S&S Cycle 4.250" Big Bore Cylinder & Piston Kit Highlighted - 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.
This S&S Cycle big bore cylinder and piston kit is a bolt-on upgrade for Harley-Davidson Milwaukee-Eight (M8) models, featuring a 4.250-inch bore. It's designed to increase displacement and horsepower over stock M8 engines, and is finished in wrinkle black with highlighted cooling fins for a custom look.
Why riders pick this
- Bolt-on cylinder set for Milwaukee-Eight engines
- 4.250-inch bore for increased displacement
- Wrinkle black finish with highlighted cooling fins
- Includes complete piston and ring package
- Designed to boost horsepower over stock M8 engines
- No machining required for installation
When it's time to add serious displacement and power to your Milwaukee-Eight, this S&S Cycle big bore cylinder and piston kit delivers. Engineered for straightforward installation, this kit eliminates the need for complex machining, getting you back on the road faster with a significant boost in performance. The wrinkle black finish with highlighted fins also adds a touch of custom style to your engine.
Unleash More Power
- Bolt-on cylinder set designed for Milwaukee-Eight engines
- Increases displacement with a 4.250-inch bore
- Wrinkle black finish with contrasting highlighted cooling fins
- Includes a complete piston and ring package for each cylinder
- Engineered to provide a noticeable increase in horsepower
A Foundation for Your Performance Build
Upgrading to a big bore kit is a cornerstone of any serious Milwaukee-Eight performance build. This S&S Cycle kit provides the displacement, but remember that optimizing your cam choice, air intake, exhaust system, and especially a professional dyno tune, are crucial for unlocking its full potential. Ensure your M8 is properly dialed in to handle the increased power and run reliably.
Specifications
- Brand: S&S Cycle
- Manufacturer Part #: 910-0682A
- Bore Size: 4.250 in.
- Finish: Wrinkle black with highlighted fins
- Weight: 29.56 lb
- Category: Engine Components / Piston Sets - Powersports
Common questions
What horsepower gain can I expect with this big bore kit?
Horsepower gains vary significantly by final displacement, engine setup, and tuning. For specific dyno results, we recommend contacting S&S Cycle or your trusted Harley-Davidson dealer for figures relevant to your model.
Do I need to retune my Milwaukee-Eight engine after installing this kit?
Yes, a fuel and ignition tune is strongly recommended and often required after installing a big bore kit. This ensures optimal performance, drivability, and engine longevity with the increased displacement.
Is professional installation recommended for this cylinder and piston kit?
While this is a bolt-on kit, engine internal work requires precision. Professional installation by an experienced V-twin mechanic is highly recommended to ensure proper assembly, clearances, and a reliable build.
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 | T14-852156 |
| WEIGHT | 29.56 lb |