Syiono Primary Cover Gasket & Seal Kit for Harley Twin Cam 1999–2006 — Complete O‑ring, Mainshaft & Inspection Gaskets

Syiono Primary Cover Gasket Clutch Inspection Seal Kit is a complete replacement gasket and seal set engineered to reseal the primary cover and inspection ports on 1999–2006 Harley-Davidson Twin Cam FLH/T Touring and Electra Glide/Road Glide/Road King models.

This kit gathers every commonly replaced O-ring, oil seal, mainshaft seal and primary/inspection gasket you need when servicing the primary cover on Twin Cam Touring Harleys from 1999 through 2006. Rather than hunting multiple part numbers, the Syiono kit provides the seals and gaskets matched to the original fitment so you can restore a leak-free primary case and properly protect the clutch assembly from oil intrusion. Each component in the package is molded from durable material selected to match OEM sealing properties and to withstand the heat and oil exposure common in primary housings.

Which specific parts are included in the kit?

The Syiono kit consolidates the common replacement pieces required for a primary cover service on supported Harley models. It contains O-rings, oil seals, mainshaft seals and several gaskets used around the derby, inspection cover and primary cover.

• 11147 O-Ring for specified sealing points
• 12052A oil seal and 12066 mainshaft seal
• 25416-99C derby/clutch cover gasket
• 34906-85 series inspection gaskets and 34901-94 series primary gaskets plus locating screw gasket

How does this kit help when replacing a leaking primary cover?

Replacing worn seals and gaskets is the standard way to stop leaks and restore correct oil containment in the primary housing. Using fresh, correctly fitted seals reduces the chance of oil seeping into the clutch or dripping externally, which helps maintain clutch function and keeps the bike cleaner.

• Replaces degraded or flattened gaskets that no longer compress properly
• Fits OEM-style grooves and bolt patterns to ensure proper seating
• Prevents oil migration into the clutch or onto the ground
• Allows you to reuse a good primary cover instead of buying expensive replacement covers

Will these seals fit my Harley model and engine year?

The kit is specified for 1999–2006 Touring models equipped with the Twin Cam engine family, including FLH and T-series baggers and common variants like Electra Glide, Road Glide and Road King. Cross-check the part numbers in the list with your service manual or existing parts to confirm fitment before installation.

• Compatible with Harley-Davidson FLH/T Twin Cam Touring models 1999–2006
• Includes part numbers used on Dyna, FXD and FLSTF/FXST Twin Cam bagger applications
• Not intended for non-Twin-Cam or significantly modified primary housings

What should I expect during installation and service intervals?

Install the kit during a primary cover service when you replace clutch plates, inspect the chain/torque assembly, or whenever you discover oil leaks. Proper cleaning of mating surfaces and using correct torque on fasteners are essential for a long-lasting seal. If you find corrosion or warpage on the mating surface, consider machining or replacing the cover before fitting new gaskets.

• Clean mating surfaces and remove old gasket material before installation
• Apply proper sealants only where specified by the manual; avoid over-application
• Torque bolts to factory specs and recheck after initial heat cycles
• Inspect seals periodically for damage during routine maintenance

Who is this for: The Syiono Primary Cover Gasket Clutch Inspection Seal Kit is aimed at DIY mechanics, independent motorcycle technicians and restoration shops working on 1999–2006 Harley-Davidson Twin Cam Touring bikes. If you are planning a primary cover service, clutch job, or troubleshooting oil leaks around the primary housing, this kit supplies the common replacement seals and gaskets to complete the repair with OEM-compatible parts.