Kb Pistons Hypereutectic Cast Piston - Pistons EVO 80ci 10.5:1 .005 — Harley-Davidson (1984-1999)

KB Pistons Hypereutectic cast piston for EVO 80ci engines at 10.5:1 compression, made with 16% silicon content for low thermal expansion and tight piston-to-wall clearance. Engineered for air-cooled engines running on pump fuel with reduced noise and wear compared to cast-iron designs.

Features

• 16% silicon hypereutectic alloy
• Low thermal expansion rate
• Tight piston-to-cylinder wall clearance
• .005 in oversized
• Optimal ring seal and reduced engine noise

Specifications

• Brand: KB Pistons
• Manufacturer Part #: KB266.005
• UPC: 800745061362
• Compression Ratio: 10.5:1
• Engine Displacement: 80 cubic inches (EVO)
• Oversized: .005 in
• Length: 9.6 in
• Width: 4.8 in
• Height: 4.6 in
• Weight: 2.65 lbs
• Country of Origin: Mexico

Fitment

Fits air-cooled EVO 80ci engines with 10.5:1 compression ratio or lower running on pump fuel.

Frequently Asked Questions

What compression ratio do these pistons support?

KB266.005 is rated for 10.5:1 compression or lower. Higher-compression applications require different KB piston sets.

Why are hypereutectic pistons better for air-cooled engines?

The 16% silicon content reduces thermal expansion, allowing tighter piston-to-wall clearance, which improves ring seal, quiets engine operation, and decreases wear.

Can I run these on premium fuel?

These pistons are engineered for pump fuel (87–91 octane). Premium fuel is not required and provides no benefit.

What does the .005 in oversized measurement mean?

The piston is .005 inches larger in diameter than standard, requiring a matching honed cylinder bore to fit properly.