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Start ShoppingCometic C9179F5 Evo Big Twin Primary Housing Gasket - High-Performance Replacement for Harley-Davidson
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Description
Ensure optimal engine performance with this high-quality primary housing gasket designed for Harley-Davidson Big Twin engines. Cometic's advanced fiber/composite material (F5 series) delivers superior sealing and durability, making it an ideal upgrade for riders seeking enhanced reliability and longevity.
Key Features
- Material: Cometic Fiber/Composite (F5 Series) for heat resistance and long-term durability
- Application: Precision-engineered for Harley-Davidson Big Twin/Twin Cam primary housing
- Sealing Performance: Prevents oil leaks and maintains critical engine compartment integrity
- Construction: Reinforced composite structure withstands high temperatures and pressure
Why Choose This Product
Upgrade your engine's reliability with a gasket engineered for extreme conditions. This Cometic primary cover gasket offers superior sealing capabilities compared to OEM parts, reducing maintenance intervals and preventing costly engine damage. Its USA-made construction ensures consistent quality, while the F5 series material provides exceptional resistance to thermal degradation and chemical breakdown. Perfect for both daily riders and performance enthusiasts looking to maintain peak engine efficiency.
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Ensure optimal engine performance with this high-quality primary housing gasket designed for Harley-Davidson Big Twin engines. Cometic's advanced fiber/composite material (F5 series) delivers superior sealing and durability, making it an ideal upgrade for riders seeking enhanced reliability and longevity.
Key Features
- Material: Cometic Fiber/Composite (F5 Series) for heat resistance and long-term durability
- Application: Precision-engineered for Harley-Davidson Big Twin/Twin Cam primary housing
- Sealing Performance: Prevents oil leaks and maintains critical engine compartment integrity
- Construction: Reinforced composite structure withstands high temperatures and pressure
Why Choose This Product
Upgrade your engine's reliability with a gasket engineered for extreme conditions. This Cometic primary cover gasket offers superior sealing capabilities compared to OEM parts, reducing maintenance intervals and preventing costly engine damage. Its USA-made construction ensures consistent quality, while the F5 series material provides exceptional resistance to thermal degradation and chemical breakdown. Perfect for both daily riders and performance enthusiasts looking to maintain peak engine efficiency.| SKU | GM04AB36AB |
|---|---|
| MPN | C9179F5 |
| Brand | Cometic |
| Category | Gaskets/Seals |
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Frequently Asked Questions
Generally no—Cometic primary housing gaskets are designed to be installed dry on clean, flat surfaces. Follow your Harley-Davidson service manual; if it doesn’t call for sealant, install the gasket dry.
Primary cover gaskets are considered single‑use. For best sealing and to avoid leaks, replace the gasket every time the primary cover is removed.
Cometic gaskets are high‑quality aftermarket parts typically using robust composite materials and precise die‑cutting. Many builders and shops use them as an equal or upgraded alternative to OEM, especially for leak resistance.
It will address leaks caused by a worn or damaged primary cover gasket, but leaks from seals (mainshaft, shifter, stator grommet, etc.) will require those specific parts to be replaced as well.
Yes. You should drain the primary/transmission cavity before removing the primary cover, then refill with the correct fluid and volume after reassembly.
Installation Guide
Difficulty
Medium
Est. Time
1 hr 0 min
Tools Required
- Harley-Davidson service manual for your exact model
- Socket set and ratchet (SAE)
- Allen/hex keys or Torx bits (model dependent)
- Torque wrench capable of low torque settings
- Primary fluid drain pan
- Plastic or rubber scraper (for old gasket removal)
- Brake cleaner or suitable solvent
- Lint‑free rags
- Primary drive locking tool or similar (depending on model, if removing compensator/clutch)
- New primary fluid and new derby cover O‑ring (recommended)
Pro Tips
- Test‑fit the gasket on the primary cover before installation to confirm orientation
- Clean both mating surfaces thoroughly and ensure they are flat and dry before installing
- Hand‑start all cover bolts, then tighten in a criss‑cross pattern to factory torque spec
- Allow any recommended cure time (if using threadlocker) before riding
- Replace primary fluid and inspect chain, tensioner, and stator while the cover is off
- Check for nicks or damage on the primary cover and engine case sealing surfaces; dress lightly if needed
Common Mistakes to Avoid
- Reusing old or damaged primary gasket instead of replacing
- Not fully removing old gasket material, causing sealing issues
- Using metal scrapers that gouge aluminum sealing surfaces
- Over‑tightening or unevenly tightening primary cover bolts
- Skipping torque sequence specified in the service manual
- Using RTV or sealant where a dry gasket is specified (can cause leaks or squeeze‑out)
- Not cleaning bolt holes of old threadlocker or fluid
Comparison vs Stock/OEM
Cometic C9179F5 is an aftermarket replacement for the OEM Harley-Davidson primary cover gasket for specific Evo Big Twin and Twin Cam models. Cometic uses high-quality composite materials and precise die-cutting intended to meet or exceed OEM sealing performance.
Improvements
- High-quality composite material designed for better long-term sealing compared to many generic aftermarket gaskets
- Precise cut and bolt hole alignment for consistent fit
- Commonly preferred by performance engine builders and shops
Considerations
- Must confirm exact model/year fitment using a catalog or retailer fit tool, as Big Twin and Twin Cam primary gaskets vary by year and model
- Installation quality (surface prep, torque, and cleanliness) has a large impact on leak prevention regardless of gasket brand
Durability & Warranty
Expected Lifespan
Intended to last the service life of the primary cover installation; typically replaced only when the primary cover is removed again or if disturbed.
Warranty
Standard Cometic limited warranty against defects in materials and workmanship (specific terms vary by distributor).
Maintenance
No direct maintenance; periodically inspect primary case for leaks and correct fluid level as part of regular service.
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