Cautionary Tale of 20r Aisan Carb

Discussion in '1976-1983 Build-Up/Project Threads' started by Davo, Jul 26, 2020.

  1. Davo

    Davo Newbie

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    How many times have you read a thread where someone reported rough, high idle and, usually, gas dripping from the booster? Help! My mixture screw does nothing! Yup. That was me. I searched many a forum because this was the problem I had with my rebuilt 1978 pickup's 20r. New stock carb, vacuum hoses right, rebuilt head, all stock emissions...I tried everything. Well, almost. After 2 months of reading and learning, 5 repair manuals and the FSM, I determined that my idle circuit was not operating. I will end the suspense. Wasn't a vacuum leak or a clogged port. It was...drum roll, please...the electric idle stop solenoid. I read in one place that since my year wasn't equipped with a plug for this, just ignore it. I finally figured out that it plugs up the idle circuit...Aisan apparently underestimated our ability to fiddle with the carbs various screws until it would run and sort of idle even with the circuit blocked. Needless to say, once I applied power and ground to this solenoid, the mixture screw magically started working. My truck now idles perfectly and quietly at 900 rpm. Well, if you understand this post, feel free to add your story or elaborate further on anything I missed.
     
  2. Davo

    Davo Newbie

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  3. fred heath

    fred heath Veteran

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    Location:
    Raleigh, NC
    Truck:
    1978 Toyota Galavan Motorhome.
    Aisan carbs are a PITA. So many things that can go wrong. I switched to a Weber 32/36 and couldn’t be happier.
    Glad it worked out for you.
     

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