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Doing the 750 Seca's Forks.. (Rebuild.. now a HOW TO!)

Discussion in 'XJ DIY How-To Instructions' started by Chorca, Jun 11, 2009.

  1. Chorca

    Chorca Member

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    Well, as I'm getting all the necessary parts in for redoing the front brakes and such, I figured I'd might as well attempt to get the anti-dive working as well, which means tearing apart the anti-dive valves, and while I'm at it, I might as well tear down the forks and rebuild them.

    Decided to do a small photo-journal of how it goes. Things are set up in the back yard here, on our patio. Have a couple tables for working on, and I'm going to take as many pictures as I remember to take and post them here for everyone to see and maybe help out!

    Any of the pictures I post may be clicked on for a larger size.

    So, without further ado:

    Day 1
    ----------------------

    Set the bike up on a jackstand using the front crossbar. It seems to be pretty stable on that and the center stand.
    Got out the Haynes manual and started going through it.

    First they want you to pull the anti-dive actuators from the valve units..
    [​IMG]


    Only thing is, it's very hard to get an allen wrench down inside behind the caliper to undo the screw on the opposite side. I figured out that the reason they were telling you to do it this way is if you do not plan on draining and refilling the brake system. So, I decided to leave the anti-dive units intact and just pull all the brake lines (since I'm replacing them with stainless steel)


    So I pulled the brake cables and then removed the calipers.
    [​IMG]
    [​IMG]


    After this, you can pull the speedo cable and it's mounting bracket up and out of the mount and fender, then remove the axle from the wheel. I pulled the pin on the castellated nut, took the nut off, and removed the pinch bolt from the opposite side. A quick, light tap with a hammer tapped it through, and after gripping it lightly with some vice grips on the other side, I slid it the rest of the way out.
    [​IMG]

    I then found that my camera's white balance was horribly wrong.

    I forgot/didn't know that the speedometer piece is separate, so after I pulled the axle out and moved the wheel a little, it promptly fell to the ground.
    [​IMG]


    I then removed the wheel, wiggling it a little, and it slid right out from between the forks.
    [​IMG]


    Now I was able to get to the fender bolts, and removed them, along with the brake cable mounts and the fender itself. (Which it turns out used to be red, and as was pointed out to me, there's red in several other places.. looks like this used to be a maroon model.)
    [​IMG]


    I could now begin to tackle the forks. I referred back to the Haynes manual, but for the Seca configuration, it refers to "Fork Cap Bolts", Hoses, and other such things which confused me. This is in part because it refers Seca disassembly procedure to the 750J instructions which I think may be different. This is how I was able to remove it.

    The Haynes manual states you need to relieve the air pressure in the fork first by removing the cap, then using something small to push in the Schrader valve's pin, relieving the air.

    Next, I loosened the top and bottom pinch bolts (3 total) and actually down the line had to remove the lower pinch bolts completely. I removed the allen head bolt that holds the front emblem in (which was long gone on my bike) and then began to twist and pull down on the fork.

    I moved it down a couple inches, and then slid the air fitting ring back up and off of the end of the tube. This ring has a pair of o-rings inside it to seal the bracket around the tube, and a small hole in the chrome upper allows the air to be added and removed from the main fork itself. There is a very small metal ring that's set into a groove just below this, that will need to be removed before you can slide the fork out of the pinch bracket. Just lightly tug it open and slide it up off the end of the fork.

    I then started to work the fork leg off of the bike. This was very difficult because the previous owner had (spray?) painted the upper chromed sections of the forks black. This was an issue because the lower pinch bracket has very tight tolerances.. it's not easy to get the fork out even when it's clean. The paint had obviously not stuck very well at all to the chrome inners and had begun to bubble and flake off, making the surface that much "larger" in diameter.
    This paint caused the fork to seize on the way out several times, and I eventually resorted to removing the lower pinch bracket bolts, and tapping a pry bar into the slot to stretch the bracket open a bit wider, enough to wiggle the fork out.

    This finally worked, and I was left with a fork with a lot of paint scraped off of it..
    [​IMG]

    and a pinch bracket full of paint shavings.
    [​IMG]


    It was getting quite dark out and the mosquitoes started to really get bad, so I called it a night and moved all the tools back inside. I will take more pictures tomorrow with the removal of the right fork, which will hopefully go a little faster since I've done it once now.. :p
     
  2. Chorca

    Chorca Member

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    This is my first real how-to, so if there's incorrect information here, please let me know so I can fix it.. I'm just going off of what I saw and did, not necessarily best practices...

