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DIY! How to Replace Front Fork Oil Seal Taught by Professional Mechanic

oils

When you noticed the oil leaking from the front fork….. The brake performance will significantly reduce if the fork oil flows and adheres to the brake disc or caliper.

If you want to replace the fork oil seal immediately, you need to be cautious and watchful to avoid damage to the surrounding parts when replacing. Now, let’s challenge the fork oil seal replacement!!


1. There are types that the fork oil seal can be pulled out by sliding the inner tube!

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I am trying to disassemble the “upright front forks”. If the front fork after disassembly is not operated in a stable state, it is easy to damage the parts. Please think of a workbench and large vise as necessities.

Here’s a close-up look of the concrete “fork seal exchange.” “Even though the fork oil seal was replaced, another oil leak has occurred…!?” This kind of trouble is surprisingly common. Here are some tips for replacing the fork oil seal.

There are two types of front forks: upright type and inverted type, but I will explain the work points based on the subject “upright type”. The following are the required things to do before removing the front forks from the motorcycle body:

① Loosen the top bolt at the top of the inner tube in advance.
② Loosen the seat pipe (also called a damper pipe) fixing bolt that is tightened from below the bottom case.

It is OK to loosen just enough to release the tightening torque. Actually, it is easy to loosen the upper and lower bolts, if the front fork is still attached to the motorcycle. The top bolt is easy to loosen if the clamp bolt on the stem side (under the bracket side) is not loosed that secures the inner tube because the inner tube can not rotate.

Also, right after removing the front wheel, the seat pipe tightening bolts might be easily loosened. The reason is that, before removing the top bolt, since the inner front fork spring is still compressed, the seat pipe is difficult to idle, so it means it is easy to loosen the bolt.

After disassembly, remove the top bolt and seat pipe tightening bolt of the upright fork, fix the bottom case with a large vise so as not to damage it, and remove the retaining circlip of the fork oil seal. Then slide the inner tube and remove the fork oil seal.

Since there is no slide metal to the inner tube of the old motorcycle, it can often be removed smoothly, but since there are many cases in which slide metals are installed into models after 1980, the fork seal that inserted at low pressure can be pulled out by a sliding metal.

POINT

・Check the parts list before disassembling to know the presence or absence of the sliding metal, so you don’t have to be confused when working.
・If the fork oil seal is with metal, it can be pulled out by sliding the inner tube.


2. Handle the fork oil seal carefully!

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I replaced the fork oil seal with the OEM product. Depending on the model, special parts with low friction loss (sliding resistance) are also available, so when purchasing parts be sure to check whether the special parts are compatible.


3. Rubber grease required for smooth insertion

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When installing the fork oil seal, be sure to use rubber grease, the grease lubrication is to prevent damage to the seal lip into which the inner tube is inserted. Rubber grease is a grease used to reduce the resistance of metal to rubber parts. Silicon grease can also be substituted.


4. The technique when inserting into the inner tube!?

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If the fork oil seal is carelessly inserted at the end of the inner tube, it may cut off the important seal lip or cause damage. Although it is not limited to the fork oil seal, in such situations, let’s insert an oil seal instead of a plastic bag as a protection tool.

POINT

・Let’s order the parts that match the model in advance.
・When installing, use rubber grease to increase the lubricity.
・The most important thing is not to damage the seal lip!!


5. Techniques and procedures for successful press-fitting

Prepare a fork seal driver of the special tool, and adjust the driving piece into 3 equal parts (120 degrees), then to strike and press-fit by using the weight. Slowly drive the fork oil seal in while keeping the balance of it. If the fork oil seal is tilted, strike hard only the shallow side to maintain the equilibrium.

Click here for Fork Seal Driver

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The front forks for models in the 1980s and beyond has a sliding metal in the inner tube, and the fork oil seal is pulled off together with the inner tube when pulled off it. But in the case of an old motorcycle, there is no sliding metal, and only the inner tube is removed, and the fork oil seal remains in the bottom case. In such a case, use a special tool.

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There are various types of special tools for removing the oil seal, so choose a tool that matches your situation. If you have several kinds of special tools, you can perform more reliable maintenance. It is important to remove the fork oil seal in order not to scratch the inside of the bottom case.

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If the oil seal is forcibly removed by using a flathead screwdriver or tire lever, it may scratch the oil seal press-fit portion of the bottom case (internal circumference). This vertical scratch may adversely affect the oil seal and cause oil leakage and bleeding again.

POINT

・If the oil seal is tilted at the time of press-fitting, try to respond quickly in order to maintain the equilibrium.
・If you continue to press-fit forcibly while in the tilted angle, the fork oil seal will deform and it will cause oil leakage.


6. “Various Special Tools” for front forks that are convenient to use

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Various types of fork seal drivers and pullers are sold from various tool manufacturers. As the name implies, a “special tool” that is effective for special tasks is one that it is better to have a variety of products (I used Hasco special tools this time). For the finishing of the maintenance, the fork oil is injected and the left and right oil level (oil surface height) is adjusted. The most convenient oil level adjustment syringe is made by DAYTONA.

Click here for DAYTONA Fork Oil Level Adjustment Tool

POINT

・By relying on the oil seal puller of the special tool, clean extraction can be done.
・Scratches on the inner wall of the bottom case can cause oil bleeding.
・When press-fitting the fork oil seal with an oil seal screwdriver, hit the whole thing on balance don’t hit just one place.

See Accessories of DAYTONA
See Accessories of SUPER ZOIL

Webike staff

Webike staff

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Webike Moto News Editor

Our mission is to look for unique and valuable news that are from Japan and Asia related to motorcycles and publish to the world. "Webike staff" is name of a team who edit, translate and draft the articles we publish that are brought from all our branches around the world. Not all of our employees ride motorcycle, but find worth living to bring reader say "wow".
 

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