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missing above 6000 RPM

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  • #1

    missing above 6000 RPM

    Hey guys, I'm new to this forum, just found it tonight. I've got a '79 xs11 SF that I'm going crazy trying to get "right". She pulls hard up to around 6k and then starts to ease off. After looking at this forum tonight(which is unbelievable), I'm wondering if the problem could be the pick up coil problem I've read about here. It seems to do fine unless you crack the throttle wide open. It anyone has any other ideas, please let me know.

    Thanks in advance,
    XSDADDY
    Tags: None
  • #2
    A pick-up coil problem results in an immediate loss of two cylinders and a corresponding drop in power. When the break comes back together, you're instantly back up to full power. Your problem sounds more like a dirty air filter or carbeuration. If you look through some of the technical articles, you'll see lots of good stuff about how to get your bike properly tuned up and synchronized. Also look for information on using sparkplug colour to diagnose jetting or float level problems.

    Welcome to the land of XSives....
    Ken Talbot

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    • #3
      Re: missing above 6000 RPM

      The pickups are a good thing to check out. It almost seems to me as if it may not be a pick-up coil problem. Usually those things cut spark farily abruptly, and when that happens, torque does not "taper off", instead, you feel a deceleration, possible vibration, and maybe a rumbling sound.

      The motion of of of the slides could be sticking at the upper end (or a diaphragm hole), or the main jet could have a collection of corrosion around the hole. Even with an inline filter, the jets can get restricted.

      Originally posted by XSDADDY
      She pulls hard up to around 6k and then starts to ease off. (snip) It seems to do fine unless you crack the throttle wide open. Thanks in advance,
      XSDADDY
      Skids (Sid Hansen)

      Down to one 1978 E. Stock air box with K&N filter, 81H pipes and carbs, 8500 feet elevation.

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      • #4
        Re: Re: missing above 6000 RPM

        PS, I caused a fuel delivery problem in one of my standard's petcocks. It would act as if the pick-ups were bad. I though I could stretch the petcock spring a little to help it stop leaking (more pressure on the plunger). Problem is, the associated carbs would run low on fuel supply at highway speeds unless I switched over to prime.
        Skids (Sid Hansen)

        Down to one 1978 E. Stock air box with K&N filter, 81H pipes and carbs, 8500 feet elevation.

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        • #5
          Checked out the advanced mechanism and it actually looked great, the wiring almost looked and felt new.After riding it some more this morning, I feel that you guys are right, it probably is something with the carbeurators. I've gone thru them a couple of times making sure they were clean (when I got the bike it had been sitting for about three years with gas in the carbs). I will check out the float levels and the diaphragms. Thanks for the help, I'll let you know once I get it fixed.

          XSDADDY

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          • #6
            I had a problem like this in the past. If I remeber, it was a fuel delivery problem. It was a while back. I can't remeber for sure what was the resolution. Could have been a fuel line kink or misadjusted float valve.

            I would start there.
            Owned by a pair of XS11's. An 80 Standard and a 79 Special.

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            • #7
              Got it!!! I adjusted the float levels about 2mm to richen the mix and all I can say is this thing is almost dangerous now. The beast now pulls hard all the way to the red!!! I sure do appreciate the help guys, I've been fighting this since I first got it running two years ago. I had the float levels set to specs but guess that just wasn't going to work for this one. I love this site!!!

              Thanks,

              XSDADDY

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              • #8
                Glad you were able to get it fixed. It was frutrating to me for a bit and I couldn't figuire out why I could not get it much above 6k. Kinda seems wierd that changing the amount of fuel in the float bowl will effect performance so much.
                Owned by a pair of XS11's. An 80 Standard and a 79 Special.

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                • #9
                  It definitely had me stumped. Man what a difference having the correct amount of fuel in the carbs makes!!!

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