Harley Davidson Flush Mount Gas Cap Problems [Quick Fixes]

Harley Davidson motorcycles epitomize freedom on the open road, quality craftsmanship, and the spirit of adventure. 

However, even the most iconic machines experience their share of issues, and among them, the Flush Mount Gas Cap problems have gathered notable attention from worldwide riders. 

In this article, we will dive into the challenges riders face with the flush mount gas cap and the possible solutions.

Harley Davidson Flush Mount Gas Cap Problems

Users often report difficulties in opening and closing these caps, which can become exceptionally challenging under colder conditions. 

However, there have been instances where the gas cap does not create a proper seal, potentially leading to fuel vapor leaks. 

This not only poses a safety risk but can also impact the motorcycle’s fuel efficiency. 

1. Loose Gas Cap

A loose gas cap not only poses a risk of fuel leakage but can also lead to the evaporation of fuel, which decreases fuel efficiency and increases emissions. 

This problem may manifest through the “Check Engine” light appearing on your dashboard, a clear indicator something is amiss. 

The cause of a loose gas cap can range from wear and tear over time to not being correctly tightened after refueling.

To address the issue, ensure the gas cap is tightened correctly. After refueling, twist the cap until you hear it click, indicating it’s securely fastened.

Over time, the gas cap and its gasket can wear down. Examine for any signs of damage or wear. If the gasket is cracked or the cap is warped, it’s time for a replacement.

If you’ve identified visible damage to the gas cap or the gasket, it’s advisable to replace them. 

Gas caps are relatively inexpensive and can be purchased from most auto parts stores or directly from Harley dealerships.

After addressing the loose cap issue, check if the “Check Engine” light is still on. 

If it persists, you may need to visit a mechanic to reset the code or investigate other potential issues.

2. Stuck in Place

When the gas cap gets stuck, it can be more than an inconvenience; it can prevent riders from refueling their bike, potentially leaving them stranded.

The issue primarily occurs due to the gas cap mechanism getting jammed or due to the build-up of dirt and debris around the cap. 

This problem is noted especially in environments with a lot of dust or after long periods without cleaning. 

Moisture can also cause the cap’s locking mechanism to corrode over time, making it difficult to open.

In order to mitigate the issue, applying gentle pressure and attempting to twist the cap open can work. Avoid using excessive force to prevent damage.

Sometimes, penetrating oil is applied around the edges of the cap. Allow it to sit for a few minutes; this can help break up any dirt or corrosion.

If it does not work, then use a soft brush and gently scrub around the cap to remove any dirt or debris that might be causing it to stick.

3. Trim Ring Won’t Stay Down

One common issue Harley owners encounter is with the trim ring of the flush mount gas cap refusing to stay down. 

This problem can arise from various causes, such as dirt and debris accumulation, wear and tear of the rubber seal, or even a malfunctioning spring mechanism.

Sometimes, removing the gas cap and the trim ring and cleaning the area with a mild cleaner to remove any dirt or grime solves the issues.

Make sure to clean the rubber seal, too, as debris on the seal can prevent a tight fit.

If cleaning doesn’t work, inspect the spring mechanism beneath the gas cap. Over time, this spring can weaken or get damaged. 

If the spring appears to be the problem, replacing it is usually a straightforward process.

The rubber seal around the trim ring is crucial for a snug fit. Inspect it for any signs of wear or damage. If the seal is cracked or degraded, replace it immediately.

4. Gas Cap Rattles

This problem can be annoying and worrying, as it raises concerns about potential fuel leakage or evaporation. 

The cause of this rattle is often due to the gas cap not fitting snugly enough, which allows it to move slightly when the motorcycle is in motion. Over time, the seal can also degrade, exacerbating the issue.

Begin by examining the rubber seal around the gas cap. If it’s worn or damaged, it needs to be replaced. Even minor imperfections can prevent a secure seal.

Sometimes, the solution can be as simple as tightening the gas cap more securely. However, avoid over-tightening, as this can damage the seal.

If it does not work, then consider adding a small piece of foam or rubber padding under the cap. This can reduce the rattle, but it’s more of a temporary solution.

If the issue persists, the best option might be to replace the gas cap entirely. Choose a high-quality replacement that fits your model perfectly.

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

To prevent future problems with flush mount gas caps, follow these simple yet effective steps.

Firstly, always ensure the cap is correctly aligned and seated after fueling your vehicle; this prevents air from entering the tank, which could lead to pressure issues. 

Secondly, regularly inspect the gas cap’s seal for any signs of wear or damage, such as cracks or deformities, and replace it as needed to maintain a secure fit and prevent leaks. 

However, lubricate the cap’s mechanism periodically with a silicone-based lubricant to maintain smooth operation and prevent sticking, which can cause improper sealing. 

It’s also crucial to use only manufacturer-recommended or high-quality aftermarket gas caps to ensure compatibility and reliability. 

By adhering to these simple steps, you can significantly reduce the risk of flush mount gas cap issues, maintaining your vehicle’s performance and safety.

How to Open a Harley Gas Cap Without a Key?

Opening a Harley-Davidson gas cap without a key, while not recommended due to safety and security reasons, might become necessary under certain circumstances. 

Here’s a guide on how to approach this situation with care:

• First, determine if your Harley has a locking gas cap or a non-locking quick-release type. Most solutions apply to locking gas caps since non-locking caps can be opened by simply turning them.
• You can try using a can of compressed air. Insert the plastic straw into the keyhole and give a few short bursts. Sometimes, the pressure can pop the cap open if dirt or grime is causing it to stick.
• Another method involves using a small plastic wedge or a thick plastic card. Insert the wedge into the gap between the cap and the tank and gently apply pressure. This might allow the locking mechanism to disengage, but be cautious to avoid damage.
• If you’re with some lock-picking skills, a commercial lock-picking tool can be used. However, this requires understanding how to manipulate the pins inside the lock, which varies depending on the model of the cap.

Caution: It’s important to proceed carefully with these methods to avoid damaging the gas cap, tank, or paint. 

Why Do Harleys Have 2 Gas Caps?

Harley-Davidson motorcycles often feature two gas caps, a design choice that intrigues many enthusiasts and riders. 

This unique configuration serves functional and aesthetic purposes. The primary reason for the two gas caps is related to the split-tank design found on many Harley models. 

This design divides the fuel tank into two separate sections, which are interconnected. The right-side cap is the functional one, where fuel is added. 

It usually contains the fuel gauge or is directly connected to the fuel pump in more modern models. 

The left-side cap, on the other hand, is often decorative and maintains the tank’s symmetry, enhancing the bike’s visual appeal.

The split-tank design is not only about looks; it also allows for the accommodation of the motorcycle’s electronics and air intake systems, cleverly utilizing the space under the non-functional (left) side of the tank. 

This layout helps to distribute weight evenly, contributing to the bike’s balance and stability.

If you’re unfamiliar, refueling a Harley with this dual-cap system is straightforward. You only fill fuel through the functional (right-side) cap. 

If your model has it, this side will also give you access to check the fuel level, either via a traditional gauge or a more modern digital readout. 

The left cap typically doesn’t open or is just a twist-off without a filler hole beneath it.