My r90 restoration.

Discussion in 'Airheads' started by blaine.hale, Dec 29, 2009.

  1. Kai Ju

    Kai Ju Long timer

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    Didn't you say that those were new diaphragms ?
    If so, how did they get damaged so quickly ?
    Is it possible that the replacements you just installed suffered the same fate ?

    If they are torn again, and on the same side, you may have an issue with your carb body, or installation method.
    Something to look at.

    The more I look at that photo of your diaphragms, the more I see a cut caused by pinching. The cuts are evenly spaced and on the same vertical plane.
    And from your description of the test ride, it sounds like it happened again.
    I've had good luck by placing a spacer, like a dowel, under the slide so it's at full throttle and installing the carb top with the slide in that position.
    Make sure to remove the dowel before you run it :rofl
  2. blaine.hale

    blaine.hale Long timer

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    I wish it happened again and the solution were that easy. However, I pulled them both again to check and the new ones were still in perfect shape and keeping the top side dry.
    I went to swap the carb sides today but didn't have spare fuel line to make the distance and the throttle cables need to be re-routed for that to function.
    Here's a video of what's going on. Keep in mind, it only will start doing this after warming up and running around for maybe 10 minutes. Cold start, it will function normal.


    <iframe width="640" height="360" src="http://www.youtube.com/embed/eyIh8HzHEC4" frameborder="0" allowfullscreen></iframe>
  3. Beater

    Beater The Bavarian Butcher

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    Your solution is quite easy.

    Mikuni.


    :hide
  4. blaine.hale

    blaine.hale Long timer

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    *gasp!
    If only Mikunis grew on trees :)

    I've got the right carb soaking in some good ol' Berryman carb dip for tonight. Running out of ideas short of finding a new, matching carb somewhere.
  5. Airhead Wrangler

    Airhead Wrangler Long timer

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    I hope you took every last piece of rubber out of it or the berryman's will do that for you. Be sure to follow it up by blasting out every last little passage with compressed air. Make sure the choke goes back in right too. Good luck. May the bing force be with you.
  6. brocktoon

    brocktoon Been here awhile

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    Nobody in the Georgia area has a matching, known-functioning carb to help this guy diagnose the problem? I thought there was a big Airhead community down there, as well as a spirit of southern hospitality.
  7. Beater

    Beater The Bavarian Butcher

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    Brad offered his which are set up for an R80 ... I have a set of 40mm Bings that are not tuned quite right for an R100 engine ... and my other bike has Mikunis which are dead on for a higher compression R100 engine.

    None of us have an R90. Sad I know. I don't know of anyone close with an R90 and 32mm Bings.
  8. blaine.hale

    blaine.hale Long timer

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    I am one of an isolated species :)

    Maybe the carbdip will clean out some unknown oddity that I couldn't get back when I ultra sonic cleaned it and did the ol' pinesol bath.

    Just to keep sanity...still sounds like a carb issue, right?
    I mean...it's pretty damn obvious it is when I tug on the right throttle and nothing happens, heh.
  9. hardwaregrrl

    hardwaregrrl ignore list

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    I offered mine as well...32 bings just rebuilt this summer.
  10. blaine.hale

    blaine.hale Long timer

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    Bring some bings by this saturday for the tech day, we'll have a bing party!!
  11. Wirespokes

    Wirespokes Beemerholics Anonymous

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    It sounds to me like it's running rich at idle - that's what the popping sounds like. Unburnt fuel going off in the hot exhaust.

    If that's the case, the problem isn't a blocked passage.

    And just swapping the carbs without attaching cables would certainly tell whether the popping migrated also. Hell, you don't even need to attach fuel lines for a short test. Just have them full when swapping. I can run a couple miles on the contents of the float bowls.
  12. blaine.hale

    blaine.hale Long timer

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    That would make sense with it only happening when it's warmed up. Would "over fueling" drop a cylinder like that, though? I assume the plug would be rather wet, when pulled, as well?
  13. bmwblake

    bmwblake upside down parker

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    2 thoughts:

    1. since the issue only happens once things are nice and warm i'd suspect a coil or something electrical that would have an issue only when warm but work well at colder temps. i'm guessing that you've testing everything with a meter but have you done so at fully warmed up temps when the issue is happening as well as at cold temps to compare the results?

    2. the video sounds like a possible air leak, but that wouldn't happen only at full temp. have you sprayed ether around your carb to head connections to make sure they're tight? if you spray and the engine speed increases you have an air leak.
  14. supercreep

    supercreep _______________

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    are you using an electronic ignition? one of my harleys had an intermittent fault in the ignition module that would cause problems once it came up to temp.

    i would be looking at the ignition on this bike if i were you - best of luck!
  15. blaine.hale

    blaine.hale Long timer

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    Just to re-post what's been done since it's been a while.

    Coils would show themselves as an issue when I crossed the cables (the issue would migrate to the other cylinder but did not.)
    Point ignition is currently mounted up. Went through the boyer electronic as well. 3 sets of known good coils and spark cables were tried as well.

    I'm going to try bumping the idle mixture back down to the stock jets tonight then swap the carbs, if I'm able to get the throttle cables to fit that way.
    Other than that...that's all I have until I can find a new, matching carb to try out :)
  16. Airhead Wrangler

    Airhead Wrangler Long timer

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    Have you checked compression when hot?
  17. blaine.hale

    blaine.hale Long timer

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    When hot, no.
    Wasn't aware there would be too much variance there.
    I pulled the carbs and checked when luke warm and they both were above 145psi within 2-3 psi of each other.
  18. Airhead Wrangler

    Airhead Wrangler Long timer

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    I'm still betting this is mixture or ignition related, it's something worth eliminating. You said you tried several sets of plug wires, but did you try different caps as well?
  19. blaine.hale

    blaine.hale Long timer

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    Yup. Each cable has different caps. 1 set was brand new out of the box, stock. Another set was from the r75 with 19k miles and another set was the euromoto high resistance set.
  20. Airhead Wrangler

    Airhead Wrangler Long timer

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    Weird. Does the exhaust coming out of that side smell really rich like unburnt gas when it's sputtering like that? It's got all the indications of running too rich. Is the choke assembled correctly? The rotor isn't upside down?