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XJ750RK FROZEN FRONT WHEEL

Discussion in 'XJ Technical Chat' started by NJRIDER1, Nov 23, 2009.

  1. NJRIDER1

    NJRIDER1 Member

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    I'M TOTALLY AT A LOSS AS TO HOW THIS BRAKE/ANTI-DIVE SYSTEM OPERATES... GOT THE BIKE SATURDAY THE GUY DROVE IT TO MY HOUSE, HAD TROUBLE BACKING IT UP TO PARK IT, I HAD TROUBLE MOVING IT INTO MY GARAGE THE FRONT WHEEL WAS REAL TIGHT. NOW IT SEEMS FROZEN. THE FRONT BRAKE LEVER IS VERY MUSHY, THE BRAKE SYSTEM IS SOMEHOW CONNECTED TO THE FRONT SHOCK ASSY (ANTI-DIVE ) CAN ANYONE TELL ME???
    1) HOW TO FREE THE FRONT WHEEL??
    2) WHAT'S THE THEORY BEHIND THE BRAKE/SHOCK SETUP, WHAT IF ANYTHING CAN BE DONE TO RESOLVE THE TIGHTNESS IN THE FRONT WHEEL?
    3)IS IT ASSOCIATED WITH THE ANTI-DIVE MECHANISM??
    I THINK I HAVE THE BASIC CONCEPT... THERE'S A VALVE OF SOME SORT IN THE BOTTOM OF THE SHOCK THAT IS ACTIVATED WHEN THE BRAKE IS APPLIED, THE VALVE RESTRICTS TO FLOW OF OIL, IN THE SHOCK, TO PREVENT THE FRONT END FROM DIVING DOWN DURING HARD BRAKING... DO I HAVE THAT MUCH RIGHT???? I'M GOING TO ATTEMPT TO ATTACH A PHOTO OF THE FRONT BRAKE ASSY, IT IS A CABLE AT THE LEVER THAT RUNS TO BETWEEN THE FORKS SOMEWHERE.
     
  2. NJRIDER1

    NJRIDER1 Member

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    PICS DIDN'T SHOW I'LL TRY AGAIN
     

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  3. bigfitz52

    bigfitz52 Well-Known Member Premium Member

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    You have the concept. Although the anti-dive itself is probably not the culprit; you most likely have one (or both) calipers simply hanging up. VERY COMMON on a bike that's been sitting for a while.

    You're probably going to need to rebuild them.

    The cable from the handlebar disappears on its way to connect to your REMOTE master cylinder, which is indeed down there under the headlight somewhere.

    The effectiveness of the anti-dive is an ongoing debate; a lot of folks simply block them off as they don't work well enough to justify the added complexity.
     
  4. Robert

    Robert Active Member

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    You will find that the front wheel is locked up because the brake master cylinder is filled with crud. There are two small (and I do mean small) holes in there that, once filled with crud, will lockup the front brakes. Release the brake caliper bleed nipples and relieve the pressure. I had this bite me in the can years back.
    Then order in a new master cylinder rebuild kit, two caliper rebuild kits and new brake lines. About $200 in parts but you will need to do it. Don't take chances with your brakes, your life depends upon them working correctly each and every time. You might want to give our pal Chacal a holler.
    Best of luck to you!
     
  5. SQLGuy

    SQLGuy Well-Known Member

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    First of all, the anti-dive is probably not the problem.

    The anti-dive system works by having brake fluid pressure activate plungers at the base of the forks that restrict oil flow through a lock system in the stanchion bottom... increasing the fork damping. The thoery is that when you decellerate quickly with the front brake, you don't want the bike to nose dive.

    The problem you have, though, is probably a blocked passage in the master cylinder that's not allowing fluid to flow back into it.

    The master cylinder is (in)conveniently located on the frame under the triple tree. Rebuild kits are available, but note that the grommet seal between the fluid reservoir and the MC body is not included in the kit, nor is it available separately that I know of.

    It's also possible you just have a stuck caliper piston, and, since the history of the bike is unknown, a full brake system check, fluid change, etc, should be a first order of business. I assume you have verified that loosening up the brake cable didn't help things?

    Cheers,
    Paul
     
  6. bigfitz52

    bigfitz52 Well-Known Member Premium Member

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    if opening the caliper bleed screws doesn't release the brakes, then the pistons are STUCK.

    Robert's right you know; you will need to replace the lines, and rebuild both calipers and the MC anyway. The components are over 25 years old; it's a 130-mph bike and you should rebuild the brakes before you ride it.

    CHECK THE REAR too, and right away; delamination of the linings from the shoes is an all-too-common occurence on these bikes.
     
