CP-Carrillo CPN2-3897 Piston Ring Set 99mm Bore 1.0x1.2x2.0mm

The CP-Carrillo CPN2-3897 is a high-performance piston ring set designed for a 99mm bore with a ring pack configuration of 1.0mm top ring / 1.2mm second ring / 2.0mm oil ring. Engineered to CP-Carrillo's exacting standards, this ring set delivers superior sealing, reduced friction, and exceptional durability for powersports and performance engine applications.

Ring Pack Specifications:

• Bore Size: 99.000mm (3.897")
• Top Ring: 1.0mm gas nitrided steel — silver in color for easy identification
• Second Ring: 1.2mm cast iron with taper hook groove (Napier) face — acts as a wiper to push oil away from the combustion chamber
• Oil Ring: 2.0mm Flex Vent design, nitride coated stainless steel
• File Fit: No — pre-gapped for direct installation
• Sold as a complete kit

Key Features:

• Gas nitrided top ring provides outstanding wear resistance and excellent ring seal under high cylinder pressures
• Napier-style second ring efficiently scrapes oil from cylinder walls to minimize oil consumption
• Flex Vent oil ring delivers consistent radial tension for reliable oil control
• Engineered and manufactured by CP-Carrillo in Irvine, California to strict quality control standards
• Compatible with CP-Carrillo CPN2-series piston applications — cross-references part ID 3245

CP-Carrillo recommends plateau honing the cylinder bore to a 35–40 degree cross-hatch angle before installing CPN2-series rings. The bore must be round to within 0.0002" for maximum ring seal and optimal performance. These rings are a proven choice for powersports engine builds demanding reliability and consistent power delivery.