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

S&S Cycle 131" cylinder and piston kit for 2017+ Harley Milwaukee-Eight engines, delivering massive displacement without machine work or visible modifications. Bolts directly into stock crankcases and retains original engine height and appearance for a true sleeper build.

Features

• 4.250" bore, 4.625" stroke displacement
• 11.0:1 compression ratio
• Works with stock M8 crankcases
• No machine work required
• Includes all gaskets for installation
• 131" cam cover badge included
• Powder coat finish matches factory finishes

Specifications

• Brand: S&S Cycle
• Manufacturer Part #: 320-0622
• Bore: 4.250 in
• Stroke: 4.625 in
• Compression Ratio: 11.0:1
• Weight: 70 lb
• Category: Engine Components / Piston Sets - Powersports

Fitment

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

Frequently Asked Questions

Do I need to have my cylinder bored or any machine work done?

No — the kit bolts directly into stock M8 crankcases with zero machine work required.

Will this change the look of my engine?

The kit retains stock engine height and appearance, keeping the sleeper look. An optional 131" cam cover badge is included if you want to advertise the upgrade.

What's included in the kit?

Cylinders, pistons, all necessary gaskets, and a 131" cam cover badge.

Will my original engine serial number stay the same?

Yes — the kit retains your original engine serial numbers, so registration and title remain unchanged.