Kb Pistons Super Duty Piston - 4.250" Bore M8 107 TO 124" +.005 11.8:1 — Harley-Davidson (2017-2021)

KB Pistons Super Duty pistons for Harley Milwaukee-Eight 107 to 124 cubic inch engines, sold as a pair with rings and wrist pins included. Built with anodized crown, Line2Line abradable skirt coating, and premium Hastings steel nitride rings for durability and quiet operation.

Features

• Anodized top ring groove and crown
• Line2Line abradable skirt coating (.003" thickness) for tight, quiet running clearance
• Round wire wrist pin locks
• Premium Hastings 1.2mm steel nitride top ring with ductile Napier second ring
• Forced wrist pin oiling
• Flat-top design with 1.2cc dish and 1.083" compression height
• Valve pockets sized for 1mm oversize valves
• Sold as a pair with all rings, wrist pins, and locks included

Specifications

• Brand: KB Pistons
• Manufacturer Part #: KB595LCA.005
• UPC: 800745276162
• Bore: 4.250 in
• Engine Size: M8 107–124 cubic inches
• Compression Ratio: 11.8:1
• Compression Height: 1.083 in
• Top Ring Groove: Anodized
• Weight: 2.5 lbs
• Country of Origin: Mexico
• Quantity: Pair (2 pistons)

Fitment

Fits Harley-Davidson Milwaukee-Eight (M8) engines from 107 to 124 cubic inches with +.005 overbore.

Frequently Asked Questions

What's included with these pistons?

The pair of pistons, Hastings steel nitride top and ductile second rings, wrist pins, and round wire locks — everything needed for installation.

Do these require a machine shop for installation?

Yes — piston installation requires professional engine work, cylinder boring, and honing to proper clearance. Do not attempt this as a DIY job.

Will these fit a 117 or 124cc stroker kit?

These are sized for 4.250" bore. Verify with KB Pistons or your engine builder that this bore matches your specific stroker package.

What's the Line2Line abradable skirt coating?

A thin (.003") polymer coating that provides zero initial clearance and self-hones to the cylinder for a tight fit and reduced piston noise during break-in.

Can I use different rings than the Hastings premium set?

These pistons are designed around the included Hastings ring dimensions. Mixing ring brands or sizes can affect blow-by and clearance — stick with the included set or consult KB Pistons before swapping.