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5.2k rpm wall.

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  • #16
    I has a similar problem with two of my XS750's independently. They ran fine until the RPM got to 5k, the they would stumble and RPM would not increase.

    In both cases, the main jets were clogged with corrosion. It was strange because in both cases, the carbs had been rebuilt 2-3 years before the incidents.

    This happened during a period when I drained the carb bowls for winter storage. Believe it or not, I have not any more trouble (yet) since I stopped draining the carb bowls for storage about 6 years ago.

    I don't know if this is related to your problem, but it's more information for you.

    Click image for larger version

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    -Mike
    _________
    '79 XS1100SF 20k miles
    '80 XS1100SG 44k miles
    '81 XS1100H Venturer 35k miles
    '79 XS750SF 17k miles
    '85 Honda V65 Magna ~7k miles
    '84 Honda V65 Magna 48k miles (parts bike)
    '86 Yamaha VMAX 9k miles

    Previous: '68 Motoguzzi 600cc + '79 XS750SF 22k miles +'84 Honda V65

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    • #17
      3 things that I've experienced causing similar issues. 1) restricted exhaust will cause RPMs to flatten due to back pressure 2) pinholes in slide diaphragms not allowing slides to go up far enough 3) Slides improperly clocked after diaphragm replacement. There is a small air bleed hole in the slide that has to be directly front and center engine side in order for the slides to work correctly. Just tossing those out there as things to check.
      Greg

      Everybody is a genius. But if you judge a fish by its ability to climb a tree, it will live its whole life believing that it is stupid.”

      ― Albert Einstein

      80 SG Ol' Okie;79 engine & carbs w/pods, 45 pilots, 140 mains, Custom Mac 4 into 2 exhaust, ACCT,XS850 final drive,110/90/19 front tire,TKat fork brace, XS750 140 MPH speedometer, Vetter IV fairing, aftermarket hard bags and trunk, LG high back seat, XJ rear shocks.

      The list changes.

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      • #18
        Originally posted by BA80 View Post
        3 things that I've experienced causing similar issues. 1) restricted exhaust will cause RPMs to flatten due to back pressure 2) pinholes in slide diaphragms not allowing slides to go up far enough 3) Slides improperly clocked after diaphragm replacement. There is a small air bleed hole in the slide that has to be directly front and center engine side in order for the slides to work correctly. Just tossing those out there as things to check.
        Ditto on the exhaust. No wall without it. I was running a cheapo Amazon basics pipe. Straights are just too loud. Need to get an exhaust with no back pressure.

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        • #19
          Originally posted by Banshee's Veil View Post

          Ditto on the exhaust. No wall without it. I was running a cheapo Amazon basics pipe. Straights are just too loud. Need to get an exhaust with no back pressure.
          Yeah. My bike HATES back pressure an altitude above 8000 feet. I bought a MAC flare tip exhaust and put straight through perforated baffles wrapped in SS steel wool in it.
          Greg

          Everybody is a genius. But if you judge a fish by its ability to climb a tree, it will live its whole life believing that it is stupid.”

          ― Albert Einstein

          80 SG Ol' Okie;79 engine & carbs w/pods, 45 pilots, 140 mains, Custom Mac 4 into 2 exhaust, ACCT,XS850 final drive,110/90/19 front tire,TKat fork brace, XS750 140 MPH speedometer, Vetter IV fairing, aftermarket hard bags and trunk, LG high back seat, XJ rear shocks.

          The list changes.

          Comment

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