How to Tune a Weber

Written by carl pruit
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Tuning a Weber carburettor will keep the motor running efficiently and give you better fuel mileage. The Weber carburettor has two adjustment screws in the front and an idle stop screw on the side, next to the carburettor choke. Tuning the carburettor regularly will keep the engine working longer. You may tune the Weber carburettor in just a few minutes with some basic tools, saving you time and money.

Skill level:
Moderately Easy

Things you need

  • Screwdriver
  • Vacuum gauge

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  1. 1

    Turn both Weber carburettor idle-adjustment screws clockwise with a screwdriver until they are completely seated. Use caution to avoid over-tightening them. Adjust both screws back counterclockwise two full turns with the screwdriver to set the adjustment starting point.

  2. 2

    Start the motor and let it warm up until the carburettor choke plate opens up inside the barrel of the carburettor --- about five minutes. Adjust the idle mixture screw on the right side of the carburettor by turning the screw clockwise a quarter turn at a time until the engine begins to stall out. Turn it back a quarter turn.

  3. 3

    Turn the idle mixture screw counterclockwise a quarter turn at a time until you hear the motor start to stall. Turn it back clockwise a quarter turn. Remove the rubber vacuum hose from the vacuum port on the front of the carburettor and attach a vacuum gauge to the port.

  4. 4

    Adjust the idle speed screw by turning it a quarter turn at a time until the vacuum gauge reads between 700 to 900rpm. Locate the idle stop screw next to the choke cable on the side of the carburettor and turn the screw clockwise until the screw is not touching the throttle stop lever.

  5. 5

    Set the idle stop screw by turning it counterclockwise 1 1/2 turns. Remove the vacuum gauge from the vacuum port. Reattach the rubber vacuum hose to the Weber carburettor vacuum port and shut off the motor.

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