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jammed Front Brake piston.

Discussion in 'XJ Technical Chat' started by gark32, Oct 6, 2011.

  1. gark32

    gark32 New Member

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    1981 750 seca, got it for $400 in a non-running state. over the past ten days i've rebuilt the carbs, sync'd everything up with a couple of home-made tools (YICS, vacuum gauge thingerbob) that i learned to make as i lurked on this great forum. well, she runs like a dream, but the last issue i have left on her is that the front left brake caliper has the piston almost all the way out, but stuck hard. i can't pop it out to save my life. also, the master cylinder seems pretty much dry, and probably has been for a couple of months at least. i'm thinking of filling the cylinder, totally bleeding the front calipers, and hoping that a good squeeze will pop the jammed piston out so i can deal with it. does this ring any alarm bells with anyone, before i try it? i really don't want to bugger up anything being overzealous, and i'm sure i can find a used caliper somewhere if i absolutely have to, i'd just rather not spend the time and expense running one down.

    also, assuming it does pop out, what should i do then? hone the caliper? chuck it out anyway?

    any help or suggestions will be much appreciated.
     
  2. adrian1

    adrian1 Active Member

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    search on seized caliper. plenty of info on that.....some suggest compressed air others use a grease gun. I prefer just using the bike's own system. restrain one caliper using a block of wood/steel and 2 G Clamps then pump the lever until the offending piston falls out. The piston and/or seals will need replacing go here:

    http://www.xjbikes.com/Forums/viewforum/f=23.html

    Welcome to the site (officially) :wink:
     
  3. gark32

    gark32 New Member

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    thanks. not sure why it didn't occur to me to search, since that's how i figured out how to do the rest of the stuff. looks like filling er up and squeezing the handle should work, so that's saturday's chore. will update when i get to it.
     
  4. bigfitz52

    bigfitz52 Well-Known Member Premium Member

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    Once it's apart, you clean and inspect.

    The calipers are very simple; just a piston and a couple of hard as a rock 30-year old rubber seals. If the piston isn't pitted, it can be reused, otherwise replacement would be in order. Honing rarely required.

    But you won't know until it's apart. Realize this: You're going to NEED to rebuild the front brakes completely, or the bike won't be safe. That means both calipers, the master cylinder, and new lines, pads and shoes. The original brake lines were supposed to last 4 years. They gotta go.

    Oh, and before you kill your motor, check the valve clearances. Original check was to have been at 3K miles, and every 5K afterward. If ignored long enough, bad things happen. Often ignored on these bikes.

    HOWEVER: First and foremost-- the rear brake. Read: http://xjbikes.com/Forums/viewtopic/t=15874.html and http://xjbikes.com/Forums/viewtopic/t=34257.html
     
  5. gark32

    gark32 New Member

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    i've got the o-ring kits for both front brakes, i was planning on redoing them anyway. PO said he replaced rear brakes last riding season, but i suppose i've got no good reason to believe him about anything that i can't verify directly.

    Valve clearances is probably saturday's chore, as well. guess i'll have to set the vacuum sync gauges back up. good thing i'm not married, i've never got a honey-do beyond my own priority list :)

    thanks for the suggestions, Fitz.
     
  6. bigfitz52

    bigfitz52 Well-Known Member Premium Member

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    Don't trust the 30-YO brake lines; they deteriorate from the inside out. When you replace them, it's worth the couple extra $$ to make the upgrade to stainless steel.
     
  7. gark32

    gark32 New Member

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    that's gonna be a job for a couple weeks down the road. i'm kinda working on a shoestring here, and if i have to get a new caliper or piston it's gonna be a good sized chunk of my bike budget. definitely need to do it, but not this week.
     
  8. bigfitz52

    bigfitz52 Well-Known Member Premium Member

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    That was why I said "clean and inspect."

    Quite often a piston LOOKS like it's in really bad shape, until you get it cleaned up. It's stainless, so it really doesn't rust but can be corroded.

    Here's one that came out of a 550. Look closely, you'll see a little bit of pitting. But that pitting is beyond the area swept by either seal, so this piston was fine to put back in service, it's in one of my bikes right now.

    [​IMG]


    Understand something about the original brake lines. The factory recommended replacement interval was 4 years. Granted, that was a bit "conservative." But now they're over thirty years old. You can't SEE anything wrong with them, and you won't-- until one POPS when you least expect it (like under hard braking.)

    This is a 500+ pound, 130+ mph motorcycle. Don't ride it until you get the brakes fully overhauled. The results could be a lot more expensive than you might even imagine.
     
