S&S Cycle 4.250" Bore Cylinder & Piston Kit - Harley Milwaukee-Eight
About S&S Cycle
S&S Cycle has built American V-twin performance parts in Viola, Wisconsin since 1958 — flywheels, carburetors, cams, cylinder heads and complete crate engines. When a Harley owner talks about a 124, a 128 or a 131 build, they are usually talking about S&S. Few names carry more weight with engine builders in this space.
Unleash the full potential of your Milwaukee-Eight engine with the S&S Cycle 4.250" Bore Cylinder & Piston Kit. This kit provides a significant boost in displacement, transforming your stock M8 into a true performance V-twin. Engineered for power and durability, it's the foundation for serious engine builds.
Why riders pick this
- Designed for 2017+ Milwaukee-Eight engines
- Increases engine displacement for more power
- Direct replacement or performance upgrade
- Robust construction for high-output builds
When you're chasing more power from your Milwaukee-Eight, the S&S Cycle 4.250" Bore Cylinder & Piston Kit delivers the displacement needed to get there. Designed as a direct replacement or an upgrade for custom high-performance builds, these components are built to handle the demands of a high-output V-twin. This kit is a critical step for riders looking to uncork their M8 and lay down serious torque.
Built for Bigger Power
- Engineered for 2017 and newer Milwaukee-Eight engines
- Increases engine displacement for enhanced torque and horsepower
- Direct replacement for stock components or a foundation for larger builds
- Pistons feature oversized pins for robust performance
The Core of a Performance Build
Installing a big bore kit is a fundamental upgrade for any M8 rider looking to push their bike's limits. These S&S cylinders and pistons are precision-matched to ensure optimal performance and longevity. Pair this kit with an S&S cam and a proper dyno tune to fully realize the power gains and create a Milwaukee-Eight that truly stands apart.
Specifications
- Brand: S&S Cycle
- Manufacturer Part #: 920-0148
- Bore Size: 4.250 in
- Stroke: 4.625 in
- Oversized: 0.010 in
- Weight: 3.22 lb
- Category: Engine Components / Piston Sets - Powersports
Common questions
Will this kit fit my specific Milwaukee-Eight model?
This S&S Cycle kit is designed for 2017 and newer Milwaukee-Eight engines. Please use our Shop by Bike tool to confirm fitment for your exact year and model.
Do I need to modify my engine cases for this kit?
This kit is designed to be a direct fit for Milwaukee-Eight engines. However, the cylinders require boring and honing to the 4.250" diameter before installation.
Will I need a new engine tune after installing this kit?
Yes, increasing your engine's displacement will require a professional dyno tune to optimize fuel delivery and ignition timing for the new setup.
Ordering from Vtwinbikers
- Brand new, sourced through authorized US distribution — never used, never grey-market.
- Not sure it fits? Use Shop by Bike to filter by your year and model, or email us and we will confirm before you order.
- Harley-Davidson and Indian Motorcycle is all we do, so you are talking to people who ride what you ride.
| BRAND | S&S Cycle |
| TYPE | Piston Sets - Powersports |
| SKU | T14-662031 |
| WEIGHT | 3.22 lb |
