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Thread: Master Cylinder Rebuild Kit for 17mm

  1. #1
    Registered User b25bsaboy's Avatar
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    Master Cylinder Rebuild Kit for 17mm

    Happy New year! I trust all are staying warm, as I know the temperatures here in Western canada are brutal and eastern canada is getting hammered with snow and freezing rain. My heart goes out to all of you that are without electricity and heat.

    Making good headway in rebuilding the 76 R 75/6. I am doing a twin disc brake conversion on the front and the piston for the master cylinder needs new rubber seals. Did some checking at the various supplier sits and I can believe that one cannot just buy the seals as it seems that you can only buy a kit. Is that a correct statement.

    Here is one that I found:

    34311234927_1_B.jpg

    All I need is the circlip, and the seals as the piston is in good condition.

    Does anyone know where to go to retrieve these items without paying a Kings ransom?
    Rick MacPherson
    Success is Not a Destination, But a Journey.
    Accredited Motorcycle Appraiser
    1968 BSA Starfire, 1976 BMW R75/6, 2009 R1200RT

  2. #2
    Administrator 20774's Avatar
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    Doesn't look like it...the BMW fiche don't show any of the parts inside the M/C listed separately.
    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!

  3. #3
    Registered User b25bsaboy's Avatar
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    Quote Originally Posted by 20774 View Post
    Doesn't look like it...the BMW fiche don't show any of the parts inside the M/C listed separately.
    That's what I thought!
    Rick MacPherson
    Success is Not a Destination, But a Journey.
    Accredited Motorcycle Appraiser
    1968 BSA Starfire, 1976 BMW R75/6, 2009 R1200RT

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    If you are going to the expense of a dual disk setup how about going to a 'bar mounted master cylinder? From what I have read and heard the remote under tank setup was less than satisfactory.
    Mark

    Current - '74 TR5T : '93 R100R : '06 ST3s ~ Past - Variety of British, French, Italian, Czechoslovakian, and German bikes from the '70s, '80s and '90s

  5. #5
    Registered User b25bsaboy's Avatar
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    Quote Originally Posted by R100RT_Mark View Post
    If you are going to the expense of a dual disk setup how about going to a 'bar mounted master cylinder? From what I have read and heard the remote under tank setup was less than satisfactory.
    Hi Mark,

    You make a good point about having the brake master cylinder being at the handle bar level rather than at underneath the fuel tank. Being a newby to the Beemers, I not sure where to begin as I will be greeting the that cross road real soon.

    Thank you for the feed back.
    Rick MacPherson
    Success is Not a Destination, But a Journey.
    Accredited Motorcycle Appraiser
    1968 BSA Starfire, 1976 BMW R75/6, 2009 R1200RT

  6. #6
    Monza Blue 1974 R90/6
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    Rick, remember this thread where you were asking about the dual disks a couple of years ago?

    http://forums.bmwmoa.org/showthread....t-Up-To-R-75-6

    "mymindsok" later posted in some detail about the components needed for the handlebar mounted master cylinder. Should be easy to find with search on his posts.

    Also, some detailed discussion About the mod in the BMW forum on advrider.

    Finally, I think Max BMW will be able to tell you exactly the parts to order if you talk with the parts Dept.

    Barron

  7. #7
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    Quote Originally Posted by R100RT_Mark View Post
    If you are going to the expense of a dual disk setup how about going to a 'bar mounted master cylinder? From what I have read and heard the remote under tank setup was less than satisfactory.
    I think the only real advantage would be the ease of checking the fluid level. Maybe parts might be more readily available.
    "The difference between death and taxes is that death doesn't change every time congress meets." - Will Rogers

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    Registered User jad01's Avatar
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    For what it's worth from my experience, I think I prefer the under-tank MC as opposed to the bar-mounted version. I never liked having the reservoir full of brake fluid up high over the painted surfaces of the bike (on any of my bikes over the years). I don't find a perceptible difference in the braking performance of the two types. It is easier to monitor the fluid level in the bar-mounted one, but I don't think it's difficult to pull the tank to check the under tank model. Having just rebuilt both types in December (under-tank on my /7 and bar-mount on my RS), the under-tank one was somewhat easier to complete, although the parts were more expensive.

    I did the dual disc conversion on my /7 a few years ago. I really like the upgrade for riding two-up with my wife. In retrospect, I kind of wish I had gone ahead and converted to the Brembo caliper front end from an early eighties bike since I was already running cast wheels. I have found the performance of the Brembo calipers are a nice step up from the ATE's. None-the-less, it was a good improvement over the original single disc arrangement.

    Good luck!
    Jim
    '78 R80/7 and '84 R100RS (Blues Brothers), '86 K75C (Icy Hot)
    '90 and '93 Mazda Miatas (Jelly Bean and Red Hot), '02 325ci (Blue Streak)
    '96 Giant Upland (big Kendas & freshly greased bearings!)

  9. #9
    Registered User b25bsaboy's Avatar
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    Quote Originally Posted by barron_williams View Post
    Rick, remember this thread where you were asking about the dual disks a couple of years ago?

    http://forums.bmwmoa.org/showthread....t-Up-To-R-75-6

    "mymindsok" later posted in some detail about the components needed for the handlebar mounted master cylinder. Should be easy to find with search on his posts.

