• General Troubleshooting Chart

    • 04/28/2022
    • Gabrielle Mersereau

    This is by no means an exhaustive list, but it includes some of the most common problems with carburetion symptoms and some troubleshooting ideas. Condition Possible Cause Correction COLD STARTING SYMPTOM Engine cranks but will not start 1) Choke not closing (frozen)2) Choke linkage binding 1) inspect choke plate and…

  • Downdraft, Updraft, Sidedraft

    • Gabrielle Mersereau

    These are general examples of how each type of carburetor moves air. Generally speaking these are not interchangeable, you can’t swap a downdraft or an updraft for example. Downdraft Updraft Sidedraft

  • Governors

    • Gabrielle Mersereau

    Some carburetors are equipped with a governor of which there are many types. The governor limits engine speed and are typically found on heavy equipment such as trucsk and buses. This image is just one example of how a governor might work

  • Vacuum in the Rochester 4G

    • Gabrielle Mersereau

    This shows the air movement in a particular 4jet style base. The vacuum draws air for the automatic choke from a tube running through the heat crossover passage, the heated air passes through the choke housing, moves into the carburetor flange, goes around the primary bores and then is drawn…

  • How a Carburetor Works: Bypass Jet (Full Power Circuit)

    • 04/27/2022
    • Gabrielle Mersereau

    Some carburetors don’t use a metering rod. The main discharge jet remains a fixed size. Another jet, called a power jet, will open and allow additional fuel to pass through the main discharge tube. This additional fuel enters the discharge tube via a bypass opening. The power jet can be…

  • How a Carburetor Works: High Speed ‘Cruising’ Circuit

    • Gabrielle Mersereau

    When the throttle valve is opened past the idle and low speed ports, it allows air to start flowing through the air horn. This will build a vacuum in the venturi, and the main discharge nozzle will begin to feed fuel.At this time, the idle and low speed ports are…

  • How a Carburetor Works: Low Speed Circuit

    • Gabrielle Mersereau

    You will see a slot opening just above the throttle on the throat of the carburetor. This is the idle port which opened into the idle fuel passage.When the throttle valve starts to open, this port is uncovered and it will begin to supply fuel mixture to the engine. This…

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