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

S&S Cycle big-bore cylinder and piston kit for Harley Milwaukee-Eight engines, boosting a 107" to 129" or a 114" to 132" displacement without requiring crankcase machine work. Direct-bolt installation onto stock M8 crankcases with included MLS head gaskets and cubic-inch cam cover badge.

Features

• 4.320" bore cylinder
• Works with stock M8 crankcases — no machine work
• Huge displacement gain (22-18 cubic inches)
• Powder coat finish matches factory
• MLS multi-layered steel head gaskets included
• Retains stock engine height
• Made in USA

Specifications

• Brand: S&S Cycle
• Manufacturer Part #: 910-0844A
• Bore Diameter: 4.320"
• Category: Engine Components / Piston Sets - Powersports
• Weight: 29.56 lb
• Country of Origin: USA

Frequently Asked Questions

Will this fit my 107" Milwaukee-Eight?

Yes — this kit increases 107" displacement to 129" cubic inches. Also fits 114" engines, bringing them to 132".

Do I need to machine my crankcase?

No — S&S designed this kit to bolt onto stock M8 crankcases without any machine work.

What's included in the kit?

Cylinder, piston, rings, wrist pin, MLS head gaskets, hardware, and a cubic-inch cam cover badge.

Will the engine height stay the same?

Yes — the kit retains stock engine height, so frame modifications are not required.

Is installation difficult?

This is a full engine teardown and rebuild job. Most riders need a qualified Harley shop or experienced mechanic to handle the installation.