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 Milwaukee-Eight (M8) engines, featuring a 4.250-inch bore and wrinkle black finish. Bolt-on design increases displacement for added horsepower and torque on stock or modified M8 platforms.

Features

• 4.250 inch bore
• Bolt-on cylinder design for M8 engines
• Wrinkle black finish
• Without highlighted cylinder fins

Specifications

• Brand: S&S Cycle
• Manufacturer Part #: 910-0683A
• Bore Size: 4.250 inch
• Finish: Wrinkle black
• Weight: 24.85 lb
• Category: Engine Components / Piston Sets - Powersports

Fitment

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

Frequently Asked Questions

Does this fit Twin Cam or Milwaukee-Eight engines?

Milwaukee-Eight (M8) only — 2017 and newer. Twin Cam models require a different S&S Cycle big bore kit.

What horsepower gain can I expect?

Horsepower increase depends on your specific M8 model, fuel octane, and other modifications. Contact S&S or your dealer for dyno estimates.

Do I need a tuner with this kit?

A fuel controller or ECU tune is strongly recommended to optimize performance and drivability with the larger displacement.

Is this a complete engine rebuild, or just the cylinders?

This kit includes cylinders and pistons. You will need gaskets, push rods, and other engine internals from your engine builder or S&S for a full rebuild.

What's the warranty on this kit?

Refer to S&S Cycle's warranty documentation. Most engine components carry limited manufacturer warranty — verify before installation.