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Nothing at idle on #4 carb

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    #1

    Nothing at idle on #4 carb

    Howdy.

    Just rebuilt a rack off an '82 1100GL that had been sitting wrecked in a guy's garage since '86. Had 5k on it when someone crossed the double-yellow which resulted in a 90mph head on. Ouch. Spent 7 months in the hospital but is still riding today. Bought was was left of the bike from him for $300. (Engine, carbs, rear-wheel, swingarm & coils/ignitors) Now for the carbs.

    Anyway, I rebuilt them and I'm not getting anything out of #4 at idle. The plug is getting spark and the gap is good but when I turn the air screw or pull the plug wire it doesn't make any difference to the bike's idle. The other three react the way that you'd expect.

    Both float height and sync are good. I checked the hole under the air screw and it's clear.

    Any ideas?

    Thanks,

    Rob
    Tags: air screw, rough idle
    #2
    Have you tried swapping the plugs?
    79 GS1000S
    79 GS1000S (another one)
    80 GSX750
    80 GS550
    80 CB650 cafe racer
    75 PC50 - the one with OHV and pedals...
    75 TS100 - being ridden (suicidally) by my father

    Comment

      #3
      Clean out the pilot jet and make sure you can see a pin of light through it.
      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.

      Comment

        #4
        Originally posted by hampshirehog View Post
        Have you tried swapping the plugs?
        No, didn't. Too late, already pulled and drained them.

        I just did throw on the known working rack, though and it reacts as expected so it's gotta be something with the other carb.

        Maybe something is still plugged?

        Rob

        Comment

          #5
          Originally posted by chef1366 View Post
          Clean out the pilot jet and make sure you can see a pin of light through it.
          Pulled it and it looked squeaky clean. Could see light through the tiny opening at the end. Ran a wire through it again anyway. Shot some air down the tube while it and the air screw were out and got good flow.

          I should probably mention that I had a heck of a time getting the pilot screws out. It took an extended soak and some heat to free them. They had some black gunk on them that had completely clogged them. The carb dip dissolved it pretty good, though.

          Comment

            #6
            If you blow carb cleaner in the pilot air jet it should come out the pilot jet.
            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.

            Comment

              #7
              Does the #4 cylinder fire with the slightest throttle move ment or if you turn the idle up?
              1984 GS1100GK newest addition to the heard
              80 GS 1000gt- most favorite ride love this bike
              1978 GS1000E- Known as "RoadKill" , Finished
              83 gs750ed- first new purchase
              85 EX500- vintage track weapon
              1958Ducati 98 Tourismo
              “Remember When in doubt use full throttle, It may not improve the situation ,but it will end the suspense ,
              If it isn't going to make it faster or safer it isn't worth doing

              Comment

                #8
                Originally posted by hjfisk View Post
                Does the #4 cylinder fire with the slightest throttle move ment or if you turn the idle up?
                Yeah, it was firing when I was synching at 3k. (Well, that header got really hot, so I'm guessing that it was firing.)

                Comment

                  #9
                  I'm going to disassemble and dip/clean the whole carb again 'cause something ain't right. Can't hurt.

                  I'll update tomorrow.

                  Rob

                  Comment

                    #10
                    Originally posted by ChicagoRob View Post
                    Yeah, it was firing when I was synching at 3k. (Well, that header got really hot, so I'm guessing that it was firing.)
                    So if it fires with a slight throttle adjustment , then I would tend to have to think that the throttle plate is closing to much on that cylinder, if all else is good and clean, which would mean the syn is off a little.
                    1984 GS1100GK newest addition to the heard
                    80 GS 1000gt- most favorite ride love this bike
                    1978 GS1000E- Known as "RoadKill" , Finished
                    83 gs750ed- first new purchase
                    85 EX500- vintage track weapon
                    1958Ducati 98 Tourismo
                    “Remember When in doubt use full throttle, It may not improve the situation ,but it will end the suspense ,
                    If it isn't going to make it faster or safer it isn't worth doing

                    Comment

                      #11
                      You were syncing them with a set of gauges correct
                      1984 GS1100GK newest addition to the heard
                      80 GS 1000gt- most favorite ride love this bike
                      1978 GS1000E- Known as "RoadKill" , Finished
                      83 gs750ed- first new purchase
                      85 EX500- vintage track weapon
                      1958Ducati 98 Tourismo
                      “Remember When in doubt use full throttle, It may not improve the situation ,but it will end the suspense ,
                      If it isn't going to make it faster or safer it isn't worth doing

                      Comment

                        #12
                        Originally posted by hjfisk View Post
                        You were syncing them with a set of gauges correct
                        Yep, a Morgan CarbTune Pro (The 4 tube model). 1 & 4 slightly higher than 2 & 3. Takes me a few tries because I still haven't mastered tightening down the nut without turning the screw a little.
                        Last edited by Guest; 05-19-2013, 08:35 AM.

                        Comment

                          #13
                          Ok, finally got back to it. Yesterday was so nice, the wife and I took a drive in the country.

                          The dip worked! Musta been a clogged tube because I have a smooth idle now. But...

                          During the test ride, any cruising with the throttle cracked (think 25mph cruising at 3k) it feels like one cylinder isn't firing. It's jerky and kinda sputtering in the 2.5k to 4k range with small throttle. Full on throttle is strong and smooth all the way to 9k (Well, the first attempt stumbled a little over 8k but the second and third attempts didn't). Highway cruising at 4 to 5k is smooth. I'm also getting a lot of decel pops especially in the 4 to 6k to throttle off range.

                          I should mention at this point that it's stock carbs, finally a stock air box with full snorkel (the old one was cutoff very low) and a recently repacked V&H 4to1. The airbox is sealed well with new foam all around and a clean/oiled K&N filter.

                          Runs like crap cold and gets better with heat. Sync is still good and all of the valves are between 5 and 9.

                          What's the thoughts on the low throttle stumbles and the decel pops?

                          Thanks,

                          Rob

                          Comment

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