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High hanging idle

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  • High hanging idle

    This is the same old 1990 katana frame ive been running for 8 years. right now with a 2003 b12. I've been running this engine no issues for 1.5 years. redone the carbs plenty of times and never an issue. Recently just tuned up my carbs and put in a carb kit(rubbers and float needle/valve seat assembly).

    SYMPTOM: the bike starts right up with choke and idles perfectly right after.. once i've run it around and is very warmed up, the idle hangs high.. i'll back out on the idle screw and it'll drop down back to where it should be. and repeat this at every redlight/stopsign. i end up backing it up so much that the idle screw no longer in contact with the butterfly assembly, BUT it still remains to idle high

    All this even after checking for vacuum leaks with carb spray(no idle changes found) and syncing carbs. My a/f mix screws are set beyond where i usually have it.

    I pulled the spark plugs and porcelain is white showing it's running lean as i expected

    My first thing will be to switch back to old float needle/valve seat assembly.

    Anyone have any comments on this? i feel i've must've missed something somehow cause this is a weird issue that i couldn't seem to fix in a few hrs last night.

    edit: i know someone might say adjust the throttle cable. i can feel i have a few mm of play on the cable. On cold start it won't idle without 5-10 seconds of choke and it only idles high after its been warmed up/ran for 10 minutes.
    Last edited by Fkat; 11-06-2019, 11:00 AM.

  • #2
    I would definitely at least check the float needle and seats to make sure nothing is out of place. Also double check the float levels and adjust a little to the rich side. Something is not right, that is for sure. You should never have to back off the idle adjustment screw that far. I admit I am a little rusty on my carb tuning, and hopefully someone else will chime in with more/better advice.

    Greg

    COURAGE -

    Freedom is the sure possession of those alone
    who have the courage to defend it.

    First Sergeant(Ret) - US Army - 21 years

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    • #3
      I finally got the time to go through things. there was a difference of the float needle seat inner diameter old(larger) from new(smaller). I think i tried an ebay/amazon rebuild kit this time around and potentially wrong parts received. everything switched back to old setup and I'm going to start her up tomorrow.

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      • #4
        That will do it. Smaller diameter was most likely leaning out the mixture just enough. Best of luck to you!!

        Greg

        COURAGE -

        Freedom is the sure possession of those alone
        who have the courage to defend it.

        First Sergeant(Ret) - US Army - 21 years

        Comment

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