V-Twin Mfg Billet Wagner Style Rear Master Cylinder 5/8 Bore for 1958-1979 Harley-Davidson FL FX

V-Twin Mfg Billet Wagner Style Rear Master Cylinder 5/8 Bore for 1958-1979 Harley-Davidson FL FX

For a vintage Big Twin restoration or a period-correct custom build, the master cylinder sets the tone for every stop the bike will ever make. This V-Twin Mfg Wagner reproduction installs in the original bracket location and delivers the brake pedal authority riders of this era expected — solid, direct, and dialed in from the first press.

Key Features

• Reproduction of the original Wagner offset-mount design for correct installation on 1958-early 1979 Big Twin frame locations without modification
• Offset mounting geometry distinguishes this from the Kelsey Hayes inline style — verify your mounting hole pattern before ordering
• 5/8″ bore pairs with multi-piston aftermarket calipers for upgraded braking performance over the stock single-piston setup
• 1/8-27 NPT inlet is compatible with standard hard-line brake fittings
• Suitable for period-correct restorations and custom chopper and bobber builds with matching 2.25″ bracket spacing

Technical Specifications

• Bore Size: 5/8″
• Style: Wagner offset mount
• Inlet Size: 1/8-27 NPT
• Mounting Hole Diameter: 3/8″
• Mounting Hole Spacing: 2.25″ on center
• Mounting Offset: 3/8″
• Length: 4″
• Width: 1.5″
• Height: 3.125″
• Construction: Chrome-plated billet aluminum
• Fluid Requirement: D.O.T. 5 Silicone Brake Fluid (recommended)
• OEM Cross-Reference: 41761-58 (1958-1972), 41761-78 (1973-1979)

Fitment Notes

• 1979 fitment applies to early production only; late 1979 models transitioned to the Kelsey Hayes inline mount — see Kelsey Hayes master cylinder listings
• Wagner offset mount is NOT interchangeable with Kelsey Hayes inline brackets — verify your mounting hole pattern before ordering
• 5/8″ bore requires multi-piston aftermarket calipers; verify caliper bore requirements before installation
• D.O.T. 5 Silicone brake fluid recommended; verify compatibility with your caliper manufacturer
• Bench bleeding strongly recommended before final installation
• Custom applications require 2.25″ center-to-center bracket spacing
• Review the Fitment tab for the complete year and model breakdown