Common FXR Gas Tank Problems and How to Fix Them
If you ride or restore an FXR, you already know how important the gas tank is. Beyond holding fuel, it defines your bike’s lines, affects range, and even impacts resale value. But like any older component, FXR gas tanks can develop issues over time.
In this guide, we’ll break down the most common FXR gas tank problems and how to fix them — whether you’re working on a stock restoration or a custom build.
The FXR platform was produced by Harley-Davidson between 1982 and 1994, so many original tanks are now 30+ years old. That means wear, corrosion, and fitment issues are common — but most are fixable. Genuine OEM Harley Davidson FXR Center Fill Red Gas Tank FXRT FXRS
1. Rust Inside the FXR Gas Tank
The Problem
Internal rust is the most common issue, especially on bikes that have sat for years. Moisture buildup inside the tank leads to corrosion, flaking metal, and contaminated fuel.
Symptoms
- Fuel filter clogging
- Carburetor issues
- Visible rust flakes
- Brown or dirty fuel
How to Fix It
Light Rust
- Drain fuel completely
- Flush with a rust remover solution
- Rinse thoroughly
- Dry completely
Severe Rust
- Use a professional tank cleaning and sealing kit
- Apply an internal tank liner
- Replace tank if metal is too thin
👉 Pro Tip: Always dry the tank fully before resealing to prevent trapped moisture. Genuine OEM Harley Davidson FXR Center Fill Red Gas Tank FXRT FXRS
2. Leaking Petcock Bung
The Problem
Over time, the threaded petcock bung can leak due to stripped threads or worn seals.
Symptoms
- Fuel dripping underneath tank
- Strong fuel smell
- Wet petcock area
How to Fix It
- Replace petcock gasket or O-ring
- Use thread sealant (fuel-safe only)
- Install a new petcock
- If threads are damaged, install a threaded insert
If the bung itself is cracked, welding repair or tank replacement may be required.
3. Misaligned Mounting Tabs
The Problem
FXR tanks rely on front and rear mounting tabs. Over time — or with poor-quality aftermarket tanks — alignment can be slightly off.
Symptoms
- Tank doesn’t sit flush
- Bolt holes don’t line up
- Excessive vibration
How to Fix It
- Loosen all bolts before tightening fully
- Use small spacers or washers
- Carefully bend tabs (only if minor misalignment)
- Replace poorly manufactured aftermarket tank
⚠ Always test fit before painting a new tank. FXR Gas Tank Fitment Guide by Year (1982–1994)
4. Fuel Cap Leaks or Venting Issues
The Problem
A faulty fuel cap can cause leaking or pressure build-up.
Symptoms
- Fuel spilling during rides
- Tank vacuum causing fuel starvation
- Hissing sound when opening cap
How to Fix It
- Replace vented cap
- Check for clogged vent passages
- Ensure correct cap type (vented vs non-vented)
Incorrect venting can cause poor fuel delivery, especially on carbureted FXRs.
5. Cracked Weld Seams
The Problem
Vibration from the Evolution engine can stress weld seams over time.
Symptoms
- Hairline cracks near mounts
- Fuel seeping from seams
- Visible stress marks
How to Fix It
- Drain and purge tank completely
- Have a professional welder repair seam
- Pressure test tank before reinstalling
Never weld a tank without proper fuel vapor removal — it’s extremely dangerous.
6. Paint Bubbling or Blistering
The Problem
Ethanol fuels can damage older paint jobs and internal coatings.
Symptoms
- Paint lifting near filler neck
- Bubbling on tank surface
- Peeling clear coat
How to Fix It
- Strip affected area
- Sand to bare metal if necessary
- Repaint with ethanol-resistant paint
- Ensure proper tank sealing inside
If repainting, always confirm tank is fully clean and free of fuel vapors.
7. Aftermarket Tank Fitment Problems
The Problem
Not all aftermarket FXR gas tanks are created equal.
Symptoms
- Seat doesn’t align
- Petcock hits engine case
- Tank sits uneven
How to Fix It
- Verify model year compatibility
- Measure mounting spacing before ordering
- Choose high-quality, thick-gauge steel tanks
- Avoid extremely low-cost options with poor weld quality
Proper fitment prevents vibration damage and stress cracks later.
Preventative Maintenance Tips
To avoid common FXR gas tank issues:
- Keep tank at least half full during storage
- Use fuel stabilizer
- Inspect mounts yearly
- Replace petcock seals proactively
- Store bike in dry environment
Preventative care extends the life of your tank significantly.
When Should You Replace an FXR Gas Tank?
Consider replacement if:
- Rust has eaten through metal
- Weld seams are severely cracked
- Mounting tabs are broken
- Repairs exceed tank value
For restorations, OEM-style tanks are ideal. For custom builds, quality aftermarket options offer great fit and fresh steel. harleydavidson.com