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S&S Cycle M8 High Compression 132/136 in. Big Bore Kits 910-0909A
Part Number: SSY-910-0909A
S&S Cycle M8 High Compression 132/136 in. Big Bore Kits
2017+ M8 Models 132in/136in Big Bore Cylinder Kit +8.5cc Dome (Blk w/ Fins) - 4.320in Bore
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Estimated Ship Date: Dec 16, 2026 Would you rather pick it up?
Overview
Brand:
Manufacturer's Part Number:
910-0909A
Part Type:
Product Line:
Summit Racing Part Number:
SSY-910-0909A
Cylinder Included:
Yes
Pistons Included:
Yes
Piston Material:
Forged aluminum
Piston Rings Included:
Yes
Wrist Pin Included:
Yes
Wrist Pin Bearing Included:
No
Head Gaskets Included:
Yes
Base Gaskets Included:
Yes
Cam Chain Tensioner Gaskets Included:
No
Exhaust Gaskets Included:
No
Valve Cover Gaskets Included:
No
Quantity:
Sold as a kit.
Notes:
A 4 5/8 in. stroke flywheel (not compatible with Harley® 4 5/8 in. stroke flywheel) is required for a 136 c.i. displacement and includes +8.5cc dome pistons. Cylinders are wrinkle black with highlighted fins.
S&S Cycle M8 High Compression 132/136 in. Big Bore Kits
S&S Cycle M8 high-compression 132/136 in. Big Bore kits are high performance engine upgrades for 2017+ Harley-Davidson® Milwaukee-Eight engines, designed to maximize displacement without boring the engine case. They offer significant torque and horsepower gains using 4.320 in. bore cylinders, with the 132 in. kit designed for stock stroke, while 136 in. requires a stroker flywheel.
Key details:
* Performance: Drastically boosts horsepower and torque, offering a "thrilling" ride with improved throttle response
* No case machining: Engineered to fit stock crankcases, avoiding expensive and time-consuming case boring
* Components: Includes 4.320 in. bore cylinders, premium forged pistons, and gaskets
* Compatibility: Fits 2017–25 Touring models and 2018–25 Softails
* Factory appearance: Powdercoated finish matches stock engine finishes
* 132 in. vs 136 in.: The 132 in. kit operates with the stock 4.5 in. stroke, while the 136 in. kit requires a 4.625 in. stroker flywheel to achieve maximum displacement.
* These kits are intended for performance-oriented riders looking for a "bang for buck" upgrade, often requiring supporting modifications like high-flow exhaust, air cleaners, and dyno tuning to achieve best results.
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