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Thread: Gs450, suggested jets?

  1. #11
    Join Date
    Sep 2019
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    OC, California
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    Never mind, why wouldn't I do that stuff after a carb change.
    1982 GS 450L aka Lil' Red
    1980 GS 1000G aka Big Red (Resto-mod WIP)

  2. #12
    Join Date
    Dec 2014
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    In the doghouse, usually.
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    I do believe you have just answered your own question.

    If you set your mixture, THEN change the jets, you will have to set your NEW mixture.

  3. #13
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    Sep 2019
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    OC, California
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    Hmm.. I've swapped only the jets, up to 117.5.

    She runs ok at high RPM, until I hit WOT, then starts sputtering a little. If I relax my wrist by even a little bit, she's good. Lower RPMs, also sputtering, and difficult to keep running. Slightly better with choke.

    Gonna check for air leaks, but this is pretty weird. I used my colortune on cylinder 1 (didn't have time for cyl2), she's misfiring almost every other cycle, even popped hard enough that my vacuum line popped off.

    Sheesh.
    1982 GS 450L aka Lil' Red
    1980 GS 1000G aka Big Red (Resto-mod WIP)

  4. #14
    Join Date
    Sep 2012
    Location
    New Zealand
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    146

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    Spluttering at WFO is rich on the main jet. Rolling off brings the needle jet metering back into play and back into correct mixture. A WFO plug chop will confirm. You only need bigger jets to compensate for more air. Unless you've modified the engine to flow more air, bigger jets will reduce power because the fuel air ratio is now sub-optimal (not enough oxygen to burn the extra fuel). Jetting sets the fuel/air ratio and is like Goldielocks -too rich bad, too lean worse, has to be just right.
    Last edited by KiwiAlfa156; 12-03-2021 at 10:21 PM.
    Darryl from Kiwiland

    1982 GSX1100S Katana
    1982 GSX750S Katana
    1982 GS650G Katana

  5. #15
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    Sep 2019
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    OC, California
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    It's the strangest thing. I've put the original jets back in, tested for air leaks by spraying with starter fluid.. she's having a really rough idle regardless. Argh!

    Colortune is showing a mostly blue, blue-green flame, I moved the balance around between carbs until I could get max RPMs at idle. Not sure what could be wrong, other than a clogged idle passage? She'll idle roughly for a while, but the rpms slowly decrease on their own over about 2-3 minutes until the engine coughs and dies.
    1982 GS 450L aka Lil' Red
    1980 GS 1000G aka Big Red (Resto-mod WIP)

  6. #16
    Join Date
    Mar 2020
    Location
    Portland, OR
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    39

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    Did you ever sort the issue? Are all the passages on the carb cleared out? I assume you have played around with the idle screw along with the fuel screws? How many turns out are the fuel screws? On my gs425 I have in 1 size up on the pilot jets (25), and 2 turns out on the fuel screws. Any more is too rich and any less the idle is lean and Iíll get some slight popping on decel.
    1979 GS425

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