S&S Cycle 4.320" Big Bore Cylinder & Piston Kit - Wrinkle Black for 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 and newer Harley-Davidson Milwaukee-Eight with the S&S Cycle 4.320" Big Bore Cylinder and Piston Kit. This kit is engineered for a substantial increase in displacement and performance, bolting directly into stock crankcases without the need for machining.
Why riders pick this
- 4.320" bore with 4.500" stroke for M8
- No crankcase machining required for installation
- Includes forged pistons and MLS head gaskets
- Wrinkle-black powder coat finish
- Retains stock engine height, includes cam cover badge
Designed for riders who demand more, this S&S Cycle big bore kit features precision 4.320" bore cylinders and forged pistons, ensuring durability and significant power gains. The wrinkle-black powder coat finish blends seamlessly with your M8's factory engine components, maintaining a clean, performance-oriented look while delivering a punch.
Enhanced Performance, Seamless Integration
- Features a 4.320" bore with a 4.500" stroke for increased displacement
- Works with stock M8 crankcases, eliminating the need for machining
- Includes high-quality forged pistons and MLS head gaskets for reliability
- Durable wrinkle-black powder coat finish matches factory aesthetics
- Retains stock engine height, preserving bike geometry
Ready for the Open Road
This S&S Cycle big bore kit is a premier upgrade for any Milwaukee-Eight owner looking to maximize their engine's output. The straightforward bolt-on installation makes it an accessible performance modification. After installation, a professional dyno tune is highly recommended to optimize fuel delivery and timing, ensuring your M8 runs at its peak with the new displacement.
Specifications
- Brand: S&S Cycle
- Manufacturer Part #: 910-0846A
- Bore: 4.320 in.
- Stroke: 4.500 in.
- Weight: 29.56 lb
- Category: Engine Components / Piston Sets - Powersports
Common questions
Do I need to machine my crankcase for this kit?
No, this S&S Cycle kit is engineered to bolt directly into stock M8 crankcases without any machine work, simplifying the installation process.
Will this change my engine height or appearance?
The kit is designed to retain stock engine height, so your bike's proportions will remain unchanged. The wrinkle-black powder coat finish is also designed to match factory components.
What is the benefit of a 4.320" bore?
A 4.320" bore significantly increases your Milwaukee-Eight's engine displacement, leading to substantial gains in both horsepower and torque for improved acceleration and pulling power.
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 | T14-852167 |
| WEIGHT | 29.56 lb |