Bar Mounted MC Upgrade, Question On Throttle Cables

Discussion in 'Airheads' started by jchussey, Dec 4, 2018.

  1. jchussey

    jchussey Adventurer

    Joined:
    Aug 25, 2017
    Oddometer:
    29
    Location:
    Centennial, CO
    Although I'm a stickler for originality when it comes to my '75 R90/6, I have finally decided to do a bar-mounted master cylinder. I'm going with the 12mm unit, part number 32722302367, but it appears to be built for just one throttle cable while the /6 has 2. Is it simply a matter of swapping the cover to accommodate the second cable? (I have the later, squarish cover and the larger diameter, 2-cable 33 throttle cam disc). Thanks.
    #1
  2. Plaka

    Plaka Brevis illi vita est

    Joined:
    Jun 19, 2010
    Oddometer:
    5,142
    Dubious.. You will have to go with the single cable setup and the cable splitter (2 into 1) under the frame backbone. The fitting on the chain end is different for one vs. two cables and fits a different groove in the lower handlebar housing AND the cover. But I don't have an old dual cable setup to compare anymore. I'm willing to bet the cam has a different rate but I kinda think that will work out, just a different feel. I think I have a spare single setup around if you want to come up here some WARM day and play with it. I'm in Longmont.
    #2
  3. craydds

    craydds Long timer

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    Not sure of the part number (will research my past posts) but I got a bar-mounted MC with a dual throttle cable for my '75 R90s; so, no changes to my dual cable set-up. I have another MC at the house, brand new in the box, ready to go on my son's '76 R90s; I'm sure it's the same one I used, so same part number. I do recall that I had to get a new throttle grip and cam to fit with the MC; most likely have those new parts for my son's bike at the house. Will get part numbers for you if you need them.
    #3
  4. beemerphile

    beemerphile Unreconstructed Southerner Supporter

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    Location:
    Danielsville, GA USA
    I have a factory new bar mounted 13mm master cylinder that has dual throttle slots. It is part number 32 72 2 310 746. Available if you are interested.

    [​IMG]
    #4
  5. 2WheelTraveler

    2WheelTraveler backinthesaddleagain Supporter

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    May 29, 2013
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    If you want to use a single cable throttle/MC unit then a splitter will be needed. Or, you could use a dual throttle MC unit. All parts needed are available from BMW, or you can find them on ebay. A little searching on Max BMW's website (fiche) will yield part numbers.
    #5
  6. jchussey

    jchussey Adventurer

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    Aug 25, 2017
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    Centennial, CO
    Thanks guys. I have tried a 13mm MC. It is too hard and not progressive enough with the single ATE for my tastes, so I am set on going with the 12mm size. But my searches on Max have not turned up anything in the two cable variety. I'm not opposed to go into a splitter, but would like to avoid it if possible due to added expense.
    #6
  7. Solo Lobo

    Solo Lobo airhead or nothing

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    Mar 16, 2004
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    Shoreline, WA
    I think that Tiggum has a NOS two-cable perch that he might part with...
    #7
  8. bmwrench

    bmwrench Long timer

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    The easiest way out is a set of cables and junction box, along with the throttle cam for an R80S/T, or an '84-'85 R65.
    #8
  9. AntonLargiader

    AntonLargiader Long timer

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    #9
  10. Tiggum

    Tiggum Retired

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    Mar 2, 2015
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    Nope, Solo, I am going to use the entire 2 cable unit, and I am going to use 2 new throttle cables from a R100RS. I have a complete single throttle cable, splitter and two carb cables which came off my R65LS which I will be happy to sell (and remember, while it's 35 years old, it only has 789 miles use). And Anton, thank you for all your super informational postings. Really a great resource.
    #10
  11. nobbylon

    nobbylon Been here awhile

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    Aug 13, 2012
    Oddometer:
    622
    I nearly went bar mount mc a couple of years ago on my 90s. Happy I didn’t and bought a new under tank mc. It just looks cleaner. Granted mines a double disc and it’s always had superb stopping power with the goodridge lines. My 75/6 is a single disc and really could use some more brakes.
    #11
  12. jchussey

    jchussey Adventurer

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    Aug 25, 2017
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    Location:
    Centennial, CO
    #12
  13. Kiwiabbo

    Kiwiabbo Been here awhile

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    Apr 16, 2014
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    379
    409F9ED1-521A-44CF-8EE0-1EC9C8A7E4DE.jpeg
    Well I have both, and from this I can happily report that the handlebar mount makes a lot of difference, however if you haven’t tried it then you won’t know the difference so you’ll be happy with what you have. I’m luck enough to have two of these with my father and can do comparisons with different set ups.
    #13