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Thread: Harley 9B carb help needed.

  1. #1
    Join Date
    Sep 2003
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    Default Harley 9B carb help needed.

    After years of problem free operation my 1913 9B has started to spray or 'pulse' fuel from the bottom of the float bowl (main nozzle). After inspection I replaced the float which was cork and had deteriorated and then re-assembled it but the problem remains. I have checked the carb settings, all the usual stuff. I'm sure the problem must be the carb but the pulse relates to the stroke so I also rechecked the inlet timing. No leaks, easy starting and the motor runs great but the spray is a problem. The only recent alteration has been installing a new throttle shaft. Can anyone point me in the right direction please.
    Thanks.
    Ian Biddle
    www.f-head.com

  2. #2
    Join Date
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    Central Illinois, USA
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    Default

    What kind of replacement float did you install, Ian?

    There's some HX boat anchors out there, both brass and molded.

    The next thing I would inspect would naturally be the airvalve.

    ....Cotten
    Last edited by T. Cotten; 09-22-2019 at 10:39 AM.
    AMCA #776
    Dumpster Diver's Motto: Seek,... and Ye Shall Find!

  3. #3
    Join Date
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    Default

    I used a moulded Nitrofill (Nitrile) type. They seem good and are what I have used on my other teensters.
    The Schebler manual also suggests the air valve. The stem might be loose in the adjuster but I wondered if I am missing anything more obvious before I tackle the valve.
    Thanks for your advice.
    Ian Biddle
    www.f-head.com

  4. #4
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    Default

    Did you weigh your new float, Ian?

    Or at least compare them, hand to hand?

    (And beware of swelling in USA fuels...)

    ....Cotten
    PS: There's been at least thirteen different Nitrophyls, not counting the counterfeits.
    Only the very last has proven itself against P4gas, and nobody (except auto manufacturers) paid the royalty to mold it.
    Last edited by T. Cotten; 09-22-2019 at 03:04 PM.
    AMCA #776
    Dumpster Diver's Motto: Seek,... and Ye Shall Find!

  5. #5
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    Sep 2003
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    Default

    Hi Cotten, no I did not weigh the two floats but the old cork and the new Nitrile floats are similar in size.
    There is plenty of clearance in the bowl, no binding and good movement when fuel rises.
    The new float has only been in a few days so no swelling yet! I presumed Nitrile would not swell.
    I was not aware this was such an issue.
    Is your suggestion that the density of the float might mean there is still too much flow of fuel?
    Thanks.
    Ian Biddle
    www.f-head.com

  6. #6
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    Please consider, Ian,...

    If the same size of float weighs three times as much.

    T'aint nothing "nitrile", no matter what you bought... (Since the proprietor of the original Nitrophyl won't protect their name, its become "generic".)

    Stay away from P4gas, or it won't stay the same size either.

    ....Cotten
    AMCA #776
    Dumpster Diver's Motto: Seek,... and Ye Shall Find!

  7. #7
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    Default

    Thanks again, I'll get the weighing scales out tomorrow.
    Ian Biddle
    www.f-head.com

  8. #8
    Join Date
    Sep 2003
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    Default

    The old cork float was 2.5 grams and the Nitrile was 5 grams. The depth of the latter was also much deeper (18mm v 12.5mm). I turned the Nitrile one down in size removing 2 grams.
    After refitting I still had the same problem. Now I will look at the air valve.
    Ian Biddle
    www.f-head.com

  9. #9
    Join Date
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    Buoyancy, Ian,..

    Isn't just about weight, but also volume.

    Making the float lighter doesn't help if it makes it smaller.

    A buoyant float can be set to book spec, saving a lot of tail-chasing.

    ....Cotten
    PS: Please note in this jar of fuel are four different 'nitrophyl' Linkert replacements, including the one on the bottom
    Making it smaller won't make it float.
    Attached Images Attached Images
    Last edited by T. Cotten; 09-24-2019 at 09:55 AM.
    AMCA #776
    Dumpster Diver's Motto: Seek,... and Ye Shall Find!

  10. #10
    Join Date
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    1 mile east of the Rocky Mountains.
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    Default

    Ian, buy one of Tom's Durable lifetime guarantee floats and the float variable will be removed from the equation.

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