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" displacement cylinder and piston kit is designed for 2017-later Harley Milwaukee-Eight engines, offering substantial horsepower and torque gains. This kit bolts directly into stock crankcases without requiring any machine work or boring, making it a straightforward path to big-inch performance.
Why riders pick this
- Achieve 131" displacement for significant power gains
- Bolts into stock crankcases, no machine work needed
- Retains factory engine appearance and height
- Includes all gaskets and hardware for installation
- Powder coat finish matches OEM components
Unleash serious power from your Milwaukee-Eight with the S&S Cycle 131" Big Bore Cylinder and Piston Kit. This kit is engineered to provide a massive increase in displacement, translating into significant gains in both horsepower and torque for your Harley-Davidson. The best part? It's a true bolt-on upgrade, meaning you can achieve these performance benefits without the need for complex and expensive machine work on your existing crankcases.
Performance Gains, Factory Look
- Delivers 131 cubic inches of displacement
- Bolts directly into stock crankcases, no machining required
- Retains stock engine height and original engine serial numbers
- Powder coat finish matches OEM engine components
- Includes all gaskets and hardware for installation
- Comes with a 131" cam cover badge
Effortless Power Upgrade
Designed for the rider who wants maximum performance without altering the factory appearance of their engine, this S&S Cycle kit is a game-changer. It maintains the original engine height and serial numbers, allowing for a stealthy yet potent upgrade. With all necessary gaskets and hardware included, you have everything you need for a complete and professional installation, transforming your Milwaukee-Eight into a powerhouse on the road.
Specifications
- Brand: S&S Cycle
- Manufacturer Part #: 320-0623
- Displacement: 131 cubic inches
- Bore: 4.250"
- Stroke: 4.625"
- Compression Ratio: 11.0:1
- Weight: 70 lb
- Category: Engine Components / Piston Sets - Powersports
Common questions
Do I need to have machine work done on my crankcase to install this kit?
No, this S&S Cycle 131" kit is designed to bolt directly into stock Milwaukee-Eight crankcases without any boring, honing, or other machine work required.
Will this kit alter the appearance or height of my engine?
This kit is engineered to retain the stock engine height and appearance, allowing your engine to look factory while delivering enhanced performance. An optional 131" cam cover badge is included.
What is the compression ratio of this 131" kit?
The S&S Cycle 131" cylinder and piston kit features an 11.0:1 compression ratio, optimized for performance with Milwaukee-Eight engines.
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 | T14-1026225 |
| WEIGHT | 70.0 lb |