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New member, need help with brakes

Discussion in 'XJ DIY How-To Instructions' started by YamahaHooligan, Dec 28, 2015.

  1. YamahaHooligan

    YamahaHooligan New Member

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    Hey everyone, sorry if this is been answered before, I've been searching the thread and haven't been able to find one that talks about my specific problem.

    So I have a 82 seca xj750rj and my front brakes locked up to where it won't roll, but I can release the bleeder bolts and tighten them back and it will roll again, but after a couple days they lock up again. Also I can't use front brakes or they will lock up a lot quicker, how do I fix the issue or what do I need to do
     
  2. k-moe

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

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    The return port on your master cylinder is plugged, or the master cylinder is overfilled. What you need to do is rebuild the entire brake system if you have not done so already.

    In the meantime, STOP RIDING IT. faulty brakes will send you to one of two places: the hospital, or the morgue.

    Some reading material for you.

    http://www.xjbikes.com/forums/threads/why-you-need-to-replace-original-brake-lines-w-pics.41400/

    http://www.xjbikes.com/forums/threads/how-to-rebuild-your-master-cylinder.18377/ (your master cylinder is somewhat different, but the procedure for rebuild is the same).

    http://www.xjbikes.com/forums/threads/why-you-need-to-rebuild-your-caliper-and-m-c-w-pics.41403/

    You also have anti-dive units on the forks, which are driven by the braking system. This link shows you what the inside of the forks look like. You don't have to disasemble the anti-dive units, but you may want to because the small piston tends to stick from brake fluid buildup. http://www.xjbikes.com/forums/posts/368361/

    Your brake system just happens to be a royal PITA to get bled properly. Once you get to that stage I'll walk you through the method that works for me (it's not the only method that works however).

    You should also pull the rear brake and take a look: http://www.xjbikes.com/forums/threa...r-brake-bike-owners-please-take-a-look.15874/
     
    Last edited: Dec 28, 2015
  3. YamahaHooligan

    YamahaHooligan New Member

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    So I got my bike back to my home and am starting to take it apart...but I think I'm in over my head with this wiring nightmare, it is absolutely confusing
     
  4. YamahaHooligan

    YamahaHooligan New Member

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    IMAG0169.jpg here is a picture of my M/C
     
  5. k-moe

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

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    The rust on the MC lever and the piston rod will clean up. You'll want to get a new cable as there looks to be corrosion creeping under the lead near the end. Chacal has rebuild kits for that MC in stock.


    What wiring nightmare are you referring to?
     
  6. YamahaHooligan

    YamahaHooligan New Member

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    The wiring nightmare is all the wiring behind the headlight. I took tape and numbered each wire as I took em apart. But as I am new to working on bikes in general, I don't have all the tools/knowledge to work on my bike at the moment...and unfortunately this bike is my only form of transportation and I know I shouldn't drive it with this problem, so I feel as if I am S.O.L with the whole situation
     
  7. k-moe

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

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    Slow down, be calm. The wonderful thing about Yamaha is that they thought about this very problem when designing the wiring harness. You almost can't hook anything up incorrectly. The only part of the headlight bucket harness that can be plugged in wrong is the bullet connectors for the turn signals, and the wires are color-coded to help eliminate that issue.

    This thread might help. The problem is not yours, but the photos and wiing diagram should be of use. http://xjbikes.com/forums/threads/82-xj750-no-idea-what-im-looking-at-with-wiring.47634/
     
    Last edited: Dec 31, 2015
  8. YamahaHooligan

    YamahaHooligan New Member

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    IMAG0170.jpg

    So here is my M/C bore and M/C completely off the bike, it's in not so good shape, going to be placing an order for a rebuild kit soon
     
  9. YamahaHooligan

    YamahaHooligan New Member

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    So for the time being...since I have to keep my bike outside as I don't have a garage or anything, I put my M/C back on and for sh*ts and giggles I put brake fluid in and tried to bleed my brakes and everything, well now my brakes won't build up pressure and they won't bleed. Any help on what went wrong or how to fix it?
     
  10. k-moe

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

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    Yes. Wait and rebuild the master cylinder, and the calipers, and fit new lines. You could bleed them now, but that's going to take you about an hour to do. Our model has a system that is tricky to bleed. I'll tell you the process of you really want, but IMHO it's not worth the time unless you have a brake system that has been rebuilt; otherwise you're just going to be lucky if it builds pressure.
     
  11. YamahaHooligan

    YamahaHooligan New Member

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    Well, I do have new ss brake lines on the way, they should be here Friday, unfortunately I don't have a whole lot of money to spend right now so 100-200 bucks for a mc is kinda outta the question at the moment, as for rebuilding the calipers, don't have money for that either. Honestly, I'm finding this bike to be more of a headache that I can't afford. I'd love to fix it....but being right now it is my only means of transportation, I need a quick fix so I'm not stuck without a way to go anywhere such as work or anything else.
     
