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82 XJ550R Seca won't rev past 8K - Help!

Discussion in 'XJ Technical Chat' started by Mordred, Jul 17, 2021.

  1. k-moe

    k-moe Pie, Bacon, Bourbon. Moderator Premium Member

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    One thing that would help greatly is a full understanding of the baseline for all related systems prior to the trouble occuring.

    Please list:
    Pickup Coils: Tested and in spec? New or old?
    Ignition Coils: Tested and in spec? Nwe or old?
    Plug wires: Tested and in spec? New or old?
    Spark plugs: Brand and model? Photos of the business end would be helpful.
    Pods: Brand?
    Jetting: Stock? Not stock? What pilot, main, and air jets are installed? What jet needle is installed? What are the fuel levels set to? What are the idle mixture needles set to (# of turns out)?
    TCI: Have you acess to a known-good TCI to swap out and check?
    Petcock: Rebuilt, and flowing freely?
    Fuel filter: Installed? If so, what type?

    This is not exhaustive, but covers what I think of as the most likely suspects.
     
  2. Blackbird

    Blackbird Member

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    Reading the original post brings back memories of the same issue I had (have) with my 81 Suzuki GS550. Pulled great up until 7000 rpm. I read a ton of stuff on the internet and it might be helpful to you to do the same if you haven't already. It's a pretty common problem with all makes and maybe you'll come across the answer. I finally found something that helped me a fair amount but not completely eliminated it. I bought a DigiSync off ebay (hate the liquid Synchronizers) and synced the carbs. Not saying that's your problem but searches like the one I left a link for may provide some more ideas.
    https://www.google.com/search?client=firefox-b-1-d&q=motorcycle+wont+rev+past+7000+rpm
    And if you do find the issue I would be very interested to know what it was.
     
  3. Kickaha

    Kickaha Active Member Premium Member

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    You're making the cylinder bigger while still squashing it into the same size combustion chamber how can that lower the compression ?
     
  4. chacal

    chacal Moderator Moderator Supporting Vendor Premium Member

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    You are absolutely right, I was wrong, was looking at the formula "backwards", so yes boring with no other changes will increase the compression ratio!
     

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