This oversize piston ring kit is a precise rebuild solution for TRX 420 Rancher ATV engines from 2007 to 2013, engineered to restore peak compression and curb oil blow-by after years of wear. Designed specifically for an oversize bore of 0.25 mm, it delivers tighter sealing and improved combustion efficiency, helping your trail or farm work feel like-new again. By renewing the ring pack, this kit helps reclaim power, throttle response, and fuel economy without the sticker shock of OEM parts.

What sets this aftermarket kit apart is its focused approach to common wear issues—ring groove wear, carbon buildup, and deteriorating piston seals—that gradually sap performance on older Rancher engines. Built as a reliable aftermarket replacement, it offers durable materials and a precise fit that translates to dependable sealing under demanding riding conditions, whether you’re carrying loads or navigating rugged terrain. The result is smoother operation, reduced oil consumption, and restored confidence during long days in the field.

Comprehensive Vehicle Fitment

Product Specifications

OEM & Aftermarket Cross-Reference Information

What's Included

This kit includes the essential components of the piston ring set for a proper engine rebuild:

• Piston Ring Set (includes all rings as a single assembly)
• Top Ring
• Second Ring
• Oil Ring (x2)
• Oil Ring Spacer

Note: This kit does not include a piston, wrist pin, circlips, base gasket, head gasket, or other gaskets.

Why Choose This Aftermarket Replacement?

• Direct-Fit Compatibility: Engine rebuild-ready kit designed to fit the TRX 420 Rancher family without modifying the cylinder or bore.
• OEM Cross-Reference: Cross-referenced to the factory part numbers, ensuring correct specifications and reliability.
• Premium Materials: High-carbon steel with chrome-plated top ring for superior wear resistance and oil control under heavy use.
• Precision Oversize Fit: 0.25 mm oversize matches honed bores to restore proper ring-wall sealing and compression.
• Performance Restoration: Reclaims lost power, throttle response, and fuel efficiency by renewing seal integrity.
• Cost-Effective Alternative: A dependable aftermarket option that delivers OEM-like performance at a lower price point.

Installation Notes:

• Measure and Prepare: Inspect the bore for wear; hone to the 86.75 mm oversize if needed and verify ring groove condition before installation.
• End-Gap and Orientation: Set ring end gaps to 0.25–0.40 mm and offset the top and second rings by 0.5–1.0 mm to minimize gas leakage.
• Lubrication: Apply a light coat of engine assembly lube to all rings and the piston skirts during assembly.
• Ring Orientation: Install rings in the correct orientation with the chamfers and stamped markings facing the correct direction; avoid twisting rings during placement.
• Clean Assembly: Clean the piston groove and bore thoroughly; keep debris away from the ring lands to prevent scoring.
• Follow Break-In Guidelines: After startup, avoid high RPM and heavy loads for a proper break-in period to seating the rings and ensure long-term sealing.

Why Upgrade?

Worn piston rings allow blow-by, reduce compression, and increase oil consumption, which degrades power and reliability on rugged trails or demanding farm tasks. Upgrading to this OS 0.25 mm kit restores sealing and compression, delivering consistent performance and reduced oil use during tough work sessions.