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1986 Yamaha XJ700-X - Top End Rebuild

Discussion in 'XJ Technical Chat' started by Shelby Biggs, Jun 20, 2025.

  1. Shelby Biggs

    Shelby Biggs Member

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    IMG_0552.jpeg IMG_0525.jpeg I’m doing a top end rebuild on my XJ. Not having any issues, just curious if anyone can explain why the large lower cylinder O-rings were protruding out of the gasket, and what purpose do they serve as they don’t seem to seal anything but rather just fill the space?
     
    Shelby Biggs, Jun 20, 2025
    #1
  2. Huntchuks

    Huntchuks Well-Known Member

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    I couldn't figure out what they were for either when I had my engine apart.
     
    Huntchuks, Jun 22, 2025
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  3. Franz

    Franz Well-Known Member

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    They prevent oil getting between the steel liner and the surrounding aluminium. They sit in a groove and have probably been dislodged when you removed the cylinders from the crankcase.
     
    Last edited: Jun 22, 2025
    Franz, Jun 22, 2025
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  4. Franz

    Franz Well-Known Member

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    Just wondering if crankcase windage plays apart in this? Does it help with the sealing of the o rings preventing gasses getting out in combination with the base gasket?
     
    Franz, Jul 5, 2025
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  5. Shelby Biggs

    Shelby Biggs Member

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    Franz - unrelated but figure you might have an idea; I got the bike back together and went to test fire today and it blows the 10amp fan fuse every time I switch the ignition switch to “run”. Any ideas? I’d think it would blow the ignition 10amp fuse but it is not
     
    Shelby Biggs, Jul 12, 2025
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  6. Franz

    Franz Well-Known Member

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    I meant to post my reply in this thread :D.
     
    Franz, Jul 13, 2025
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