How to Install a Custom Fuel Cap Assembly on 2023.5+ Harley-Davidson Models

2023.5+, fuel cap, fuel door, Harley-Davidson, how to, installation guide -

How to Install a Custom Fuel Cap Assembly on 2023.5+ Harley-Davidson Models

Install Video

The Brock Black Designs custom fuel cap assembly is a complete replacement for the factory fuel door on 2023.5+ Harley-Davidson models. It swaps in as a full unit — decorative cap, hardware, and all — giving your tank a custom look without any permanent modifications. Watch the full install video above, then follow the step-by-step guide below.

Before You Begin

Inspect the kit and all components to confirm everything is present and undamaged. If anything is missing or damaged, contact Brock Black Designs at 208-705-0028 (US & Canada only) or visit brockblackdesigns.com.

Fitment / Compatibility

This fuel cap assembly fits 2023.5 and later Harley-Davidson models with the updated fuel door design. Verify fitment for your specific model at brockblackdesigns.com. If you're unsure, contact us before ordering.

Tools Required

  • T27 Torx screwdriver or bit
  • Torque wrench (inch-pounds capable)
  • Clean microfiber cloth
  • Optional: mild degreaser for cleaning the tank surface

Safety First

  • Allow the engine and fuel system to cool completely before starting. Never work on the fuel system with a hot engine.
  • Work in a well-ventilated area away from open flames or sparks.
  • Have a clean rag ready to catch any fuel residue when the cap is removed.
  • Do not smoke or use open flames near the fuel tank at any point during installation.

Step-by-Step Installation

Step 1 – Let the Bike Cool and Relieve Fuel Pressure

Make sure the engine has been off long enough to cool completely and fuel pressure has dissipated. Do not rush this step — working on a warm fuel system is a safety hazard.

Step 2 – Clean the Tank Surface

Wipe down the area around the fuel door with a clean microfiber cloth. Remove any wax, grease, or debris from around the mounting area. A clean surface makes it easier to see the mounting hardware and prevents contamination during the swap.

Step 3 – Remove the Factory Fuel Cap Assembly

Using your T27 Torx bit, remove the screws securing the factory fuel cap assembly to the tank. Keep all screws — you may reuse them depending on your kit's hardware. Carefully lift the factory assembly free. Have a clean rag ready to catch any fuel residue from the opening.

Tip: Work slowly around the perimeter and note how the factory assembly seats — your new unit installs the same way.

Step 4 – Inspect the Fuel Opening

With the factory assembly removed, inspect the fuel opening and surrounding tank surface:

  • Wipe away any fuel residue with a clean rag.
  • Check the sealing surface for debris or damage.
  • Confirm the new assembly's gasket or seal will seat cleanly.

Step 5 – Position the New Fuel Cap Assembly

Lower the new Brock Black Designs fuel cap assembly into position over the fuel opening. Align the mounting holes with the tank's threaded inserts. Before tightening anything:

  • Confirm the assembly sits flush and level on the tank surface.
  • Check that the design is oriented the way you want it — step back and look from a few feet away.
  • Make sure the gasket or seal is fully seated around the fuel opening with no gaps.

Step 6 – Secure the Assembly

Thread the mounting screws in by hand first to confirm they're not cross-threading. Then tighten in a cross pattern to ensure even clamping pressure on the seal.

Do not overtighten — snug and firm is correct. Overtightening can crack the assembly, damage the tank threads, or compromise the fuel seal. If your kit includes a torque spec, use a torque wrench to hit it precisely.

Step 7 – Final Inspection

Before riding:

  • Confirm all screws are tight and the assembly is flush with no gaps around the seal.
  • Wipe down the tank and assembly with a clean microfiber cloth.
  • Start the bike and let it idle briefly — visually inspect around the fuel cap assembly for any signs of fuel seepage. If you see any, shut the bike off immediately and recheck the seal seating.

Tips for a Perfect Install

  • Watch the install video at the top of this page before starting — seeing the process once makes the steps much clearer.
  • Tighten in a cross pattern, not in a circle — this ensures even pressure on the seal and prevents warping.
  • Never skip the post-install fuel seepage check. It takes 60 seconds and confirms everything is sealed correctly.
  • If the assembly doesn't sit perfectly flush, loosen all screws and reseat it before retightening.

Shop 2023.5+ Fuel Cap Assemblies

Browse our full lineup of custom fuel cap assemblies for 2023.5+ Harley-Davidson models:

Questions about fitment or your specific model? Call 208-705-0028 or send us a message — we're happy to help.

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