Announcement

Collapse
No announcement yet.

79 XS with 82 XJ carbs - runs rough

Collapse
X
Collapse
 
  • Page of 1
  • Filter
  • Time
  • Show
Clear All
new posts
Previous template Next
  • #1

    79 XS with 82 XJ carbs - runs rough

    I've got a 79 XS that I had taken my 82 XJ carbs off of just to see if it would run and right away it started and ran pretty good. But it only ran well at full choke. Once I let the choke off it idled down very low and then killed. The XJ carbs were off my good running bike so I know they're in good shape but is there a difference with the carbs - maybe a Yics thing? Can I use these carbs for the time being with some adjustments. I have it running now even with the choke off but just barely. I've increased the idle speed to keep it running but it seems to run XSively hot (golden headers) or are blue headers hot? It's not roadworthy the way it's running now.

    Tom B.
    Tags: None
  • #2
    Have you sync'd the carbs?
    Ken Talbot

    Comment

    • #3
      Did you hook up the XJ choke cable to them or did you install the lever on the side? You would have had to swap that metal rod that connects all the chokes because the XJ's doesn't stick out far enough for the lever to attach. That may have put them a touch out of adjustment. Also, it might be as simple as the idle screw being set to different heights. Run it up enough to get it to idle, and see how it does.
      Those carbs were jetted to run with the bigger XJ valves, so with the XS head, it may run a little on the lean side and need the extra fuel from the choke?? <<< Just guessing there??

      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

      Comment

      • #4
        Carbs were sync'd last summer and ran great. I've had the XJ down for a starter clutch and I found a good deal on the 79 in the mean time - besides - who doesn't need two of these things...

        So you're saying the XJ has bigger valves? That could certainly account for some of the issue. The choke lever I just left as the XJ version. I didn't transfer the cable and haven't yet transfered the two position handle from the 79 but I'm just putting a screw driver into position bettween the choke lever and the carb body just to hold it there for now. I don't want to use these carbs permenantly, just for a while to run the bike and get all the kinks worked out.... then I'll give it more kinks with the 79 carbs after I rebuild them.......

        I was thinking that because I had to open up the idle speed adjustment, which opens the butterfly more (letting more air in) that maybe I've increased the airflow enough and now I'm starving it of gas. I also am using (as I used on the XJ) the pod filters. I'll try fattening it up tomorrow.

        Is it possible that a weak battery would cause a weak spark and give this same kind of problem?

        Tom B.

        Comment

        • #5
          I was thinking that because I had to open up the idle speed adjustment, which opens the butterfly more (letting more air in) that maybe I've increased the airflow enough and now I'm starving it of gas.

          These carbs work from air pulling the fuel into the motor.... opening the butterflies more lets more air in... which pulls in more fuel. Changing the butterfly position isn't going to change the "Ratio" at which this happens. The fuel mixture screws do that. "If" in fact the XJ carbs are making it run lean to begin with, then the pod filters are certainly making that even more of an issue.

          You say you had the carbs synched a year ago, but has it sat any length of time since then? They could need to have it done again. Maybe just some fuel run through them would help, but if you have the pods on them, I would take them out and give them a little cleaning.... if it was mine.

          And of course there's the real possibility that I have no idea what I am talking about... lol. Anyone else??

          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

          Comment

          • #6
            ANY time you put a set of carbs on a "new" engine, you MUST sync them, or face the GURU's rath. The different engine will have each cylinder pulling a little more or less than the last engine. SYNC THE CARBS!!
            I will be out there soon, so be warned!!
            Ray
            Ray Matteis
            KE6NHG
            XS1100 E '78 (winter project)
            XS1100 SF Bob Jones worked on it!

            Comment

            • #7
              Sorry Guru but I haven't sync'd the carbs just yet. Please spare your wrath for a few more days..... I put the battery from the XJ in there and it solved the problem - must have just had a weak spark. There's still an occasional "cough" through one of the carbs but I should be able to dial that in with the mixture and of course synchronizing.

              Thanks guys.

              Tom B.

              Comment

              Previous template Next
              Working...
              X