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Question on Caliper Rebuild

Discussion in 'XJ Technical Chat' started by Robb, Sep 8, 2016.

  1. Robb

    Robb Member

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    Hi, new member, name is Robb. I just bought a new/used XJ750 Seca... it's in really nice condition, relatively low mi (14K) but has a ridiculously hard brake pull on the fronts. I pulled the calipers off and found both pistons were froze solid. Was surprising the front brake even worked. Just bought the K&L Brake Caliper kit 32-1602 from Amazon and I've never been so confused when ordering bike parts before. It seems K&L is the ONLY manufacturer that makes a rebuild kit for the XJ750 Seca Even if I go to my local Yamaha dealer they only carry the K&L kit, no OEM. For some reason K&L refuses to say exactly what this kit contains, only saying "contains all the necessary rubber parts to rebuild one brake caliper. One of the main sources of my confusion lies in the fact that when I disassembled the calipers, there wasn't a dust cover on the outside of the cylinder that the piston passes through, as shown in some diagrams. Instead, the cylinder has 2 grooves for 2 O ring seals. Does one of these grooves act as a dust seal and the other as a fluid seal? Even the online Haynes manual shows the piston coming through a bellows type dust seal. There was a heavy ring of crud around the outside of the cylinder where the piston passes through, which I suppose contributed to both pistons freezing in the cylinders.

    Also a note on K&L... typical arrogance from a company with a niche monopoly. Customer service very unfriendly and unhelpful, and today marks the 3rd day that they've been sitting on my order which is yet to be processed let alone mailed. But enough with them... one of those companies you're forced to deal with. My main concern is what's the deal with the double grooves in the cylinder and do I need to order that outer dust seal or will the 2 O rings/seals inside the cylinder suffice?

    Finally, I've been lurking a bit and this is my first post. I look forward to exchanging ideas and picking up tips from all of you. I really enjoyed riding my new/old bike for a week before I just couldn't take the hard brake pull anymore (had been hoping things would loosen up as the bike woke up from a 3 year coma the PO left it in) I sold my FZ1 earlier in the summer, being a few grand short on a new car I was buying... got a great deal on this bike, only problem is this brake thing. And the XJ fills the void beautifully.... and for just a few hundred bucks. Thanks in advance for the responses and nice meeting you all.
     
  2. schmuckaholic

    schmuckaholic Well-Known Member

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    Send a message to a user on here named Chacal -- he is our resident parts supplier, possesses a wealth of knowledge, and is an all-around good egg.

    Yes. That is exactly it.

    I don't have the manual right in front of me, nor a Seca, but IIRC the bellows seals are for the pins that the brake pads fit over, and not the pistons.

    Hopefully you've gone through and gotten everything else straightened out first... if it's been sitting a while, it's likely going to need more than just front brakes.
     
  3. Robb

    Robb Member

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    After looking closer I noticed that I had been looking at the diagram for the XJ60... totally different The diagram a couple pages below for the 750 shows just the way mine is. That recessed dust seal seems like a great way for crud to enter the cylinder. At least it's good to know that my rebuild kit is right.

    Surprisingly, other than the brakes the only problem I could find was some low speed carb goofiness.... very long warm up, missing at low speeds that cleared up with power increase. I threw a bottle of Chemtool B12 in the tank and that was the first time an additive of any kind has ever worked for me. Within 5 miles bike was running smooth as silk and was ready to ride in 30 seconds vs. 4 to 5 minutes warmup. The result was a very high idle after the motor got up to temp, probably caused by the PO cranking up the idle to make up for the clogged idle jets. After I reset the idle all is fine. Other than that, tires seem pretty new and rubber is still nice and soft. Naturally I needed a new battery but other than that it runs perfectly. If there's anything else you can think of to check please let me know. That sticky on the delaminating rear brake shoe threw a scare into me and I did pull the drum apart and checked out the shoe.
     
  4. XJ550H

    XJ550H Well-Known Member Premium Member

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    specs ask for seal rebuild every 2 years
     
  5. chacal

    chacal Moderator Moderator Supporting Vendor Premium Member

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    There ARE small "bellows" rubber dust boots on the PIN that holds the caliper body to the retainer/mounting "block", and those boots can become awful "yucky" with age, etc. Those pin boots are not included in the K&L kits, but are available from us as separate pieces.

    Also note that the fluid and dust seals are different sizes, don't get them reversed!

    Yes, that dust seal is all that keeps crud out of the piston bore, bad design but there it is......
     
  6. Robb

    Robb Member

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    Thanks guys. All that's left to do right now is sit back and wait for the parts to roll in. Coming up on day 4 and K&L still hasn't blessed me with the processing of my order. There's a manufacturer I would love to never do business with again. Too bad they're the only game in town or they'd be out of business.
     
  7. k-moe

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

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    As mentioned above, they are not the only game in town. There are several manufacturers of carb rebuild kits for your carbs, and our local parts source carries all the ones that actually fit.

    Chacal keeps parts in stock, and you will get what you order within a few days.

    Also, don't expect that you're done with tending to the carbs, or anything else. You bought an old motorcycle; there will be dcades of wrongness and neglect to correct bfor you can be sure that it's safe and reliable.

    Begin reading:
    TECH TOPIC: The Real Costs of Maintenance

    The Information Overload Hour

    IN THE CHURCH OF CLEAN
     
  8. luvmy40

    luvmy40 Member

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    Far from the only game in town. Chacal has everything you'll likely ever need for your Seca at fair prices too.
     
  9. luvmy40

    luvmy40 Member

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    I happen to be parting out an '82 Seca 750 if you need any odds and ends.
     
  10. Robb

    Robb Member

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    Got the rest of my parts today and rebuilt the calipers. OH... MY.... GOD... what a PIA bleeding these brakes. I've changed fluid on double caliper bikes before and it's always a PIA but not like this. Totally insane putting the MC under the bars like they did. There's no way I can figure out how not to make a huge mess. The worst thing is (and I know I'm preaching to the choir here) that you have absolutely no idea what the fluid level is in the MC. So I hooked u a funnel and tube and taped it to the bars and just keep filling it till it runs out, then take a rag and wipe everything down... pump and release the bleeder a few times, refill till it runs out and makes a mess... clean up the mess, pump some more, etc etc. Fking with it for about an hour this afternoon, just barely seems like it's gotten a little firmer but still handle doesn't grab on anything yet. What were these people thinking?
     

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