If you’re a Harley-Davidson owner or planning to customize your bike, the flush mount gas cap might have caught your eye. Its sleek, low-profile design promises to add a touch of elegance to your ride, and for many, it’s an appealing way to streamline the look of their motorcycle. However, before you take the plunge and install one, it’s important to know the potential problems that can arise with these seemingly harmless cosmetic upgrades.
In this article, I’ll take you through the common issues I’ve encountered with the Harley-Davidson flush mount gas cap, why they happen, and what you can do about them. These problems aren’t just theoretical; they’re based on real-world experiences, and I want you to feel equipped to make the best choice for your bike. So, let’s dive in!
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The Appeal of the Flush Mount Gas Cap
First things first, let’s talk about why people choose the flush mount gas cap in the first place. It’s all about aesthetics. Harley-Davidson’s flush mount gas cap gives your bike that “clean” look — a smooth, uninterrupted fuel tank profile that appeals to customizers who want their bike to stand out. For many, it’s a simple upgrade that makes a big difference without requiring a major overhaul.
But as good as it looks, the flush mount gas cap comes with its own set of challenges. Problems with this part can range from minor annoyances to significant safety concerns. From my experience and feedback from other riders, there are a few specific issues that keep popping up. Let’s explore the most common ones.
1. Sticking Pop-Up Mechanism
One of the most frequent complaints about the Harley-Davidson flush mount gas cap is the sticking pop-up mechanism. The pop-up design is supposed to make it easy to unscrew the cap, but in practice, it doesn’t always work as it should. Owners have reported that the cap doesn’t pop up after the quarter-turn release, making it frustrating to remove.
At first, this may seem like a minor inconvenience. You might think, “I’ll just give it a little push,” but when the pop-up function stops working altogether, you’re left in a bind. You might even find yourself stuck at the gas station, unable to refuel. This issue doesn’t just happen on older models, either — it can affect newer bikes, too.
Some riders have gone so far as to remove the decorative trim ring in an attempt to pry the cap off, but that’s hardly a convenient fix. It’s clear that the pop-up mechanism is a weak point in the design, and for many, it leads to a much bigger headache than expected.
2. Fuel Leaks and Fumes
Now, let’s talk about something far more serious: fuel leaks. I’ve heard from riders who have experienced fuel “puking” out of the filler neck while riding or when stopped at a light. Not only does this waste fuel, but it’s a serious safety risk, especially with the heat from the engine. Fuel leaking onto a hot exhaust pipe can lead to dangerous situations.
Beyond the obvious risk of fire, fuel leaks also lead to an overpowering fuel smell. I’ve experienced this myself — you park your bike and it reeks of gasoline. Worse yet, when riding, the fumes can be so strong that it becomes hard to breathe, and it’s even been described as choking riders at speed.
There are two potential causes for these leaks: external and internal. External leaks are typically easy to spot. If the cap isn’t tightly sealed or the O-ring is damaged, you may notice gasoline dripping out. But the real challenge comes with internal leaks, where fuel or fumes escape through the pop-up mechanism itself. It’s difficult to diagnose this type of leak without a closer inspection, but it’s important to know that simply replacing the O-ring might not solve the issue.
3. Venting Problems
Another issue that riders face with the flush mount gas cap is related to venting. The gas cap plays a key role in the bike’s fuel tank evaporative emission (EVAP) system. A properly functioning gas cap allows air to enter the tank as fuel is consumed to prevent a vacuum, and it also allows pressure to escape when the fuel heats up.
When the venting system fails, you might notice fuel starvation, where the engine stalls as if it’s run out of gas. This often happens when the vacuum in the tank becomes too strong. I’ve heard stories from riders who’ve had to open their gas cap to relieve the pressure, only to find that fuel flows more freely once the cap is off. On hot days, if the vent is blocked, fuel can overflow or the cap can pop up, causing leaks.
In short, a poorly functioning venting system can affect your bike’s performance and potentially leave you stranded.
4. Fitment Issues
Lastly, there’s the issue of fitment. While Harley-Davidson flush mount caps are designed to fit specific models, they don’t always do so perfectly. Some riders have reported issues with the threads not matching up properly, causing the cap to either fail to screw in or not sit flush with the tank. In some cases, the trim ring doesn’t align well, leaving visible gaps.
