S&S Cycle Flywheels — Harley-Davidson Street Glide, Softail Fat Boy 114, Road King Special (2017-2026)

S&S Cycle flywheels are the foundation of any high-performance Milwaukee-Eight engine, engineered from heat-treated 4140 material that is twice as strong as stock. Built with precision machining and full-width wristpin design, they handle elevated RPM and power output while maintaining strict balance tolerances.

Features

• Heat-treated 4140 material — twice as strong as stock
• Full-width wristpin design requires S&S Performance Pistons
• Finite Element Analysis eliminates weak spots
• Balanced for S&S 1213g performance piston weight
• 4-5/8" stroke compatible with S&S 131 cubic inch kits
• Gear drive cam ready with balance gear pre-installed
• Consistent precision machining and balancing

Specifications

• Brand: S&S Cycle
• Manufacturer Part #: 320-0605
• Category: Drivetrain / Flywheels
• Weight: 40 lb

Fitment

Fits Harley-Davidson Milwaukee-Eight platform.

Frequently Asked Questions

Do I need S&S pistons to use these flywheels?

Yes — the full-width wristpin design requires S&S Performance Pistons (1213g weight) for proper fitment and balance.

What stroke is this flywheel?

4-5/8 inch stroke, designed to work with S&S 131 cubic inch engine kits.

Can I use these with a gear drive cam?

Yes — the balance gear is pre-installed and ready for gear drive cam applications.

How do these compare to stock flywheels?

S&S flywheels are heat-treated 4140 material, more than twice as strong as OEM, and balanced to tighter tolerances for higher RPM capability.

Will these support a high-horsepower build?

Yes — engineered through Finite Element Analysis to eliminate weak spots and handle elevated power output without crankpin welding.