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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. Rooster53

    Rooster53 Well-Known Member Premium Member

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    Check to make sure you don't have a damper rod spring laying around. The length is determined by the inner tube and the damper rod, provided the damper rod is properly secured.. You should be able to feel the damper rod spring if you pull on the inner tube trying to extend it to its fullest length.

    upload_2017-9-18_15-41-38.png
     
    Last edited: Sep 18, 2017
  2. xjmat

    xjmat New Member

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    I took apart the short fork again for photos (since it wan't yet full of oil), and I have kept it in the order of assembly (in photos).

    When I was first removing the oil seal, it was stuck like a bastard and took days of work and persuasion to get it out. It also turns out it doesn't match the other side oil seal (suspicious). That aside, see the photos here. Note, it seems one of the bushings can almost slide over the other easily, and the washer above the bushing can slide over the bushing. I feel like I will have to take the other apart also to check it out. A shame since it is full of oil. Oh well, new seals all round (x2).
     

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  3. xjmat

    xjmat New Member

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    well, I think I have found the problem. It is, as suggested, about one shim-length of an issue. The washer that goes above the shim is different in the left and the right. I think I need to somehow source a new washer :/ see the attached pic! you can see one washer is cup-like and the other washer is ridge-like. The cup-like washer (original, I think) doesn't even look like it might go over the shim. The ridge-like washer goes over the shim. Ohhhh b-jessus...

    anyone have an idea where I might get a new washer?

    I think this is the description:
    Fits: Yamaha
    Product Number: 1KH2314700
    CMS Product Number: YA0003.9920
     

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    Last edited: Sep 28, 2017
  4. ManBot13

    ManBot13 Well-Known Member Premium Member

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    I've got a spare set of forks for a 750 seca that I was going to offer for the cost of shipping, but then realized you're in Australia...I could see if I've got that washer in the forks (probably do) but it's be $30-40 US to ship just the washers in a small box if you can't find another option
     
  5. chacal

    chacal Moderator Moderator Supporting Vendor Premium Member

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    This is what you need, note that the currently available version are slightly different in appearance/shape, but perform properly. The washer in the "lower" fork pictured in IMAG0633.jpg is the correct (original style "cupped" washer) one:


    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:
    $
     
  6. shirali

    shirali Member

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    Great tutorial!
    One question tough, if i shorten the spring (to make the bike lower), is it the same process with opening and reassembly?
     
  7. k-moe

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

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    1. Yes.
    2. Shortening the spring alone will not make the bike ride lower without causing problems. You have to also make a spacer for the damper rod to limit travel or the fork will slam itself around internally.
    Also just shortening the spring will tend to make the suspension ride like crap. It's better to slide the forks upward in the triple tree (you'll have to move the air collars up above the top clamp), or swap the front end from another model of motorcycle.

    3. You will also need to pay attenion to the rear suspension, since altering the ride height at the front also alters the suspension geometry, and handling. The Seca 750 is already somewhat prone to headshake (under some conditions); lowering the front will make that more likely to occur.

    4. If you already know all of that, then go ahead with the work. This commentary is also here for others who may not know.
     
    Last edited: Oct 7, 2017
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  8. wera90ex

    wera90ex Member

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    Anybody ever loose one of these? I just bought 25 of them. Let me know if you need a couple. fullsizeoutput_291.jpeg fullsizeoutput_28f.jpeg fullsizeoutput_28d.jpeg
     
  9. k-moe

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

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    That isn't the correct part.
    Those aren't dust caps that are in the anti-dive, and what you have will very likely make the anti-dive inoperative.
    Chacal has the correct part.
     
  10. 50gary

    50gary Member

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  11. 50gary

    50gary Member

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    " swap the front end from another model of motorcycle.

    3. You will also need to pay attention to the rear suspension, since altering the ride height at the front also alters the suspension geometry, and handling. The Seca 750 is already somewhat prone to head shake (under some conditions); lowering the front will make that more likely to occur."



    I have no idea what the Seca 750 geometry is in stock configuration but my 82 750 Maxim is listed at 31.5* de-raking results in a greater front end load on the bike. I would think that in general more weight on the front end and less rake (caster) would help eliminate head shake? I have never liked the leading axle feature either. I am changing the front end on my Maxim.
    Cheers, 50gary
     
  12. Tim morris

    Tim morris Active Member Premium Member

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    Great work very helpful only thing I really think it's good idea to get everything clean as heck I use starting fluid soft cotton paper towels and air then cotton no lint towels . That was a lot of dirty stuff in the bottom of my tubes my brother-in-laws Exxon research and development and he told me that all or oil has microbes in it in the microbes actually do eat the oil and what they secrete in the process is that black muck same thing to be found in the bottom of a home heating oil tank and just as brake fluid turns black when it absorbs water that water also corrodes parts God smiles on the details
     
  13. Tim morris

    Tim morris Active Member Premium Member

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    Any Post on anti dive rebuild ???
     
  14. k-moe

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

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    Nothing aside from this and the thread with all the parts laid out.
    Anti-Dive Fork Explosion
    The anti-dive units themselves are pretty simple. Just a piston and a few seals. Once you have it off of the forks it becomes pretty evident what to do IMO.
    Chacal has all of the replacement parts for the anti-dive.
     
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  15. Tim morris

    Tim morris Active Member Premium Member

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    We need more YouTube videos LOL
     
  16. k-moe

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

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  17. Tim morris

    Tim morris Active Member Premium Member

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  18. Tim morris

    Tim morris Active Member Premium Member

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    My seca 750 XJ anti-dive is different I got it apart it does look very simple I ordered the parts from Lenny but under the top where the bleeder screw is looks like there's a center pin not sure if it comes out or moves to actuate the spring anti dive system tried to pull them out but they won't budge now I'm thinking you there just a casting not knowing thanks for your replies
     
  19. k-moe

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

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    Look closely at the anti-dive fork explosion thread I linked earlier. The top of the brake-side piston does look like a centering pin. I did (mostly) rebuild mine several years ago (most parts weren't available at the time).
     
  20. chacal

    chacal Moderator Moderator Supporting Vendor Premium Member

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    Yes, the piston is what you are calling the "pin" in the upper part of the entire anti-dive unit (that is the piston that moves down in response to brake fluid pressure entering the housing)….that pin then pushes down onto the piston in the lower (main body) of the anti-dive unit, and the movement of that piston is what controls/restricts the fluid movement thru the fork damper rod assembly, and helps to moderate the compression of the fork tubes during braking (and the harder the braking, the more the upper and lower pistons move "down", and thus the more the fluid flow is restricted, and thus the stiffer the fork becomes, hence "ant-dive during hard braking"……..).
     
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