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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. Tim morris

    Tim morris Active Member Premium Member

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    Do we have a parts break down jpg showing location s of parts for assembly??? For I laid them out but things happen!! Hate second-guessing
     
  2. chacal

    chacal Moderator Moderator Supporting Vendor Premium Member

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    Tim, have you opened up your package? There should be an instructions sheet with parts diagram with the rebuild kit...….
     
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  3. Tim morris

    Tim morris Active Member Premium Member

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    Yes thank you sure instructions are great if you can read !and know what part is what lol diograms picture s always help the situationlike when you're in the middle of it and you got to walk away and come back and look at it again and say oh my God what did I do you know what I mean short-term memory getting bad the older I get
     
  4. k-moe

    k-moe Pie, Bacon, Bourbon. Moderator Premium Member

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    I linked both the parts fiche (diagram) and the photo thread of the parts layout earlier.
     
  5. Tim morris

    Tim morris Active Member Premium Member

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    That deems to be a very simple overhaul once you dive in , Thanks to all of you :) 1 note spring goes in loaded side down into the forks I think .?hope I'm right got time before I add oil and seal it all up going to use fork tree to hold it all 20190911_200128.jpg 20190911_200128.jpg together whilst I compleat other tasks.
     

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  6. StarGeneral

    StarGeneral Active Member

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    Thanks so much for all this info everyone, I'll be tackling both forks and the anti-dive on my 81 750 Seca soon...cheers!
     
  7. StarGeneral

    StarGeneral Active Member

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    So I'm going through this job right now, and I'm having trouble removing the damper rod bolt. My bike is a 1981 SECA 750RH, and my damper rods do NOT have the fluted 3/4in ends that other describe. I am in the same situation as OP, except my bolts did not crack loose. I am also unable to see any point in the lower anti valve hole where an Alan key can fit through both the aluminum valve AS WELL as the actual rod itself.

    Any advice? A heat gun will only take me so far. One fork tube I was able to take the bolt right out. The other one is spinning pretty freely :(
     
  8. StarGeneral

    StarGeneral Active Member

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    You can see here....no fluting...and the hole in the damper rod is way too far away for you to put something through both the valve and the rod. The question becomes...if there is no way to hold the rod how does one tighten to spec?
    20210313_220610.jpg 20210313_220650.jpg
     
  9. StarGeneral

    StarGeneral Active Member

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    Well...I got it out with the rattle gun. I guess ill have to just get it PFT when I put the tubes back together. Even with the spring and cap back on it wasn't nearly enough to hold the rod still - even when compressed!
     
  10. StarGeneral

    StarGeneral Active Member

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    To follow up on this (Sorry for spamming this thread). I just did a second set of identical forks and it took me all of 15 minutes to break both damper bolts loose. This is the sequence of steps I used to avoid the situation I had last time:

    1. Leave the fork fully assembled before attempting to remove the bolt.
    2. Turn each fork upside down (so the bolt is pointing towards the sky, and spray the bolt with PB blaster. Let it soak in for a few hours.
    3. Give each bolt a few good taps with a hammer to shock the threads.
    4. Use a heat gun and heat the bolt for 2-3 minutes.
    5. Brace the fork against something and try to break er' loose.

    When I did it this way they both broke loose the first try around with very little difficulty. I still have to solve the problem with tightening them up to spec when finished, but I hope this helps someone else.
     
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  11. Bilalgio

    Bilalgio New Member

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    I'm about to do mine on a 81 Seca as well lol so spam away, the more info the better. I've had this bike sitting for almost 4 years now and it's gonna run this year dammit. I got super tied up in life but this bike on the road is all I want right now.
     
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  12. k-moe

    k-moe Pie, Bacon, Bourbon. Moderator Premium Member

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    I nearly moved your comments to a separate thread, but realized that there is a previoulsy unknown difference between the '81 and the later fork internals.
    That's worthy of keeping it in this writeup.

    As a general rule the writeups are not the place to go into depth asking questions about a individual motorcyle. Keeping all the work you do to your specific machine in a single thread in Technical Chat is preferred.
     
    Last edited: Mar 22, 2021
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  13. StarGeneral

    StarGeneral Active Member

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    I just completed my fork rebuild. All I have to do is add oil.

    I discovered a trick to get the damper rods tightened to spec. Using a wooden dowel is a fools gambit - it does not put nearly enough pressure on the rod to hold it to allow 14 ft/lbs of torque.

    In order to get the damper rod bolt tightened to spec I used a 5/8's spark plug socket and put a 5/8's head Temperature sender adapter screw into the end of it (the one where the thread diameter most closely matched the inside diameter of the top of the damper rod. I then electrical taped the temp sender screw to the socket well enough that I knew they would not separate. I also taped the threads so that they would bite into the inner diameter of the damper rod without actually scratching the metal.

