Siebenrock 1070 big bore touring kit

Discussion in 'Airheads' started by cbi, Oct 31, 2012.

  1. AliBaba

    AliBaba Been here awhile

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    With a long-stroke crank you can even get 1160cc.
    #21
  2. RGregor

    RGregor Been here awhile

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    A friend has an engine with 102mm bore.
    [​IMG]

    Full story (in german) here.
    http://www.boxerkunst.de/content.php?80-Der-Alpenbrenner
    Pistons were from Werner Fallert, cylinders are custom made.
    No long term experience yet.
    #22
  3. gsd4me

    gsd4me 90% bluff

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    That goes for polishing various outer parts as well; some may think it looks good, but it makes the engine run much hotter.
    #23
  4. pommie john

    pommie john Long timer

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    Not much room between the bore and the studs.
    #24
  5. RGregor

    RGregor Been here awhile

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    The 98mm Siebenrock cylinders have a very short and thin (1mm) skirt.
    #25
  6. RGregor

    RGregor Been here awhile

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    Close to none. I'm wondering if they last ...
    #26
  7. craydds

    craydds Long timer

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    Yes, they do last... for 10 hours. For race motors only.
    #27
  8. RGregor

    RGregor Been here awhile

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    It's not a racer but a normal street bike.
    And it's intended to last.
    I'll report, if it doesn't.
    #28
  9. craydds

    craydds Long timer

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    Sign me up for a set.
    #29
  10. Airhead Wrangler

    Airhead Wrangler Long timer

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    I've never seen an open oil ring like that. It seems like you'd get some accelerated wear where the oil ring enters the grooves on both sides of the wrist pin. Is he using a normal 70.6mm stroke? Longer rods or shorter barrels?
    #30
  11. RGregor

    RGregor Been here awhile

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    I don't regard that open ring as a good idea, too.
    Stroke is stock, rods are 148mm long, so that the piston stays completely outside the crank case.
    #31
  12. bmwrench

    bmwrench Long timer

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    Is there no teflon or aluminum button behind the oil ring?
    #32
  13. RGregor

    RGregor Been here awhile

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    According to the owner there is some kind of button to stabilize the ring and to prevent it from rotating.
    Never seen it or an image of it.
    #33
  14. tofgasp

    tofgasp Adventurer

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    #34
  15. supershaft

    supershaft because I can

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    The gasket surfaces don't only seal the combustion chamber and crankcase. They also seal the rocker arm oil and oil return in the pushrod tubes. Therein is the trouble. I have worked on race bikes with that ring setup. They ran like scalded apes for the longer rods. What I don't know is if it is better to go that route or just two rings.
    #35
  16. RGregor

    RGregor Been here awhile

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    I know the 97mm and 98mm kits don't make trouble here. No personal experience with 100 or 102mm bore.

    The Siebenrock kit comes with 151mm (standard kit, additionally versions with - 0.5 mm for the touring and +0.5 mm for the race kit) rods and three-ring pistons in standard setup. I doubt there is the need for such an open ring setup anyway.
    #36
  17. RGregor

    RGregor Been here awhile

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    Another effect of the long rods in combination with the lighter pistons: these engines run very smooth.
    In my former engine (SR-Replacement) all parts were balanced and it ran really smooth. But compared to the SR BBK I have now there's still a big diff.
    #37
  18. supershaft

    supershaft because I can

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    151mm rods are 16mm longer than stock for a 2.13:1 rod length ratio. Standard three ring setup? There is only so much room. 16mm less than stock. Three rings above the pin will have to be a lot higher and closer together than BMW's standard. You can only run them so high and so close together. I do know from experience that that setup pictured works. Lots of tuners have run rings like that with good results.
    #38
  19. RGregor

    RGregor Been here awhile

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    With "standard" I meant, that the rings don't go through the pin hole. Of course the rings are different and closer together than in stock arrangement. Have to be to gain the needed mm.
    This is the Siebenrock BBK piston

    http://foto.arcor-online.net/palb/alben/74/170374/1400_6635373638386334.jpg
    http://foto.arcor-online.net/palb/alben/74/170374/1400_6539363936613062.jpg
    http://foto.arcor-online.net/palb/alben/74/170374/1400_3364643937333338.jpg
    #39
  20. Ras Thurlo

    Ras Thurlo Desert Lion

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    #40