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Flat spot in the cold

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    #1

    Flat spot in the cold

    Hi guys,
    Is there something that I can do to my 400s carbs to help it run better in the cold (-25C which is -25F as well aparently)? My problem is that I have a major dead spot in the throtte response after I shift from a normal RPM. So, when I shift into 3rd gear for example I have to let the bike slow down to an idle and hammer the throttle to force my way through this invisible barrier where my carbs don't work. It runs from about 2000-4500 RPM. Another thing I can do is shift from 7-8000 RPM but it is kind of dangerous to do in the cold so I prefer to lug the engine rather than power shift.

    Thanks for the tips, Steve
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    #2
    HI Steve What you are having is a lean spot caused by the denser/drier air.You will have to raise the main needles 1 or 2 notches to richen it and raise the float level to the max.I do that with mine and it "runs like a scalded ape" when it is COLD out.

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      #3
      Yep, I agree that the weather conditions are so different that the lean running is exposed. A touch of carb icing may occur, but I have not heard of that problem with GSs

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        #4
        Steve,

        It's 25 degrees below Zero!
        GET A CAR!!!

        Steve

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          #5
          I own an old Econoline 150 that I use for travelling and moving house but it really sucks compared to cars and bikes...as a result it usually sees 20 000km a year of driving over about 30 days.

          As for raising the needles. Are these the needles that are found when the top of the carbs are removed? Also, are the notches only on aftermarket kits? I have read a lot about carbs but I haven't dared to take mine apart yet.

          The comment on the frozen carbs is correct. I have had a bit of experience dealing with this on a Topaz but that only happened when it was -40C. On the bike the carbs are kept warm and protected from the wind by the cylinders.

          Thanks again guys, Steve

          Comment

            #6
            It is possible that the do not have notches (to stop chnaging emmissions etc). In that case use small washers under the needle clip to raise it. This may get you close.

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              #7
              Originally posted by saaz
              It is possible that the do not have notches (to stop chnaging emmissions etc). In that case use small washers under the needle clip to raise it. This may get you close.
              It is a snap job steve. I assume you have the diaphram type carbs. I can adjust my needles(with washers) without removing the carbs from the bike.

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                #8
                Modern bikes are jetted lean. The gs series is no exception. Very cold air intensifies the problem. A flat washer, (.035-.040) should get you close to the equivalent of one notch on an adjustable needle. Also, removing the plugs on the fuel mixture screws, and making sure they're backed out about 2 turns from seated makes a difference, regardless of temps. This can also usually be done, if you're careful, without carb removal

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