Kb Pistons Super Duty Piston - 4.250" Bore M8 107 TO 124" STD 11.4:1 — Harley-Davidson (2017-2025)

KB Pistons Super Duty piston set for Harley Milwaukee-Eight engines, sized to 4.250" bore with flat-top design and 11.4:1 compression ratio. Built for durability with anodized crown, abradable skirt coating, and premium ring package for tight running clearance and reliability.

Features

• Anodized top ring groove and crown
• Line2Line Abradable skirt coating (.003" thickness) for zero initial fit and quiet operation
• Round wire locks
• Premium Hastings Steel Nitride top ring with Ductile Napier second ring
• Forced wrist pin oiling
• Flat-top design with 1.2cc displacement and 1.083" compression height
• Accommodates 1mm oversize valves
• Rings, wrist pins, and locks included

Specifications

• Brand: KB Pistons
• Manufacturer Part #: KB576LCA.STD
• UPC: 800745266941
• Bore: 4.250"
• Compression Ratio: 11.4:1
• Displacement: 1.2cc
• Compression Height: 1.083"
• Weight: 2.5 lbs
• Country of Origin: Mexico
• Quantity: Pair

Fitment

Fits Harley-Davidson Milwaukee-Eight (M8) engines 107 to 124 cubic inches. Standard size for stock bore.

Frequently Asked Questions

What's included in this piston kit?

A pair of pistons, premium ring set, wrist pins, and round wire locks — everything needed for installation.

Can I use these with stock-size cylinders?

Yes — this is standard size for stock M8 bore. Oversized pistons require matching cylinder boring.

What does the Line2Line Abradable coating do?

The .003" skirt coating provides zero initial clearance and hones in during break-in for a tight, quiet running fit.

Will these pistons fit 107cc and 124cc engines?

Yes — these standard-bore pistons work across the M8 displacement range from 107 to 124 cubic inches.