R100GS sputtering at speed

Discussion in 'Old's Cool' started by Cirbo, Nov 18, 2009.

  1. StephenB

    StephenB G(/)S ... what else!

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    I am quite sure it isn't coated.
    #21
  2. durtwurm

    durtwurm Talented Amateur

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    Tim, I am pretty sure my petcock filters are original ('78 RS). And they represent no problem, plus they look "fine'"as you mention. I think I will change them though I have cleaned 'em up. Cannot hurt.
    #22
  3. StephenB

    StephenB G(/)S ... what else!

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    Are you talking about the screens inside the tank or the in-line paper filter that can be used?

    +1 if you're talking external paperfilters (VW-type): they seem very restrictive and when I am on reserve the pressure of the remaining 4-5l isn't enough to let gas flow through them when you let them run dry.
    #23
  4. Tim McKittrick

    Tim McKittrick Long timer

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    I was referring to the little clear after-market external filters commonly installed between the petcock and carburetor. All of the BMW's I have ever owned have had them but they never came out of the factory with them. I've seen both pleated paper style units (I think that would be the VW sort referred to above) as well as the sintered bronze style. I had the ones that had the bronze element in them, and they appeared fine. I honestly only replaced mine (instead of eliminating them altogether) as it was easier to plug in a new filter than to find a double ended hose barb to rejoin the sections of fuel line, and I'm a lazy, lazy person.

    The filter socks in the tank can be reached by unscrewing the petcock and are easily cleaned- these usually catch the majority of the crud.
    #24
  5. durtwurm

    durtwurm Talented Amateur

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    The in line filters if used should be changed yearly. The plastic ones are cheap; the metal filters with replaceable innards are more expensive initially. I was wondering. I thought you were referring to the petcock filters and always thought they just need a little periodic cleaning.
    #25
  6. boxerboy81

    boxerboy81 Stay Horizontal

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    Believe me when I write, it's not your bowel! :rofl Though this problem is frustrating enough to have that effect. Someone will usually do that typo in such a thread.

    My bike has shown similar symptoms in the past. Riding along and a poor stuttering response that improves if slowing down for a while. It tends to repeat itself unpredictably/inconsistently at higher speeds. A diaphragm problem would be more consistent and predictable.

    Advice to me at the time was:
    • float bowl level...hadn't been touched, looked correct.
    • fuel flow problem. Nope, flowed well from the tap, no ext. filter.
    • diaphragms..were ok
    • hall effect sensor. Never tested.
    • ht leads/plugs. Replaced.
    Then whilst on a 4K+ ride, and 1600k from home it happened and wouldn't go away. It proceeded to deteriorate.

    I holed up in a motel, went thru the usual trouble shooting checks to no avail. I found a local airhead owner (known via another forum) and he generously helped me the next day. We repeated the checks and got no where. A quick call to a BMW mechanic, who offered the same advice as we'd already performed.

    Then he said..."have you pulled the main jet and checked it"?

    [​IMG]

    Haven't had a problem since.

    Simple things first. Bowl level, the jet, fuel flow, diaphragms, electrics.
    #26
  7. durtwurm

    durtwurm Talented Amateur

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    And while you're in there go to your nearest auto parts dealer and replace the o-ring! These are stock items and will be carried at Carquest and NAPA, etc. That black item looks like an old o-ring. Is it?
    #27
  8. H96669

    H96669 A proud pragmatist.

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    :D :D :D Looks like someone else had "The little piece of crap floating around the bowl.......sometimes impeding the fuel flow until it finally jams up there and blocks the jet".:uhoh :uhoh :uhoh

    Very frustrating the first time, but second time around only a 5 minutes repair job.:super
    #28
  9. Uncle Pollo

    Uncle Pollo Long timer

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    You just reminded me of putting appart the petcocks and cleaning the screens.

    From inexpensive and easy to expensive and hard; that is how troubleshooting is done!
    #29
  10. Bill Harris

    Bill Harris Confirmed Curmudgeon

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    Give us a quick maintenance history of the bike, as long as you've owned it.
    #30