S&S Cycle Flywheels — Harley-Davidson Electra Glide, Softail Heritage Classic, Electra Glide Classic (1955-2026)

S&S Cycle flywheels are high-strength crankshaft assemblies built for Harley-Davidson performance engines, forged from heat-treated 4140 steel and balanced to exacting tolerances. Designed with Finite Element Analysis to handle extreme power and higher RPM while maintaining the reliability that made S&S the industry standard for over 60 years.

Features

• Heat-treated 4140 material — harder and twice as strong as stock
• Full-width wristpin design requires S&S Performance Pistons
• Balanced for 1213g piston weight
• Eliminates need to weld crankpin on stronger assembly
• Capable of sustained higher RPM operation
• 4-1/2 inch stroke fits 114 or 128 cubic inch builds
• Balance gear pre-installed
• Precision-machined and consistent across production

Specifications

• Brand: S&S Cycle
• Manufacturer Part #: 320-0603
• Weight: 42.7 lb
• Category: Drivetrain / Flywheels

Fitment

Fits Harley-Davidson engines. Compatible with 114 and 128 cubic inch builds using the 4-1/2 inch stroke configuration.

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 fit and balance.

Can I use these with a gear drive cam?

Yes. These flywheels are designed to work with S&S gear drive cam systems for reliable high-RPM operation.

What displacement will these support?

With the 4-1/2 inch stroke, these flywheels work in 114 cubic inch and 128 cubic inch builds.

Are they balanced from the factory?

Yes. They ship pre-balanced to the piston weight spec and include the balance gear, ready to install.

Why use 4140 steel instead of stock material?

4140 is heat-treated to be twice as strong as OEM material, eliminating weak points and allowing safe higher-RPM operation without crankpin welding.