Why Do My Fork Seals Keep Leaking?

That moment you see even the smallest trace of fork oil on your fork tube your heart sinks.  You know it is just a matter of time before you have a gusher springing from your fork seal.  This will cause your suspension to turn in a pogo stick with no damping.  This is not fast, nor is it safe.  To add salt to the wound, the fork oil will inevitably soak your front brake pads.  Now you have another safety issue, plus you have to add new brake pads to the suspension bill at the dealership.  Basically, something as simple as a leaky fork seal can ruin a ride or race day.

Fork seals leak from normal wear and tear, age, and debris getting into the seals. Imperfections and nicks in the chrome can also make your fork seals leak. However, the majority of the time your fork seals are leaking it's simply because debris is caught in the seal holding it open and allowing fork oil to sneak by.  

When you first notice the leak is the best time to take immediate action.  While you may be tempted to ignore it for now so you can keep racing, you know what will happen if you do ignore it. If you’re tearing out your hair, wondering why your fork seals keep leaking, read on to discover the issues and how to fix them so you can get back to racing quickly.

Index
1	How Do Fork Seals Work?
2	First, What To Look For
3	What Makes Seals Leak in the First Place?
4	What Can You Do to Fix Fork Seals?
5	Why Do Fork Seals Keep Leaking?
6	Conclusion

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How Do Fork Seals Work?

Modern motorcycle suspension is simply amazing.  The amount of travel they have and the components inside controlling the speed of compression and rebound is all thanks to over 100 years of evolution in motorcycle design. 

One reason today's suspension is so good is the use of oil as a speed controlling medium in the suspension.  However, the challenge is keeping the oil where it belongs while also allowing the suspension to travel up and down thousands and thousands of times.  The only component holding that oil in, even under high pressure during quick compression, is a tiny “lip” of rubber called the oil seal. 

To bring it down to the basics, this tiny “lip” sits between the inner and outer fork tubes.  As you can imagine, the connection between the inner fork tube and the oil seal needs to be perfect for it to prevent the oil from leaking.  If the oil seal gets old or hard, it will no longer prevent the oil from leaking.  Also, as described above, if something gets lodged in between the seal and the fork tube, it will allow oil to leak by.

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First, What To Look For

As mentioned above, look for oil dripping down from the fork seal.  Sometimes the oil is hard to see, but don’t worry, the oil attracts dirt and soon you will see a dirty mess around your fork seal (traditional forks) or at the bottom of your fork tube near your front axle (upside-down forks like on modern motocross bikes).  Basically, Oil dripping down the front shaft should be your first clue that your fork seals are leaking. 

Another obvious clue is when there is a puddle of oil under your forks, or your suspension just feels like an uncontrolled and bouncy spring. When enough oil leaks out, your bike becomes unsafe to ride.

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What Makes Seals Leak in the First Place?

Seals Leak From Normal Wear and Tear

Seals take a lot of beating from normal use, and even more of a beating when ridden harder than normal. Dirt bike racing or riding off-road on dirt trails makes your seals work even more to keep the dirt and other junk out. Because they have a hard life, you should maintain your fork seals or change your seals after 40 hours of riding time.  Most people simply wait until they leak to maintain or replace, but serious racers should be prepared and never let a leaky fork seal ruin a race day or their race results.

Even if you don’t ride your bike very often, you should change the oil and seals every two years because the idle time will dry out your fork seals and cause leaks.  

Dirt and Other Debris Can Get in the Seals

As already mentioned, dirt, sand, and other junk gets between the seal and inner fork tube, creating an incomplete seal. If that is what is happening, you need to clean them out following the methods described in the next section. 

Inner Fork Tube Imperfections Can Cause Leakage

When riding, rocks and other debris will inevitably fly up and dent the innertube or cause the fork to have scratches or chips. When this happens, it causes your seals to leak before they are worn out. You need to check the fork every so often to make sure this is not happening.

If it does, you can use 400 grit sandpaper to buff them out, using a side-to-side motion, rather than an up and down movement is better, but the best is a “crosshatch” pattern, similar to honing a cylinder.  If your fork tube had an imperfection it is likely it also damaged the fork seal. 

You may need to fix the imperfection and replace your fork seal to fully correct the leak.  If you only replace the fork seal, the imperfection in the fork tube will simply damage the new fork seal as well. 

Be aware, however, that not all chips or dents can be buffed out 100%. If that happens to your bike, you may think about re-chroming it. Suspension companies like SGB Racing can recoat your fork tube, and even put higher-performing plating improving the function of your suspension.  

Extended Pressure from Tie Down straps

Those poor fork seals already take enough abuse, and then if you use a tie-down system that compresses the front forks when you are transporting you are putting a constant source of tension on the fork seals. Check out Risk Racing Lock and Load Systems they undoubtedly extend the life of your fork seals aside from making your life easier transporting your bike(s).

