S&S Cycle 124″ Big Bore Kit For Harley 107″ Milwaukee-Eight 2017-2026

S&S 124″ Big Bore: Unlocking the Heart of the M8 for 2026

The S&S Cycle 124″ Big Bore Kit for 2017-2026 Harley-Davidson 107ci Milwaukee-Eight models represents the 2026 pinnacle of bolt-on engine architecture. In the M8 era, displacement is the most direct path to massive torque, but traditionally, reaching these figures required a complete engine teardown and expensive crankcase machining. S&S has engineered a solution that allows 107ci owners to reach 124ci displacement using high-precision 4.250″ bore cylinders that fit directly into the stock case spigots. This kit transforms the power character of your motorcycle, providing an immediate and violent increase in acceleration and passing power. For the rider seeking secure, industrial-strength utility and a displacement that commands respect, the S&S 124″ kit is the definitive 2026 upgrade for the 107″ platform.

Forged Precision and Thermal Stability

What sets the S&S 124″ kit apart in the 2026 marketplace is the uncompromising quality of its internal components. The kit features forged aluminum pistons with an 11.0:1 compression ratio, which provides a significant boost in “snap” and throttle response while remaining compatible with 2026 pump fuels. These pistons are engineered with advanced skirt coatings to reduce friction and mechanical noise, ensuring your engine remains whisper-quiet at idle but ferocious under load. The cylinders themselves are constructed with high-tensile cast-in liners that resist warping under the extreme cylinder pressures of a high-output 2026 build. This thermal resilience is critical for maintaining a perfect ring seal, preventing oil consumption, and ensuring the high-output 2026 presence and longevity that professional engine builders demand.

Expert Installation & Performance Advice

As specialists in Milwaukee-Eight engine dynamics, we recommend the 124″ kit as the foundation for any serious 2026 project. Pro Tip: To truly unlock the potential of 124 cubic inches, pair this kit with an S&S 550 Cam and the S&S 55mm Aluminum Manifold to ensure the engine isn’t “choked” at high RPM. Installation Note: Always check your piston-to-valve clearance if using high-lift aftermarket cams with this kit. Maintenance Note: Proper 2026 break-in is essential; follow a strict heat-cycle regimen and change the oil after the first 50, 500, and 1,000 miles to ensure the rings seat perfectly. Safety Note: Because this kit vastly increases airflow and compression, a professional dyno tune via Dynojet Power Vision is mandatory to prevent detonation and ensure your 2026 engine runs cool and powerful.

The Professional Standard for M8 Displacement Upgrades

Choosing the S&S Cycle 124″ Big Bore Kit means investing in unmatched mechanical stability and a refined power signature. It offers a unique combination of modern metallurgical strength and a proven design that honors the performance legacy of the Harley-Davidson brand. For the rider who wants a high-output 2026 presence and a flawless engineering finish, the S&S 124″ Kit is the unmatched leader. Supersize your power, eliminate the lag, and ride the distance.

Features

• 107″ to 124″ bolt on bore kit (no machining required)
• 4.250″ Bore
• Forged pistons
• 11.1:1 Compression ratio
• Includes gaskets and hardware