Namura NA-40004K Standard Bore Top End Kit for 2001–2005 Yamaha YFM660R Raptor

The Namura NA-40004K Standard Bore Top End Kit is a complete replacement solution for the top end of select Yamaha YFM660R Raptor engines from 2001 through 2005. Designed for dependable fitment and reliable performance, this kit includes a piston, piston rings, wrist pin, retaining clips, top-end bearing, and gasket kit. It is engineered to restore compression and support consistent engine operation during demanding off-road riding.

The piston features MOS2, or Teflon/Molybdenum, coated skirts applied through a rolled-on process for a durable bond. This coating helps reduce friction, improve heat transfer, and minimize the risk of cold seizures. Machined smooth heads help reflect combustion heat and reduce carbon buildup, while the anodized dome improves heat resistance and durability. The hypereutectic casting process adds silicon for reduced expansion, increased wear resistance, and improved performance under elevated cylinder temperatures.

Designed as a standard-bore replacement, the Namura NA-40004K top end kit supports the original engine configuration when properly installed with compatible components. Verify engine condition, bore specifications, and service requirements before installation. This kit fits 2001, 2002, 2003, 2004, and 2005 Yamaha YFM660R Raptor models.

Features:

• Complete Top End Kit: Includes piston, rings, wrist pin, retaining clips, top-end bearing, and gasket kit
• Standard Bore Piston: Designed for replacement applications using the original standard cylinder bore
• MOS2-Coated Skirts: 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 crown
• Anodized Dome: Improves heat resistance and piston durability under demanding operating conditions
• Hypereutectic Casting: Higher silicon content supports reduced expansion and increased wear resistance
• Fitment: Fits 2001–2005 Yamaha YFM660R Raptor models