S&S Cycle 128 Power Package Fits Harley-Davidson Oil-Cooled M8 114 and 117 2017-2022

S&S Cycle 128 Power Package Fits Harley-Davidson Oil-Cooled M8 114 and 117 2017-2022

Lift a stock oil-cooled Milwaukee-Eight 114 or 117 to 128 cubic inches with one bolt-on big-bore kit. The S&S Cycle 128 Power Package is a no-case-machining cylinder, piston, cam-chest, and oil-pump conversion built around the larger-bore M8 architecture.

Key Features

• Complete 128 cubic-inch big-bore conversion kit, bolt-on with no case machining required
• S&S 114/117-to-128 inch big-bore cylinder set with 4.250 inch bore and S&S forged pistons at 11.1:1 compression
• S&S 550 cam designed to fit big-bore applications, available in chain-drive or gear-drive configuration
• S&S precision-machined billet aluminum oil pump and cam plate with removable passage plugs for servicing, independent scavenge sections, debris screens, a cam-chest magnet, increased flow capacity on both supply and scavenge sides, and an adjustable pressure-relief valve
• S&S Quickee pushrods with chrome covers
• S&S precision tappets and hard-anodized black billet aluminum tappet cuffs – stronger than stock material, eliminates distortion
• S&S high-performance conical single-wire valve springs that support cams up to .605 inch lift
• Chain-drive variations include the S&S precision billet aluminum cam-chain tensioner
• Available finishes: Black/Highlighted Fins, Black/Non-Highlighted Fins, Black Granite/Highlighted Fins

Technical Specifications

• Displacement: 128 cubic inches (from 114 or 117 ci stock)
• Bore: 4.250 inch
• Compression Ratio: 11.1:1
• Camshaft: S&S 550, chain-drive or gear-drive
• Oil Pump and Cam Plate: S&S precision-machined billet aluminum, removable passage plugs, independent scavenge, adjustable pressure-relief valve
• Pushrods: S&S Quickee with chrome covers
• Tappets: S&S precision with hard-anodized billet aluminum tappet cuffs
• Valve Springs: S&S conical single-wire, supports up to .605 inch lift
• Country of Origin: United States

Fitment Notes

• Compatible with Harley-Davidson 2017-2022 oil-cooled Milwaukee-Eight Touring and Softail chassis with 114 or 117 cubic-inch base displacement.
• Excludes 107 cubic-inch M8 platforms (covered by the 124 Power Package) and excludes Twin-Cooled configurations (covered by the 128 Power Package WOC family).
• S&S M8 head bolts (PN 900-1006) are required for installation and sold separately.
• The kit assumes a serviceable 2017-2022 oil-cooled M8 114 or 117 crankcase as the installation base; throttle body, intake, exhaust, and ECM tune are not included.
• The new 128 displacement requires an ECM calibration flash.
• Refer to the Fitment tab for the full platform breakdown.
• Not affiliated with or endorsed by Harley-Davidson.