OS 0.25 Piston Kit for Honda TRX 350 (years 2000–2006) is an aftermarket replacement designed to restore compression and rebuild peak power for the TRX350 engine family. Specifically suited for Honda TRX350FE, TRX350FM, TRX350TE, and TRX350TM variants, this kit is machined to precise bore tolerances to maintain consistent performance between rebuilds. It’s the smart choice when you’re renewing a worn top end and chasing reliable, field-ready power on the trail or farm.

This oversize +0.25mm piston kit delivers a reliable, durable option for riders who push their machines hard in tough conditions. Worn piston rings, scored cylinders, and degraded combustion can sap throttle response and fuel economy; this aftermarket replacement is engineered to restore tight ring seal, reduce oil consumption, and sustain steady compression under load. Built to match the TRX350 bore, it provides predictable performance and long-lasting reliability for active trail and utility use.

Comprehensive Vehicle Fitment

Product Specifications

OEM & Aftermarket Cross-Reference Information

What’s Included

A concise package designed to renew your top end.

• Piston
• Rings
• Wrist Pin
• Cir Clips

Note: Related top-end gasket sets or additional seals are not included unless specified in a separate listing.

Why Choose This Aftermarket Replacement?

• Direct-Fit Compatibility: Engineered to match the TRX350 bore and wrist pin dimensions for a trouble-free install.
• OEM Cross-Reference: Clear cross-reference support with Honda’s TRX350 specifications to ensure dependable replacement compatibility.
• Premium Materials: Forged aluminum construction delivers strength with controlled expansion under heat, helping maintain ring seal.
• Precise Oversize Fit: Oversize +0.25 mm restores compression and power without sacrificing reliability on high-mileage engines.
• Performance Restoration: Restores throttle response, consistent power delivery, and smoother combustion across the TRX350 family.
• Durability in Tough Conditions: Built for trail and farm use where heat and load cycles are frequent resistors to wear.

Installation Notes:

• Follow the service manual: inspect bore condition and verify bore diameter before installation.
• Use a proper ring compressor and ensure rings are installed in the correct orientation with gaps offset from each other.
• Lubricate the piston skirts and rings with engine oil during assembly; lightly oil the wrist pin and circlips before seating.
• Check ring end gaps as per the kit’s recommended specification and adjust if required by machinist guidance.
• Clean and inspect the cylinder and head surfaces; replace or verify the head gasket and ensure proper seating of the cylinder.
• Reassemble using the service manual torque specs and break-in procedures to seat rings and rings lands properly.

Why Upgrade?

Running a worn piston kit in a TRX 350 can lead to compression loss, reduced power, and tougher starts, especially under load on trails or in agricultural work. Upgrading to this OS oversize piston kit restores compression integrity, improves throttle response, and revives dependable performance for reliable, long days in the field.