31320-80 Gaskets, O-rings and Seals for Aluminum Primary on 4 Speed Big Twin 1965-1986

For those running an aluminum primary on a 1965–1986 4-speed Big Twin, a proper seal is essential to prevent leaks and protect your drivetrain. This Athena gasket is a direct replacement for OEM 31320-80, fitting FX and Touring models from that era. These gaskets are engineered to provide a secure, long-lasting seal against the aluminum housings, which can be prone to weeping if not properly fitted. Whether you are doing a clutch service or a full primary inspection, using a high-quality Athena gasket ensures a professional result. It is a dependable choice for any mechanic looking to keep their classic Shovelhead or early Evo 4-speed primary drive clean and oil-tight.