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Thread: Rear Master Cylinder Help

  1. #1
    czucker
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    Rear Master Cylinder Help

    So I was changing the rear brake line on 1990 K75 and I ended up stripping the threads on the master cylinder.

    I was going to try to use one of those Heli Coil kits, but I'm not certain of the thread size.

    Anyone know what thread size the brake lines are off hand? Or does anyone have any experience with these thread repair things?

    Any help would be greatly appreciated.

    Thanks,
    Chris Z.

  2. #2
    DrPaul DrPaul's Avatar
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    Quote Originally Posted by czucker View Post
    So I was changing the rear brake line on 1990 K75 and I ended up stripping the threads on the master cylinder.

    I was going to try to use one of those Heli Coil kits, but I'm not certain of the thread size.

    Anyone know what thread size the brake lines are off hand? Or does anyone have any experience with these thread repair things?

    Any help would be greatly appreciated.

    Thanks,
    Chris Z.
    I found a good used rear MC on eBay recently and paid less for it than the price of a Heli-Coil set. Besides, do you really want a part that important Heli-Colied? Just my $0.02.
    DrPaul - 2008 K1200GT, 1973 R75/5
    2004 R1150RT - sold,1974 R90/6 - sold
    2002 R1150RT - sold,1987 K75S - sold

  3. #3
    kayseventyfive
    Guest
    I would not trust a Heli Coil to be leak-free. If you must do a repair, consider a Time Sert with Loctite as a sealant.

  4. #4
    czucker
    Guest
    Thanks. The Time serts look much, much better than the Heli Coils.

    However, I buckled and found a used cylinder for a decent price. The idea of having a band aid on my breaks wasn't ultimately satisfying.

    Thanks guys.

  5. #5
    jcridge
    Guest
    Quote Originally Posted by czucker View Post
    Thanks. The Time serts look much, much better than the Heli Coils.

    However, I buckled and found a used cylinder for a decent price. The idea of having a band aid on my breaks wasn't ultimately satisfying.

    Thanks guys.
    Order a rebuild kit before installing. 18 year old seals and brake lines are not what you want to be relying on to stop with.

    Typically you would install the line on the master cylinder before installing on the bracket, then install the swivel fitting on the caliper, right?.

  6. #6
    czucker
    Guest
    That sounds right. I think that when I stripped the threads I must have been screwing the line in at a slight angle. I will be much more careful this time.

    As for the rebuild, the seals look absolutely perfect. I can't say whether the cylinder was rebuilt before I purchased the bike (about 5 years ago now), but everything looks really clean and good. New lines are also going on as soon as I receive the cylinder.

    While we're talking about break lines and such, does anyone know if I can just walk into a hardware store and pick up those brass washers for the line? I'm short on washers for my new front lines.

    Thanks,
    Chris

  7. #7
    kayseventyfive
    Guest
    Quote Originally Posted by czucker View Post
    Thanks. The Time serts look much, much better than the Heli Coils.

    However, I buckled and found a used cylinder for a decent price. The idea of having a band aid on my breaks wasn't ultimately satisfying.

    Thanks guys.
    Yeah, a good used one is the way to go, but I would not characterize Timeserts as a band aid. Such engine companies as Allison, GE, Pratt and Whitney and Buccialli have used similar Rosan inserts and Timeserts in their aluminum cases since long long ago. I have done a number of Timesert repairs that lasted thousands of flight hours with no problems.

  8. #8
    BUDDINGGEEZER
    Guest
    Quote Originally Posted by czucker View Post
    That sounds right. I think that when I stripped the threads I must have been screwing the line in at a slight angle. I will be much more careful this time.



    While we're talking about break lines and such, does anyone know if I can just walk into a hardware store and pick up those brass washers for the line? I'm short on washers for my new front lines.

    Thanks,
    Chris
    Yes, if you are talking of the banjo bolt washers. I have at Advance Auto Parts.

    Ralph Sims

  9. #9
    3 Red Bricks
    Join Date
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    They are aluminum (or copper) "crush washers".


    LONG MAY YOUR BRICK FLY!

    Ride Safe, Ride Far, Ride Often

    Lee Fulton Forum Moderator
    3 Marakesh Red K75Ss
    Mine, Hers, Spare

  10. #10
    mrich12000
    Guest
    http://www.beemerboneyard.com/


    Give him a call, great parts and no worries about a flogged rear wheel brake cyl.

  11. #11
    BUDDINGGEEZER
    Guest
    Quote Originally Posted by 98lee View Post
    They are aluminum (or copper) "crush washers".


    Correct. Any auto parts store. Copper will work also.

    Been there, done that.

    Ralph Sims

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