How to Remove a Needle Jet for a Mikuni Carb

Written by thomas west
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Mikuni is a Japanese company that manufactures carburettors for cars, trucks and motorcycles. A carburettor is used to supply an internal combustion engine with the correct air-to-fuel ratio. A Mikuni carburettor contains many jets and orifices that control certain aspects of the air-to-fuel ratio under different conditions. If your vehicle is experiencing stumbling when the accelerator is depressed 15 to 60 per cent of the way down, you may have a faulty needle jet in your Mikuni carburettor.

Skill level:

Things you need

  • Phillips screwdriver
  • 2.5mm hex wrench

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  1. 1

    Locate the carburettor. Open the bonnet and remove the air cleaner assembly on cars and trucks. Check on the side of a motorcycle between the cylinder head and the air cleaner assembly.

  2. 2

    Turn the idle adjustment screw at the base of the carburettor with a Phillips screwdriver in a counterclockwise direction fully to bottom out the throttle valve inside the carburettor. Count the number of turns so that the screw can be returned to its original position.

  3. 3

    Remove the screws from the top cover of the carburettor with a Phillips screwdriver. Lift the cover straight up and place it aside.

  4. 4

    Loosen -- but do not remove -- the hex screw on the needle retainer slide visible in the top of the carburettor after the cover has been removed with a 2.5mm hex head wrench.

  5. 5

    Move the needle jet retainer to the side. Lift the needle jet straight up and out of the carburettor.

Tips and warnings

  • Replace the needle jet in the reverse order of removal. Ensure the needle retainer is positioned over top of the "E" ring on the slide and that the plastic washer is in the correct position under the hex screw before tightening it. Return the idle adjustment screw to its original position.

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