Riding a Dirt Bike with Leaking Fork Seals


If you landed on this page, I am assuming that your dirt bike has a leaking fork seal, but you do not have enough time to replace it before an upcoming weekend ride. Now you are wondering what risks are involved if you decide to ride with the leaking fork seal.

Leaking fork seals are a common problem for many dirt bike riders because seals experience wear and tear after prolonged used. The life of a fork seal depends on how the bike is used, where it is used, and regular maintenance measures.

In this article we give you more information on leaking fork seals, and what you should do when you spot them.

How to Recognize Leaking Fork Seals

You can easily identify leaking fork seals by inspecting the fork tube just beneath the dust seal. If it is leaking, you will notice fork oil on the exterior of the tube.

This problem should not be ignored because the oil will continue to drain out of the fork. This will affect the fork’s performance and can make the dirt bike unsafe to ride.

Leaking fork seals should be repaired or replaced right away, and it is better to replace the seals and lubricant in both of the forks at the same time. If you are not sure about how to do this, you can seek the services of a local bike mechanic.

Before you repair the problem, you can save yourself some trouble by getting some inexpensive seal savers. These can help to prevent the problem all together.

What is the Cause of Leaking Fork Seals?

The problem of leaking fork seals can be brought about by several causes such as:

  1. General Wear and Tear

The seals do a huge job of preventing dirt, debris and junk from entering the inside of the fork. They are built to last for long, but they should endure for 40 hours riding time or more before they require replacement.

How long they last is dependent on how you ride, where you ride, and how keen you are on cleaning and maintaining them. Bikes that are ridden on high impact roads will require seal replacement more often than those which are ridden more calmly.

Every few years you need to change the fork oil and the seals regardless of the usage and maintenance. This is because the oil gets dirty and loses its lubricant properties with constant bike usage.

  • Imperfections on the fork tube

Pieces of stone, scratches, elevations and dents on the fork tube will wear away the seals because they will slide over them when in use and lead to premature leaks. When changing the fork seals, you should never forget to check for any imperfections and just sand them off with the help of very fine sandpaper.

As you sand, ensure you only sand with side to side movements, and not up and down. If it is not possible to sand out the imperfection 100%, the seals might require re-chroming.

  • Dirt, grit or dust trapped inside

Your leaky fork seals might simply have some dust, debris or grit wedged between the inner tube (fork tube) and the seal leading to an unfinished seal. In such a case you can fix the problem by carefully cleaning the dirt out using a thin piece of filmstrip or any other suitable tool that fits in between the fork tube and the seal.

Dangers of Riding a Bike with a Leaking Fork Seal

Loss of fork oil reduces the ride safety of a dirt bike significantly depending on where and how you plan to ride the bike. The falling levels of oil change the behavior of the front suspension and therefore the bike’s control.

If the problem is left unfixed for too long, the fork oil can soak slowly into the bike’s brake pads, leading to a significant drop in the efficiency of the braking mechanism.

How to Clean Fork Seals

If you have leaking fork seals and do not have enough time to get another one before your next ride event, there is still something you can do. You can try to clean the seals by pulling down the wipers and running a thin sheet of plastic film, a feeler gauge or even a playing card between the lip of the seal and the fork tube.

Using some 35mmm film stock, and a bit of sheet plastic can do the job very well, or you can use a commercial seal cleaner. In many cases, the leak is caused by grit or muck being stuck between the seal and the fork tube, therefore running some thin plastic in-between there will remove the grit and the seals will be able to seal properly again.

This seal cleaning trick can solve your problem and keep them leak free for many miles. If this works out, you can use the money you had intended for replacing the seals to purchase more gas. As a matter of fact, most leaking seals do not require replacement, cleaning off the debris stuck between the seal and tube can solve the problem.

The following is a detailed procedure on how to clean fork seals and dust seals:

  • Start by removing the lower fork guards so that you can have better access to the seals.
  • Use a clean, lint-free cloth to wipe off dirt and oil from the fork legs at the lower part.
  • With the help of a flat head screwdriver, separate the dust seal from the upper part of the fork tube. Do this very carefully so that you do not damage the dust seal or the fork.
  • Cover the tip of a small screw driver with a lint-free cloth and use it to remove any grit that is concealed beneath the lip. Cotton swabs also do the job perfectly.
  • Take a thin piece of filmstrip (you can also use Seal Mate or the Risk Racing Seal Doctor) and slide it up beneath the inner seal carefully and move it upwards and downwards around the fork tube. The point is to remove any grit that might be stuck in the seal, therefore be sure to move the thin film piece forwards with the start of the piece at the front. This is to avoid forcing the grit deeper inside.
  • Compress the forks several times and wipe off any oil you notice on the lower end of the fork tube. You might have to repeat the process several times until there’s no oil leaking onto the fork tube.
  • After the lip is freed of dirt, clean the dust seal in the same way and put it back in its place with the help of your fingers.