    Also, some detailed discussion About the mod in the BMW forum on advrider.

    Finally, I think Max BMW will be able to tell you exactly the parts to order if you talk with the parts Dept.

    Barron
    Morning Barron,

    Thank you for reminding me of the on going issues and eventual solutions. I have to admit in looking at your thread link this first reared it's head with regards to updating from a single disc to a double disk as far back as 2010. Because of my work load, 2 R100RT coming and going, finding and keeping an R1200RT, doing a complete engine rebuild on a 1971 Norton Commando and doing some major house additions, I now wonder why I couldn't remember s#*t till you reminded me.

    I was forced into retirement last June and started on the R75/6 project to get it done. My biggest concern was trying to remember how and where everything goes. Just finished the rewiring into the head light bucket and needed some insight and help from the various people on this board, which I am not sure if it would have been successful without their guidance.

    To the front brake setup. I bought a complete second lower fork tube, rotor, calliper, stainless steel brake cable and mater cylinder from a chap in the US for some $ and I traded a set of Dell'Orto carburetors.

    Here is where I am at today with the rebuild:

    P1020675.jpg
    This is the master clinker that is temporally attached to top frame spine. Internally the bore has some slight pitting, but I don't think that will an issue?

    P1020684.jpg
    The front end of the R75/6 with the fender attached.

    My concern is do I put the master cylinder as attached in the above picture or place it at the handle bar level.
    Rick MacPherson
    Success is Not a Destination, But a Journey.
    Accredited Motorcycle Appraiser
    1968 BSA Starfire, 1976 BMW R75/6, 2009 R1200RT

  10. #10
    Registered User b25bsaboy's Avatar
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    Quote Originally Posted by jad01 View Post
    For what it's worth from my experience, I think I prefer the under-tank MC as opposed to the bar-mounted version. I never liked having the reservoir full of brake fluid up high over the painted surfaces of the bike (on any of my bikes over the years). I don't find a perceptible difference in the braking performance of the two types. It is easier to monitor the fluid level in the bar-mounted one, but I don't think it's difficult to pull the tank to check the under tank model. Having just rebuilt both types in December (under-tank on my /7 and bar-mount on my RS), the under-tank one was somewhat easier to complete, although the parts were more expensive.

    I did the dual disc conversion on my /7 a few years ago. I really like the upgrade for riding two-up with my wife. In retrospect, I kind of wish I had gone ahead and converted to the Brembo caliper front end from an early eighties bike since I was already running cast wheels. I have found the performance of the Brembo calipers are a nice step up from the ATE's. None-the-less, it was a good improvement over the original single disc arrangement.

    Good luck!
    Morning Jim,

    Appreciated your comments and I agree with going from a single disc brake to a double setup.

    One question came up from your comments: I have found the performance of the Brembo calipers are a nice step up from the ATE's. This I agree with, but because of the lower tubes being designed to accept the ATE calipers, would you have to change these out in order for the Brembo's to be able to attached? Similar to what came on say a later R100RT?
    Rick MacPherson
    Success is Not a Destination, But a Journey.
    Accredited Motorcycle Appraiser
    1968 BSA Starfire, 1976 BMW R75/6, 2009 R1200RT

  11. #11
    jimmy armour
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    master cylinder

    Hi, years ago I replaced the under tank master cylinder, on my 1977 r100s/rs for a 13 mm handle bar mounted type and noted a vast improvement, ,but this wont be period correct, going smaller diameter gives more braking power,I know Im happy with the conversion,and don't notice much difference between it and my friends brembo,s,hope this assists Jimmy

  12. #12
    Registered User b25bsaboy's Avatar
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    Quote Originally Posted by jimwjarmour View Post
    Hi, years ago I replaced the under tank master cylinder, on my 1977 r100s/rs for a 13 mm handle bar mounted type and noted a vast improvement, ,but this wont be period correct, going smaller diameter gives more braking power,I know Im happy with the conversion,and don't notice much difference between it and my friends brembo,s,hope this assists Jimmy
    Jimmy,

    Thank you for the comments, however from a riding standpoint which is more important, period correct or safety?

    We know the answer to that question.
    Rick MacPherson
    Success is Not a Destination, But a Journey.
    Accredited Motorcycle Appraiser
    1968 BSA Starfire, 1976 BMW R75/6, 2009 R1200RT

  13. #13
    Monza Blue 1974 R90/6
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    Rick, nice job. Bike looks great.

    Barron

  14. #14
    Monza Blue 1974 R90/6
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    One more thing, if you decide to stay with the under tank cylinder, but are worried about the pitting, consider getting the master cylinder sleeved.

    Here is an example of a company that does it:

    http://www.applehydraulics.com/

    Send them the cylinder and the rebuild kit.

    Couple other places that do it, Apple is just one example.

    Barron

  15. #15
    jimmy armour
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    nice job

    Quote Originally Posted by b25bsaboy View Post
    Jimmy,

    Thank you for the comments, however from a riding standpoint which is more important, period correct or safety?

    We know the answer to that question.
    Hi again, sorry with all the goings on, I forgot to say how good your bike looks!!,looking forward to seeing it completed,Jimmy

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