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Thread: Right side rough running at cold '75 R90/6

  1. #1
    Registered User zenduddhist's Avatar
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    Right side rough running at cold '75 R90/6

    Hi Folks,

    I am getting an R90 up and running. When I get the back started, the right side kind of coughs and sputters until she is finally warmed up. It may take 5 minutes or so of idling and easy riding but finally, when it's ready, she runs pretty good without any of the sputtering. Can anyone give me some direction on where to start the troubleshooting?

    Thanks much,

    Chris McCarthy

  2. #2
    ABC,AMA(LIFE),MOA,RA,IBMW MANICMECHANIC's Avatar
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    Are the chokes on both sides operating the same, ie "in sync"? Sounds like the right side might be trying to run cold in a lean condition.
    F.O.G.Rider, Rounder #6,
    Ambassador, Biergarten co-chair
    BMWRA Wisconsin Region Rep, camping chair

  3. #3
    Grammarian no, Rider yes ISAMEMON's Avatar
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    choke cable, choke arm on carb. those would be my first checks

  4. #4
    Registered User donbmw's Avatar
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    Check the orifice in the fuel bowl where the choke system gets its fuel. This could be stoppedup. Had this happen to me on my R90.

    Don

  5. #5
    Grammarian no, Rider yes ISAMEMON's Avatar
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    ohhhh..........good one
    could very well be a pick up or orfice

  6. #6
    Registered User zenduddhist's Avatar
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    Where to get parts?

    Well, I checked the orifices in the choke pick up and everything looks clean. However, one of the screws that holds the butterfly to the throttle arm is stripped. Where is the best place to get parts for the Bing 64 carb?

    Thanks for your help everyone.

  7. #7
    rabid reader dbrick's Avatar
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    The US Bing agent: http://www.bingcarburetor.com/ or BMW dealers.
    David Brick
    Santa Cruz CA
    2007 R1200R

  8. #8
    Registered User amiles's Avatar
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    I wonder that you might check the carburetor to head rubber tube and it's clamp points. Not too pricy to change & should be done every few years. Perhaps as the machine heats up the rubber swells & seals?

    You can test with WD40 spraying it & checking to see change in idle speed etc.

    Of course if you changed them yesterday please disregard.

  9. #9
    Monza Blue 1974 R90/6
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    You can get the carb parts direct from BMW as well as Bing. For example, take a look at the Max BMW "fiche". They have complete rebuild kits with all the gaskets and you can add floats, and diaphrams, if you want to.

    They also have individual parts, like your butterfly holder with the strippped threads ($10) and the screws that hold the butterfly.

    Depending on your level of interest and how long it has been since the carb was apart, you might consider the needle, the float needle, and the four screws that hold the top on as good candidates for replacement while you have everything apart.

    Barron

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