Harley Davidson Flush Mount Gas Cap Problems [Explained]

The flush mount gas caps in the Harley Davidson tend to wear out after years of continuous use. Issues like loose or worn-out caps are very prevalent. In addition, fuel leaks and cap rattling are also common. 

It is crucial to have a functioning flush mount gas cap. Debris settling or fuel evaporation is reduced to a great extent. Otherwise, issues will be a regular thing.

Let’s look at those issues and discuss what you can do to take measures.

Troubleshooting And Fix For Harley Davidson Flush Mount Gas Cap Problems

Prolonging the existing problems in the Flush Mount Gas Cap won’t benefit you. Below here are some troubleshooting techniques and fixes you can try for the prominent issues.

1- Loose Trim Ring

The trim ring protects the paint around and helps to avoid bubble formation. 

It successfully avoids gasoline chipping under the paint around the fuel tank filler area and ensures no paint bloats.

But adhesive loosening up around the gas cap and trim will deter the function of the trim. 

The fix for this problem is simple, as you require using a new adhesive. You can use a black silicone sealant or a clear option for non-black tanks. 

While doing so, you must press down the trim ring and wipe the extra adhesives from the edges. The last step would be using tape to make it more secure.

Moreover, the total fix will cost you around $10-15, which includes the cost of both adhesives and tape.

Loose Trim Ring
Loose Trim Ring

2- Rattling Gas Cap

A faulty flush mount gas cap would produce a lot of rattling sound while you ride your Harley. Eventually, it might cause some problems in riding and hamper the bike performance. 

Rattling means the gas cap is loose, enabling air to contact the gas in the tank. It will decrease the fuel economy of the bike and get the performance to be on the leaner side.

The fix for this problem is tightening the gas cap with the wrench. Just use a regular wrench and tighten the cap as per convenience. If that doesn’t work, you can use adhesives as a resort.

Rattling Gas Cap
Rattling Gas Cap

Read Also: Vacuum Operated Petcock Problems On Harley Davidson: 4 Issues And Their Fixes 

3- Crack In The Cap

The debris often settles in the cap and results in metal components getting rusted. Cracks often may form on those components making the gas cap almost irreparable.

Replacing the flush mount gas cap with a new one is the only solution. To replace the gas cap on your Harley Davidson bike, follow the steps as mentioned below:

  • Start the process by removing the old gas cap, which you can do by twisting the cap up
  • Take a microfiber and clean around the opening of the gas cap
  • Ensure that you don’t spill anything into the tank while cleaning
  • Let the surface around the cap dry appropriately after cleaning
  • Take the new gas cap and twist it first so that the top will come up
  • Put the new cap in the hole and tighten it down
  • Push the cap down once you tighten it right, and then turn it a quarter right
  • Place the trim and rotate it along the surface of the tank until there is no gap
  • Use the painter’s tape to align the gas cap and trim perfectly
  • Mark the tape to keep track of the alignment 
  • Remove the covering of the adhesive under the trim
  • Place the trim carefully, and then you are done

In between all these, the pricing of the new gas cap would range around $225-230. Or else labor costs will add up to another $70-90 for this particular issue.

4- Jammed Up Cap

The cap springs may get loose due to dirt settling, reducing their tension. As an outcome, the spring doesn’t work as it should, and the cap gets jammed.

Most of the time, this happens when your bike is out of use for a long time. As a result, dirt gets stuck and makes the gas cap jammed.

The fix for this problem is to clean the dirt from the cap. You can use a small piece of cloth or a brush to clean. 

Applying grease to the gas cap after clearing the dirt stuck in the spring. It will enable you to remove the cap easily with no shucking up.

Read Also: 6 Common Harley Davidson Ignition Coil Problem: Troubleshooting and Fix

Tips To Prevent Harley Flush Mount Gas Cap Problems

To avoid the gas cap issues in your Harley, you can always take a few preventive measures. These measures will include everything that makes the gas cap prone to failure. Let’s have a look at those:

  • Inspect the gas cap components and connections regularly.
  • Ensure the bolts and hoses connecting the tank and fuel system are in good condition.
  • Clean the gas cap at least once a month.
  • Tune up your Harley on time.
  • Always keep a check on the adhesives of the trim and see whether it is coming off.
  • Be careful while cleaning or twisting the gas cap so that you don’t end up damaging it.

Read Also: Harley Davidson Electronic Throttle Control Problems [Troubleshooting And Fix Guide]

Is It Safe To Drive Harley With Flush Mount Gas Cap Issues?

Driving your Harley Davidson bike without a properly functioning gas cap isn’t recommended. If there is no other way, you shouldn’t ride the bike for more than 10-15 miles.

There are issues with poor performance and the possibility of engine stalling. 

On the other hand, if you remove the gas cap during this time, there will be issues like debris getting into your fuel tank.

In both scenarios, your Harley Davidson bike will be harmed, and there will be a drastic decrease in performance. 

Therefore, you should immediately replace or fix the cap if the existing one isn’t working correctly.

Read Also: What Are The Common Harley Davidson Switchback Problems?


A faulty gas cap in your Harley may bring up a lot of queries in your mind. To help you with this, we have answered some of the most asked questions in the section below. Let’s have a look at those!

Is A Fuel Leak An Indicator Of A Faulty Gas Cap On Your Harley Davidson?

If you can smell gasoline after parking your bike, there are issues with the flush mount gas cap seals. The seals, in this regard, are worn-out and need a replacement.

What Is The Problem With The Leaking Gas Cap On Harley Davidson?

The leaking gas enables fuel vapors to evaporate in the air and allows a passage of dirt and debris into the fuel tank. This dirt may affect the injectors and hamper engine performance in the long run.

Can A Faulty Mount Gas Cap Cause Erratic Idling?

Yes, idling or stalling can occur when the gas cap is not properly functional. Fuel pressure goes above par, resulting in uneven idling.

Final Thoughts

Eliminating gas cap issues is crucial, as they will hamper engine and bike performance. We recommend you regularly check the adhesives and spring of the flush mount gas cap.

That said, inspecting minor symptoms before it leads to something big should always be your tactic. So, for an enjoyable riding experience, there is no alternative to solving gas cap issues.

Read Also: 3 Probable Harley Automatic Primary Chain Tensioner Problems

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