Kb Pistons Super Duty Piston - 4.250" Bore M8 114/117 TO 128" STD 11.7:1 — Harley-Davidson (2017-2025)

KB Pistons Super Duty pistons for Milwaukee-Eight (M8) big-bore engines, built for street and mild boost applications up to 128 cubic inches. This pair features anodized grooves, abradable skirt coating, and premium Hastings rings for tight tolerances and quiet operation.

Features

• Anodized top ring groove and crown
• Line2Line abradable skirt coating (.003" thickness) for zero initial clearance and self-honing fit
• Premium Hastings 1.2mm steel nitride top ring with ductile napier second ring
• Forced wrist pin oiling
• Flat-top design, 1.2cc dish, 1.083" compression height
• Accommodates 1mm oversize valves
• Round wire wrist pin locks
• Sold as a pair with all rings and pins included

Specifications

• Brand: KB Pistons
• Manufacturer Part #: KB596LCA.STD
• UPC: 800745276186
• Bore: 4.250 in
• Engine: Milwaukee-Eight (M8) 114/117 to 128 cu in
• Compression Ratio: 11.7:1
• Compression Height: 1.083 in
• Weight: 2.5 lbs per pair
• Country of Origin: Mexico

Fitment

Fits Harley-Davidson Milwaukee-Eight (M8) engine builds from 114 cubic inches through 128 cubic inches with 4.250 in bore and 11.7:1 compression ratio.

Frequently Asked Questions

What's included in this piston kit?

A pair of pistons, all rings (top and second), wrist pins, and round wire wrist pin locks. Everything needed for both cylinders.

What's the Line2Line abradable skirt coating?

A proprietary .003 in coating that starts at zero clearance and self-hones as the engine runs, settling into tight, quiet operating clearance.

Will these pistons fit my 114 ci M8 build?

Yes — these are rated for M8 stroker builds from 114 ci through 128 ci with 4.250 in bore.

Do I need oversized rings or valves?

Rings are standard size. The piston design accommodates 1mm oversize valves if your cylinder head calls for them.

Are these suitable for forced induction?

Yes — rated for mild boost applications in forced-induction setups up to 128 ci.