  12. k-moe

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

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    Ok I can understand that.

    What I do to bleed the system.
    1. get a large syringe from a farm store and about a foot of vinyl tubing (you can also use a 2-stroke oil mixing syringe).

    2. Cut 6" of tubing and attach that to the end of the syringe. Remove the Syringe plunger. You now have a funnel to fill the master cylinder with.

    3. Break loose all four bleed fittings (be sure to put down cat litter or drip pans).

    4. Tie the brake lever to the grip.

    5. Fill the master cylinder and syringe.

    6. Wait overnight (or at least a few hours)

    7. You should now see brake fluid coming out. Close the bleeders, and untie the brake lever.

    8. Bleed the brakes as normal, starting with the anti-dive bleeders, then the brake caliper bleeders. Remove the funnel.

    9. You aren't done yet. There will still be some air in the system. The next step cures that, no matter what mehtod you use to fill and bleed the system.

    10. Use a vibratory sander (no sanding pad) and slowly run it along the brake lines, calipers, and distribution block from bottom to top. This will move any remaining air bubbles up into the master cylinder. Tap (or vibrate) the master cylinder to get the air bubbles to come out of the return hole. This process can also be done with a box-end wrench or other simmilar tool, and tapping the calipers and lines (it just takes longer).

    11. Do one final bleed normally, just to be certain that the calipers are fully bled.

    12. Use a flashlight to check the fuid level in the master cylinder. It should be below the fill neck. Unfortunately there is no dip-stick or sight glass on this master cylinder, so unless you empty it and measure out the fluid you will need to just eyeball it. If the fluid level is too high the brakes can hydrolock and not release.
     
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  13. PJC750

    PJC750 Member

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    20220711_125423.jpg 20220710_015736.jpg
    Hi Kmoe,

    Thank you fir the bleeding description for 1981 xj750 Remote MC.

    1) How does my order and orientation of seals look?

    1a) During my rebuild 3 mos ago,I rememember hearing a 'pop' like sound the first time I pulled the lever , after that the lever actuation would Not force fluid into the lines. Hydrolock???)

    2)I have rebuild kit from Len so I rebuilt but the system would not pressurize. I reverse bled, even loosened the top inlet of the metal "S" to ensure no air in horizontal ' bar' below. Still no ability to build pressure.

    3) Upon re-assembly, and before I put on bike, can I press the piston to test it? I add a little fluid hust to lube cylinder and seals. how freely or smoothly should the dry piston move, if I press by hand, before it goes on the bike? I assume easy, with smooth springback.

    4)Any way to prime the cylinder with fluid, after I attach the reservoir to cylinder? If there's a bunch of air between the piston seal and the spring seal ,how does fluid ever get in that space( around the piston threads etc)?
    This is my last try to pressurize. Next step is to order the $115 handlbar replacement and end the madness.
    Thanks

    Patrick

    20220710_015736.jpg
     
  14. PJC750

    PJC750 Member

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    5) When reinserting Spring and seal..why does seal try to tilt or come out of seat...my gut tells me this is what happens...as soon as pressre is applied ,...the spring seal becomes off kilter and does not seal properly.
     
  15. k-moe

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

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    Last edited: Jul 14, 2022
  16. k-moe

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

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    When you tore the master cylinder down did you clean it, polish the bore, and make sure that the return port was absolutely free of debris? If the return port is clogged fluid can't go anywhere.

    Did you rebuild any of the other brake components?

    This thread may be of some use to you.
    https://xjbikes.com/forums/threads/master-cylinder-750-seca.113872/
     
  17. PJC750

    PJC750 Member

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    I used 1000grit over a AA battery to polish. I have had firm brakes on this bike in the past. I used a guitar string (.12) to clear the tiny hole in the side of the cylinder. I pushed any air with loaded syringe from the fork bleeder up thru the caliper bleeder, closed ea of those off now will go from caliper to MC. I was gonna open both calipers and use your method of tying the lever to allow fluid to run over night.
     
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  18. k-moe

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

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    And the anti-dive units; any work done there?
    Calipers?
     
  19. PJC750

    PJC750 Member

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    Replaced one caliper, no leaks from either piston, they moved freely with air pressure when I reinstalled new pads.
    I am bleeding with hand lever now and the MC is moving fluid down the line. I rigged a 3rd clear plastic bottle of br fluid with a thumb operated shutoff valve and 10" of copper brake line. Its thin enough for me to stick in the filler, AND see the MC fluid level. The floppy plastic hose is a nuisance for filling and its too close to diameter of filler. I am going to open the Caliper bleeder now and try pushing any air back up thru the MC with syringe.
    I guess I can hold the lever open( tape it) while i do this,while keeping an eye on MC level.
     
  20. PJC750

    PJC750 Member

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    buying a 4th syringe, which I can fill with crushed ice Woodfords,sweet vermouth, orange rind and a cherry.....
     

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