Beginner's Guide to Fork seal replacement
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Thread: Beginner's Guide to Fork seal replacement

  1. #1
    Senior Member B-dub's Avatar
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    Intro - My older brother Mike and I both had to rebuild the forks on our TW's recently. We thought it would be a good idea to share the procedure so others could avoid some of the mistakes that I made. A couple of my mistakes are recorded on film, but I believe the write-up is pretty accurate. If you see the need for improvement in this guide, please share so we can make it as good as possible.



    Here's another guide Admiral completed a little over a year ago. His guide has additional insight, better pictures, and of course, Admiral's great sense of humor. I encourage you to take a look at his guide also.



    Additionally, Lizrdbrth has provided some great info on fork oil, fork service, and fork tuning or setup. I encourage you to take a look at his fork info as well. You can find it here.



    Tony recommends marking the fork tubes so they can be replaced in the same orientation as when they were removed. If the tubes are bent slightly and they are not re-installed the same as when they were removed it can adversely affect handling.



    Apparently All Balls seals are slightly bigger and tougher to install. Canadainshiver published his ingenious approach to getting them seated here starting at post #9.



    When you have the forks out is an excellent time to service the head bearings. Rainman has provided an excellent guide on the procedure for head bearings here.









    Fork Removal



    Begin by getting your bike in the air, so the front wheel is suspended. Make sure the bike is secure and will not tip over.







    Using a 10mm wrench or socket loosen the fork clamp bolts on the top triple crown.



    Next, stand astraddle the front wheel looking back, and use a 19mm socket to loosen the caps at the top of the forks.



    Use a 10mm socket or wrench to remove the clamp holding the front brake cable to the fork.



    Pull the speedometer cable mount from the front fender.



    Remove the cotter key, and with a 22mm socket or wrench loosen the axle nut. Run the nut out so it's even with the end of the axle, and tap it with a mallet or hammer to start it through. Remove the nut.







    From the other side pull the axle through and allow the wheel to rest on the ground, or on your knee. Move the wheel slightly forward to clear the forks and pull the brake backing plate from the wheel. You may have to loosen the brake adjustment to get the backing plate out. Of course, this step is unnecessary if your TW has a disc brake.



    Allow the backing plate to hang from the cables and remove the wheel.







    Use a 10mm socket or wrench to remove the fender and reflectors from the forks. Alternatively the fender may require a 5 mm allen wrench.



    With a Phillips head screwdriver loosen the clamp at the top of the fork boot.







    While holding the fork use a 12mm socket or wrench to loosen the bolts on the bottom clamp. The fork should then slide from the clamps. If not, utilize a tip by Lizrdbrth. Apply a few drops of oil in the chamfer where the tubes pass through the upper and lower triple clamps. Tap the caps of the fork tubes a few times to help distribute the oil. You may have to give it a few minutes for the oil to penetrate the clamps. The fork tubes should then slide out. As a last resort, you may need to spread the ears on the clamps very slightly by wedging a screwdriver or chisel into the opening between them. Be careful to not scratch the tube.
    Last edited by B-dub; 12-29-2014 at 11:40 PM.
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  2. #2
    Senior Member B-dub's Avatar
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    Fork disassembly







    Begin by sliding the fork boot from the forks. If you're still running OEM boots you'll have to use a straight blade screwdriver to release the bottom of the boot from the lower fork.



    Next, raise the cap end of the fork slightly and remove the cap.







    Reach into the fork and remove the spacer, washer, and spring. You may have to collapse the fork slightly to be able to reach the spring. Pull the spring out slowly so you don't pull a bunch of oil out with it.



    Pour the oil out into a container. Cycle the fork once or twice to help get the residual oil out.







    Next, you will need to remove the bolt at the bottom to separate the two parts of the fork. To do that you will need a tool to reach into the fork and hold the damper rod inside. I used a 12mm coupling nut, available at the hardware store. It's just a nut that is about 1 1/2 " long. The coupling nut fits in a 19mm socket and sticks out far enough to engage the damper rod. Put a piece of paper towel (or something similar) over the end of the socket, then push the coupling nut into the socket. This will prevent it from falling out. You will also need to add some extensions to the socket to be able to reach the head of the damper rod inside. Use a 5/16"¯ or 8mm allen wrench to hold the bolt at the bottom, and with a ratchet on your home-made tool loosen the damper rod inside. Use a rag under the top tube to cushion it and prevent scratches.



    With the damper rod loose, you can simply pull the two halves of the fork apart.



    Pull the spacer from the end of the damper rod, then invert the top half of the fork and shake it around a little bit to get the damper rod to come out.







