Kb Pistons Super Duty Piston - 4.125" Bore M8 114/117 TO 120" STD — Harley-Davidson (2017-2025)

KB Pistons Super Duty piston pair for M8 Harley-Davidson engines from 114 to 120 cubic inches, with 4.125" bore and 1.2cc flat-top design. Built with anodized grooves, abradable skirt coating, and premium Hastings rings for tight clearances and quiet operation.

Features

• Anodized top ring groove and crown
• Line2Line abradable skirt coating (.003" thickness) for zero initial fit
• Round wire wrist pin locks
• Premium Hastings 1.2mm/1.2mm/3.0mm steel nitride top ring with ductile Napier second ring
• Forced wrist pin oiling
• Flat-top 1.2cc design with 1.083" compression height
• Valve pockets sized for 1mm oversize valves
• Includes all rings, wrist pins, and locks

Specifications

• Brand: KB Pistons
• Manufacturer Part #: KB542LCA.STD
• Bore: 4.125 in
• Engine: M8 (114-120 cu in)
• Design: Flat-top, 1.2cc
• Compression Height: 1.083 in
• Quantity: Pair
• Length: 6 in
• Width: 5 in
• Height: 5 in
• Weight: 2.5 lbs
• Country of Origin: Mexico

Fitment

Fits Harley-Davidson Milwaukee-Eight (M8) engines from 114 to 120 cubic inches with 4.125" bore.

Frequently Asked Questions

What's included in this kit?

A pair of pistons with all rings, wrist pins, and wrist pin locks ready to install.

Can I use these in a 124" or larger stroker?

No — this part is sized for 114-120 cu in M8 builds. Larger displacement requires a different bore or part number.

Do these require a hone or break-in procedure?

Yes. The Line2Line abradable skirt coating seats during initial break-in for a tight, quiet running fit. Follow standard piston break-in procedure.

Will these work with 1mm oversize valves?

Yes — the valve pockets are sized specifically to accommodate 1mm oversize valves without interference.

Is forced wrist pin oiling necessary?

This piston is designed with forced oiling provision. Ensure your engine block or connecting rods support oil galleries to the wrist pin boss.