Harley Davidson Flush Mount Gas Cap Problems and Their Solutions

You’ve got a Harley Davidson and want to help it deliver beast-like performance for years. But there’s one problem: the flush mount gas cap.

That’s right, the one that keeps the fuel secure inside the fuel tank without allowing dirt, grime, and exterior gas to enter it. However, over years of use, the gas cap can become problematic. And when you see a Harley Davidson flush mount gas cap problem, it frustrates you. So, what’s the fuss about the gas cap and ways to solve it?

Usually, the gas cap gets worn out or loose due to years of use. Also, grime and dirt may build around it to stop it from locking correctly. Here, we’ll show you how to solve Harley Davidson flush mount gas cap problems. We’ll provide some key pointers on the damaged gas cap indicators. So, stay tuned.

Harley Davidson Flush Mount Gas Cap Problems

What Are Harley Davidson Flush Mount Gas Caps

What Are Harley Davidson Flush Mount Gas Caps

Many riders have needed help with their flush mount gas caps not fitting correctly. It can be particularly irritating if you’re trying to get back on the road. The flush cap has become loose and won’t lock properly. Then, you are forced to get stuck at a service station trying to make it all work.

So, what exactly is a flush-mount gas cap? Also, why does it need special attention? The flush mount gas cap is designed for Harley Davidson motorcycles to keep the fuel tank secure. It sits right on the entry point for fuel and stops it from leakages. This way, the flush mount gas cap stops the gas emissions, saving up to 35L of fuel yearly.

The gas cap on Harley Glide In Motorcycles has a lower profile than other motorcycle industry caps. It helps keep the overall look of the Harley bike streamlined and clean. Unfortunately, the caps often don’t fit quite right or won’t stay in place. This can leave you with an annoying leak that damages your ride.

What Are The Indicators Of A Bad Gas Cap?

What Are The Indicators Of A Bad Gas Cap

The most apparent sign is fuel leaking out of the tank. If the fluid is dripping, the O-ring seal on which the flush mount gas cap rests is probably wrong. Hence, you must check the O-ring. If it has worn out, replace it. You can perform the O-ring replacement for less than $10.

When the pressure in your fuel system gets too high, it can cause erratic idling or stalling. This could be a sign that your gas cap isn’t working correctly. It allows air into the tank as you drive. The air increases the pressure and causes uneven idles.

  • Fuel Leaks
  • Gas Smell
  • Erratic Idles
  • Difficulties Coming Out Of Gear

Diagnosing Harley Davidson Flush Mount Gas Cap Problems

Test the venting system. Before you start troubleshooting, ensure that the venting system is working correctly. The vent should open and close freely when the cap is installed and removed from the tank. Inspect for any damage or debris development.

Check for cracked or broken areas around the flush mount gas cap. Cracks in the flush mount gas cap or its components could prevent it from sealing correctly. Inspect all parts for signs of damage before proceeding to the next step. Fortunately, diagnosing the gas cap problem is easy. You can check the following three steps for it.

  • Testing The Venting System
  • Look For Debris And Damage
  • Check For Cracks

Fixing The Harley Davidson Flush Mount Gas Cap Problems

Fixing The Harley Davidson Flush Mount Gas Cap Problems

Have you been riding a Harley Davidson for a while now? If so, you know its flush mount gas cap is prone to problems. For instance, you may have noticed the lid getting loose over time. Or else the lock mechanism stops functioning. Even worse, rainwater can enter through a crack and enter the tank.

Fortunately, there are easy fixes for this problem. With the right supplies and a little effort, you can quickly get your gas cap back to functioning. Scroll down to get details on Harley Davidson flush mount gas cap problems.

Step 1: Clean The Area Around The Cap

Clean The Area Around The Cap

The first thing to do is clean off any dirt or debris around the cap. The cleaning ensures it’s free of any obstructions. This will make removing and replacing it much more manageable. You can use a soft-bristled brush and WD-40 commercial cleaner to wipe out any hard debris. And for easier ones, you may use an old piece of cloth quickly.

Step 2: Securely Unscrew The Cap

Using a pair of pliers or screwdrivers, unscrew the Harley Davidson flush mount gas cap from its position. You should feel it loosen as you continue twisting until completely removed. Be careful during this process. Because too much force could cause damage to either the cap or the bike itself.

Also, after unscrewing, keep the screws safe for future uses. If the screws are lost, it can be tough to find the exact matches.

Step 3: Try Tightening The Old Gas Gap

Try Tightening The Old Gas Gap

You must check the old gas cap for damages. If there’s no damage, try reinstalling and tightening it correctly. Most times, gas caps become loose due to years of use. At this moment, tightening it can fix the leaks. Also, tightening the old gas cap should fit correctly into the flush mount fuel cap and fuel tank opening.

Step 4: Replace With New Cap

If nothing works, you must get a new flush-mount gas cap. Once you’ve removed your old gas cap, replace it with a new one from an authorized motorcycle parts retailer. This will guarantee quality and better performance than generic replacements. Ensure that fasteners are tightened properly before moving on to complete installation.

