Overview

S&S Cycle M8 136 in. Big Bore Kits

S&S Cycle M8 136 in. Big Bore kits are high performance engine upgrades for 2017+ Harley-Davidson® Milwaukee-Eight (M8) engines, maximizing displacement to 136 cu. in. while retaining stock engine height and serial numbers. They are among the largest bolt-on options available, designed to fit stock crankcases without machining, available for touring and softail models.

Key details:

* Massive displacement: Creates 136 cu. in. (4.320 in. x 4.625 in.) by increasing the bore, designed to work with a 4 5/8 in. stroke flywheel
* Compatibility: Designed for 2017-23 Harley Touring (oil-cooled) and 2018+ Softail models
* No case machining: Fits directly into stock crankcases, retaining original engine serial numbers
* Components: Includes high-quality pistons, cylinders, rings, and gaskets, with finishes that match factory power coating
* Performance: Delivers high torque and horsepower, often requiring upgraded tires, brakes, and a high-performance clutch
* These kits are a "sleeper" performance option, meaning they maintain a stock appearance while providing significant power increases, often aimed at users looking for maximum power. They typically require an S&S 4 5/8 in. flywheel assembly and other supporting upgrades for best results.

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