S&S Cycle 131" 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.
The S&S Cycle 131" cylinder and piston kit for 2017-later Harley Milwaukee-Eight engines delivers massive displacement without requiring any machine work. This kit bolts directly into stock crankcases, retaining original engine height and appearance for a true sleeper build.
Why riders pick this
- Massive 131" displacement for significant power increase
- Bolts directly into stock M8 crankcases, no machining needed
- Retains stock engine height and original appearance
- Powder coat finish matches OEM engine components
- Includes all gaskets for installation
Unleash the full potential of your Milwaukee-Eight with the S&S Cycle 131" Big Bore Cylinder and Piston Kit. This comprehensive kit provides a significant boost in displacement, translating directly into substantial horsepower and torque gains. Designed for ease of installation, it eliminates the need for costly and time-consuming machine work on your factory crankcases, making it a highly accessible performance upgrade.
Bolt-On Power and Stealth Appeal
- Achieves 131 cubic inches of displacement
- Works with stock M8 crankcases, no machine work required
- Retains stock engine height and original appearance
- Powder coat finish matches factory engine components
- Includes all gaskets for a complete installation
- Comes with a 131" cam cover badge
Performance Without Compromise
This S&S Cycle kit is engineered for riders who demand serious power but prefer to maintain a factory-like aesthetic. By keeping the stock engine height and look, your bike will have a stealthy advantage on the street. The kit includes everything necessary for a complete and professional installation, ensuring a smooth transition to a higher-performing Milwaukee-Eight engine. Experience the thrill of a big-inch motor without the typical complexities of such an upgrade.
Specifications
- Brand: S&S Cycle
- Manufacturer Part #: 320-0622
- Bore: 4.250 in
- Stroke: 4.625 in
- Compression Ratio: 11.0:1
- Weight: 70 lb
- Category: Engine Components / Piston Sets - Powersports
Common questions
Do I need to have my cylinder bored or any machine work done for this kit?
No, this S&S Cycle 131" kit is designed to bolt directly into stock Milwaukee-Eight crankcases with zero machine work required, simplifying the installation process.
Will this kit change the visible appearance of my engine?
The kit retains stock engine height and appearance, keeping a 'sleeper' look. An optional 131" cam cover badge is included if you choose to highlight the upgrade.
Is everything I need for installation included in this kit?
Yes, the S&S Cycle 131" cylinder and piston kit includes all necessary gaskets, cylinders, pistons, rings, and wristpins for a complete bolt-on installation.
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 | T14-1026224 |
| WEIGHT | 70.0 lb |