Usually, the gas cap replacement is an inexpensive investment. You can get the new cap for around $60 to $90. However, gas caps come in two types: Henceforth, you must check the right one for your Harley motorcycle. Or else, contact a certified Harley dealer for the replacement.

How To Prevent Future Fuel Vent Issues

How to Prevent Future Fuel Vent Issues

It’s essential to regularly check that all gas cap connections are tight and secure. It includes checking all bolts, screws, clamps, and hoses that connect to the tank and fuel system. Ensure you stay up to date with regular tune-ups and services for your bike.

It is essential during long trips or rides, often in extreme weather conditions. Regular maintenance helps you keep the Harley bike in its best condition. Ensure the motorcycle gas cap is properly tightened. You should tighten the flush mount gas cap whenever you fuel your tank.

Learn how to properly maintain your fuel vapor system, regularly check your fuel gauge, and implement fuel economy practices to avoid potential fuel vent issues in the future.

  • Regularly inspect and clean the gas cap
  • Avoid overfilling your tank
  • Use high-quality fuel
  • Perform regular maintenance

What Are The Effects Of Gas Cap Check Engine Light Problems?

What Are The Effects of Gas Cap Check Engine Light Problems

Many owners have reported check engine light problems when their gas cap has become loose. When your engine is running, fuel might escape from the tank. It escapes through the seal on the flush mount gas cap, which can cause emission system errors.

As a result, the check engine light will pop up on the dashboard. Also, an unsealed gap cap allows dirt to enter the gas tank. It contaminates the fuel, causing the check engine light issue. If you see the check engine light, there are some universal symptoms and effects. One of the effects of gas cap check engine light problems is the potential malfunction of various fuel gauges, leading to a lack of fuel flow in the vehicle.

Slow Acceleration And Engine Stumbling

When fuel escapes from the tank, it increases the ratio of air and fuel in the tank. It can affect how well your engine performs. This leads to sluggish acceleration and engine stumbling. As it happens, your Harley motorbike will not accelerate smoothly. It becomes acute when you have to stop and go in heavy traffic.

Poor Gas Mileage

The more fuel your bike loses due to faulty caps, the less mileage you get for each gas gallon. Experts suggest you may lose 25L to 35L gas due to faulty and leaky gas caps. It hits your wallet, and the unnecessary gas emission pollutes the environment, too.

Fuel Smell

You’ll notice an unpleasantly strong gasoline smell when you drive around with a check engine light turned on. It happens when it’s running for an extended period. That’s fuel escaping from the tank via a leaky seal on your flush mount gas cap. It is one of the surefire signs you need to replace the gas cap. We noticed a strong fuel smell from the fuel level gas cap and the left fuel tank cover.

How Far Should You Drive Without A Gas Cap?

How Far Should You Drive Without a Gas Cap

Your Harley flush tank gas cap may have gone missing. So, you may be wondering how far you can drive without it. Generally, you shouldn’t drive your Harley Davidson any more than 10-15 miles without a gas cap. Sure, you can make it further. However, leaving your tank open will eventually lead to dirt and debris entering your tank.

It will lead to clogs in the fuel line, engine damage, and decreased performance. Plus, fuel evaporation and loss are risky without a gas cap. It may seem like only a tiny amount of fuel is lost over time! Those little amounts can increase, especially with today’s fuel prices.

So, consider investing in one instead of driving without a gas cap! There’s an extensive range of Harley Davidson flush mount gas caps. These are designed to keep water, dust, and debris out on the road.


Does your Harley Davidson have an improperly installed flush mount gas cap? There are steps you can take to solve it. You should examine the gas cap for warping, cracking, and disc. Also, inspecting the tank’s body and cap for misalignment will help determine the exact problem.

If it hasn’t, you can repair it yourself. You either require minor adjustments to the mounting screws or replace the faulty parts. Then, consider reinstalling the new ones. Solving the Harley Davidson Flush mount gas cap problems will keep your bike in peak condition. It ensures a fun, enjoyable, and safe riding experience. It saves fuel costs by stopping gasoline emissions.


Can A Loose Gas Cap Cause Engine Misfire?

No, a loose gas cap cannot cause an engine to misfire. Issues with the ignition system, fuel system, or engine components typically cause engine misfires.

Can A Bad Gas Cap Cause Low Fuel Pressure?

Yes, a bad gas cap can cause low fuel pressure. A faulty gas cap can lead to a loss of pressure in the fuel system, allowing air to enter the tank and disrupt the proper flow of fuel.

What Problems Can A Loose Gas Cap Cause?

A loose gas cap can cause several problems. Firstly, it can result in fuel evaporation, leading to decreased fuel efficiency. Additionally, it can trigger the check engine light to illuminate, indicating a potential issue with the vehicle’s emissions system.

Can A Bad Gas Cap Cause Starting Problems?

No, a bad gas cap typically does not cause starting problems. The gas cap is primarily responsible for sealing the fuel tank to prevent fuel evaporation and maintain pressure in the fuel system.

Can Not Having A Gas Cap Cause Engine Problems?

Yes, not having a gas cap can cause engine problems. The gas cap is a seal to prevent dirt, debris, and moisture from entering the fuel tank.

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