airhead problem need help please

Discussion in 'Airheads' started by upsman, Jul 5, 2004.

  1. upsman

    upsman Been here awhile

    Joined:
    Jun 2, 2002
    Oddometer:
    274
    Location:
    michigan
    long story short, riding my 78 R80/7 yesterday when it went down to one cylinder without warning. i have checked all the usual things , spark, fuel, timing, compression they all check out good but i still cant get it to run on the right hand cylinder, it backfires out the carb on this cylinder and wont clean out, the bike has a dyna 3 electric ignition and is otherwise stock.

    any help or advice appreciated :hair thanks greg
    #1
  2. Rubber Cow

    Rubber Cow GS Dork

    Joined:
    Jul 9, 2001
    Oddometer:
    5,346
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    Aloha... yes, Aloha, Oregon
    Have you checked the carb main jet for debris or inspected the carb diaphragm for tears?
    Dyna coils have been know to fail but I haven't heard of their ignition module/booster failing for this vintage BMW.
    Hope this helps.
    Jorge
    #2
  3. upsman

    upsman Been here awhile

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    Jun 2, 2002
    Oddometer:
    274
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    michigan
    yes we checked the carb and put on one from another bike and still nothing, thanks for the input thats what im looking for, we have tried everything and nothing made a bit of difference so far. thanks again greg
    #3
  4. Chopperman

    Chopperman I am dead

    Joined:
    Sep 17, 2001
    Oddometer:
    27,033
    Couple things

    Dynas have been known to blow a channel resulting in one side barfing like that. But also check the ring on the cam where the points used to be. That ring will sometimes slip and the timing will get fuxored.
    #4
  5. RockyRaccoon

    RockyRaccoon Found:Gideon's Bible

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    Have you determined whether it's getting spark? Take out the plug and hook it back up to the wire, make sure it's grounded and then turn it over and see if you can see a spark. Sometimes the spark plug wires and caps go bad. :dunno
    #5
  6. Cpt. Ron

    Cpt. Ron Advrider #128

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    Take the left plug wire and put in the right side, and vice-versa. See if the problem changes sides. If it doesn't, it's a fuel or compression issue. If it does, it's an ignition issue.

    Fuel/compression problems: blocked main jet, torn diaphragm, broken throttle cable....

    Ignition: worn out spark plug caps, old spark plugs, broken coil, bad connections....
    #6
  7. Possu

    Possu de-nOObed!

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    Remove right plug, tip a little fuel down the plug hole, re-fit the pug & cap etc & see if it fires up briefly on both cylinders.

    If it does, then it may well be a carb blockage as mentioned previously.

    If not, then probably ignition related.

    Worth trying as there's no cost except 5 minutes of time.
    #7
  8. storymitchell

    storymitchell Member of the proletariat

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    Lazy turd that I am, I simply shoot a bit of ether into the carb in question whilst cranking the starter. Same outcome, though, I suppose.
    #8