Kb Pistons Hypereutectic Cast Piston - Pistons EVO 80ci 8.6:1 .010 — Harley-Davidson (1984-1999)

KB Pistons Hypereutectic cast piston for EVO 80ci engines at 8.6:1 compression, featuring 16% silicon content for high thermal barrier properties and low expansion. Ideal for air-cooled applications, delivering tight ring seal and reduced wear on pump fuel.

Features

• Hypereutectic alloy with 16% silicon content
• Low thermal expansion rate
• Tight piston-to-cylinder clearances
• Suited for stock or mild compression ratios to 10.5:1
• Designed for air-cooled engines

Specifications

• Brand: KB Pistons
• Manufacturer Part #: KB258.010
• UPC: 800745060365
• Compression Ratio: 8.6:1
• Engine Displacement: 80 cubic inches
• Piston Oversize: .010 inch
• Length: 9.5 in
• Width: 4.8 in
• Height: 4.6 in
• Weight: 2.65 lbs
• Country of Origin: Mexico

Fitment

Fits Harley EVO 80 cubic inch air-cooled engines. Designed for stock or mildly boosted compression ratios up to 10.5:1 running on pump fuel.

Frequently Asked Questions

What compression ratio are these pistons rated for?

These hypereutectic pistons are best suited for stock or mild compression ratios up to 10.5:1 on pump fuel.

Why hypereutectic over forged pistons?

Hypereutectic alloy has 16% silicon content, giving superior thermal barrier properties and low expansion—ideal for air-cooled engines where tight ring seal reduces blow-by and wear.

Are these pistons OEM replacements?

No — KB pistons are performance/replacement units. Compare the part number to your engine's original specification before ordering.

What oversize is this piston?

This is a .010 inch oversize piston, requiring a matching hone to your cylinder bore.