Why Choose Cometic EST Gaskets?
Harley-Davidson Evolution Big Twin engines are known for their distinctive air-cooled V-twin design, but age, thermal cycling, and gasket deterioration can lead to oil seepage and combustion sealing problems.
Cometic’s EST gasket technology combines embossed stainless steel components with specialized rubber-based sealing materials.
The cylinder head gasket construction is designed to manage heat around the combustion sealing area and distribute it across the gasket surface.
When installed on properly prepared mating surfaces, these components help maintain sealing integrity throughout normal engine operation.
Common Signs Your Harley Evolution Top End Needs Attention
An aging Evolution Big Twin may develop several symptoms associated with deteriorating top-end gaskets:
- Oil seepage around the cylinder bases
- Oil leaks near rocker box covers
- Combustion leakage at the cylinder head joint
- Reduced compression caused by sealing problems
- Persistent oil residue collecting around the engine
These symptoms can have other causes, so inspect and diagnose the engine before disassembly.
Installation Recommendations
- Confirm the motorcycle model and Evolution Big Twin engine configuration.
- Verify the cylinder bore remains compatible with the 3.500-inch gasket opening.
- Inspect the cylinder heads and cylinder sealing surfaces.
- Check cylinder base and rocker assembly mating surfaces for damage.
- Clean all mating surfaces without scratching or gouging them.
- Install the correct gaskets and O-rings in their designated locations.
- Follow the Harley-Davidson service manual for fastener tightening procedures.
- Verify pushrod adjustment and valvetrain assembly as applicable.
- Reassemble the engine and check fluid levels.
- Inspect for oil and combustion leaks after startup.
Frequently Asked Questions
Does Cometic C9635 fit a 1997 Harley-Davidson Fat Boy?
Yes. The 1997 FLSTF Fat Boy with its original compatible 1340cc Evolution engine is a listed application.
Will this kit fit a 1998 Harley Road King?
Yes. The 1998 FLHR Road King is included in Cometic’s published fitment list.
Does C9635 fit a 2000 Harley-Davidson Twin Cam engine?
No. This kit is intended for the earlier Evolution Big Twin engine family, not Twin Cam engines.
Does this kit include rocker gaskets?
Yes. The C9635 is a top-end kit intended to include rocker assembly sealing components as well as cylinder head and base sealing components.
Can this kit be used with big-bore cylinders?
Not automatically. Its 3.500-inch head gasket opening is intended for compatible standard-bore applications. Enlarged-bore engines require appropriately sized gaskets.
Is this a complete engine gasket kit?
No. It is a top-end gasket kit. It does not replace a complete engine overhaul gasket set covering every lower-engine sealing component.
Restore Your Harley Evolution Engine with Cometic
The Cometic C9635 EST Top End Gasket Kit provides the sealing components needed for compatible 1992–1999 Harley-Davidson 1340cc Evolution Big Twin top-end rebuilds.
With MLS cylinder head gaskets, stainless steel sealing components, and specialized EST technology, this kit offers a comprehensive solution for maintaining your classic Harley-Davidson V-twin.
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