Overbore 421.81cc Piston Kit
Kawasaki Ninja EX400cc Overbore +2 mm Ceramic Dome Engine Kit Pistons/Cylinder/Gaskets - Image 2
Kawasaki Ninja EX400cc Overbore +2 mm Ceramic Dome Engine Kit Pistons/Cylinder/Gaskets - Image 3
Kawasaki Ninja EX400cc Overbore +2 mm Ceramic Dome Engine Kit Pistons/Cylinder/Gaskets - Image 4
Kawasaki Ninja EX400cc Overbore +2 mm Ceramic Dome Engine Kit Pistons/Cylinder/Gaskets - Image 5

Kawasaki Ninja EX400cc Overbore +2 mm Ceramic Dome Engine Kit Pistons/Cylinder/Gaskets

Spears Racing Piston Kits have been winning races and Championships all over the world for over 4 decades. Spears Racing pistons have been in several of the race wins in close course racing and in road circuits in Europe and has won the Isle Of Man TT Twins race several times.

 

 

$79.98 – $1,759.97

SKU SP012-320 Kit Ceramic-1 Categories , , Tags , ,

Description

Spears Racing Overbore 421.81cc Piston Kit with Thermal Barrier Crown Coating – 12.8:1 Compression
For over four decades, Spears Racing, in collaboration with JE Pistons, has crafted high-performance race pistons using state-of-the-art CNC machining and advanced manufacturing. Committed to innovation, Spears Racing delivers pistons with proprietary forgings, treated wrist pins, and custom piston rings, rigorously developed to exceed industry standards. Proven on dyno rooms and racetracks worldwide, these pistons have powered championships, including multiple Isle of Man TT Twins victories.
Kit Overview
The Spears Racing 421.81cc Overbore Piston Kit (+2mm) is designed for the Kawasaki Ninja EX400, featuring JE Pistons’ advanced 3-ring FSR Slipper Skirt forging. Lighter than OEM pistons, this high-compression (12.8:1) kit includes:
  • 2 Pistons with JE’s Thermal Barrier Crown Coating
  • Piston Rings (x2 sets)
  • Lighter Wrist Pins (x2)
  • Cir Clips (x4)
  • Custom +2mm Head Gasket (special thickness)
  • Bored and Re-Plated Cylinder with proprietary Nickel Silicon Carbide (NSC) plating
Advanced Cylinder Plating
The OEM cylinder is bored, inspected, and coated with a superior NSC plating process by Millennium Technologies, trusted by professional race teams globally. This plating outperforms factory standards and comes with a Limited Lifetime Warranty, ensuring durability under extreme conditions.
JE Pistons’ Thermal Barrier Crown Coating
The kit features JE’s proprietary ceramic gold coating (.0015” thick) on the piston crowns, engineered for unmatched durability and performance:
  • Heat Reflection: Rejects combustion heat, reducing thermal stress on the piston crown.
  • Prevents Annealing: Minimizes material softening, extending piston lifespan indefinitely under proper conditions.
  • Boosts Efficiency: Reflects heat into the combustion chamber, improving exhaust gas velocity and power output.
This coating ensures reliability for high-performance street and track applications, protecting against deformation and material degradation.
Piston Design Features
Spears Racing pistons are engineered for extreme performance, incorporating:
  • Anti-Detonation Grooves: Reduce piston-cylinder contact at high temperatures and RPMs, protecting the top ring from detonation waves.
  • Accumulator Groove: V-shaped groove between top and second rings reduces ring flutter, improving seal and longevity.
  • Double Pin Oilers: Deliver twice the oil to the wrist pin, enhancing lubrication and durability.
  • Precision Pin Fitting: Honed pin bores with clearances from 0.0003” to 0.003” for optimal performance.
  • Optimized Cam and Barrel: Custom skirt shapes ensure tighter clearances, less noise, better ring seal, and increased power.
  • Custom Laser Marking: Each piston is serialized with part number, batch.
Installation Recommendations
Spears Racing recommends using surface gap spark plugs:
Kit Components
  • Bored and re-plated cylinder (NSC-coated)
  • 2x Pistons with Thermal Barrier Crown Coating
  • 2x Wrist Pins
  • 2x Piston Ring Sets
  • 4x Cir Clips
  • Custom +2mm head gasket and base gasket
Proven Performance
Spears Racing piston kits have dominated closed-course racing, road circuits, and prestigious events like the Isle of Man TT. Engineered for professional competition, this 421.81cc kit delivers unmatched power, durability, and precision for extreme applications.
“Preferred Performance” by Spears Racing – Elevate your engine with a kit designed to win.

Additional information

Weight 8 lbs
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