  7. apato632

    apato632 Member

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    Man, I've had two of those bikes and both came to me with the stock master cylinder removed and a regular one installed on the handlebars. Obviously they're enough of a pain that people are making the mod. You might want to consider doing the same.

    That brings up a question for you wizards that NJRIDER and I would probably both like to know.
    On my modified XJ750 the master cylinder is on the bars. The bolt going into it has two holes to feed fluid into the brake cables (steel braided) and directly into the calipers. Is that a safe? Wise modification?

    If so, NJRIDER can probably get steel braided cables and a used master cylinder for a little bit more $ than the rubber lines and a rebuild kit would cost.
     
  8. CaptNemo

    CaptNemo Member

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    Fitz is right. When mine did this if I cracked a bleeder fluid would squirt out, once the pressure was off it would roll again temporarily. That is a good way to confirm.
    SQL is right, you might damage an unobtainable grommet to get to the plugged hole.
    Tha calipers should be rebuilt and the lines changed now whether they are contributing to this or not for safety.
     
  9. Hillsy

    Hillsy Member

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    If you mean not having a splitter, then that is fine. They do that on all the sports bikes for braided line upgrades. Reason? - it's cheaper to make 2 single lines than to make a line with a splitter.

    If you mean bypassing the anti-dive and going straight to the calipers, then the front end might be a bit soft under brakes, although I've never really liked anti-dive in any of the bikes I've owned. It's still "safe" though.
     
  10. schooter

    schooter Active Member

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    nj rider, i have the same problem, mine are stuck, i tried bleeding the system clean, still stuck, so i think im going to remove the WHOLE front brake assy. for the winter and slowly rebuild what I can, and dont worry, It will do back on :D
     
  11. TIMEtoRIDE

    TIMEtoRIDE Active Member

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    I have 4 stainless lines, a caliper with a broken tab, freshly rebuilt 2 years ago, the "hidden" master CYL, and maybe the factory cable and lever.
    My brakes absolutely ROCK !!
    I think it's the stainless lines.
     
  12. bigfitz52

    bigfitz52 Well-Known Member Premium Member

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    The stainless lines, and
    Ya gotta do it. Can't ride around with 25 year old hoses, so...

    Since the lines have to be replaced anyway, I heartily recommend using SS lines; I have them on both my 550s and that is the single biggest improvement you can make on the stock brakes.
     
  13. wamaxim

    wamaxim Active Member

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    NJ, THere is a little key just above the left <shift> key and directly to the left of the <A> key. It's called the Caps Lock key. Please make sure that it hasn't been pressed when you create or respond to a post. It gives us all headaches when you SCREAM in all CAPS.

    Thanks buddy and best of luck on those brakes. You're gonna love your ride when you get 'er going! They are feisty and hoot to ride when they are 83% or better!

    Loren
     
  14. NJRIDER1

    NJRIDER1 Member

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    thnx so much for all the replys and knowledge, i do appreciate it and will try to remember not to yell at you all when posting from now on... it's a bad habit but for me it's easier to see the upper case when typing, old eyes don't work as good as they used to.
    since this bike is a winter project i'll have plenty of time to find the parts to rebuild and the time to do it.
    here's a pic of the bike as i got it 26k on the clock, starts right up, small dent in tank, all elect lights, computer, etc working (except batt,he just installed a sealed batt and removed the cell sensor), came with nylon saddle bags and tank bag, $550...does it sound like a decent price?? as i've stated b4 i'm new to 4 cyl engines so once i start fixin' this bike up i'll probably have alot more questions, thnx again NJrider
     

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  15. Robert

    Robert Active Member

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    Nice deal. Now get those brakes up to scratch! If your battery sensor idiot light annoys you, you can build an idiot light bypass. I've got plans for one in my gallery.
     
  16. NJRIDER1

    NJRIDER1 Member

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    robert thanks for the heads up on the battery sensor, i figured there was some way to bypass it but your explanation and drawing will make it simple...nice FZR did you need to put alot of $$ into it to get it going can't believe it was a freebie...thnx again NJrider
     
  17. Robert

    Robert Active Member

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    It was just as free as the lovely state of California was willing to let it be. I got it free because it had over $300 in back fees due on it. I got it mobile for about another $200 (new tire, sprockets and chain) so you might call it cheap. I have to confess, as much fun as it is, I'm prefer my hypoid whine over chain noise any day.
     
