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Engine hesitation

Discussion in 'XJ Technical Chat' started by Gohnmad, May 20, 2017.

  1. Gohnmad

    Gohnmad New Member

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    Hello, my 82 Seca 550 hesitates around 6000/6500 RPM. The previous owner had the carbs jetted and synchronized. The bike has a 4 into 1 exhaust and stock airbox with k&n filter. I've done this; rebuild fuel cap, fuel petcock, new fuel line and filter, spark plugs, flushed the tank, checked the cam chain tension. Any thoughts?
     
  2. Toomanybikes

    Toomanybikes Well-Known Member

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    That's the transition point from needles to main jet.
    Do a plug chop at that rpm to see if it's lean or rich
     
  3. Gohnmad

    Gohnmad New Member

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    Thanks for responding, by chop do you mean pull plugs and check color?
     
  4. Toomanybikes

    Toomanybikes Well-Known Member

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    Yes chop is hitting kill switch when accelerating through that trouble rpm range and then pull over and remove plugs,then take a pic and then post it
     
  5. XJ550H

    XJ550H Well-Known Member Premium Member

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    change the k&n air filter back to the emgo paper filter
    Condition: New Brand:
    Emgo
    Manufacturer Part Number:12-94410


    put new plugs in for the chop

    also if filter does not solve the problem

    I would check the asperator tubes under the main jets to make sure they are clean if the little holes in them are clogged it will cause you problems

    main jets are well into play at 5k rpm

    do you know what jets were replaced and the sizes of them?

    do you know the brand of 4 to 1 exhaust?
     
  6. XJ550H

    XJ550H Well-Known Member Premium Member

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    TALKIN' TECH: Various thoughts on various issues

    from section on plug chops
    "The pilot fuel circuit is active from idle up to about 2500-3500 rpms, and at about 3000 rpms the main fuel circuit starts becoming involved, and by 4000+ rpms the main fuel circuit is responsible for about 80%+ of the engine's fuel supply conditions. So where you do the "chops" tell you not only what the fuel mixture and combustion conditions are like, but also, which circuits are responsible for those conditions."
     
  7. XJ550H

    XJ550H Well-Known Member Premium Member

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    back to basics
    are your valves clearances in spec?
     
  8. Gohnmad

    Gohnmad New Member

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    Thanks again for all of the info. It is a kerker 4 to 1. I got the bike with 9340 miles last summer. It came with the factory's exhaust in a box in mint condition. Engine is very quiet, runs nice and smooth just cruising till about 70mph. I have storms in the area today so not riding till tomorrow. Thoughts on putting factory exhaust back on?
     
  9. Toomanybikes

    Toomanybikes Well-Known Member

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    Yes
     
  10. XJ550H

    XJ550H Well-Known Member Premium Member

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    my kirker was rusted out in the headers:(. factory exhaust is very heavy compared to a mac4 to 1 do not know compared to kirker.

    stock is nice I would stay with the kirker unless you are going for the complete original look.
     
  11. Gohnmad

    Gohnmad New Member

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    Mine is rusted as well. The muffler has a hole rusted through on the bottom. I do like the factory look. You have been a huge help. Thanks again. Tomorrow I shall do the chop.
     
  12. Gohnmad

    Gohnmad New Member

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    I forgot, I have not checked valve clearances. I need to find a gasket first. This bike was rode very little, less than 500 miles a year in Wisconsin. Once I get all the bugs out, on to paint work.
     

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