S&S Cycle 117-128 CI 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.
Unleash serious power from your 2017-later Harley-Davidson Milwaukee-Eight engine with the S&S Cycle 117–128 cubic-inch big bore cylinder and piston kit. This comprehensive upgrade delivers a substantial increase in displacement and performance, ideal for riders seeking a competitive edge.
Why riders pick this
- Increases M8 displacement to 117–128 CI
- Forged pistons with 11:1 compression ratio
- Bolt-on installation requires no machining
- Includes all gaskets and mounting hardware
- Wrinkle black finish with highlighted fins
- Rated for closed-course competition use
The S&S Cycle big bore cylinder and piston kit is engineered to transform your 2017+ Milwaukee-Eight engine, boosting its displacement to a potent 117–128 cubic inches. This kit features high-quality forged pistons designed for durability and performance, allowing your M8 to produce significantly more horsepower and torque. It's a direct upgrade for those looking to maximize their V-twin's output.
High-Performance Engine Upgrade
- Increases Milwaukee-Eight displacement to 117–128 cubic inches
- Features robust forged pistons with an 11:1 compression ratio
- Designed for bolt-on installation without any crankcase machining
- Includes all necessary gaskets and mounting hardware for a complete swap
- Wrinkle black finish with highlighted fins for a custom look
Built for Competition
This S&S Cycle big bore kit is specifically rated for closed-course competition use, offering the displacement and compression needed for aggressive riding. The careful engineering ensures a straightforward installation process, letting you get back on the road or track sooner. For optimal results, consider pairing this kit with a performance cam and a professional dyno tune to fully harness the newfound power.
Specifications
- Brand: S&S Cycle
- Manufacturer Part #: 910-0733A
- Bore x Stroke: 4.25in x 4.5in
- Displacement: 117–128 cubic inches
- Compression Ratio: 11:1
- Piston Type: Forged
- Finish: Wrinkle black
- Weight: 29.75 lb
- Category: Engine Components / Piston Sets - Powersports
Common questions
Will this kit fit my 2017+ Milwaukee-Eight Touring or Softail model?
Yes, this S&S Cycle big bore kit is compatible with all 2017 and newer Harley-Davidson Milwaukee-Eight engines, across both Touring and Softail platforms.
Does this kit require additional engine machining?
No, this S&S Cycle kit is designed for a bolt-on installation, meaning no machining of your crankcases is required.
Is this kit street legal?
No, this S&S Cycle big bore kit is explicitly rated for closed-course competition use only and is not intended for street use.
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 | T14-852160 |
| WEIGHT | 29.75 lb |