Harley Davidson Flush Mount Gas Cap Problems & Solutions

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Flush mount gas caps are an important component in protecting the fuel tank of your Harley Davidson motorcycle. 

Not only do they prevent dust and debris from entering the tank, but they also help to reduce fuel evaporation. 

Unfortunately, these components tend to develop problems over time. 

In this article, you will learn about common flush mount gas cap problems that you may encounter in your Harley Davidson with their solutions.

Harley Davidson Flush Mount Gas Cap Problems

Harley Davidson Flush Mount Gas Cap Problems

1. Loose Gas Cap

One of the most common problems with the flush mount gas cap problem in Harley Davidson is it becomes loose over time or if you fill in too much oil. 

This is really common in older models because the rubber seal on the cap deteriorates with time. 

If your Harley Davidson flush mount gas cap is loose, you should tighten it up. However, if tightening doesn’t work, then you will need to replace the seal which seals the cap shut. 

To do this you will need to buy a new seal and then need to install it yourself. 

If your motorcycle gas cap is still loose or changing the seal doesn’t work, then you will need to use some kind of adhesive. Because many people found success with using Gorilla glue to secure the cap. 

However, the biggest con of this solution is if you ever want to remove the cap for any reason, you won’t be able to do that. 

Therefore, I would suggest this only as the last solution.

2. Stuck in Place

Another common problem with the Harley Davidson flush mount gas cap is it gets stuck and doesn’t come off the tank. This usually is because of loose springs. 

When springs in the cap lose their tension, it becomes difficult to turn or take off the cap. If you are not using your motorcycle for a long time, then it may be because of dirt build-up around the cap. 

Also, the double-sided tape that helps to hold the ring around the cap in place deteriorates with time, which makes it difficult to open the cap for you. 

You can easily fix these issues yourself. First, you should clean the debris or dust from the cap with a cloth or brush. Then you should lubricate the cap with WD-40 or grease. Due to this, you will be able to move the cap easily. 

If these methods don’t work, then you will need to carefully pry off the ring around the cap with the help of a flathead screwdriver and make sure to free it from its current position.

3. Trim Ring Won’t Stay Down

Some people have found that the trim ring of their Harley Davidson gas cap doesn’t stay down. 

Mostly this happens because the trim ring is not properly fitted and pops up easily. 

To fix this problem, you should use 3M adhesive tape. 

However, if it doesn’t work, then you will need to clean the area around where the trim ring will be placed before using adhesive tape. 

Because this will provide better adhesion and make sure that the trim ring remains in place. 

You should also check that all edges of the trim ring are firmly pressed against the surface for maximum hold. 

4. Gas Cap Rattles

Another problem that you can face is the Harley Davidson flush mount gas cap loose with time and rattles while riding. 

This can decrease the performance of your motorcycle because when the cap is loose it allows the air to come into the tank which causes your motorcycle to run lean and also will decrease fuel economy.

To fix this problem, you will need to tighten it up with a wrench. 

However, if it doesn’t work, then you should pour the silicone or other adhesive on both sides of your cap to tighten it.

Solution of Harley Davidson Flush Mount Gas Cap Problems

One of the best ways to fix any flush mount gas cap problem of your Harley Davidson is to buy a new cap. 

You can get a new one from the official Harley website and its cost is around 85$ to 90$

You can also buy from Amazon for 16$ to 20$. However, it is not of great quality. 

Therefore, I would recommend you buy from an official store. 

If you buy from the official website then they provide detailed instructions along with some troubleshooting tips if you face any problems while fitting the new cap. 

How to Prevent Flush Mount Gas Cap Problems in the Future?

These are the things that you should do to avoid flush mount gas problems in the future.

Inspect damages

You should regularly inspect the gas cap for damages such as cracks in plastic or rusting on metal components. 

If you find these things, you should fix them immediately.

Clean regularly

Also, clean the gas cap regularly with the help of a soft cloth or alcohol. 

Because this will remove dirt and debris that could interfere with metal.

Lubricate properly

Make sure to properly lubricant the gas cap with silicon-based lubricants at least once a month. 

This will keep the cap in good working condition and prevent it from becoming stuck.

How to Open a Harley Gas Cap Without a Key?

If you do not have the key to open your Harley gas cap, you can still open it.

  1. You can open the gas cap by locating a small slot that is open to the front. You can then slip something up from the front of the tank and trip the lock.
  2. Another way is to replace the lock with a push-button that can be bought at a dealer or bike shop. 
  3. You can also use any barrel-type key to open the cap. Even if it’s from an old U-lock bicycle lock.

Why Do Harleys Have 2 Gas Caps?

Harley Davidson has two gas caps because the two-valve design allows air to enter the tank and fuel to exit, which creates a vacuum effect that helps keep your fuel from evaporating. 

This is important because the fuel vapours can cause explosions. 

Also, the two caps provide a layer of protection against water and debris.


You can easily solve any of Harley Davidson’s flush mount gas cap problems by yourself.

Whether the issue is loose or stuck in place, rattling or trim ring won’t stay down, there are solutions to each problem. 

If these fixes don’t work then you should replace the gas cap and we recommend buying from the official Harley website. 

Also, keep in mind if you will use any adhesive it should only be as a last resort because removal of the cap will not be possible after this point.

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