Replacing Fork Seals

By:Panne

Ok, here goes:
I’m not the world’s greatest DIY guy unless DIY’s the acronym for Destroy It Yourself. The oil seals on my 950’s forks had to be replaced and I decided to tackle this myself. With some advice from Lito and a tool acquired from Runner, it actually went swimmingly in the end. This is what you would need to do:

Step 1

You will need a bench vice to clamp the fork. I do not have one, thus I used my old triple clamp like so:

Step 2

Fork inserted and pinch bolts tightened. Ready to loosen fork cap.


Step 3

Now, you will need the tool pictured below. Got mine from Runner. You can also fashion a similar tool but please DO NOT use a punch and hammer to loosen the fork cap.


Step 4

Unscrew the fork cap.


Step 5

Compress the front spring and insert a thin 22mm open-end spanner to hold the damper rod in position. Remove the fork cap using a 24mm spanner as depicted.


Step 6

Remove the preload spacer and then the fork spring


Step 7

Remove the adjustment tube.


Step 8

Turn the fork upside down over a suitable container to allow old oil to drain. You can also move the damper rod up and down a few times which will help it drain faster. I left mine overnight to ensure it drained properly.


Step 9

Using a 19mm socket, remove the compression piston. If it turns with the fork cartridge, bend the damper rod a bit to the side to prevent this. Patience is the keyword here, it took me a while and a few curses to remove it.

Step 10

Loosen the dust wiper (white arrow), use a flat blade screwdriver if necessary, and slide it down the fork leg. Using a small blowtorch, warm the upper fork tube in the region of the red arrow. Do not make it too hot, you only want the DU bush inside and the upper tube to expand in order to separate the fork tubes. Separate the fork tubes by pulling the tubes in opposite directions.


Step 11

Remove the old oil seal, the support ring underneath it and the DU (copper) bush. This step completes the disassembly.


Step 12

Clean and dry all the fork components properly. I used brake cleaner to clean the inside of the fork tubes, both upper and lower. To remove oil from the rest of the components, use paper towels. I’ve found that it works quite well because it is so absorbent. Now, we are ready to start with reassembly.

Step 13

First of all, wrap some insulation tape around the top of the lower fork tube. This will prevent damage to the dust wiper and oil seal when re-installing them.


Step 14

Grease the inside of the dust wiper using waterproof grease (Bel-Ray or whatever brand floats your boat).


Step 15

Slide the dust wiper onto the lower fork tube.


Step 16

Next comes the circlip which holds the oil seal in place.


Step 17

Grease the inside of the new oil seal with waterproof grease and apply fork oil to its outside.


Step 18

Slide the oil seal onto the lower fork tube. Do this carefully, as you do not want to damage the new seal.

Step 19

Next slide over the support ring for the oil seal.


Step 20

Slide the DU (copper) bush onto the lower fork tube.


Step 21

Gently slide the upper fork tube onto the lower tube.


Step 22

Here is where you will make a cheap tool to seat the oil seal and DU bush. Take a length of 50mm PVC pipe, you will need a piece which is approx. 150mm long. From this, you will cut 2 pieces. The first piece should be roughly 60mm long and the second slightly longer, about 70mm long will do. Cut both these pieces lengthwise as illustrated below.


Step 23

Put the longer PVC piece onto the lower fork leg and then put the shorter piece over that. Clamp both pieces together using an ordinary hose clamp. Ensure that it is tight enough to prevent it from slipping on the fork leg. Now, you can move the upper tube towards your PVC tool which will then press the DU bush into its seat in the upper tube. Move the PVC tool and then do the same with the oil seal. Be careful not to damage the oil seal.


Step 24

With the oil seal properly seated, insert the circlip. It is VERY IMPORTANT for the circlip to be properly fitted into its groove, as it holds the oil seal in place!!!


Step 25

Seat the dust wiper.


Step 26

Insert the fork cartridge.


Step 27

Replace the compression piston and torque it to 25Nm. If it turns with the fork cartridge, bend the damper rod a bit to the side to prevent it from doing so. Again, patience is the keyword here.

(Ed. Penne is a member of the South African Wild Dog Adventure Forum)