S&S Cycle Big Bore Cylinder & Piston Kit 4.250" Bore - Harley Milwaukee-Eight Touring
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.
The S&S Cycle Big Bore Cylinder and Piston Kit is a bolt-on solution to significantly increase the displacement of your Harley Milwaukee-Eight Touring engine. This kit delivers increased power and torque without the need for costly machining, featuring forged pistons and a 4.250" bore. It's a direct path to a larger, more potent V-twin powerplant.
Why riders pick this
- Bolt-on installation, no machining required for cases
- Forged pistons with 11:1 compression ratio
- 4.250" bore cylinders for increased displacement
- Includes all gaskets and installation hardware
- Wrinkle black finish with highlighted fins
- Designed for Harley Milwaukee-Eight Touring engines
For riders seeking a substantial bump in power from their Milwaukee-Eight Touring engine, the S&S Cycle Big Bore Cylinder and Piston Kit offers an impressive upgrade. This kit is designed for straightforward installation, eliminating the need for complex and expensive machining often associated with big bore conversions. By increasing the bore to 4.250" and utilizing high-quality forged pistons, your engine gains significant displacement, translating directly into more usable torque and horsepower across the RPM range. It's a complete package for transforming your V-twin's performance.
Unleash More Displacement and Power
- Bolt-on installation requires no machining of your engine cases
- Includes durable forged pistons with an 11:1 compression ratio
- Features 4.250" bore cylinders for increased displacement
- Comes complete with all necessary gaskets and installation hardware
- Stylish wrinkle black finish with highlighted fins for a custom look
Effortless Power Increase
This S&S Cycle kit makes big bore performance accessible, providing everything you need for a significant displacement increase in one package. The inclusion of all gaskets and hardware simplifies the installation process. While designed for a bolt-on fit, S&S recommends pairing this kit with their specific head bolts for optimal security and performance in all big bore applications. A proper dyno tune will be essential to maximize the benefits of this upgrade and ensure your engine runs optimally with the increased displacement and compression.
Specifications
- Brand: S&S Cycle
- Manufacturer Part #: 910-0625
- Bore Diameter: 4.250 inches
- Compression Ratio: 11:1
- Displacement Range: 107-124 cubic inches
- Weight: 31 lb
- Category: Engine Components / Piston Sets - Powersports
Common questions
Do I need to machine my engine cases for this big bore kit?
No, this S&S Cycle Big Bore Cylinder and Piston Kit is designed for bolt-on installation and does not require any machining of your engine cases.
Will I need a new fuel tune after installing this kit?
Yes, increasing your engine's displacement and compression will require a proper dyno tune and updated fuel map to ensure optimal performance, prevent damage, and unlock the full potential of the upgrade.
What is included with this cylinder and piston kit?
This kit includes the 4.250" bore cylinders, forged pistons with an 11:1 compression ratio, and all necessary gaskets and installation hardware for a complete bolt-on 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 | T14-619446 |
| WEIGHT | 31.0 lb |
| 11 | 1 Compression |
