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Start ShoppingCometic C9173 Evo Big Twin Primary Housing Gasket - High-Performance Fiber Graphite Gasket for Harley-Davidson
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Description
Upgrade your Harley-Davidson Big Twin's primary housing seal with Cometic's C9173 gasket. This high-performance fiber/graphite composite gasket delivers exceptional sealing reliability and durability for demanding powersports applications.
Key Features
- Cometic AFM Material: Advanced aluminum foam matrix with graphite composite provides superior heat resistance and sealing integrity.
- Specifically Designed for: Harley-Davidson Big Twin primary cover applications with no metal core construction.
- Non-Reusable Design: Single-use gasket ensures optimal sealing without risk of degradation from repeated installation.
- Easy Installation: Pre-coated elastomer surface eliminates need for RTV unless specified by service manual.
- Complete Replacement: Single gasket included for full primary cover sealing system.
Why Choose This Product
Cometic's C9173 gasket is engineered for high-performance powersports engines, offering enhanced durability and sealing reliability compared to standard OEM gaskets. The fiber/graphite composite construction resists compression set and thermal breakdown, ensuring long-term sealing integrity. This non-metal core design eliminates potential friction points while maintaining exceptional oil and gas sealing capabilities. Ideal for riders seeking reliable performance during primary drive or clutch service operations.
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Upgrade your Harley-Davidson Big Twin's primary housing seal with Cometic's C9173 gasket. This high-performance fiber/graphite composite gasket delivers exceptional sealing reliability and durability for demanding powersports applications.
Key Features
- Cometic AFM Material: Advanced aluminum foam matrix with graphite composite provides superior heat resistance and sealing integrity.
- Specifically Designed for: Harley-Davidson Big Twin primary cover applications with no metal core construction.
- Non-Reusable Design: Single-use gasket ensures optimal sealing without risk of degradation from repeated installation.
- Easy Installation: Pre-coated elastomer surface eliminates need for RTV unless specified by service manual.
- Complete Replacement: Single gasket included for full primary cover sealing system.
Why Choose This Product
Cometic's C9173 gasket is engineered for high-performance powersports engines, offering enhanced durability and sealing reliability compared to standard OEM gaskets. The fiber/graphite composite construction resists compression set and thermal breakdown, ensuring long-term sealing integrity. This non-metal core design eliminates potential friction points while maintaining exceptional oil and gas sealing capabilities. Ideal for riders seeking reliable performance during primary drive or clutch service operations.| SKU | GM3E414C0B |
|---|---|
| MPN | C9173 |
| UPC/GTIN | 191070004705 |
| Brand | Cometic |
| Category | Gaskets/Seals |
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Featured Review
| Make | Model | Years |
|---|---|---|
| Harley-Davidson | Big Twin models (Evo and early Twin Cam with cable clutch) | 1989-2006 |
Frequently Asked Questions
Yes, C9173 is cataloged for Evolution Big Twin primary covers and early Twin Cam Big Twin models that use the same style primary housing. Always confirm with your specific year/model and OEM part number.
No. Cometic primary housing gaskets like C9173 are designed as single‑use service gaskets. Replace it every time the primary cover is removed.
In most cases, no additional RTV sealant is required on the main sealing surface—install it dry on clean surfaces as per your Harley‑Davidson service manual. Some manuals may call for a small dab of sealant at specific joints; follow the factory procedure.
No, Cometic C9173 is only the primary housing/cover gasket. Derby cover gaskets, inspection cover gaskets and shaft seals are sold separately or in complete gasket kits.
Fitment is primarily listed for Evo Big Twin and early Twin Cam 88 models. Later Twin Cam primaries often use different gaskets. Verify by year, model, and OEM part number before ordering.
Installation Guide
Difficulty
Medium
Est. Time
1 hr 0 min
Tools Required
- Harley-Davidson service manual for the specific model
- Socket set and ratchet (SAE)
- Allen/hex wrenches (for derby and inspection covers as applicable)
- Torque wrench (inch‑lb and ft‑lb, depending on model)
- Primary fluid drain pan
- Plastic scraper or gasket scraper (plastic/nylon recommended)
- Brake cleaner or suitable solvent for cleaning gasket surfaces
- Shop rags
- New primary fluid
Pro Tips
- Dry‑fit the gasket on the cover or case first to confirm orientation before applying it for final assembly.
- Clean both sealing surfaces thoroughly and ensure they are dry and free of oil before installing the new gasket.
- Use a plastic scraper to remove old gasket material to avoid gouging the aluminum.
- Follow the factory torque sequence and specs exactly to prevent warping the cover.
- Refill primary with the correct type and amount of primary fluid, then check for leaks after a short test ride.
Common Mistakes to Avoid
- Re‑using old primary gasket instead of replacing it
- Over‑tightening primary cover bolts and distorting the gasket
- Not cleaning old gasket material completely from mating surfaces
- Failing to check and replace worn seals (mainshaft, shifter, inspection cover O‑rings) while the primary is open
- Installing gasket backwards or misaligned over locating dowels/bolt holes
- Not torquing bolts in a criss‑cross pattern to spec from the service manual
Comparison vs Stock/OEM
Per retailer descriptions, Cometic replacement primary gaskets meet or exceed OEM sealing performance at a lower cost.
Improvements
- High‑quality gasket material designed to resist oil saturation and breakdown
- Consistent thickness and cut for reliable fitment
- Often preferred by performance engine builders who favor Cometic sealing products
Considerations
- Does not include any additional OEM hardware or seals—only the primary cover gasket
- Always follow OEM torque specs and procedures; gasket alone will not compensate for warped or damaged covers
Durability & Warranty
Expected Lifespan
Designed to last until the next primary service or cover removal; typical interval can be tens of thousands of miles when properly installed and surfaces are in good condition.
Warranty
Standard Cometic limited warranty against defects in materials and workmanship (terms vary by seller; check retailer or Cometic warranty policy).
Maintenance
Periodically inspect around the primary cover for signs of oil seepage. If the cover is removed again for service, replace the gasket rather than re‑using it.
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