    I also had two of these apart at once to swap out the chrome inners.. (mine were basically solid rust).

    [​IMG]

    On to the goods!



    Any of the photos in this post can be clicked on for larger.. and even MUCH larger sizes.

    Disassembling and reassembling the forks is actually fairly easy, provided you have time, patience, and some common mechanic's tools.

    This is written from experience and from someone who had never taken forks apart before, so all of the instructions and ideas are from an actual teardown and rebuild. :p

    This procedure is documenting how to replace the oil and dust seals on an '82 Seca 750. There's already a great writeup on the 650, but I thought I might be able to provide a different angle for those who it doesn't click with, or for those who want something that includes those anti-dive valves and such.

    You should have a set of oil and dust seals, a bottle of fork oil (new stuff) and something to measure it with. (graduated cylinder, syringe, etc)

    For tools, you will need a set of allen wrenches (for the anti-dive and damper rod screw) a internal/external ring tool (these are about $10-20 at Sears), and a set of screwdrivers and something small (tiny screwdrivers, pick set, etc) to get some small items out of their homes.

    Make sure you have a clean area to lay everything out on, as well as plenty of rags, paper towels, etc., as it gets pretty big and messy when the fork is fully torn apart. Also, have a cup or other container to pour the fork oil out into, or you'll be running around your kitchen holding a fork, trying to find a jar. A normal-sized plastic cup (the ones at parties) is plenty large enough to catch the oil.


    Disassembly:

    As the previous post shows, remove the fork from the bike. You'll need to slide the fork down, remove the air cap (it just slides up and off) and the circlip before the fork will come out of the pinch clamps.

    [​IMG]

    Once it's off and you've got it on your table/floor/countertop, you're ready to start.

    [​IMG]

    We'll start out by removing the dust seal. The new dust seals that Chacal sells and the ones that are on the bike now are going to look a little different, but they work the same, so don't be alarmed.

    To remove the dust seal, you need to gently tap a screwdriver or other prying instrument in between the dust seal and the lower fork. This is because the dust seals have hardened after years and years of sitting out there in the sun, and they will not be very cooperative. Tap the tool in about 1/8" and then slowly pry back.

    [​IMG]

    You'll see the dust seal begin to slide upwards.
    [​IMG]

    From here, you should be able to work the tool around the seal and pry the rest of it out. Be careful not to damage the metal lower as you pry and remove the seal!

    After we slide the dust seal off, we are greeted with a very large and mean looking e-ring.

    [​IMG]

    This is where your tool will come in handy. You need to pull this ring off, which can be somewhat challenging, but usually from the ring wanting to pop off of the tool.

    [​IMG]

    Work at this a bit, and you'll be able to slide it right up and out of there.

    [​IMG]

    Beneath the clip ring there is a washer.

    [​IMG]

    I pulled this off before hand so it didn't get lost when I go swinging the thing around later. A couple small picks or screwdrivers will help ya nudge it up and out of there.

    [​IMG]

    Beneath this is the actual oil seal.

    [​IMG]

    Now we need to start actually pulling the fork apart.

    Get your cup ready, locate your phillips screwdriver or other object with a pointy tip and as large a handle as you can find, as you'll need to push down on the dimple in the middle of that metal piece in the top of the fork.

    [​IMG]

    (Can't see a metal piece? Did you pull the plastic/rubber cap off the fork?)

    What you need to do here is push down on that metal plug (It will move about 1/4") while prying the metal circlip out from it's indentation inside the tube. You may run into a problem where the metal plug is stuck, just tap it a few times with a hammer or the back of your screwdriver to pop it loose and get it moving again.

    [​IMG]

    The easiest way I've found is to hold the fork with your legs or in a vise, push down quickly and hold pressure, then pry one end of the circlip inwards. You can then release pressure somewhat on the metal while it pinches against the circlip and then reposition your screwdriver or fingers to pull the ring the rest of the way out when you push down again on the metal plug.

    [​IMG]

    The Haynes manual itself says that this step requires patience, it took me a few tries the first time (more like 10 or 15) but after I got the technique down it got easier.

    Now that you've got the circlip removed, we need to remove the metal plug. Two things have happened now, the spring tension has been released, making the metal plug want to pop up, and the fork's chrome inner tube is now not being held up anymore by that circlip, so it's going to want to fall down. Make sure you hold onto the chrome inner while you slowly release pressure on the metal plug.

    [​IMG]


    If it doesn't pop out, quickly get your hand over top of it, and gently tap the side of the chrome inner. It should pop upwards about 3/4", and stay there. Remove the metal plug and set it aside along with the circlip.