  18. NJRIDER1

    NJRIDER1 Member

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    just an update and question on frozen front brake...
    i was able to pry the piston open enuf to remove the front wheel and caliper assy's. the pistons are frozen in the caliper... should i be able to move them freely or are they supposed to be extremely tight (they won't budge)...i sprayed them with some penetrating oil in an attempt to remove them, i plan to replace them anyway...what's the best way to remove them????
    here's the plan...
    1) front caliper rebuild kit $30
    2) new front pistons $125
    3) new front brake pads $57
    4)new set of s/s brake hoses $100
    5) new set of s/s anti-dive hoses $78
    6) clean and rebiuld master cyl
    7) new rear brake shoes $39
    for about $450 i should have a better than new brake system, you can't put a price on your safety!!! oh yea! i need new rubber too... approx $300 that will bring the total to about $750 (only paid $550 for the bike so i guess if i keep it for awhile it will be worth it)
    did i miss anything in my plan that i should address b4 putting the rubber on the road thnx NJrider
     
  19. SQLGuy

    SQLGuy Well-Known Member

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    Usually, with the wheel out, just squeezing the brake lever will pop the pistons mostly (or entirely) out. It would be good to do this with the calipers sitting in a bucket to catch the brake fluid.

    If you've already drained the fluid, then you can remove the caliper, close the drain screw, and feed compressed air into the line connection to pop the piston.

    If you don't have compressed air, you can attach a grease fitting and use a grease gun (and grease) to pop them, but then you'll have to clean out the grease.
     
  20. NJRIDER1

    NJRIDER1 Member

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    thnx SQL i think i have a spare brake fluid reservoir and lever assy in the shop i'll hook it up and give it a try, am i mistaken in thinking that i should be able to move or rotate the piston with a pair of channel-lok pliers?, i tried and the piston seems frozen.
     
  21. hogfiddles

    hogfiddles XJ-Wizard, Host-Central NY Carb Clinic Moderator Premium Member

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    The piston should move with steady pressure. There will be some resistance but a slow steady pressure should move the piston into the bore pretty smoothly. If you're really cranking on it then it's time for a rebuild/cleaning/honing/etc........I wouldn't try to rotate it too much. Use grease to press it out. The grease will help lube the bore and then help to clean the bore. Air can work too, but when it pops, watch out--- those suckers can become a projectile (think potato gun, air rifle, etc........compressed air can really cause things to fly. Compressed grease will not. Once it's out clean everything really well, and check the condition of the rubber ring. Also, check the condition of the dust seal. Often what happens it the dust seal gets a nick, cut, or hole in it then dust and water get up in there. The water wicks into the cylinder bore and then as it sits it will oxidize and corrosion will build up. Been there done that.

    YMMV

    Dave Fox
     
  22. Robert

    Robert Active Member

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    Did you check with Chacal on those prices?
     
  23. bigfitz52

    bigfitz52 Well-Known Member Premium Member

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    That was going to be my comment; those don't sound like chacal's prices...

    The pistons get seemingly welded into place with corrosion and dried out brake fluid; if you're planning to replace them you can get on them with a big pair of channel locks and muscle them out, but you'll wreck them in the process.

    Air won't move them if they're truly stuck; grease will.
     
  24. NJRIDER1

    NJRIDER1 Member

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    yes,those are prices from chacal, i finally got the pistons out (lots of penatrant oil and muscle) and am going to order the parts listed b4 and rebuild the complete assy i don't want those suckers to stick unexpectedly at 70mph...thnx 4 your replies, NJrider
     
  25. RickCoMatic

    RickCoMatic Well-Known Member

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    You don't have to fight with a Stuck Caliper Piston.
    Hook-up the Caliper to a Grease Gun.
     
  26. bigfitz52

    bigfitz52 Well-Known Member Premium Member

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    NJ The key to the caliper rebuild is to get the channels in the bores where the seals go CLEAN clean. You'll need to fab up a hooked pick of some sort, or use a fine brass or nylon wire brush attachment on a Dremel to get the channels clean. You don't want to scratch or gouge the caliper in the process. This is the most tedious part of the job; take your time and be patient and do it right. A well-lit work area is a must, plan on taking a couple hours to get them completely cleaned out.

    A $25 investment in a Mity-Vac will save you a lot of grief when it comes time to refill the system, BTW.
     
  27. NJRIDER1

    NJRIDER1 Member

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    fitz. thnx i've already cleaned out the grooves for the piston seal and dust seal with a pick set and nylon wheel on the dremel. after cleaning the bore with the same wheel i used a bit of mothers polish and brake cleaner to finish the job, when i get the caliper rebuild kit i'll get them back together and start on the master cyl and splitter assy (this isn't the kind of job i enjoy but it is esential to me gettig the bike safely on the road so i;ll just take my time)... thnx NJrider
     

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