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Carburetor (carburettor) adjustment  and settings

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​OVERALL DIFFICULTY INDEX: 4/10
  • IF YOU HAVE NO TOOLS, YOU PAY $25 TO GET THEM FOR THIS JOB
  • IF YOU HAVE NO EXPERIENCE YOU SPEND 1 HOUR TO CARRY OUT THIS JOB
  • NO SAFETY CONCERNS


BEFORE YOU START
  • The below pictorial shows the most common adjustments that can be made to any carburetor. Some carburetors require more adjustments which are not covered here.
  • For adjusting mixture and idle, refer to the "engine tuning" tip.
DISCLAIMER:
Our pictorials are of informative nature and do illustrate works carried out by ourselves at our own premises for our own use and satisfaction.
Readers who envisage to carry out similar works inspired by the below method shall do this at their own risks and liability.
Note: The below pictorial concerns a Solex 34-34 Z1 (34/34 Z1) carburetor found on Citroën BX, Citroën XM 2.0, Peugeot 305, Peugeot 309, Peugeot 505 2.0, Peugeot 605 2.0, etc. Works on other carburetors remain much similar.

Tuning a carburetor

Click on the below link for carburetor tuning while engine is running.
​How to set the carburetor air fuel ratio screw and adjust engine idle speed.

Checking the carburetor base if bent

1- Control the base with a straight edge like the one of this steel plate pictured here. Rotate the plate all around and check if the base is bent like this one.​
2- Use a marker pen to mark the corner that is most bent.

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3- Adjust it with a file. Keep in mind that compressed air will be required to blow out the metal particles. You can also use a soft brush.
4- After the marks disappear, check again with the plate that the result is satisfactory.
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5- Use a thicker base gasket. See our specific page for carburetor gasket fabrication.​
6- The replacement gasket can be as thick as 3 mm.
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Adjusting the carburetor float level

1- Fit a new gasket in place and measure the height of the floats when they press the fuel inlet valve. You need to know to which measure this value is to be adjusted by looking for your carburetor 's adjustment settings.
2- Delicately bend the latch that presses the valve's ball. Use long nose pliers or your fingers. Always make your adjustments little by little.
3- Remeasure to check if the correct value is reached. Make sure this applies to both floats if your carburetor has two of them.
4- Make sure your setting results in the floats pressing the ball before touching the carburetor body.

Adjusting the carburetor cold throttle opening

1- Turn upside down your fully assembled carburetor. Look at your throttle to check it is open by some value when the choke is closed. Such value is to be obtained from your carburetor's setting values. It is usually about a few mm (5 to 6).
2- You also need to know which screw adjusts the throttle and turn it in or out until the correct setting is obtained. Use a drill bit of the same diameter than the required spacing and insert it between the throttle and the body.
3- This opening sets the idle speed of your engine when cold with the choke completely closed.


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​See also our other carburetor related pictorials and available parts at our partners' store:

For mixture adjustment while engine is running, visit our engine tuning page.