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Thread: Problems bleeding 1993 R100RS

  1. #1

    Problems bleeding 1993 R100RS

    Doesn't matter how much brake fluid passes through this system and there's no air coming through. The lever at the bars comes too far back. I have a clear tube on the 'last' of the two front brakes and it goes up before coming down !

    Should I conclude the seal at the bar end is damaged and therefore NOT allowing pressure to be created ?

  2. #2
    Administrator 20774's Avatar
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    Have you had this kind of problem in the past, or has brake bleeding gone fairly "normal". If you're not getting any air to come out and there's no pressure building at the hand lever, then likely the master cylinder o-rings are shot. I think you have Brembos on this bike...not familiar with where the bleed ports are on the front calipers...if they're not near the top of the caliper, air could still be trapped.
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    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

  3. #3
    Bleed nipples are at the top. The bike's new to me and I have had the forks off and done other work, so this is a refill from empty. I'm concluding this is a master cylinder rebuild. Summer's finally arrived in Chicago and this wasn't in the project scope !!!!!!!!!!!!!!!

  4. #4
    Administrator 20774's Avatar
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    Not sure this will work or help...I'm thinking more of the under-tank setups. But usually when finished with bleeding, it helps to pull the hand lever back and tie it down and leave it overnight. This will let trapped bubbles work there way up to the master cylinder. No harm in trying.
    Kurt -- Forum Administrator ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

  5. #5
    Aspiring Profligate Jeff488's Avatar
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    You also might try removing the caliper and swivel/turn it while holding it so that any trapped bubbles can make their way to the top or bleed valve.
    Easily done, so worth a shot.
    '08 BMW R1200RT
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  6. #6
    Not to be too inquisitive, but are you bleeding correctly?

    Close bleed port, and press lever, and hold it, while loosening the bleed port. Be sure to close bleed port before lever has a chance to come all the way back.

    Repeat as many times as necessary until a solid feel is achieved.

    Also, along the way, fill master cylinder with fluid so as not to allow it to get so low that you actually add air to system.

    I am assuming that is what is done for your bike as that is the way I do mine.
    "The difference between death and taxes is that death doesn't change every time congress meets." - Will Rogers

  7. #7
    If the master cylinder o-rings are shot, you should be seeing leakage at the handlebar. I expect your M/C is fine.

    Filling from empty is usually no fun. I have the best luck by pressure filling through the bleed fitting. Another thing that sometimes finds the trapped air is tapping the calipers and hoses many times with a wrench to break the air bubbles loose. Also partially squeezing the brake lever and then instantly releasing it letting it snap against its stop will sometimes break some bubbles loose.

  8. #8
    I've been squeezing and bleeding for a long time. Not seeing any air come out. It's a 1993 so I don't have the earlier under the tank issues. I am using a clear tube that goes up a foot before coming down into a jar. Took master cylinder piston out and the seals look good - that's how desperate I am. Now I have it apart I will replace the seals for good measure.

    I will then re-assemble and tap pipes and wiggle calipers. What a pain this is

  9. #9
    Quote Originally Posted by sfletcher04 View Post
    I will then re-assemble and tap pipes and wiggle calipers. What a pain this is
    I would seriously consider the bottom up pressure fill. I use a 60cc syringe with the tubing held on with wire tires.

    The last bike I bled the brakes from dry on was a 1992 R100RS.

    Lee

    DSC04243-M.jpg


    DSC04246-M.jpg

  10. #10
    Sometimes air gets trapped at the MC/brake line junction. Cracking that bolt while squeezing the lever is the cure. This has to be done carefully as there is a high possibility of spraying brake fluid everywhere on the tank, fairing, etc. The other trick, which I did on an old Duc and which I've seen on newer Ducs, is to replace the MC banjo bolt with one that has a bleed nipple.
    61 Gold Star, '13 690 Duke, '13 Daytona 675R, '14 Street Triple R (gone but not forgotten: '76 R75/6, '84 R100, 76 R90S)

  11. #11
    Day Dreaming ... happy wanderer's Avatar
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    +1 on Beemerphile's suggestion. Bleed from the bottom up when the system is dry. That's how the factory does it. Of all the bikes I've owned my RS gives me the most problems when bleeding. Especially the rear where the air gets trapped higher than the bleed screw. You either take the caliper off and hold it higher up while bleeding or just get a big syringe and some tygon tubing and push the fluid (and air!) UP to the top. It's easier than pushing the bubbles down.

    Before I got help building a vacuum bleeder unit I used the syringe method with good results.

    Now that I have this thing I rarely have bleeding issues. Short amateur demo video below:

    http://vid447.photobucket.com/albums...ps3fb0eeef.mp4
    MJM - BeeCeeBeemers Motorcycle Club Vancouver B.C.
    '81 R80G/S, '82 R100RS, '00 R1100RT

  12. #12
    Douglas Williams
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    I suggest you consider bench priming the master cylinder since you're starting from a dry system. Google "bench prime master cylinder".
    Doug
    Sent from a Galaxy, far, far away

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