    With a bunch of extenders, I lowered the socket into the top of the inner fork tube and held the damper rod bolt from the other end with the torque wrench. I then tightened the socket "tool" until I felt the threads engage the damper rod bolt. At that point, it's just a matter of having an assistant hold the tool in place with a ratchet while you tighten to spec. After you tighten, simple loosen the ratchet attached to the tool and it will pop right out!

    Hope this helps! Thanks Chorca for this guide!!

    I've attached some pics of the tool I made.

    [​IMG]
    [​IMG]
     
    Last edited: Apr 3, 2021
  14. Zeb

    Zeb New Member

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    Hi all,
    After a massive oil seal leak I stripped down the left fork using this incredibly useful thread, only to find that I was missing a washer and a half. The flat and spring washers on the end of the damper rod. I found the half spring washer stuck down the end of the fork leg. (see pic)
    I was wondering would these be available. I tried my usual go to parts supplier (cmsnl) but they dont have them in stock.
    Also the seal itself was only about half the height of the replacement seal that I got from cmsnl. (genuine yamaha part).
    I am now confused. Do I risk damaging the new seal to see if it will fit? Or is the lower height seal the correct one?
     

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  15. k-moe

    k-moe Pie, Bacon, Bourbon. Moderator Premium Member

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    contact info@xj4ever.com

    I do not think your supplier sold you the correct seal, but sold you a seal that Yamaha chose to substitute because of the diameter.
     
  16. Zeb

    Zeb New Member

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    Ok, Thanks,
    Here's a pic of the seals. original one is on the left. There is a couple of mil difference, I dont think the new one will fit.
     

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  17. StarGeneral

    StarGeneral Active Member

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    The one on the right looks like its for something completely different. Yeah, probably not gonna work.
     
  18. Rooster53

    Rooster53 Well-Known Member Premium Member

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    I have a spare set of Yamaha fork seals (1KH-23145-00) and they measure 10.7 mm for height.

    There is a spacer in there that I always kind of wondered why it was there, perhaps Len can verify that dimension or any changes.

    @chacal
     
  19. Zeb

    Zeb New Member

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    Yeah the larger one is 10.7mm, the original is 7mm.
    I've ordered a new one from Len, just hope it'll fit.
     
  20. chacal

    chacal Moderator Moderator Supporting Vendor Premium Member

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    You are correct, the current Yamaha (and repro versions of same) are all about 11.0 mm thick. Original seals (no longer available) were probably the 7mm (or so) thickness, although we don't have one around to verify. Sometimes oil seals will have sizing numbers "cast" into the rubber, such as 36-48-7 (ID/OD/thickness). Zeb, you should check that original seal that you have to see what numbers are on it (if any).

    Just guessing here, but the XJ750 Seca forks are specified to use 2 different spacer washers with their fork seals; one under it (which is about 3mm thick) and one on top (which is a little bit over 1mm thick). I suppose this was done to "shim up" the 7mm seal to the "proper" 11mm height:

    This washer is about 1mm thick:
    HCP12948 Aftermarket lower fork tube OIL SEAL SPACER WASHER, fits either left or right tube on the following models: all 1981-83 XJ750 Seca, XJ750 Euro, and 1980-81 XS1100 Special and Midnight Special models. One washer does one tube. This washer goes above the oil seal. Each:
    $ 6.95


    This washer is about 3mm thick:
    HCP3092 OEM lower fork tube OIL SEAL SPACER WASHER, fits either left or right tube on the following models: all 1981-83 XJ750 Seca and XJ750 Euro models. One washer does one tube. This washer goes below the oil seal, and above the metal slider bushing! NOTE: original spacer washers were "cupped" at the outer edges; these replacements are flat, but fit and perform as original. Each:
    $ 13.95



    The replacement oil seals are indeed 11mm tall, and also feature dual springs (one below and one on the top face of the seal), which supposedly makes them more "leak proof" (this is questionable, IMO, but it's what the marketing hype says.......).

    So theoretically, you could dispense of both the lower and the upper oil seal spacer washers (this saves 4mm in height), and just substitute the new/improved 11mm tall seal, and you'd be happy. @Rooster53 or @StarGeneral, is this what you did when rebuilding your 750 Seca forks, or ?????


    We do have some 36 x 48 x 8mm tall seals (HCP1814, for XJ550 Maxim, XJ650 Maxim, and a host of others), so theoretically you could use this 8mm tall seal, continued to use the lower (3mm thick) washer, ditch the upper (1mm) washer, and this set-up would also get you to 11mm in height.

    Of course, all of this assumes that the original seals WERE only 7mm in height.........
     
    Last edited: May 16, 2021

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