The 128 Power Package is a complete bolt-on engine upgrade designed to transform 114ci and 117ci oil-cooled Milwaukee-Eight engines into a high-output 128 cubic inch configuration—with no crankcase machining required. Built around proven S&S Cycle components, this kit delivers substantial gains in torque and horsepower while maintaining reliability for aggressive street use.

Engineered for riders who want maximum displacement, stronger mid-range pull, and improved oiling efficiency, this package combines big-bore cylinders, matched pistons, upgraded valvetrain components, and an enhanced oil pump/cam plate system—all in one complete solution. This is basically a Stage 2 & 3 combined into one package.

Note: Not recommended for Tri-Glide or other three-wheel models due to their lugging-style operation.

What’s Included

Big Bore Cylinder & Piston Kit

• Increases displacement from 114ci / 117ci to 128ci
• 4-1/4" bore cylinders with 11:1 forged pistons
• Designed for 4-1/2" stroke Milwaukee-Eight engines
• Direct bolt-on installation with no case machining

Oil Pump & Cam Plate Assembly

• S&S high-volume oil pump with blue anodized cam plate
• Independent scavenge sections for cam chest and flywheel cavity
• Increased oil feed and scavenge capacity
• Adjustable pressure relief valve (adjustable while installed)
• Dual scavenge debris screens and integrated cam-chest magnet
• Removable oil passage plugs for easier servicing

Camshaft

• S&S 550 cam, optimized for big-bore, high-compression applications

Valvetrain Components

• S&S premium tappets
• S&S valve springs rated for cams up to .605" lift
• High-performance conical single-wire spring design
• Hard-anodized black billet aluminum tappet cuffs for improved stability at high lift and RPM

Pushrods

• Quikee adjustable pushrods
• Chrome pushrod tubes

Installation Hardware

• All required gaskets, bearings, and hardware for a complete bolt-on installation