Engineered to meet or exceed original sealing standards, this Top End Gasket Kit provides reliable compression and oil sealing during TRX300 engine rebuilds. Designed as an aftermarket replacement, it delivers precise fitment for top-end work and supports dependable operation across the 1988–2000 Honda TRX300 range. This kit focuses on the essential top-end gaskets needed for a successful cylinder head rebuild, helping restore engine integrity and performance.

Comprehensive Vehicle Fitment

Product Specifications

OEM Cross-Reference Information

*OEM cross-reference numbers are provided for reference purposes only. These part numbers are confirmed for 1988-2000 TRX300 FourTrax models through official Honda parts diagrams . Always verify fitment using your machine's exact model, year, and original part number before ordering.*

What's Included

Based on standard top-end gasket kits for the TRX300 engine, this kit typically includes:

• Cylinder head gasket (replaces OEM 12251-HA0-004) 

• Cylinder base gasket (replaces OEM 12191-HC4-900) 

• Exhaust pipe gasket (replaces OEM 18291-MN4-920) 

• Tensioner gasket (replaces OEM 14525-HA7-690) 

• Tensioner hole gaskets (replaces OEM 12194-HC5-740) 

• Related O-rings and seals as required for complete top-end sealing

Note: This is a top-end gasket kit focusing on cylinder head and associated gaskets. For complete engine rebuilding, full gasket kits including oil seals and additional components are available from aftermarket suppliers .

Why Choose This Aftermarket Top End Gasket Kit?

• Direct-Fit Compatibility: Precision-engineered for Honda TRX300 FourTrax 2WD and TRX300FW FourTrax 4x4 models spanning 1988 through 2000 .

• OEM Cross-Reference: Cross-references genuine Honda part numbers 12251-HA0-004 (cylinder head gasket) and 12191-HC4-900 (cylinder base gasket) for confident replacement .

• Proven Aftermarket Support: Multiple respected aftermarket brands manufacture compatible gasket kits for the TRX300:

  • Athena offers complete gasket kits (P400210850300) entirely engineered in Italy, using latest generation laser cutting technology and surface treatments to compensate irregularities .

  • Vertex provides complete overhaul gasket kits (811900) containing all OEM-specified gaskets, o-rings, and engine oil seals, plus formed rubber valve cover gaskets with high-performance MicroPore interface material .

  • Outlaw Racing supplies engine gasket kits (OR3568) constructed from materials such as Stainless Steel, Fluoroviton and Teflon, made to exact OEM specs but with better materials for longer life .

  • WSM and Wiseco offer complete top-end rebuild kits including pistons, rings, and all necessary gaskets .

• Premium Materials: Outlaw Racing gaskets are manufactured using advanced materials including Stainless Steel, Fluoroviton and Teflon to exceed OEM specifications . Vertex kits utilise MicroPore interface material for consistent sealing under heat and pressure .

• Restores Compression: New head and base gaskets ensure proper cylinder sealing for optimal engine performance.

• Prevents Leaks: Complete sealing kit prevents oil seepage and maintains clean engine operation.

Installation Notes:

• Ensure all mating surfaces are clean and free from old gasket material before installation.

• Follow manufacturer torque specifications and tightening sequences for cylinder head bolts.

• Use new gaskets only—do not reuse old gaskets once removed.

• Check valve clearance after head installation and adjust if necessary.

• After installation, run the engine and check for any signs of leaks.

• Note that complete gasket kits may include oil seals; verify kit contents before ordering .

Why Upgrade?
Worn or damaged gaskets can cause compression loss, oil leaks, and contamination—leading to poor performance and potential engine damage. Restore your Honda TRX300 FourTrax engine's sealing integrity with this quality aftermarket top end gasket set, designed to keep you riding with confidence.

Order your top end gasket kit today and get back on the trail with confidence.