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 2017+ Harley-Davidson M8 models, featuring a 4.320 in. bore that bolts into stock crankcases without machine work. Includes wrinkle-black powder coat cylinders, forged pistons, and MLS head gaskets for a substantial displacement increase and power gain.

Features

• 4.320 in. bore with 4.500 in. stroke
• Works with stock crankcases — no machining required
• Forged pistons and MLS head gaskets included
• Wrinkle-black powder coat finish
• Retains stock engine height
• Cubic Inch cam cover badge included
• Made in USA

Specifications

• Brand: S&S Cycle
• Manufacturer Part #: 910-0846A
• Bore: 4.320 in.
• Stroke: 4.500 in.
• Weight: 29.56 lb
• Category: Engine Components / Piston Sets - Powersports

Fitment

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

Frequently Asked Questions

Do I need to machine my crankcase for this kit?

No — this kit is engineered to bolt into stock M8 crankcases without any machine work.

Will this change my engine height or appearance?

The kit retains stock engine height, so your bike's proportions remain unchanged.

What's included in the box?

Cylinders, pistons, rings, pin retainers, MLS head gaskets, and a cubic inch cam cover badge.

Is this a complete engine build, or just cylinders and pistons?

This is a cylinder and piston kit. Depending on your build, you may also need cams, rocker boxes, or ignition components from S&S or your tuner.

How much displacement does this give me?

S&S offers this kit in multiple bore sizes. Check your specific model documentation for final cubic inch rating.