    With a screwdriver remove the snap ring over the dust seal on the lower half of the fork. If you look closely you'll see the two ends of the snap ring. Pry one end out, then work your way around until the snap ring is removed.







    If you have a seal removal tool use it to remove the dust seal and the oil seal from the fork. If you don't have a seal removal tool a large wrench works well, just be sure to use a rag to cushion the fork so the wrench doesn't mar it. Rainman suggested using a tire iron which I think is a great idea. Again you just need to be careful not to nick or scratch the fork as you remove the seals.
    Last edited by B-dub; 12-29-2014 at 10:51 PM.
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  3. #3
    Senior Member B-dub's Avatar
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    Cleaning and inspection.



    Clean and inspect all the parts.







    Measure the length of the spring. The minimum length is 307mm, or 12.1 inches. 1/8"¯ is .125, so 12.1 inches would be slightly less than 12 1/8".



    Check the upper fork tube for straightness by rolling it on something perfectly flat. A piece of glass is ideal. If the fork is bent, it will be apparent. The manual says not to straighten a bent fork, but there are people on this forum who've done it successfully. I'm sure it depends on how bent the fork tube is.



    Inspect the piston ring at the top of the damper rod, and use compressed air to blow through the passages in the damper rod.



    Inspect the o ring on the cap and replace, if necessary.









    Last edited by B-dub; 12-29-2014 at 11:04 PM.
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    My handle is B-dub, I ride a T-dub, and drive a V-dub.

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  5. #4
    Senior Member Gerry's Avatar
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    Boy, that is GREAT you guys...... THANKS for thinking about the rest of us........ Your efforts will certainly help others in the future.



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    Take care my Friend.........

  6. #5
    Senior Member B-dub's Avatar
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    Assemble the fork



    Begin by installing the seals.



    If possible, locate a hammer and a socket just slightly smaller in diameter than the outside diameter of the seals. If you can't locate a socket or something similar that will work, you will have to use a punch. If you use a punch, just be super careful the punch doesn't slip and ruin the sealing surface.







    Note the shoulder machined into the fork. This determines how far into the fork the oil seal can be driven. Note also, that the open side of the seal goes in toward the fork. Using the socket or punch and your hammer tap the seal into the fork. Stop often and check to see the seal is going into the fork squarely, not tipped to one side. You should be able to feel and hear when the seal has bottomed on the shoulder. Pay attention so you don't ruin the seal by pounding on it after it has seated.



    Place the dust seal at the top of the fork and push the dust seal into place. When seated, the top of the dust seal shoulder should be even with the bottom of the snap ring groove.



    Reinstall the snap ring by starting one end in the groove, then working the snap ring around until the snap ring is seated in the groove.







    With the upper fork tube inverted, carefully push the damper rod and rebound spring into the upper fork tube until the piston ring is inside, then use your coupling nut tool to push the damper rod to the bottom of the fork tube. Use your finger, if necessary, to help guide the end of the damper rod out the bottom of the tube.







    Install the damper rod spacer, or oil lock piece onto the end of the damper rod.







    Apply some fork oil to the inside of the seals, then carefully slide the upper fork tube into the lower fork. Keep the fork horizontal so the damper rod spacer will not fall off before it's seated at the bottom.



    Insert your coupling nut tool into the fork upper tube until it engages with the damper rod. Insert the lower bolt into a new copper washer, if you have one, then apply some blue Loctite or equivalent to the threads of the bolt. Place the bolt into the bottom of the fork, and twist until it engages the threads on the damper rod.







    Using a 8mm or 5/16"¯ allen wrench and your coupling nut tool twist the damper rod and bolt together until snug, then torque to 22 foot pounds.



    The fork oil changing sticky on the Technical Help forum has a good discussion on fork oil, fork oil substitutes, fork oil weights, and amounts. I would encourage you to read it while preparing to rebuild your forks. I just ordered a 16 ounce bottle of Yamalube 10 weight fork oil when I ordered my seals. It worked fine for me. However, I recommend taking the time to do Lizrdbrth's routine to get the rebound damping to work.







    With the fork vertical, and nothing in it yet (spring, spacer, etc.), pour 8 ounces of the fork oil of your choice into the fork. Cycle the fork a time or two to distribute the fork oil through the damper rod and bleed any air out.







    Now, push the top tube down until it's bottomed, and measure from the top of the tube down to the oil level. The oil should be 135 mm, or 5.32 inches from the top of the tube. If it's not, adjust accordingly. 5/16"¯ is .3125, so if the oil is 5 5/16 inches from the top I would say that is close enough.







    Next, insert the spring, the washer, and the spacer into the fork. You'll have to raise the top tube, then install the cap and twist it in until snug. You'll torque the cap after the fork is reinstalled.







