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Exhaust Header Nut and Shim Question

Discussion in 'The Garage' started by Marc Douglas, Oct 23, 2019.

  1. Marc Douglas

    Marc Douglas XS400 New Member

    Hey Guys, new member here!

    I've been digging around the forums, but I can't find the answer to my exact question. I recently completed my first build (which is incidentally my first bike ever) and I'm running into a potential issue with my exhaust headers.

    I reused my old exhausts and purchased a lightly used set of shims (serial # confirmed) when reinstalling them. After wrapping and reassembling, there's about a 1" gap between between the large nut and the header itself. I also have a new crush washer installed as well.

    Is this gap normal, or should the nut be relatively flush with the header? I'm looking to avoid potentially breaking/shearing the header bolts, but I don't know how much the shims need to be crushed in place. Thanks in advance!
  2. Marc Douglas

    Marc Douglas XS400 New Member

    Here's a picture of what I'm referring to:

    Attached Files:

  3. xschris

    xschris a lifestyle not a trend Top Contributor

    Yes, there will be a space there. Is there a leak?
  4. Marc Douglas

    Marc Douglas XS400 New Member

    Thanks for the reply.

    Not that I know of, but I've yet to fully investigate. It had its first ride yesterday and it was very lean and popping when rolling off of the the throttle.
  5. NewHavenMike

    NewHavenMike 1976 XS360C Top Contributor

    What are those carbs and mufflers? The Mikes XS carbs? or a pair that was sourced from another bike?
  6. Marc Douglas

    Marc Douglas XS400 New Member

    The carbs are the tuned Mikuni TM32's from MikesXS and the baffles are Emgo 15" slash cuts. I was thinking it might be a back pressure issue.
  7. Lots of things can cause the problem you have. If yours has points make sure they are both set correcty.
    Make sure the timing is correct and the advance works. After you make sure all that is correct, tuned carbs are often too lean.
  8. Robsteeler66

    Robsteeler66 XS400 Addict

    Did you change everything all at once? Hard to narrow it down. Maybe put it back to stock and make sure it runs well, then make changes one at a time. When things get bad that’s your culprit.

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