    [​IMG]

    Make sure you're laying these parts out how you take them out; it'll make it a lot easier to see how they go back together!

    Now that the plug is out, and you're still holding onto that chrome inner, let it down a little and grab onto that spring. Slowly pull it out (this is where things start to get messy) and lay it out on a cloth/paper towel/etc.

    [​IMG]

    Now that the main spring is out, you need to start draining the fork oil. Pull that cup over and slowly turn the fork tube to pour the oil out into the cup. Be mindful of the little hole that's about an inch from the top of the fork! It'll leak oil if you don't have it rotated to be pointing up! At this point, begin to slowly pump the fork in and out while you hold it over the cup. This will help to speed up the process. Push the fork fully together, wait a few seconds, then pull it all the way apart, wait a few seconds, and repeat. I do this until there's not a stream anymore, just a few drips.

    [​IMG]

    Okay. You've got the forks (mostly) drained. Now you can take the anti-dive valves off. There are four screws on the anti-dive, remove those (while the anti-dive unit faces upwards!) and gently pull the unit off of the fork.

    [​IMG]

    THere will be two holes, most likely messy and coated in fork oil and gunk.

    [​IMG]

    Wipe these off if you want, but they're going to get messy again, because now you need to carefully lift the fork up and hold the now-exposed holes over your cup to drain more of the fork oil out. When pumping the fork here do this VERY SLOWLY. If you go fast, fork oil will come blasting out of those two holes all over you and your stuff. Pump the fork until you're down to just a few drops like before, then set the fork back down horizontal.

    [​IMG]

    It's a good idea to keep a rag/paper towel set at either end of the fork, cause it's probably going to be slowly leaking oil while you're doing this.

    The next step is to get the dampening rod's bolt off. This is at the bottom end of the fork.

    [​IMG]

    Unlike other forks that have been described, the ones that I am seeing (in two different sets of forks) do not have any fluting inside the damper rod to hold it still. However, I have not yet had to hold one still, as they seem to lock themselves from turning somehow.

    The best way I've found to do this is to put a long socket extension through the axle hole while you torque on it to remove the bolt. This will keep you from having to wiggle the fork on the ground and ruin the paint job.. just make sure you have the chrome end secured or the fork will spin across the table when you start cranking on it.

    [​IMG]

    After you break the bolt loose, gently remove it and slide it free.

    [​IMG]

    You will now want to drain the fork one more time, to be sure that the bulk of any remaining oil has been removed before the next step. You may also notice that the fork has a much larger extension when you pull it up, revealing a bit of different-colored metal beneath.

    [​IMG]

    If the damper rod has not come loose (You'll know, it will be trying to slide out of the end of the chrome inner) you can choose to turn the fork upside-down and tap it against a soft cloth on a hard surface to see if it will come loose. If it does not, don't worry, it's not necessary to remove it.

    [​IMG]

    Now we need to remove the oil seal and top bush. The Haynes manual has an effective and simple method to remove this. Begin by wrapping a rag/towel around the bottom hole and the two anti-dive valve holes. They will squirt bits of fork oil while you do this, so this is to keep it from going all over.

    [​IMG]

    Hold the fork horizontal, with one hand on the lower, and one hand on the upper. You will push the two together, then sharply pull them apart.

    [​IMG]

    You'll need to do this around 4-10 times, and as you do it you should see the oil seal beginning to slide further out of the lower. Once you get close to the edge, go easier as the two sections will pop apart quite readily after the oil seal and upper bush are dislodged.

    [​IMG]

    Finally, after the two halves have separated and you've got everything laid out, remove the old oil seal from the chrome inner by sliding it up and off of the top. Note the direction that it's installed in; the end with the words faces up, the side with the large gap faces down (towards the curved washer).

    The forks are now disassembled. If your damper rod came apart, it will look something like this.

    [​IMG]

    In case all the parts came apart and were flying around, here's how they go back on the damper rod. If the little washers are missing, check in both the lower tube and stuck in the bottom end of the upper.

    [​IMG]

    Put on the rebound spring, followed by the flat washer, the bent washer, then the tapered aluminum ring as shown.

    [​IMG]

    Sometimes the lower piece is stuck in the bottom, and it can sometimes be dislodged by hitting the lower upside-down on a cloth-covered hard surface.


    Reassembly:

    Reassembly is the reverse, which is always easy to say, but not always easy to do. Here's how.

    Begin by pushing the damper rod back down into the chrome inner, with it's parts attached. It is helpful to use some sort of object inside to hold the damper rod in place while you install the oil lock (that shiny metal end with the three holes drilled in the bottom). Push the tube into place inside the oil lock and then push the entire assembly up into the fork lower. It can help to do this at a diagonal, so the parts do not fall off the damper rod.

