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Thread: Dual plugging

  1. #1
    Rally Rat
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    Dec 2008
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    San Antonio, Texas
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    Dual plugging

    So, as I understand it, one of the things that dual plugging does right, is help eliminating pinging on crappy fuel.

    I'm in texas, and I can't find 'real gasoline' to save my life. it's all 10% ethanol, and my airheads will only run right on high test, and even then, it's a dicey proposition. We're also mandated to go to 15% ethanol here shortly. All of this makes for lousy gasoline with low octane ratings.

    So, I'm wondering if going back to dual plugging would be an improvement, given the state of gasoline in texas.

    thoughts?

  2. #2
    Rally Rat
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    hm.. but is 'more fuel' really gonna work? also, I already have a set of dual plug heads.

  3. #3
    Superkraut typ181r90's Avatar
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    From what I understand the reasoning behind bigger jets is to ever so slightly enrichen the mixture to lower the cylinder/head temps from the added running temp of using ethanol fuel - someone more versed in chemistry please elaborate (snowbum I think mentions something like this too somewhere).

    As for the octane, even with ethanol blends, you're still getting the octane advertised. The difference is the pre-blend octane. For example, reformulated gas comes in at an 83 octane and the ethanol boosts it to 87, premium comes in 89-91 and gets blended up to 93. Ethanol gas has been beaten to death on this forum, but the main issues with it are that it separates fairly quickly, absorbs water (and dirt), and is terrible for rubber seals
    // 1975 BMW R90/6 (cafe'd) // 1957 BMW R60 (in pieces) // 1967 Aermacchi/H-D Sprint 250 SS (custom special) // 1973 VW Type 181 Custom SOLD )

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  4. #4
    Smoooooth at 430 gch71's Avatar
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    Mmmm

    On my R60/6, high compression engine, I was also contemplating dual plugging however I have to wait for more time and $$$. In the mean time I tried a thicker cylinder base shim/ gasket to lower the compression but it made for a weaker/ less horsepower bike...I know it's already that. So I put everything back original and moved up a notch on the needle in my carbs that seems to work so far but my MPG did suffer somewhat. But for now that seems to have arrested the pinging and my plugs are a little darker but they haven't fouled just yet, by moving the needle I enrichend the mixture a bit. Try it and see.
    I should actually say I moved one notch down on the needle.
    Last edited by Gch71; 01-24-2013 at 02:54 AM.
    Glenn
    ...driving to work on my airhead
    '74 R60/6, '75 R60/6(boxes)

  5. #5
    Minnesota Nice! braddog's Avatar
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    Both of my airheads ran fine on 10% ethanol. Gas mileage, however, increases by 4 or 5 MPG's when using non-ethanol fuel.

    I never had or have any issues with pinging or bad engine performance.

    For the record, my bikes were a '77 R100RS with the 40mm carbs and pipes, and a '77 R100S. I still own and ride the RS.
    -----------------------------------------
    Brad D. - Member #105766
    '77 R100RS - Black Beauty (big pipe, baby!)
    '94 R1100RS - Sylvia

  6. #6
    Nutfarm
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    Ethanol in fuel does make an engine run slightly leaner and alcohol has less heat energy in it. It takes approximately 30% more alcohol to make the same heat energy as gasoline but it is high in octane, that's why some racers use pure alcohol as fuel.

    Sometimes just raising the needle a notch on carburetor engines will help. There are also richer needles and bigger needle jets, bigger main jets are not always nesessary.

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