This problem isn’t limited to aftermarket products either. OEM flush mount caps have been known to suffer from these fitment issues as well. Inconsistent quality control during manufacturing can lead to parts that don’t fit as they should, leaving riders with a less-than-ideal installation.
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5. Why the Flush Mount Gas Cap Fails
Some of the issues with the Harley-Davidson flush mount gas cap happen because of design flaws or defects in the factory. Understanding why these problems occur is key to fixing them. Let’s look at the main reasons behind these failures.
1. Poor Threads in the Filler Neck
One big problem with the flush mount gas cap is in the fuel tank itself. On certain Harley-Davidson bikes from 2008 to 2011, the threads inside the tank’s filler neck were not made right. This problem was so bad that Harley-Davidson had to recall those models.
When the threads were bad, it made it hard to get a good seal between the gas cap and the tank. No matter how many times you replaced the cap, it still leaked fuel. If you have a bike from 2008-2011, it’s important to get the tank’s threads fixed before replacing the cap. Just changing the cap won’t help if the filler neck threads are the real issue.
2. Harley’s Design Fix
After hearing so many complaints, Harley-Davidson made a change to the flush mount cap. They replaced the original part, number 62825-06B, with a new part, number 63135-10. This was meant to fix the sticking mechanism and leaking problems.
So, if your flush mount cap is giving you trouble, make sure you have the newer part. If you’re still using the older one, the issue might still be there. You can ask your dealer to check the part number and get the updated cap if you need it.
3. Parts Wear Out Over Time
The gas cap also suffers from wear and tear. The rubber O-ring that seals the cap can get damaged over time. Gasoline, especially fuel with ethanol, breaks down the rubber, making it brittle or stretched. If the O-ring isn’t sealing right, fuel can leak out.
It’s smart to check the O-ring from time to time. If it looks worn out, replace it. It’s an easy fix that can save you from bigger problems later on.
4. Aftermarket Caps: The Risk of Poor Quality
Some riders turn to aftermarket gas caps because they’re cheaper. But these options come with their own set of problems. One of the biggest issues is poor quality control. Aftermarket caps don’t always fit properly. Sometimes they don’t screw into the tank right, or they don’t sit flush with the trim ring. This can cause gaps and fuel leaks.
Other times, even when the cap fits, it doesn’t work well. Riders have reported broken springs or pop-up mechanisms that don’t function. Aftermarket caps are often cheaper, but they don’t always hold up.
Well-known brands like HogWorkz have mixed reviews. Some riders have had good luck, while others have had to return or replace the parts. If you’re looking for a reliable gas cap, sticking with the OEM cap might save you the headache of dealing with faulty aftermarket options.
How to Fix the Problems with Harley-Davidson Flush Mount Gas Caps
If you’re facing issues with your Harley-Davidson flush mount gas cap, don’t worry. There are several ways to address these problems without spending too much money. Whether you’re dealing with a sticking pop-up mechanism, fuel leaks, or venting issues, there are fixes you can try at home. Here’s how I’ve handled some of these problems myself.
1. Fixing the Sticking Pop-Up Mechanism
If your pop-up mechanism isn’t working, it’s usually because the internal parts have become stuck. This is especially common if the mechanism hasn’t been maintained properly. The solution? Cleaning and lubricating the mechanism.
Start by removing the cap from the bike. Then, apply a small amount of lubricant to the internal parts — the plunger, shaft, and spring. I’ve had success using light oils like 3-in-1 oil or sewing machine oil, but white lithium grease works best for long-term results. Once the lubricant is applied, move the pop-up mechanism up and down a few times to ensure everything is moving smoothly.
This fix works wonders. Regular cleaning and lubrication every few thousand miles can keep the mechanism working like new.
2. Replacing the O-Ring to Stop Fuel Leaks
If your flush mount cap is leaking, the O-ring might be the problem. It’s common for the O-ring to wear out over time, especially with the harsh chemicals in modern fuel. Fortunately, replacing the O-ring is a simple and inexpensive fix.