    It will be helpful to orient the three holes in the oil lock so that they're somewhat close to the anti-dive valve holes before you push this in.

    [​IMG]

    Once the damper rod is pushed into place, check to be sure that the middle hole in the oil lock (of the three) is centered in the bottom hole for the anti-dive valves.

    [​IMG]

    You can push a small tool down inside to nudge it back and forth, and then use something like an allen wrench or screwdriver to hold the lock in place while you reinstall the lower bolt.

    [​IMG]

    Tighten the bolt using the same method as loosening (with the socket extension in the axle hole) to 14ft-lbs (per Haynes manual on a 750).

    [​IMG]

    Push the chrome inner all the way in. We now need to get the metal bush to sit down into the small area inside. Most people use some sort of pipe, PVC or other, that's the right size to slide down into the fork.

    [​IMG]

    My pipe does not slide fully inside, so I used a screwdriver and gently tapped on opposite sides of the rounded washer using a hammer to carefully seat the bush back into place. You will know when it is seated by the feel of the hammer, and that the gap should be about 1/4" from the washer to the groove on the inside.

    After the bush is fully seated, you can install your new seals.

    [​IMG]

    Remember that the lettering faces up, the side with the large gap faces down.

    [​IMG]

    You will need some sort of pipe or other drift to push the oil seal in evenly; I found that a 1-1/2" Sch 40 PVC pipe 18" long and sanded down a little at one end works well for driving the oil seal into place.

    [​IMG]

    Use a cap at the end of the PVC pipe, and tap the oil seal into place, making sure that you can see the groove in the inside of the fork. Remember, there needs to be about 2mm gap there, between the top of the oil seal and the top of the groove, because your washer and e-ring need to fit in there.

    [​IMG]
    (This photo doesn't show it fully seated.. you'll be able to see the groove when it is.)

    After you have seated the oil seal, check the movement of the fork. It should slide smoothly and easily up and down. Now get your washer and e-ring, installing them in that order. I got the e-ring started in the bore, and then used my PVC pipe to tap it until it snapped into place.

    Finally, get the dust seal and slide it down the fork, making sure that the tapered end is pointing up.

    [​IMG]

    Push it down into the remaining space, and use your drift, or gentle tapping with a hammer around the rim to settle it into the fork.

    Try sliding the fork again, checking that it does not bind. If it feels good, all is well and you can continue on to re-install the anti-dive unit.

    After you've installed the anti-dive, it's time to get out the oil!

    [​IMG]

    Drop the large spring down into the top and make sure it's settled into place. Measure out the correct amount of fork fluid into your measuring device (I used a 2-stroke oil/gas measuring cup, as it has CCs on the side) and pour it in slowly. The Haynes manual says for the Seca 750 to use 309cc of 20W fork oil.

    Finally, recap the end using that metal plug and the tiny circlip. It may take some wiggling to get that plug to settle down into the inner as you push, but after it's in, push the circlip down with a small screwdriver or something until it clicks into place.

    Be sure you push the air valve ring down onto the top before you go turning it upside-down and shaking it all over, or else oil will come out that little hole in the top!

    That's it! You've got a pair of rebuilt forks. Reinstall them onto the bike the way you pulled them off, and you're good to go!
     
    jayrodoh likes this.
  3. Polock

    Polock Well-Known Member

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    this might come in handy
    link
     
  4. Chorca

    Chorca Member

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    Definately. That is an awesome diagram of the anti-dive units.. though I don't go into detail on the overhaul on mine, that's a great little graphic.
     
  5. SecaRob

    SecaRob Member

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    Outstanding
     
  6. chacal

    chacal Moderator Moderator Supporting Vendor Premium Member

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    Exceptional. And quick....you just got your parts a few days ago!

    I assume that there were a few trials-by-fire in regards to not pumping the forks rapidly when draining the oil........ :D
     
  7. Chorca

    Chorca Member

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    Haha.. Just one.. stopped that reeeeal quick.

    But yeah, I already had the forks all apart and such. TIMEtoRIDE came by and hooked me up with some not-as-bad chrome inners, so that's why I had two apart at once.
     
  8. woolsac

    woolsac Member

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    wow! I just ordered all the parts for my fork oil seal repair. should be delivered in a week. this is the walkthrough i have been looking for! Awesome.
     
