Complete 1.5" Primary Belt Drive Kit for Big Twin w/ 4 Speed Transmission

Everything you need to run a classic open primary—without piecing it together part by part. The 1.5" Belt Primary Kit combines several of our individual drivetrain components into one complete setup built for classic Big Twin applications running a 4 speed transmission.

This kit brings together proven components we already offer separately, including the BDL 1.5" belt drive assembly, clutch hub assembly, clutch hub retainer, clutch plate set, clutch plate springs, clutch hub stud nut, and clutch hub nut seal kit. Each part works together to create a strong, reliable clutch system with the clean, exposed look that defines a proper open primary.

The 1.5" belt drive assembly features hard anodized aluminum pulleys and clutch basket with an 132 tooth 8mm belt for strength and durability, while the front pulley is drilled and tapped for easier removal during service. Inside the clutch pack, aluminum/Kevlar friction plates paired with tempered steel drive plates deliver strong engagement and improved holding power. The plates are 20% wider than stock and come with a pre-set stack height for easier installation.

A full set of 10 Barnett clutch springs ensures balanced clamping pressure across the clutch pack, while the five-stud clutch hub assembly provides a solid foundation for classic Big Twin drivetrains. Finishing off the system are the clutch hub retainer, stud nut, and a Genuine James Gaskets clutch hub nut seal kit to keep everything properly secured and sealed.

Whether you're building a chopper, restoring a vintage Big Twin, or converting to an open primary, this kit brings all the core components together so you can spend less time sourcing parts and more time building.

This will work with most Big Twin engines 1970-1999 with splined main shafts that have a 4 speed transmission (Ratchet top or Rotory top) with a tapered main shaft. You may need a spacer for later model long shaft transmissions.