  9. gark32

    gark32 New Member

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    Update: bled the brakes down over the course of about an hour, got the piston popped out. cleaned it up and it looked just like that photo up there -- bit of pitting near the end but the rest was in very good shape. had to clean a massive amount of crap out of the groove for the seal so that the new seal would fit back into it, then the piston went back in (with a little bit of coercion). spent another hour bleeding the brakes down, then checked the brake lines -- dated 1/81. guess i've got a while before i get to ride after all. i'll probably ride about 12 miles (slowly, on back roads) to get her home from the shop where she's sitting now, but after that i'll do the valves and wait for stainless brake lines to come in. i checked the rear brakes, as well -- looks like at the beginning of the season the PO actually did replace all the brake pads/shoes/etc, no delamination at all and pretty clean inside. front brakes looked equally new. i'm not really looking forward to bleeding those damn brakes a third time, but i'd rather do that than have a line pop and get spread across half a mile of pavement.
     
  10. LVSteve2011

    LVSteve2011 Member

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    On this brake line issue, I'm sure that it's possible to "pop' one during a panic stop, but, what bigfitz is forgetting is that a simple "static" test of the brakes prior to riding should make any brake line defects visible. While safely sitting in your driveway, just grab the brake handle and squeeze with all you can muster. If you have a problem anywhere in the system you'll see it. I have owned a few old bikes with old brakes and I have not blown out a brake line yet. Can it happen? you bet, but I think it's rare as hens teeth. There is one point that should also be made here regarding the static test, there won't be the heat factor. But, heat is only a factor at the calipers. As an example, I owned a 1981 Kawasaki KZ 1300, it was 700 lbs. and really fast. All I did to the brakes after I got it home was to bleed both front calipers and refilled a dry rear MC, bled that one and I had good brakes. The result was perfect braking every time I needed to stop. BTW, I owned this bike when it was 25 years old. Mechanics tip here: if anybody has a stuck piston in their caliper, remember this, Aluminum expands faster than Steel, after all traces of brake fluid a gone from the caliper, CAREFULLY heat the caliper with a Propane torch, have the caliper oriented with the piston point down, then heat it up and the piston should just fall out, pulled by gravity. If this does not happen, use a "C" clamp to push the piston back into the bore. I should be free then. One other tip to maximize the temp differential, get a can of that computer key board spray, the kind that's a liquified gas, if you turn the can up side down and spray you will get a very cold jet of liquified gas; while heating the caliper spray the piston. I am not trying to minimize the dangers of old brake systems, it's my experience with the old bikes that I owned the brakes were just fine, I do advocate replacing old parts when there is an indication of immanent failure, the bad part comes when that indication occurs while you're in a panic stop. I hope this info helps. The key thing to also remember is to maintain your brake system with regular care. Change the fluid at least every two years, and when you change pads, check the rubber bushings and lube the slider pins with high temp grease. (If you have them.)
     
  11. bigfitz52

    bigfitz52 Well-Known Member Premium Member

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    Fitz isn't forgetting anything.

    The brake lines deteriorate from the inside.

    You can "stress test" them all you like; every "stress test" brings you closer to "popped line." YES, it can happen, it happened to me before and it's scary as hell, even when it happens in a non-life threatening situation.

    It's NOT a good idea to ride around trusting your life to 30 year old components that had a four year service life; please don't tell people that it is.
     
  12. LVSteve2011

    LVSteve2011 Member

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    I apologize bigfitz, I was not aware that you had an incident with your brakes. I also apologize for wording my post badly, sometimes I get this idea in my head that I'm a great writer. I guess being from Las Vegas makes me a gambler and I have been very lucky through out my riding career, and just in case you're wondering, I've got over 200,000 miles of experience. But I'm not bragging.
     
  13. bigfitz52

    bigfitz52 Well-Known Member Premium Member

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    No worries. I've got somewhere around 250K under my belt as well, spread over 43 years. However, one key to staying alive on two wheels is being sure your equipment is 100%. And riding around on 30-YO Yamaha brake lines is NOT part of that; they just have to be replaced.

    And with that many miles, if you've never done anything with REALLY OLD brakes except bleed them, you are VERY lucky.

    I hope you've at least inspected the rear shoes on your current XJ for signs of delamination.
     
  14. LVSteve2011

    LVSteve2011 Member

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    I understand bigfitz, stopping safely IS what everybody should be concerned about. As for me, I'm currently stuck in limbo as far as my bike is concerned due to the fact I have no garage, the bike is in storage until I can get a house. But, I will check for the delamination when I get the chance. When I first got it, the front brakes didn't work, the mc was full of very dark fluid so I drained the whole system and put in new fluid, it took a while to bleed, but it finally pressurized and even though I got this result I still plan to do a major overhaul replacing the critical parts with new ones. (caliper and mc rebuild) and yes, replacing the brake lines too. Maybe someone can invent a two piston mc that has one piston for each disc. Of course, all bikes would have to have dual discs.
     
