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How do you adapt 2002 harley fat boy fuel tank to work on a 2005 fat boy fuel injection bike
Executive summary
Swapping a 2002 Fat Boy tank (produced in both carbureted and injected variants) onto a 2005 Fat Boy EFI machine is commonly discussed in enthusiast forums; the main technical issues raised are different fuel fittings (petcock vs. EFI pump/return), presence of a fuel return port on EFI tanks, and the need to transfer or install EFI internals (pump, regulator, lines) if the donor tank lacks them [1] [2]. Aftermarket parts sellers list EFI-specific fuel lines, pumps and pressure regulators for 2002-era Softail Fat Boys, implying these components and fittings are distinct and commonly replaced when doing tank swaps [3] [4].
1. What riders mean when they say “EFI vs carb” — different plumbing, different fittings
Forum exchanges emphasize that EFI tanks differ from carbureted tanks by having additional ports and internal hardware: EFI tanks typically include a pump assembly, supply and return fittings, and a fuel pressure arrangement not present on carb tanks; this is why people note the EFI tank has a return port while older carb tanks have a single supply outlet [1] [2]. Practical consequence: a straight bolt‑in of a carb tank into an EFI bike often fails because the EFI system expects a pump and return plumbing that the carb tank doesn’t provide [1] [2].
2. What you’ll likely need to change or add to make a 2002 tank work on a 2005 EFI bike
Enthusiast posts advise buying specific adapter fittings and pump‑plate gaskets, or fabricating block‑off plates when converting tanks, and stress swapping the fuel valve/fittings for EFI compatibility [1]. Commercial parts suppliers sell EFI fuel lines, pumps, and regulators for early‑2000s Softails, which supports the point that you will need EFI‑rated lines, a pump/regulator and the correct fittings to match the 2005 EFI system if your 2002 tank lacks those internals [3] [4].
3. Common approaches discussed by owners — adapter vs donor internals
Forum contributors present two pragmatic routes: (a) fit an EFI pump plate, regulator and associated lines into the 2002 tank so it mimics an EFI tank, or (b) buy an OEM adaptor or petcock fitting from Harley to mate different tanks and then transfer the EFI internals from the original 2005 tank. One user specifically recommended buying “the petcock fitting adapter from HD along with a pump plate gasket” and making a block‑off plate for other openings [1].
4. Parts availability and aftermarket support — feasible but not plug‑and‑play
Retail listings and parts vendors show there is aftermarket support for fuel injection plumbing and regulators for Softail Fat Boys from this era, meaning you can source the pump, pressure regulator and lines needed for the swap [3] [4]. However, availability of exact donor internals or OEM adapters varies by part and year; sellers list components for 2001–2008 Softails which suggests compatibility windows but also underscores the need to confirm exact part numbers for 2002 vs 2005 models [3] [4].
5. Technical cautions owners report — fuel leaks, pump operation and electricals
Owners repeatedly point out pitfalls like incorrect fittings causing leaks or continuous pump operation; troubleshooting threads about fuel leaks and pump behavior underscore that incorrect assembly of EFI plumbing or using wrong parts can lead to fuel escape or electrical issues with pump cycling [2] [5]. That means electrical connectors, pump control, and pressure regulator setup must be correct after a tank swap.
6. Practical checklist for someone attempting the swap
Based on forum advice and parts listings: confirm whether the 2002 donor tank has EFI internals; if not, plan to install an EFI pump plate, pump, regulator and return line; acquire the correct HD petcock/fitting adapter and pump plate gasket or an OEM donor pump plate; verify fuel line and connector compatibility and source EFI‑rated hoses listed for Softails; test for leaks and correct pump operation before riding [1] [3] [4].
7. Where reporting is thin or absent in these sources
Available sources do not mention exact part numbers for a 2002-to-2005 tank conversion, step‑by‑step torque specs, or firm wiring details for pump control specific to a 2005 Fat Boy. They are mostly forum advice and parts catalog listings rather than a factory procedure; you should consult a Harley dealer service manual or OEM parts fiche for definitive part numbers and electrical diagrams before you proceed [1] [3] [4].
Bottom line: enthusiasts and parts vendors agree the swap is doable but not a simple bolt‑in — you must address differing fittings and EFI internals (pump, regulator, supply and return plumbing) and confirm part compatibility [1] [3] [4].