Gaskets & Seals
About Gaskets & Seals
Gaskets and seals hold gearbox and primary oil inside the cases. Riders shop here for a leaking transmission cover, oil on the sprocket from a worn output shaft seal, or a gasket and seal set for a rebuild.
The samples cover covers, shafts and joints: trans cover and inspection cover gaskets, derby cover gaskets, shift shaft tube gaskets, clutch gaskets, double lip seals, an output shaft seal, a clutch hub seal and O-rings. Gaskets are listed with a thickness, such as 0.030 or 0.062 inch, and with silicone for sealing, so match both to the cover. Rebuild kits, such as the M8 Softail primary rebuild kit, group the parts for one job. Clean the mating surfaces without gouging them, tighten bolts evenly to the specified torque, and fit seals square with a driver.
Brands here include Hot Rods, Jims, Drag Specialties, All Balls and Cometic. Pick your machine in the Ride Finder at the top of the page. For the parts that go with them see Bearings, Clutch Parts & Kits and Gearbox & Transmission Parts, all part of Transmission & Drivetrain.
FAQs on transmission gaskets and seals
Can I reuse a transmission cover gasket?
It is better not to. A gasket compresses to the shape of the joint, and a used one rarely seals as well. Opening the case again costs far more work than a gasket, so fit a fresh one each time the cover comes off.
Do I need sealant with a transmission gasket?
Only when the manual says so. Some gaskets are listed with silicone and some are fitted dry, and extra sealant can squeeze into oil passages. Follow your service manual for what to use and where.
How do I tell which seal is leaking?
Clean the area and run the bike, then look for where fresh oil appears. Oil on the sprocket side often points to the output shaft seal, and oil near the clutch cover points to a cover gasket or the clutch seal. Fix the source, not the drips.
How do I fit a shaft seal without damaging it?
Use a driver that bears on the seal's outer edge, keep it square, and lubricate the lip. Fit it to the depth shown in the manual with the lip facing the correct way, usually toward the oil. Protect the lip from splines and sharp edges.
Why is gasket thickness listed in the title?
Gaskets come in different thicknesses, such as 0.030 or 0.062 inch, and the thickness affects the fit of the joint. Use the thickness listed for your cover and model rather than a close match, because a gasket that is too thick or too thin can leak or change how the parts sit.
