S&S Cycle 4.320" Big 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.
Upgrade your Milwaukee-Eight with the S&S Cycle Cylinder and Piston Kit, engineered to deliver significant displacement and power gains. This kit increases your bore to 4.320 inches, transforming your M8's performance potential. It's designed for a straightforward installation without requiring any machine work to your stock crankcases.
Why riders pick this
- Significant displacement and power gain for Milwaukee-Eight
- No machine work required on stock crankcases
- Maintains factory engine height and aesthetics
- Durable wrinkle black powder coat finish
- Includes MLS head gaskets for optimal sealing
This S&S Cycle big bore kit is a direct bolt-on solution for 2017 and newer Harley-Davidson Milwaukee-Eight engines, allowing you to uncork more horsepower and torque. The carefully engineered cylinders maintain factory engine height and aesthetics while providing a substantial increase in bore. Each kit includes high-quality components designed for durability and performance, ensuring your M8 runs stronger and longer.
Bolt-On Performance for Your M8
- Increases bore to 4.320 inches for significant displacement gain
- Installs into stock crankcases without the need for machining
- Maintains factory engine height for a clean look
- Features a wrinkle black powder coat finish
- Includes multi-layered steel (MLS) head gaskets for a reliable seal
Engineered for the Modern V-Twin Rider
The S&S Cycle 4.320" Big Bore Kit is ideal for riders looking to maximize their Milwaukee-Eight's output without extensive engine modifications. This kit pairs well with a performance cam and a proper dyno tune to fully realize its potential. Experience the S&S difference in power and reliability on the open road or at the drag strip.
Specifications
- Brand: S&S Cycle
- Manufacturer Part #: 910-0849A
- Bore: 4.320 in.
- Stroke: 4.625 in.
- Weight: 29.56 lb
- Finish: Wrinkle black
- Category: Engine Components / Piston Sets - Powersports
Common questions
Will this kit fit my pre-2017 Harley Twin Cam?
No, this S&S Cycle kit is specifically engineered for 2017 and newer Harley-Davidson Milwaukee-Eight engines. Twin Cam engines require a different S&S Cycle kit.
Do I need to have my crankcases machined for installation?
No, this kit is designed for a direct bolt-in installation with stock Milwaukee-Eight crankcases, requiring no machine work.
What's included in this cylinder and piston kit?
This kit includes cylinders, pistons, multi-layered steel (MLS) head gaskets, and a cubic inch cam cover badge. All components are designed for a complete top-end upgrade.
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 | T14-852170 |
| WEIGHT | 29.56 lb |