Prewired Primary Cover Gasket Kit for Harley Touring M8 2017-up — Complete heat-resistant seal set

Prewired’s Primary Cover Gasket Seal Kit for 2017 and later Touring Milwaukee-Eight Harleys provides a complete set of seals and O-rings to stop oil leaks and restore a reliable primary clutch housing seal.

If you ride a 2017-up Harley-Davidson Touring model with the Milwaukee-Eight engine—Street Glide, Road Glide, Road King, or Electra Glide Ultra Limited—keeping the primary cover sealed is essential to prevent oil loss and maintain clutch performance. This kit supplies the commonly replaced gaskets, O-rings, shaft seal, and retaining ring you’ll need when servicing the primary cover or replacing the derby cover. Components use a metal-core foam rubber construction with a protective outer layer designed to resist heat and return to shape, improving long-term sealing under motorcycle operating conditions.

What parts are included and why they matter?

The kit bundles all primary cover sealing components you’ll typically need during service so you can replace everything at once and reduce repeat disassembly. Each piece addresses a potential leak point in the primary housing and clutch cover assembly.

• One primary cover gasket (part 25700378) — main seal between cover and housing.
• One primary housing gasket (part 25700455) — seals housing mating surface.
• Derby cover O-ring (17369-06) — seals the derby access cover.
• Multiple small O-rings (three 11105 O-rings) — for fasteners and passages.
• Inner primary mainshaft seal (12052A) — prevents oil from the mainshaft.
• Retaining ring (37909-90) — secures internal components during reassembly.

How does this gasket kit improve leak prevention?

Seals in this set are built to resist the heat and pressure typical in Milwaukee-Eight primaries while restoring the correct mating surfaces. The metal-core foam rubber with a protective outer layer helps the gaskets rebound to their intended shape after compression, reducing seepage along fastener lines and around shafts.

• Metal-core foam construction for shape recovery.
• Heat-resistant outer membrane to handle engine temperatures.
• Complete coverage of common sealing points to prevent multiple leak paths.
• Shaft seal and retaining ring address rotating component leaks.

Is this kit easy to install during routine maintenance?

Yes—components are designed as direct-fit replacements for the specified Harley Touring M8 models, allowing straightforward installation when the primary cover or derby cover are removed. Replacing all seals at once minimizes the chance of needing another service soon after reassembly.

• Direct-fit gaskets and O-rings sized for 2017-up Touring M8 models.
• Simple swap for standard primary cover and derby cover maintenance.
• Recommended to replace whenever primary fasteners are loosened or removed.
• Includes inner shaft seal and retaining ring for comprehensive service.

Will this kit keep my clutch running smoothly?

By preventing oil contamination and loss in the primary case, the gasket kit helps maintain clutch engagement and consistent hydraulic or mechanical function. Proper sealing also reduces the risk of oil reaching parts that shouldn’t be lubricated, supporting predictable clutch behavior.

• Stops oil leaks that can contaminate clutch surfaces.
• Maintains correct primary fluid levels and pressure.
• Helps avoid clutch slippage or irregular engagement from oil contamination.

Who this is for: This seal kit is aimed at Harley-Davidson owners, mechanics, and DIY technicians working on 2017 and later Touring Milwaukee-Eight models (Street Glide, Road Glide, Road King, Electra Glide Ultra Limited). It's a practical purchase if you’re performing scheduled primary service, replacing the derby cover, or addressing visible oil seepage from the primary cover area. Prewired offers technical support if you need fitment guidance or post-purchase assistance.