure that can cause catastrophic engine destruction in fractions of a second.

The circlip design features a C-shaped spring steel ring that seats in a precision-machined groove at each end of the piston pin bore. When properly installed, the clip’s outer diameter exerts radial pressure against the groove wall while the inner diameter clears the wrist pin by a controlled margin. The 15mm specification matches the wrist pin diameter exactly, with the groove geometry designed to retain the clip under all operating conditions including extreme vibration, thermal cycling, and the inertial loads generated by rapid RPM changes.

Manufactured from 65Mn spring steel wire with a diameter of 1.2mm, these clips undergo oil tempering at 400°C to achieve a tensile strength of 1,600-1,800 MPa with sufficient ductility to allow installation without cracking. The phosphate coating provides 200+ hours of salt spray corrosion resistance, protecting the clip in the hostile environment of hot engine oil and combustion byproducts. Each clip is formed with precisely controlled gap dimensions—too narrow and installation becomes impossible, too wide and retention force drops below safe thresholds.

Technical specifications: material 65Mn spring steel; wire diameter 1.2mm; phosphate coating; retention force >50N; temperature range -40°C to 200°C; sold as individual units (2 required per piston).

These clips must be replaced every time the piston or wrist pin is serviced. Never reuse old circlips, as the spring steel undergoes stress relaxation during initial installation and will not provide adequate retention force on second use. During installation, use circlip pliers with properly sized tips to expand the clip just enough to clear the piston boss bore—over-expansion can permanently deform the clip. Verify that the clip seats fully in the groove by rotating the piston and listening for rattling, and always install both clips before rotating the crankshaft.