Kb Pistons Hypereutectic Cast Piston - Pistons Twin CAM 88ci 8.8:1 .010 — Harley-Davidson Road King, Road King Classic, Electra Glide (1999-2007)

KB Pistons Hypereutectic Cast Piston designed for Twin CAM 88ci engines at 8.8:1 compression ratio with .010 oversized bore. Cast from a 16% high-silicon alloy, these pistons deliver tight ring seal and low thermal expansion ideal for air-cooled Harley engines running pump fuel.

Features

• 16% silicon hypereutectic alloy
• Low thermal expansion rate
• Tight piston-to-cylinder wall clearances
• Reduced engine noise and wear
• Stock to mild compression ratios up to 10.5:1

Specifications

• Brand: KB Pistons
• Manufacturer Part #: KB425C.010
• UPC: 800745067715
• Bore Size: .010 oversized
• Compression Ratio: 8.8:1
• Engine: Twin CAM 88ci
• Weight: 2.85 lbs
• Country of Origin: Mexico

Fitment

Fits Harley-Davidson Twin CAM 88ci air-cooled engines. Designed for stock to mild compression builds running pump fuel.

Frequently Asked Questions

What compression ratio do these pistons support?

Hypereutectic pistons are rated for 8.8:1 compression and up to 10.5:1 on pump fuel. Higher compression requires sintered or forged pistons.

Are these for .010 overbore or stock bore?

These are .010 oversized pistons — your cylinders must be bored .010 over to fit correctly.

Why hypereutectic instead of forged?

Hypereutectic alloy offers tighter ring seal, quieter operation, and lower cost than forged. Forged pistons are better for high-compression racing or nitrous builds.

Do I need new rings and wrist pins?

Check with the ring and pin supplier — KB typically requires compatible ring sets and wrist pins specific to these piston dimensions.

Can I run these on ethanol-blend fuel?

These are designed for pump fuel (up to 10% ethanol). Verify compatibility with your fuel supplier if running higher ethanol blends.