To do this, remove the cap and take a look at the O-ring. If it’s cracked, stretched, or flattened, it’s time to replace it. Harley-Davidson caps use a standard rubber O-ring, but you can upgrade to a Viton O-ring for better durability. Viton is a synthetic rubber that resists chemicals and heat better than regular rubber, making it a great choice for fuel systems.
Once you’ve replaced the O-ring, make sure the cap fits snugly and seals tightly. This should stop the leaks and prevent fuel fumes from escaping.
3. Dealing with Venting Issues
If your bike is stalling or running poorly due to venting problems, there are a few steps you can take to fix it. The venting system in the gas cap allows air to enter the tank and fuel vapors to escape. If it’s clogged or blocked, you could face problems like fuel starvation or pressure build-up in the tank.
First, check the venting system to make sure it’s clear. Some riders have found that cleaning the vent with compressed air can help restore function. If you continue to experience fuel starvation or pressure issues, you might need to replace the gas cap entirely, especially if it’s not venting properly.
4. Proper Installation and Maintenance
One of the easiest ways to prevent problems with your flush mount gas cap is to install it correctly. Follow Harley-Davidson’s instructions closely when installing the cap and trim ring. Make sure the tank surface is clean and free of debris before applying the trim ring. A little attention to detail during installation can help prevent issues down the road.
Also, remember that flush mount caps require maintenance. They aren’t “set it and forget it” parts. Regularly inspect the cap for signs of wear or damage. Tighten the cap correctly to ensure a good seal, and never overfill the tank. If the cap is too tight or the tank is overfilled, it can lead to leaks and venting issues.
Exploring the Aftermarket Options for Flush Mount Gas Caps
If you’re looking to replace your Harley-Davidson flush mount gas cap, you’ll find a variety of aftermarket options available. While these options may seem tempting due to their lower price points, they come with their own set of challenges. It’s important to weigh the pros and cons before deciding which route to go.
1. OEM Flush Mount Gas Caps: The Safe Bet (But Not Without Issues)
Harley-Davidson’s own OEM flush mount gas cap is often seen as the most reliable option. It fits well and is designed for Harley bikes, so you can expect it to perform as expected — with regular maintenance. However, it’s not without its drawbacks. The primary issue with the OEM cap is the persistent sticking of the pop-up mechanism. Despite being the most trusted option, the cap still requires routine cleaning and lubrication to keep it functioning properly.
The other downside is the price. The OEM cap is significantly more expensive than aftermarket options, which can be frustrating for riders who just want a simple, reliable solution. While the OEM cap does provide a high-quality finish and seamless integration with your bike, you’re paying a premium for that peace of mind.
2. Aftermarket Flush Mount Gas Caps: Lower Cost, Higher Risk
Aftermarket flush mount gas caps offer a much cheaper alternative to the Harley-Davidson OEM option. Brands like Kuryakyn and HogWorkz offer stylish flush mount caps at lower prices. However, these caps often come with a higher risk of problems.
Kuryakyn is known for its high-quality designs, offering options like pop-up caps and billet aluminum construction. While they’re generally seen as a solid choice, some riders report that the pop-up mechanism can be difficult to operate, and the O-ring is sometimes too thick. That can make the cap harder to screw on or lead to issues with the seal.
HogWorkz, on the other hand, is a popular mid-range choice, but it comes with a lot of variability. Some users report poor fitment, with the threads not matching up properly, making installation difficult. Additionally, the pop-up mechanism may break down over time. If you’re looking for an affordable option, be prepared to deal with some potential headaches.
3. Budget Aftermarket Caps: A Gamble
When you look at budget aftermarket caps from online retailers like Amazon or eBay, the risk increases significantly. Many of these options have received poor reviews due to a variety of issues. Some caps rattle excessively, while others fail to fit properly or leak fuel.
While the low price might seem tempting, many riders have shared stories of receiving faulty caps that didn’t work as expected. Whether it’s a non-functional pop-up mechanism or a cap that doesn’t sit flush with the tank, budget options tend to be hit or miss.
If you’re on a tight budget and willing to take a gamble, you might find a functional unit, but there’s a high chance of receiving a poor-quality part that doesn’t live up to expectations.
