S&S Cycle 4.320" Big Bore Cylinder & Piston Kit - Wrinkle Black Highlight for 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.
Experience a significant power boost for your 2017 and newer Harley Milwaukee-Eight with the S&S Cycle 4.320" Big Bore Cylinder and Piston Kit. This kit is designed for a substantial displacement increase, featuring a 4.625-inch stroke and a wrinkle-black finish with highlighted fins.
Why riders pick this
- 4.320" bore with 4.625" stroke for M8
- No crankcase machining required for installation
- Wrinkle black powder coat with highlighted finish
- Includes MLS head gaskets and cam cover badge
- Retains stock engine height for seamless integration
Engineered for performance enthusiasts, this S&S Cycle big bore kit delivers impressive gains without the need for crankcase machining. The precision-crafted cylinders and pistons are designed to bolt directly into your stock M8 cases, providing a straightforward path to more horsepower and torque while maintaining the factory engine height and a refined aesthetic.
Unleash Dominant M8 Performance
- Features a 4.320" bore with an extended 4.625" stroke
- Works with stock M8 crankcases, eliminating the need for machining
- Wrinkle black powder coat with highlighted finish matches factory look
- Includes multi-layered steel (MLS) head gaskets for a superior seal
- Retains stock engine height, preserving your bike's original stance
Engineered for the Demanding Rider
This S&S Cycle big bore kit is a top-tier upgrade for any Milwaukee-Eight owner seeking to maximize their engine's output. While the installation is a direct bolt-on, a professional dyno tune is essential to optimize fuel delivery and ignition timing, ensuring your M8 runs at its peak potential and reliability after this significant displacement increase.
Specifications
- Brand: S&S Cycle
- Manufacturer Part #: 910-0848A
- Bore: 4.320 in.
- Stroke: 4.625 in.
- Weight: 29.56 lb
- Category: Engine Components / Piston Sets - Powersports
- Country of Origin: USA
Common questions
What models does this fit?
This S&S Cycle kit is designed for Harley-Davidson 2017 and newer Milwaukee-Eight (M8) models. Please confirm your specific model year before ordering.
Do I need to have my crankcases machined?
No, this S&S Cycle kit is specifically designed to bolt into stock M8 crankcases without requiring any machine work.
Will this kit require a special tune?
Yes, after installing this big bore kit, a professional dyno tune is highly recommended to optimize your engine's performance, fuel mapping, and ensure proper operation.
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 | T14-852169 |
| WEIGHT | 29.56 lb |