The NAMURA NA-10040-4K Top End Kit is designed for Honda Rancher all-terrain vehicles requiring an 85.97 mm, plus 1.00 mm piston with an 11:1 compression ratio. This comprehensive kit includes the piston, piston rings, wrist pin, retaining clips, top end bearing, and gasket kit for a convenient top-end rebuild. The kit is engineered for dependable fitment and performance on select 2004–2007 Honda TRX400FA Rancher AT [SRA] and TRX400FGA Rancher AT GPScape [SRA] models.
The piston features NAMURA’s MOS2, or Teflon/Molybdenum, coated skirts. The rolled-on coating process creates a durable bond while helping reduce friction, improve heat transfer, and minimize the risk of cold seizures. Machined smooth heads help reflect combustion heat and reduce carbon buildup, supporting piston protection and consistent engine operation. Anodized domes further improve heat resistance and durability compared with non-anodized piston domes.
NAMURA uses a hypereutectic casting process to provide increased silicon content, reduced thermal expansion, and improved wear resistance. This construction is suited to engines exposed to elevated cylinder temperatures and demanding operating conditions. Verify the bore size, compression specification, and engine configuration before installation. Manufacturer part number NA-10040-4K and vendor part number 186-10404 identify this application-specific top end kit.
Features:
- Complete Top End Kit: Includes piston, rings, wrist pin, retaining clips, top end bearing, and gasket kit
- Application: Designed for 2004–2007 Honda TRX400FA Rancher AT [SRA] and TRX400FGA Rancher AT GPScape [SRA] models
- Piston Size: 85.97 mm, plus 1.00 mm oversize, with an 11:1 compression ratio
- MOS2 Coated Skirts: Rolled-on Teflon/Molybdenum coating helps reduce friction, improve heat transfer, and minimize cold-seizure risk
- Machined Smooth Head: Helps reflect combustion heat and reduce carbon buildup on the piston top
- Anodized Dome: Improves heat resistance and durability for demanding engine conditions
- Hypereutectic Construction: Higher silicon content helps reduce expansion and improve wear resistance
- Brand and Part Number: NAMURA NA-10040-4K; vendor part number 186-10404
Fitment:
2004 Honda TRX400FA Rancher AT [SRA]
2004 Honda TRX400FGA Rancher AT GPScape [SRA]
2005 Honda TRX400FA Rancher AT [SRA]
2005 Honda TRX400FGA Rancher AT GPScape [SRA]
2006 Honda TRX400FA Rancher AT [SRA]
2006 Honda TRX400FGA Rancher AT GPScape [SRA]
2007 Honda TRX400FA Rancher AT [SRA]
2007 Honda TRX400FGA Rancher AT GPScape [SRA]