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What Can You Do to Fix Fork Seals?

Aside from replacing the seals, there are several things you can do to fix your fork seals and be racing again before you know it. If you cannot do it yourself, you should take your bike to a qualified bike mechanic to do it for you.  Replacing fork seals can cost between $100-200 depending on how many parts need to be replaced. 

Lift the Dust Cover and Clean Underneath Them

If you know what you’re doing, carefully pry apart the dust seal using a flathead screwdriver while being careful not to scratch the fork or damage the seal. Using a lint-free cloth or a cotton swab, clean out any mud or debris stuck under the lip before putting everything back together again.

If that doesn’t take care of the problem, remove the dust seal and use a piece of camera film or another flexible thin object to wrap around the shaft, then push up until you get under the lip. Using this method can get any debris out that a cotton swab might miss. Then put everything back. 

The downside of this method is it shoves the debris that was causing the leak into the suspension.  The small valving inside the suspension cannot handle debris and therefore, further damage can be caused by fixing a simple leak in this manner. 

Use the Seal Doctor on the Fork

Leaks happen almost anywhere at the worst times, like when you’re at the track or hitting the trails having the proper tools to quickly fix a leaky fork seal can save the day. The Seal Doctor by Risk Racing is the exact tool you need.  This product received 5 out of 5 stars by all the top motocross magazines proving it is the best tool to fix leaky fork seals. 

Just lower your dust seal and snap the Seal Doctor on your fork tube, insert the tooth into the leaky seal and twist.  The design of the Seal Doctor maintains the proper position and angle as you rotate around your fork tube.  It effortlessly pulls the dirt out of the fork rather than pushing it deeper into the fork.  The bottom of the Seal Doctor has a second tooth design to clean your dust seal.

The Seal Doctor also comes with a protective holder so that it can be stored safely in your toolbox or trail pack ensuring you always have the appropriate tool for the job.  There are other products on the market that attempt to do the same thing as the patented Seal Doctor, but none do it as well.

Replace Fork Seals

Fork seals should be replaced after 40 hours of riding or two years if you don’t ride very often. Even if you regularly clean the seals, they wear out eventually and leak no matter what you do to keep a tight seal. If you don’t know how to do it, you may want to take it to your local bike mechanic or become pals with a mechanically inclined moto-buddy and learn closely. 

You will need specialty tools, like fork seal drivers, to complete the job on your own.  These tools can be expensive and specific to your bike or suspension size.  A trip to the dealership to fix this issue is also expensive.  The cheapest and quickest option would be to start with the Risk Racing Seal Doctor.

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Why Do Fork Seals Keep Leaking?

You’ve done everything you can to fix the fork seals, yet they still leak.  This can be very frustrating, but for your own safety, it is important that you get it fixed properly.

The Fork Seals Are Not Put Back Together Correctly

If the fork seal leaks immediately after replacing with a new fork seal, the issue is probably improper installation of the new fork seal.  Often, the sharp edges on the fork tube can cut the delicate seal during installation.  An experienced mechanic will know proper secrets for installing the fork seal over the sharp edges of the fork tube to prevent damage to the new fork seal.

Fork Seals Are Not Completely Cleaned

If the above doesn’t stop the leak, you may want to recheck the seals, as they may not be completely clean. Even a small speck of dirt can cause the oil to leak through. Repeat the cleaning process until you are sure you have cleaned everything out from under the seals.

Once you have the seals cleaned, be sure to wipe all the dirt and bugs from the fork after every ride.

There Are Nicks in the Chrome Under the Seal

Stones and other debris can fly up and nick the chrome under the seal, creating small dents that allow small amounts of oil to leak through. The best way to take care of that is to take a super-fine piece of sandpaper to buff out the dents or nicks. However, some scratches may not be buffed out. In that case, you may need to re-chrome the fork tube.

Haul your bike differently

If you keep getting recurring fork seal leaks after repair or replacement, consider the way you transport the bike and avoid using tie-down straps to haul your bike.  The Lock-N-Loador Lock-N-Load Pro Moto Transport Systems are the best way to transport your bike while also reducing the stress on your fork seals.

Consider the conditions you ride in or install additional protection

If you ride in sandy or muddy conditions you will be more prone to fork seal contamination.  You can install special neoprene fork seal covers to further protect contaminates from reaching your fork seals.

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Conclusion

Fork seals are finicky things and need to be maintained frequently to avoid leakages. If you follow the suggestions in this article, and your fork seals are still leaking, you may need to replace the fork tube. But until you decide to have this done, take it to your bike mechanic so he or she can look over it to find the reason they leak.

Remember that the Seal Doctor device is the best tool on the market to maintain or repair fork seal leaks.  It removes the debris from the fork to makes the process quick and easy. They are available in several sizes and work for all motorcycles, dirt and street.

If you keep your fork seals in top shape, you can enjoy racing for many years with the same bike.