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Really lean...without good reason?

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    #1

    Really lean...without good reason?

    My bike, a 1980 GS750L, has just run fantastic ever since I bought it and went through the normal stuff, air cleaner, rebuilt carbs, etc. (it hardly made it home the day I bought it). It has always run rather lean and extraordinarily well (with around 45 MPG) but recently it started sputtering and backfiring and the plugs are as white as a sheet.

    I looked for air leaks and there simply aren't any! I've adjusted it to 3 turns out, on all 4, and it's running decent but still not the way it should for a bike like that.

    My carb boots, between the carbs and the manifold, are in perfect shape and as tight as a 'frog's bottom'. The ones between the airbox and the carbs are in perfect shape..but have limited tension on a couple of the clamps...which, in my opinion, shouldn't make a heck of a lot of difference.

    So, come on my long time buddies.....what do you think is going on? As always, I appreciate your help and feel certain that you know it!!:-D

    By the way, (and I should have mentioned this) my bike is 100% stock!
    1980 GS1100E....Number 15!
    Tags: None
    #2
    Do you still have the legendary 80 Suzuki stock petcock on it? Check the screen on it and fuel flow.
    1983 GS 1100E w/ 1230 kit, .340 lift Web Cams, Ape heavy duty valve springs, 83 1100 head with 1.5mm oversized SS intake valves, 1150 crank, Vance and Hines 1150 SuperHub, Star Racing high volume oil pump gears, 36mm carebs Dynojet stage 3 jet kit, Posplayr's SSPB, Progressive rear shocks and fork springs, Dyna 2000, Dynatek green coils and Vance & Hines 4-1 exhaust.
    1985 GS1150ES stock with 85 Red E bodywork.

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      #3
      Originally posted by chuckycheese
      ...The ones between the airbox and the carbs are in perfect shape..but have limited tension on a couple of the clamps...which, in my opinion, shouldn't make a heck of a lot of difference....
      It shouldn't make a difference if the limited tension of the clamps is not allowing air into the carbs before the air filter, which will cause the bike to run lean.

      Comment

        #4
        Pingel

        I've got a Pingel which seems to work perfectly. I understand (and agree) about the limited tention...I've tried to take a look at everything and I'm stumped!
        1980 GS1100E....Number 15!

        Comment

          #5
          Hello,
          I have been rackin my brain with mine lately and thinking of all the crazy things that may be wrong with it. As a long time auto tech it always pays to check the obvious and simple things first. Correct me if I am wrong, but if you had an air leak between the airbox and the carbs would that not make it run rich due to the extra air opening the slides and letting more fuel in without the throttle plates opening enough to match the opening of the slides? Do the slides and the amount of throttle not have to work together? I could be way off, but I am thinking that there is a combo there. I realize that between the carbs and the intake would make it lean also have a high idle which I am sure you would have mentioned. With that said, it seems as if maybe you have a fuel restriction. I know the Chef is sold on petcock problems, it very well could be that also.

          Just a question, you mentioned that it has always ran a little lean, are the baffles in your pipes? Did it run lean before you rebuilt the carbs?
          Last edited by Guest; 07-27-2006, 10:26 AM.

          Comment

            #6
            Stock

            The baffles are in (it's all stock), gas is flowing through the Pingel at a steady and healthy flow. Before I rebuilt the carbs, it would barely run at all. It runs quite well now but I'm certain something's not right due to the lean condition (plugs and backfiring upon deceleration). I'm not too frustrated...but I'm getting there. Thanks for the suggestions!:-D
            1980 GS1100E....Number 15!

            Comment

              #7
              Originally posted by chuckycheese
              ...I looked for air leaks and there simply aren't any! I've adjusted it to 3 turns out, on all 4, and it's running decent but still not the way it should for a bike like that....
              I assume that you are referring to the adjustment of the pilot screws on the top front of the carburetors. The initial starting point for a pilot screw(s) adjustment might be about 1-1/2 turns from lightly seated. As the screw is opened, more of the air/fuel mixture is passed through the screw opening which normally enriches the mixture. If 3 turns of the screws still result in a too lean condition, I wonder if opening the screws this far could be letting air in through the threads. Maybe damaged pilot screw O-rings could be admitting air. 3 turns seems excessive when the bike is still running too lean.

              I would remove the screw(s) and inspect the O-rings. If the O-rings are bad, this may be allowing excess air in the carbs. If the parts are in good condition, I would readjust the screws and see if it will run OK without having to go to 3 turns.

              Comment

                #8
                Thanks

                Well, Boony, I appreciate your thoughts. I've tried just about everything. At 3 turns out, I seem to be getting close. The left 2 seem to run great but I've got a bit of a 'spit' on the right side. I rode about 20 miles today and will check out the plug colors tomorrow..(it's simply too hot to do much else). I'll stay in touch and appreciate all the help!:-D
                1980 GS1100E....Number 15!

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