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Thread: 650 Brawler, high idle unless idle screw completely off.

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    Default 650 Brawler, high idle unless idle screw completely off.

    Guys, pulling my hair out here. New 650 Brawler, mechanical. I'm trying to work out gremlins in this thing.
    Engine: 302, Trick flow heads, comp cam Duration: 274°/282° Hydraulic Roller, Weiand Stealth dual plan intake.
    Timing: 18° initial, 38° all in.
    Engine builder had the carb set with 72 main jets in the rear and 67 in the primary. Engine runs great when nice & warm. Had the idle at 700. Idle mixture screws adds at about one turn out. Plugs are off white slight tan.

    I was trying to figure out a choke issue which lead me down a rabbit hole. Pulled the carb and realized the curb idle screw wasn’t even in contact with the leaver. So I researched and determined the primaries and secondaries were off. I set the primaries to show .020" of the transfer slot. I then backed off the secondaries screw until it was just resting and turned it in 1/4 turn which opened the secondaries slightly.

    Installed everything and the engine idles at 1,800 RPM. I’m thinking vacuum leak right? Well, I first used a hose and put one end to my ear and went around everything I could with the other. No hissing sounds that I could find. I then sprayed carb cleaner along intake seam and anywhere I could. No change in RPM. I then squirted some right into the car, and RPM dropped some. I then pulled the PCV and kept it connected to the carb and put my finger on it. Good vacuum pull. I then put the PCV back into the head cover, pulled the vent cover on the other side and put a piece of cardboard over to seal. No change in RPM. When I pulled the cardboard off there was a definite vacuum.

    I’m stumped. Engine idles at 1700 RPM unless I drop the curb idle screw right down until it’s not touching. Tonight I pulled the carb again. Reset both primaries and secondaries. I then installed the secondary idle screw from the top. This way, I can at least adjust the secondaries without having to pull the carb. Just need to shut the engine off first. I’m too tired to install. Will try again tomorrow. Am I missing something? Everything points to a vacuum leak, but I can’t seem to find it.
    Last edited by Dans68; 05-18-2021 at 02:20 PM.

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