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Another Hanging Idle - Rich not Lean!

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    #1

    Another Hanging Idle - Rich not Lean!

    So after wearing out the search function, I've decided my problem may warrant some advice from the local GS gurus. First, some history:

    Bike Setup:
    Stock Airbox
    Stock exhaust (baffles may be damaged/may have holes - not quiet...)

    Maintenance done by ME:
    Carb dip/clean/o-rings
    New Petcock
    New Plugs/Caps
    Valves Adjusted
    Oil/Filter change
    Sealed Airbox
    New Airbox-side Boots
    New Intake O-rings (Intake boots were fairly new, very pliable)
    New UNI Air Filter
    Carb sync with home-made Manometer (pics soon!)

    When I finally put everything back together and before I synched the carbs, the idle would hang pretty badly, especially once it was warmed up. I checked the plugs and they were white and it was certainly running lean. Synchronizing the carbs helped quite a bit with the hanging idle problem, but it still hangs when warmed up and takes a long time to come back down to idle. When coming to a stop sign, I've been downshifting very late in order to bring the RPM down. Once I get it below 1400 or so using the clutch, it seems to stay there but sounds a little rough.

    SOOOO, last night I went hunting AGAIN for an air leak. I found the #2 intake boot was cut from the clamp and carb cleaner spayed there would increase RPM. I was happy to find the leak, but confused when all 4 plugs were black and sooty after idling for a bit. I would expect them to have lean characteristics if the idle was hanging up (also there is a lot of popping on deceleration) I "engineered" a short term patch (RTV and tape), so carb cleaner spray no longer affects the idle speed, but the revs are STILL hanging up around 3000rpm. Should I start looking for an electrical problem? Could there still be another air leak somewhere causing this? If so, why wouldn't the plugs indicate a lean condition at idle? Perhaps its not the idle/pilot circuit that's lean? I need help... Thanks guys!

    P.S. While living in Kansas really sucks as far as topography, last night it was a good thing I dont live near any cliffs... might have tested the bike's hang time
    Tags: None
    #2
    Is the choke hung up ever so slightly? if it's not returning to it's "off" position at the carbs it would raise your idle and richen your mixture. Are all your plugs evenly sooty or are some worse than others?

    Comment

      #3
      Neither the choke or throttle cable are hanging up. The choke rail and slides are all going back "home" properly. All 4 of the plugs were black on sooty and none stood out as being worse than the others. I put the mixture screws in a full turn last night (now 1 turn out) but that didn't seem to do much at all.

      Comment

        #4
        Oil on the uni-filter?

        Comment

          #5
          I oiled the filter with the red spray stuff from the auto-parts store. I've heard its easy to over-oil them, so I might not have applied enough. Tonight I'll pull it out and give it another spritz. Wouldn't that cause the plugs to look lean though?

          Comment

            #6
            Could be that your air leak is triggered at higher RPMs, but the bike is otherwise set too rich. Thus, it runs lean when returning to idle because the harder draw brings that air into the mix, but once it settles down, the lower RPMs don't pull enough from the leak.

            You could test this by getting the idle to hang and killing the bike. Then inspect the plug on that leaking cylinder. It probably will be pretty white.

            HTH

            Comment

              #7
              A while back, you said that PO had installed pods, but claimed no jet changes- maybe he was mistaken/confused and someone had changed them. Now that you've gone back to stock airbox/filter, maybe things are too big causing a rich condition?
              1981 gs650L

              "We are all born ignorant, but you have to work hard to stay stupid" Ben Franklin

              Comment

                #8
                It's possible that the jet sizes are all messed up, causing the main to run lean and the idle to run rich. I'll check that out tonight after work along with the plugs after letting the idle hang up for a bit.

                Comment

                  #9
                  I put more oil on the air filter (didn't help but I think its how it should be now). After letting the idle hang for about 30-45 seconds and hitting the kill switch, my plugs were now showing very LEAN. This is frustrating because the carb boots are all new. Is there a special clamp for the intake boots? I have regular hose clamps (worm-drive style) on there now and I think they might be cutting into the boots.

                  I haven't checked the jets yet because I can still get the RPM to react when I spray the intake boots with carb cleaner. If it is already up around 2500 rpm, the carb spray makes it climb higher. If the bike is idling, the carb spray has no effect.

                  Also, does anyone have a set of intake boots they're looking to unload? Those things aren't cheap :-\

                  Comment

                    #10
                    Yup, that'd do it...



                    I also checked the jets while I had the carbs off. The pilot jet seems to be the correct size for my bike (42.5), but the mains were 140

                    I'll be ordering some 115's tomorrow, and maybe some #40 pilot jets.

                    Here is my temporary fix until I can get some new intake boots:



                    Some high-temp AL tape to protect the sealant and boots from the clamps:



                    I guess I'll find out if that fixed it when I get the jets in Thanks for the help and the sanity checks guys!

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