FAQs: Harley Davidson Flush Mount Gas Cap Problems
1. What are the common problems with Harley-Davidson flush mount gas caps?
Harley-Davidson flush mount gas caps can have issues like sticking pop-up mechanisms, fuel leaks, venting problems, and fitment issues with the trim ring. Regular maintenance helps fix most problems.
2. Why does the pop-up mechanism on my Harley-Davidson flush mount gas cap stick?
The pop-up mechanism can get stuck due to corrosion, lack of lubrication, or wear over time. Cleaning and applying lubricant to the internal parts can help keep it working smoothly.
3. How can I fix a fuel leak in my Harley-Davidson flush mount gas cap?
Fuel leaks are often caused by a worn-out O-ring. Replacing the O-ring with a new one, or upgrading to a Viton O-ring, can stop leaks and prevent fuel fumes.
4. How do I fix venting issues with my Harley-Davidson gas cap?
Venting issues happen when the cap doesn’t allow air into the tank or lets fuel vapor escape. Clean the venting system and ensure the cap is properly sealed to fix these problems.
5. Can I use aftermarket flush mount gas caps on my Harley-Davidson bike?
Yes, aftermarket flush mount gas caps are available, but they often come with fitment and quality issues. Always ensure proper fit and check reviews before buying.
6. Should I stick with the OEM Harley-Davidson flush mount gas cap or buy an aftermarket one?
If you prefer reliability and a perfect fit, the OEM cap is the best choice, though it can have some issues. Aftermarket caps are cheaper but may come with quality or fitment problems.
7. How do I maintain my Harley-Davidson flush mount gas cap to avoid problems?
To maintain your flush mount cap, clean it regularly, lubricate the pop-up mechanism every few thousand miles, and replace the O-ring if it shows signs of wear.
8. How do I know if my Harley-Davidson flush mount gas cap is defective?
Signs of a defective gas cap include the pop-up mechanism not working, fuel leaking, or venting problems. If the issues persist, check the O-ring or consider replacing the cap.
9. Can I fix a sticky pop-up mechanism on my Harley-Davidson gas cap myself?
Yes, you can fix a sticky pop-up by cleaning and lubricating the mechanism. Use light oils or white lithium grease to keep the parts moving smoothly.
10. What should I do if my Harley-Davidson flush mount gas cap doesn’t fit properly?
If your gas cap doesn’t fit, check the threads and make sure you’re using the correct part for your bike. If fitment issues persist, consider going for an OEM replacement.
Final Thoughts on Harley Davidson Flush Mount Gas Caps
At the end of the day, the Harley-Davidson flush mount gas cap is a great way to improve the look of your bike, but it comes with its fair share of problems. If you’re considering installing one, it’s important to know what you’re getting into.
While the sleek, low-profile design is appealing, it doesn’t come without challenges. The sticking pop-up mechanism, fuel leaks, and venting issues are real problems that many riders have encountered. These issues can range from minor annoyances to significant safety concerns, especially if the fuel leaks or the venting system malfunctions.
However, all is not lost. There are ways to fix many of these problems, and proactive maintenance can go a long way in keeping your flush mount cap in good working order. Regular lubrication, replacing worn-out O-rings, and checking the cap’s fit can help you avoid some of the most common issues.
If you want a more reliable solution, sticking with the standard screw-on cap might be your best bet. These caps tend to have fewer problems, but they don’t offer the same sleek look as the flush mount cap. Ultimately, it comes down to what’s more important to you: the aesthetics of your bike or its performance and reliability.
If you do choose to go with a flush mount gas cap, be sure to choose wisely. Consider the risks of aftermarket options and the higher cost of OEM caps. Don’t forget that maintaining your cap is key to avoiding the frustrations many riders face with these parts. And if you’re one of the unlucky ones whose bike was affected by the Emissions Recall 0613, make sure your filler neck has been fixed properly.
In the end, the flush mount gas cap is a cool modification that adds style, but like any part on your bike, it requires attention and care. By staying on top of maintenance and choosing the right product for your needs, you can enjoy a smooth ride and a great-looking bike without the constant headaches.