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

S&S Cycle cylinder and piston kit for 2017+ Harley-Davidson Milwaukee-Eight (M8) engines, engineered for performance builds and high-output modifications. Available in three bore sizes to match your displacement goals.

Features

• Available in 4.320 in, 4.500 in, and 4.625 in bore sizes
• Designed for 2017+ Milwaukee-Eight (M8) engines
• S&S Cycle engineering and quality

Specifications

• Brand: S&S Cycle
• Manufacturer Part #: 920-0151
• Category: Engine Components / Piston Sets - Powersports
• Weight: 3.22 lb

Fitment

Fits 2017 and newer Harley-Davidson Milwaukee-Eight (M8) engines. Available in 4.320-inch, 4.500-inch, and 4.625-inch bore sizes.

Frequently Asked Questions

What bore sizes are available?

This kit comes in three options: 4.320 in, 4.500 in, and 4.625 in. Choose based on your displacement target and build budget.

Will this fit my pre-2017 Harley Twin Cam or Evolution?

No — this kit is designed exclusively for 2017+ Milwaukee-Eight (M8) engines. Twin Cam and Evo owners need different S&S kits.

Is professional installation required?

Yes — cylinder and piston kits require experienced engine builder installation. This is not a bolt-on part and involves significant engine disassembly and machine work.

What's included in the kit?

The kit includes the cylinder, piston, rings, and wrist pin. Gaskets and other engine seals typically require separate purchase.