  9. Chorca

    Chorca Member

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    Glad it'll help out! There's a couple little things I'm discussing with Chacal about it; I'm going to be taking some more pictures and adding a step or two to clear some parts up and add something I believe I missed.. it seems the orientation of the oil lock (round shiny bit with the plastic ring at the bottom) matters.

    I'm going to check that fork I just rebuilt and also if anyone knows the actual reason for the rotational orientation having to be by the anti-dives, chime in?
     
  10. CaptNemo

    CaptNemo Member

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    Nice job on the write up, you get my vote to do the write up on the chain guide replacement next :wink:

    I wonder if the orientation is just for the shortest route for the oil to flow?
    I know that my oil lock was pretty sludged in and having the holes lined up that way allowed me to "persuade" it loose with a tool.
     
  11. Chorca

    Chorca Member

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    Either way, there's an illustration of how it should look and how to hold it when you're fastening the bolt.
     
  12. CaptNemo

    CaptNemo Member

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    Good point on holding the bolt while tightening, that right there is probably the reason.
     
  13. Chorca

    Chorca Member

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    BTW, just as "proof" that the 750 Seca forks' damper rods don't have the slot for a tool to rest in, I took a picture of the damper rod. These are the same on two different sets of 750 Seca forks.

    [​IMG]
     
  14. Robert

    Robert Active Member

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    VERY useful write up Chorca, we owe you a debt of gratitude (due and payable upon arrival at nearest XJ member's locality). FL is a bit far but if you make it out here, a beer on me amigo!
     
  15. Chorca

    Chorca Member

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    Brake master cylinder is next...

    Then carbs and valves!
     
  16. woolsac

    woolsac Member

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    still waiting for parts to come in. need to pick up some fork oil too. had a question on what is a good solvent to use to clean out the oil fork oil, or do you just let it drip out as much as it will allow?

    Thanks!
    Mark
     
  17. Chorca

    Chorca Member

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    I didn't clean the old oil out really. Most of the gunk was at the bottom so i wiped all that I saw out with a rag and refilled.. I wasn't sure how any sorts of solvents would affect the oil so i left it alone.
     
  18. woolsac

    woolsac Member

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    Chorca
    Did you happen to start your master cylinder yet? I started my fork repair tonight and noticed that one of the damper piston assy was not working. I am thinking of now to rebuild it and bleed the brake system. DId you happen to have a how to on that is well. your instructions on fork repair was awesome. Thanks!
     
  19. BlackMax

    BlackMax Member

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    i used brake cleaner and it did a great job....was alot of crap in the bottom of the fork.
     
  20. Chorca

    Chorca Member

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    I took some pics of the master cylinder rebuild and it's extremely easy. I'm about 1500 miles from my computer though at the moment, but basically..

    1. Remove the hard line between the distribution block and the master cylinder (PLEASE use flare wrenches.. They're important to use because the flare nuts are usually on there pretty hard and flare wrenches give you an extra couple surfaces to grab with. If you don't want to get a set of them, I believe they're 10mm. You'll find many other uses for them too like working on brake lines if you have a foreign car..)

    2. Remove the cable from the brake by pushing the master cylinder lever up while tugging the cable stay out of it's seat on the master cylinder, then rotating it sideways and pulling it towards you out of that hole.

    3. Undo the two bolts holding the master cylinder to the forks, and remove it from the bike. This usually takes a bit of wiggling and pushing and tugging, but if you mess around for a bit you'll figure out how to get it out.

    4. Now that the master cylinder and reservior are off, make sure the fluid is all drained out, and then pull the reservior off the master cylinder.. There's just a flared plastic piece on the end of the reservior, so be careful cause it might break if you torque it too much.

    5. Undo the nut holding the lever to the master cylinder body. I found this much easier to take off than trying to remove that pin, which it seems is permanantly affixed in it's hole.

    6. Remove the rubber boot, remove the circlip, and everything should slide right out. Pull all those things apart, and then clean the master cylinder body out really good.

    7. Reassemble everything back together the way it came off, using the new parts. Use brake fluid for lubricant to get the pieces to all fit back into the bore.

    8. Put that boot back on, reattach the pin and lever, check to make sure your reservior switch is working, reinstall the reservior, put it back on the bike, fill it with fluid.

    9. Attach one side of the hard line to the master cylinder, then bleed it by using your finger to block the flow of air back up into the master cylinder when you release the handle, to get the cylinder itself bled properly. Then proceed to hook the other end of the hard line back up and vacuum bleed the system.

    This might not be a perfect tutorial, and I don't have pictures at the moment, but it's actually pretty straightforward. Once you get it off and get inside you'll see how simple it really is.
     

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