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  • #1

    Still trying here.

    Took the carbs off (again ) and tore them down (again ) and removed the main and pilot jets. I re-did my math and found that I was off on the jet sizes. I ordered new jets from mikesxs, and re-set the float levels. Now I have it all back together and running again. Rode to work yesterday, and it was still acting a little funny below 4k rpm. From idle to 3800 or so, it runs great as long as I keep giving it a little blip of the throttle. If I just hold the grip so I am maintaining, it runs good, the starts to flutter (like it is loading up). I can fuzz the throttle a little and it clears up for about 20 seconds, then it starts loading up again. I have the floats set where the fuel level is right at the bottom of the bowl ring on all 4, and the idle air screws are 2 1/4 turns from bottomed out.

    Here is where it gets good. Yesterday on the way home, (morning ride is about 70* and afternoon is about 95*) I was going down the highway and it felt like 2 cylinders fell off line. I was barely able to maintain speed even with a lot of throttle. I was gonna pull over, but I was pretty ticked off, and I was only a few miles from home. I get almost to the off ramp, and it bucked hard once, and all holes started firing again and it ran great the last 2 miles home. Then I rode to work this morning, with no problems at all except for the flutter/stutter from idle to 3800.

    I am running ngk bp6es plugs, (going to 7es today because it is hot here). I pulled the plugs and checked the spark by plugging the spark plug back in and laying it on the engine while cranking. all 4 plugs have kind of a weak looking spark that is more orange than blue. I am used to seeing a vilolent blue spark when I check plugs like that.


    I guess with all that I am trying to ask what could cause the stutter? I have sprayed carb cleaner on the intake boots to see if they were leaking. All is well. The only thing I can think of is a coil breaking down and causing a weak sparking.

    Sorry this was so long, I wanted yall to have all the info you need.
    79 xs11 standard with 4-1 exhaust and pod filter jetted to 147.5 mains, 45 pilots.

    Thanks for any help, Justin.
    Tags: None
  • #2
    Justin,

    My bike was doing the exact same thing as yours. You may try going the other way on the spark plug. My 79 special is running 145 mains and 45 pilots with pods, 4-1 header. BP-6ES plugs run like c#@p but BP-5ES (one heat range hotter) burn very well and run great.

    The added fuel/air mix available with pods and a header can actually lower the combustion chamber temperature. Good combustion temp is around 1200 degrees. The heat range of the plug has nothing to do with the strength of the spark but actually has to do with the amount of heat it dissapates from the combustion chamber. Around 1200 degrees the fuel/air mix will burn smoother and the temp is hot enough to keep carbon deposits from fouling up the firing tip. So provided your coils/wires are in good shape, going to a BP-5ES will raise chamber temps about 200 degrees and just may solve your problem.

    Easy to try and you can always go back.
    Mike Giroir
    79 XS-1100 Special

    Once you un-can a can of worms, the only way to re-can them is with a bigger can.

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    • #3
      Outa curiosity...
      Did you ever check the pick up coil wires?
      Also you've replaced the plug wires, have you tested the new wires with an OHM meter?


      mro
      Last edited by mro; 08-21-2007, 07:34 AM.

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      • #4
        I will try that Tadracer, thanks for the info. Never thought of that.

        I checked the wiring to the coils, but refresh my memory, are the ignition coils the same as the pick up coils?

        I am gonna just bite the bullet and buy new high performance coils from mikesxs along with wires and plug caps. I will pick up a set of plugs bp5es plugs from o-reillys today.

        Comment

        • #5
          I hate to say it... but anything from @ 4000RPM and less is the pilot jets. The mains seem to be performing as designed, so it's either the pilot jets/circuits or it simply needs the carbs synch'd. Since you have cleaned them twice, I would lean towards a good carb synch first. It sounds like they aren't all drawing the same.


          Tod
          Try your hardest to be the kind of person your dog thinks you are.

          You can live to be 100, as long as you give up everything that would make you want to live to be 100!

          Current bikes:
          '06 Suzuki DR650
          *'82 XJ1100 with the 1179 kit. "Mad Maxim"
          '82 XJ1100 Completely stock fixer-upper
          '82 XJ1100 Bagger fixer-upper
          '82 XJ1100 Motor/frame and lots of boxes of parts
          '82 XJ1100 Parts bike
          '81 XS1100 Special
          '81 YZ250
          '80 XS850 Special
          '80 XR100
          *Crashed/Totalled, still own

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          • #6
            Wires to the vacuum unit where they connect behind left side cover.
            Provide timing for when plugs fire.
            Engine can run and run fine and then start to cut out or even die, then seem to be OK agin.


            mro
            btw, BS34 carbs transision to mains starts around 3,000 RPM

            Comment

            • #7
              I used a mercury carb stick to sync the carbs, and they are pulling 16 inches of vacuum each cyl. They are all at 16, dead on.


              I will check the pickup coil if the plugs don't help it. I bought the bp5es today.

              Comment

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