127" Ultima Piston Ring Gap?

Discussion in 'Harley Davidson Extreme Modification' started by 09GLDR, Jul 6, 2010.

  1. 09GLDR

    09GLDR Member

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    Ok all you techs out there, I have been pouring all over the internet looking for the proper piston ring gap size for a 127" Ultima motor that a buddy of mine is putting together. So I thought I would throw it out here and see if anyone knows. Thank you for any feed back!
     
  2. Hoople

    Hoople Account Removed

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    I am just pulling an answer out of thin air because I am no engine builder but I would say the person to ask is the cylinder manufacture. What the cylinder is made from along with the coefficient of expansion rates would dictate the ring gap to me. Since we are air cooled, temp swings are great.

    I am sure your looking for peak power so you don't want it greater than what it needs to be.
     
  3. Jack Klarich

    Jack Klarich Expert Member

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    I would use std gap if the builder cannot be contacted. Too much gap ring and cylinder damage, too little gap less compression and oil control JMO and I would check all of the rings, filing rings aint no fun
     
  4. Hoople

    Hoople Account Removed

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    Jack, don't you mean the other way around..:p
     
  5. Jack Klarich

    Jack Klarich Expert Member

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    Dexlexia I think too fast and get it backwards:D
     
  6. Jack Klarich

    Jack Klarich Expert Member

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    .004 for every inc of cylinder bore is a rule of thumb:s
     
  7. FishHunter

    FishHunter Active Member

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    .004-.005" per inch of bore, and if running a cast-iron cylinder, .0055-.006" is not out the qusetion.
    If fitted too snug, they can/will butt togather, and the can/will break.
    THAT is NOT what you want.
    Scott