  15. bigfitz52

    bigfitz52 Well-Known Member Premium Member

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  16. LVSteve2011

    LVSteve2011 Member

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    Is there a poll or any other data that can give me an idea as to how common this is? My last XJ was a 26 year old 650, I pulled the rear wheel not knowing about delamination at that time, to see how much "meat" was left. I found the brake shoes to be firmly attached. Granted, these may not have been the original shoes, but I didn't know one way or another. I think, bigfitz you misunderstood my 'when I get a chance' statement, I meant when I get into a house with a garage. Since I am going to do a full blown restoration on this bike, the urgency of this subject is moot. I found a crack in the frame and have to get that repaired, and the crack is in an area that requires the engine be removed in order for the welder to get access to it, so I won't be riding any time soon.
     
  17. bigfitz52

    bigfitz52 Well-Known Member Premium Member

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    If it's the original set of shoes, it's quite common and doesn't appear to be affected by how the bike was stored; it happens even on inside-stored bikes.
     
  18. greg_in_london

    greg_in_london Member

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    Don't know of a poll, but I've had couple of sets of pads delaminate, but never shoes, in a lot of miles driving. That tended to be on pads that had been exposed to water or oil and/or overheated, but it shows you can't rely on the PO. You also don't know if the equipment was good quality or cheap pattern. I know I've bought and used both.

    I replace rubber hoses as soon as possible as they do not perform as well as SS ones. I bought lengths of hosing some years ago at an autojumble years ago and buy banjo connectors, olives (and bolts, if needed) whenever I require them, because I tend to be on a budget and I want to be able to fix my brakes whenever I need to.

    Oddly, though, the only brake lines I ever had fail were stainless steel ones. It was a Honda CB500T with a double adult Classic sidecar on it. The rough stainless hose rubbed through the insulation on a wire, which shorted occasionally onto the hose. The heat from this melted a pinprick hole in the internal plastic hose the sheathing was supposed to be protecting, leading to brake failure, thankfully not in an emergency situation. I use the SS hose which has a clear plastic sheath now (although some pretty colours are now available...)

    Thinking about it - I would inspect pads and shoes to check they're okay, but if they worked okay would leave them. Very old pads would not have been as effective new as modern ones though, so once I knew the bike was running okay, I would probably replace them when they were less worn than I would if I knew their history, likewise old tyres etc. I guess I'm more inclined to spend money on a bike that is running and has an MOT than one just occupying a corner of the garage.
     
  19. bigfitz52

    bigfitz52 Well-Known Member Premium Member

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  20. greg_in_london

    greg_in_london Member

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    Eh ? Who's that aimed at ?

    I read the first thread - which prompted me to say I've never seen shoes come apart, which I haven't - but not the second, which did not load.

    I always had to treat brake parts as regular consumables and kept replacements on the shelf indoors. Admittedly that means I have ten year old pads and shoes for the XJ550 waiting to be used, but I have never heard of a need for these parts to be given a shelf life if they are stored sensibly. I'm certainly not thinking of throwing away unused parts in their original packaging.

    Oil or damp penetration behind the friction materials or overheating affecting the adhesive could plausibly affect even well-made shoes and pads, but just airing for even thirty years without being taken out of the box ? I hope not.
     
  21. bigfitz52

    bigfitz52 Well-Known Member Premium Member

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    I can't answer the "how" or "why." All I know is both of my 550s were suffering delamination; the bike that sat for longer is the one that caused me to post the initial warning.

    While I don't think that NOS or newer-old brake shoes would be affected since they've never been through any heat cycles or had a chance to acquire moisture from the air, I honestly don't know. We don't know what causes the delam, only that it happens with alarming frequency.

    From what I can tell, the only "pattern" to it is that all of the affected machines have SAT for extended periods of time after being used initially. Since so many owners over here only own/owned a motorcycle as a "toy" there are a lot of long-sat bikes around.
     
  22. MercuryMan

    MercuryMan Active Member

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    This is good stuff! Experience with physics and chemistry (finished my undergrad requirements in both) tells me that the most likely reason why delamination is happening is the environment the shoes/pads are exposed to. Although entropy (decay) is always at work, it is slowed by proper conditions. Dry cool air and even better a vacuum (no O2 or H2O) will dramatically slow decay. Moisture, heat, and changes of these conditions make it increase. So your properly stored still in box parts are probably fine, but the shoes left inside a drum which can develop moisture and after they've been exposed to vibration/heat are going to be degraded. Think about the difference between leaving an old fridge slightly open or closed and not turned on. Wear parts like brakes were always meant to be used up fairly quickly and then replaced with new, so money vs saftey-i'll go with the latter.
     

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