    Slide the fork boot in place on the upper tube. You'll tighten the clamp and secure the bottom of the boot after the tube is reinstalled on the bike.

    Last edited by B-dub; 12-30-2014 at 09:01 AM.
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  7. #6
    Senior Member B-dub's Avatar
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    Gee, I guess I got so excited about getting this done that I didn't get pictures of the rest of the procedure. But, it's pretty much the reverse of removal, so not difficult at all.



    Reinstall fork



    Slide the fork back into the triple crown. Observe the marks you made previously to ensure the forks are installed the same as before they were removed. Slide the fork up until there is 6mm or 1/4"¯ from the bottom of the cap to the top of the triple crown. Snug a bolt in the bottom clamp so the fork will maintain it's position.



    Torque the two clamp bolts on the lower triple crown to 17 foot pounds.



    Lizrdbrth recommends removing the caps after the forks are installed, then allowing the forks to extend all the way before replacing the cap. This will maintain the appropriate air gap for optimum fork performance. Next, replace the cap and torque to 17 foot pounds.



    Finally, torque the upper clamp bolt to 17 foot pounds.



    Now, repeat the procedure to re-seal the other fork.
    Last edited by B-dub; 12-30-2014 at 09:03 AM.
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  8. #7
    Senior Member B-dub's Avatar
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    Reinstall fender and wheel



    Make sure the brake and speedometer cables are routed correctly, then reinstall the fender. Don't tighten the fender bolts completely just yet.



    If your front brake has been squealing, take this opportunity to use some coarse sandpaper to sand the glaze off the brake shoes.



    Stick a finger into the front wheel bearings and rotate to check for roughness or excessive play.



    If everything is good, roll the wheel between the forks of the TW. Insert the brake shoes and backing plate into the wheel. With the axle handy raise the wheel into position, being sure to align the groove in the backing plate with the protrusion on the left side fork.



    Insert the axle, and when lined up push it through.



    Place the nut on the end of the axle, then torque to 65 foot pounds. That seems like a lot, but it's what the manual says.



    Install the cotter key.



    Reattach the clamp for the brake cable, and the mount for the speedometer cable.



    While the front wheel is in the air is a good time to check the wheel for loose spokes and being true, and static balance. Refer to Chapter 6 of the main manual for more information on this.



    Lower the TW to the ground. While holding the front brake push down on the forks several times to check for proper operation. If there is no stiction or other problems go ahead and tighten the fender bolts.


    Secure the bottom of the fork boots, and tighten the clamps at the top of the boots.
    Last edited by B-dub; 12-29-2014 at 11:55 PM.
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  9. #8
    Senior Member admiral's Avatar
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    This is a great tutorial and will really help the TW populace.



    I was really impressed by your use of my favorite tool(s).









    Apparently, you like to use the proper tools for fork removal! Unlike my Modus Operandi!







    Great job, I'm sure this will be pinned!
    Hidden Content A ride in the woods helps me relax and release tension. The fact I'm dragging a body should be entirely irrelevant?

  10. #9
    Senior Member B-dub's Avatar
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    Quote Originally Posted by mrgizmow View Post
    Boy, that is GREAT you guys...... THANKS for thinking about the rest of us........ Your efforts will certainly help others in the future.





    Thanks, Gerry. A pat on the back is always appreciated. I do hope this will be of use to someone.
    My handle is B-dub, I ride a T-dub, and drive a V-dub.

  11. #10
    Senior Member B-dub's Avatar
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    Quote Originally Posted by admiral View Post
    This is a great tutorial and will really help the TW populace.



    I was really impressed by your use of my favorite tool(s).









    Apparently, you like to use the proper tools for fork removal! Unlike my Modus Operandi!







    Great job, I'm sure this will be pinned!


    Thanks, Admiral. Yes that's a very impressive collection of tools you have there. I especially like the hand painted "Persuader". My shop teacher taught me to always use the correct tools for the job, it looks like your shop teacher taught you the same thing ! I vaguely remembered you had rebuilt Truelight's forks, but forgot you had completed a guide also. Otherwise, I would've just used yours'. It would have been helpful if your guide had been pinned (out of sight, out of mind). After some searching I found it. I like your guide better than mine! Better pictures, and certainly more fun! I hope you don't mind that I made reference to it at the beginning of this guide. Additional insight is always good! I liked your idea for the damper rod removal tool, and your and Rainman's ideas for seal removal tools. Thanks for your contributions to this forum. I always enjoy hearing what you have to say.
    My handle is B-dub, I ride a T-dub, and drive a V-dub.

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