Thumbscrew style A/F mixture screw
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Thread: Thumbscrew style A/F mixture screw

  1. #1
    Senior Member CaptDanbo's Avatar
    Join Date
    Sep 2006
    Manchester, NH

    Default Thumbscrew style A/F mixture screw

    Well, I tried out this thumbscrew style air/fuel mixture screw from factory pro. I can't seem to get rid of my low end throttle stumbling. Mid range and full throttle seem fine and the bike pulls hard after I get moving. But from a stand still, it burps and sputters like crazy. I've tried 3 different pilot jets with no change. I tried the stock 55, a 58 and finally a 65. Nothing seems to help. I'm wondering if anyone else has tried this type of A/F screw and if they had any problems with it. The problem goes away when I choke it a bit and I definitely don't have any vacuum leaks. My X is running with a Hypercharger and HK slip on pipes. I'll probably pull the carb down tomorrow and re-install the original A/F mixture screw and see what happens.
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  3. #2
    Senior Member
    Join Date
    Jul 2004
    Boston Massachusetts

    Default Re: Thumbscrew style A/F mixture screw

    so it was running fine before the new fuel screw?

    Are you sure you set it at the same amount of turns out the OEM screw was set at?
    2004 1300c pearl orange

  4. #3
    Senior Member
    Join Date
    Jul 2007
    U.C 510 sunny cali.

    Default Re: Thumbscrew style A/F mixture screw

    I have FactoryPro A/F thumb screw and have no problem with it, i don't even have to choke the bike. i have aeromach UltraFlow and V&H cruzers exhaust, 195 main and 65 slow 2 1/4 turn on A/F mixture.

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