If the forks do not stop leaking that means your oil seal is damaged and requires replacement. Repair at a mechanic shop takes less than an hour.

After you have cleaned, repaired or replaced your fork seals, you need to take great care of them. Wipe off dirt, insects and road residue from your bike’s fork tubes.

Given that you have fork guards, ensure they are lined up well, and if you ride off-road consider extra fork protectors. Some manufacturers supply simple neoprene wraps for preventing dirt, mud and stones from damaging the forks.

If your fork has lost a noticeable amount of oil, you need to change the oil and the seal as well. Investing in a good pair of seal savers can help to keep the muck out. They come at a low price and are great for sand riders. However, if you ride in muddy conditions, it is better to slide these seal savers over the exterior fork because they can easily trap mud.

How to Fix Leaking Fork Seals With the Seal Mate Tool

The Seal Mate Tool is designed to repair leaking fork seals and it works with almost any type of dirt bike. In just a few minutes, you can easily reseal your fork seals without having to remove and disassemble your forks.

The following instructions show you how to repair leaking fork seals using Seal Mate:

  • Clean the whole area around the dust seal
  • With the help of a flat head screwdriver, slide away the dust seal to expose the oil seal
  • Clean the area surrounding the oil seal with contact cleaner, lint-free rug or a toothbrush.
  • Insert the rear end of the Seal Mate tool between the inner tube and the seal about ½” deep. Do this with care.
  • Slowly rotate Seal Mate around the fork tube ensuring that the hooked part is the leading end.
  • After a full rotation, continue rotating the Seal Mate tool as you remove it. Wipe down the fork tube and seal.
  • Hold the front brake and pump the forks multiple times.
  • Wipe off the fork tube and seal again and pump once more.
  • Check whether the fork tube has excess oil. If there is excess oil, grab the front brakes again, pump and wipe off the oil.
  • Clean the dust seal also and put it back to its original place.

How to Replace Fork Seals

The fork of a dirt bike is the part used to connect the main frame to the axle and the front wheel. This part helps in braking, suspension and in changing direction while riding. The fork is made up of 2 tubes containing lubricating oil and both of them have seals.

These seals are 2: the oil seal and the dust seal. The oil seal prevents the oil from leaking out of the fork leg, while the dust seal prevents dust and dirt from reaching the oil seal. 

Fork seals need to be cleaned or changed when they start to leak, because if ignored, the oil may leak onto the bike’s brake pads and damage the motorcycle or the oil could run out completely and destroy your bike. Below are detailed steps on how to replace fork seals:

  1. Put your motorcycle in gear and chock the back wheel, raise your front wheel off the ground as much as necessary with the help of a stable jack or other stand.
  2. Unbolt the brake calipers, fender and the front wheel.
  3. Disassemble the fork by loosening the bolts that attach the fork legs to the frame.
  4. Remove the dust steal, and then find the fork itself within a grove.
  5. Flush the area to get rid of dirt within the fork
  6. Pull out the fork from under the clip that puts it in place.
  7. Remove any rust and imperfections that caused the old seal to leak.
  8. Soak a lint-free rug with oil and lubricate the area where the old seal was placed.
  9. Rub oil on the inside area of the new fork seal and slide it down carefully into its place. Use a seal driver to set the new seal firmly into place.
  10. Put back the clip, the dust seal and the damping rod.
  11. Pour fresh oil into the new fork, and measure the height as needed.
  12. Do the same for the other fork leg and reassemble the bike’s front end.

If you have never replaced a bike’s fork seals before, you should take it to your local bike repair mechanic to do the job for you. It is not something you should try if are not certain on how to do it.

Both fork seals need to be replaced at the same time. It does not matter whether it is just one side that is leaking.

Conclusion

Just like any other mechanical part, fork seals are bound to wear out at some point and when they do, the fork oil can leak out. When this happens, you need to replace the leaking fork seals, or you can also opt to clean out the grit stuck between the fork tube and the dust seal. Most leaking fork seals do not require replacement, just a bit of cleaning. However, if cleaning does not solve the leaking problem, replacement may be necessary. h

Daniel Mose

Daniel is a big fan of dirt biking. I own KTM 250 SX-F. I love learning how to maintain this dirt bike and ensure it lasts long while serving me without any issues. Join me in this journey as I document stuff that we, as dirt bike lovers, ought to know.

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