S&S Cycle Cylinder & Piston Kits — Harley-Davidson Street Glide, Softail Fat Boy 114, Road King Special (2017-2026)

S&S Cycle piston and cylinder kit for 2017+ Harley-Davidson Milwaukee-Eight (M8) engines, built with precision-forged construction for top-end rebuilds and performance upgrades. Features a 4.320-inch bore and 4.375-inch stroke designed for the late-model Big Twin platform.

Features

• 4.320 in bore × 4.375 in stroke
• Precision-forged construction
• 2017+ M8 engine compatibility

Specifications

• Brand: S&S Cycle
• Manufacturer Part #: 920-0150
• Bore × Stroke: 4.320 in × 4.375 in
• Weight: 3.22 lb
• Category: Engine Components / Piston Sets - Powersports

Fitment

Fits 2017 and newer Harley-Davidson Milwaukee-Eight (M8) Big Twin engines.

Frequently Asked Questions

Will this fit my pre-2017 Harley Twin Cam engine?

No — this kit is specific to 2017+ Milwaukee-Eight (M8) engines. Twin Cam owners need a different S&S Cycle piston and cylinder kit.

Do I need to buy gaskets and rings separately?

Check the kit contents or consult S&S Cycle directly — some kits include rings and gaskets, others do not.

Is professional installation required?

Top-end rebuilds involve engine disassembly and precise torque specs. Professional installation is strongly recommended unless you have M8 engine experience.

What compression ratio will this give me?

Compression ratio depends on cylinder head choice and gasket thickness. Consult S&S Cycle's application guide for your specific setup.