(Hopefully) simple question: Kat will not hold idle

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  • morthrane
    #1

    (Hopefully) simple question: Kat will not hold idle

    Ok, so I got done and gave the kat a valve adjustment-- roughly half of them needed to tightened up a bit, and a couple were too tight for spec. Buttoned up the bike, hit the starter, no go... after charging the battery I realized it was because the carbs were dry and needed to be primed. DUH....

    which brings me to my real problem, as the bike will not hold an idle, but it will run seemingly fine as long as you feed it throttle and/or choke. I've fiddled with the idle speed adjustment screw under the carb bank, and it hasn't really changed anything-- best improvement I've had is a high idle around 1200rpm give or take, that hold with a slight touch of throttle but will eventually choke and die at true idle (zero throttle).

    #1: Can this be a spark plug problem? I pulled the #1 plug and check it, looks old but the coloration was a normal tan on the end.

    #2: Could this be a jetting issue? The bike came to me this way. It has the main airbox, but not the secondary airbox over the battery. The filter is a foam UNI
    Tags: None
    • first timer
      Forum Sage
      • Aug 2002
      • 3429
      • Tucson, Arizona
      #2
      try resynce and see what that does. after a valve job your synce can get thrown off. speaking of which i should check myself.

      -ryan
      78 GS1000 Yosh replica racer project, 82 Kat 1000, 10 990 ADV-R, Some dirt bikes

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        • KEITH KRAUSE
          Forum Guru
          Charter Member
          GSResource Superstar
          Past Site Supporter
          • Oct 2002
          • 8862
          • Angeles Forest, So.Calif./Red rocks of Southern Utah.
          #3
          Did it hold an idle BEFORE you adjusted the valves?
          Did you work on the carbs other than removing them as a unit?
          Three E-Z checks, is the throttle cable slack correct, the air filter clean and the petcock vacuum line in good shape?
          And on the seventh day,after resting from all that he had done,God went for a ride on his GS!
          Upon seeing that it was good, he went out again on his ZX14! But just a little bit faster!

            Comment

            • Dave_A
              #4
              I had a similar problem with my 450.

              The problem was traced to the lack of an airbox lid, which was missing when I got the bike (I didn't know it needed a lid)...

              Might be the missing airbox parts...

              It also might be carb synch...

                Comment

                • morthrane
                  #5
                  Originally posted by KEITH KRAUSE
                  Did it hold an idle BEFORE you adjusted the valves?
                  No. The valve cover gasket was leaking profusely, so I figured while I was fixing that, might as well adjust the valves

                  Did you work on the carbs other than removing them as a unit?
                  I haven't touched the carbs, other than molesting the idle speed screw. In theory I know about carbs, but in practice I don't know jack about 'em.

                  Three E-Z checks, is the throttle cable slack correct, the air filter clean and the petcock vacuum line in good shape?
                  1. I haven't measured the slack, but it felt correct to my wrist. I'll check that.
                  2. The air filter is clean, but it feels a tad brittle. I take it that's a sign of age? (all my bikes until this one have had paper or K&N filters)
                  3. The petcock vacuum line had cracks in it-- being unable to source such an oddball size hose (4.5mm? What the Hell were they thinking?!?!), I cut it down so that it barely manages to fit from carbs to petcock. So, assumably this is ok, as its not kinked that I can see, and I inspected the shortened hose for any other cracks/holes/etc.


                  Originally posted by Dave_A
                  The problem was traced to the lack of an airbox lid, which was missing when I got the bike (I didn't know it needed a lid)...

                  Might be the missing airbox parts...
                  I'm really hoping that this isn't the case, as the previous owner said he'd ship the original airbox and lid, but never came through. Maybe I'll have to bug him again, but its probably better than putzing through a rejet.




                  P.S. I know that the carbs need to be resynched. I don't have the tools to do it, and the Haynes manual is disturbingly vague about balance levels between the outer and inner carbs. Does anyone have that kind of information (and recommended tools for the job)?

                    Comment

                    • Dink
                      #6
                      the uneven idle and choking out on a closed throttle is blocked up idle circuits.
                      Sorry it is time to put all that theory into practice!!
                      Check your plug colour first though as this will give a fair indication if it is just to lean due to the single pod.
                      Carb synching when done with vacuum sticks with a steel ball in them the difference is half a ball with the outer cylinders the higher.
                      Dink

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