How to adjust a tillotson carburetor

Written by carl pruit
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The Tillotson carburettor is used on small engines designed primarily for go-karts. You can adjust the carburettor in just a few minutes. The carburettor uses a low-speed and high-speed set screw that you can adjust fairly easily with just a screwdriver. The high-speed set screw includes a "T" on the end, allowing you to adjust the screw by hand.

Skill level:
Moderately Easy

Things you need

  • Screwdriver

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  1. 1

    Locate the idle set screw at the very bottom of the Tillotson carburettor. Turn it clockwise with a screwdriver until you completely close it without over-tightening the screw.

  2. 2

    Find the low-speed adjustment screw with the "L" next to it on the carburettor body. Turn the low-speed screw all the way clockwise and back it out counterclockwise one and a half turns.

  3. 3

    Locate the high-speed adjustment screw with the "H" on the body. Turn the high-speed screw all the way clockwise and back it off counterclockwise three-quarters of a turn.

  4. 4

    Start the motor and let it warm up for a few minutes. If the engine is having trouble starting, adjust the low-speed screw just a bit to get it started.

  5. 5

    Turn the low-speed screw until you can hear the motor slow down. Adjust the screw as slow as you can get the engine to run without stalling out.

  6. 6

    Open the carburettor throttle all the way and adjust the high-speed screw as high as it will go while still running smoothly. Turn the high-speed screw back one-eighth and shut off the engine.

Tips and warnings

  • To avoid burn injuries, be careful when adjusting the hot carburettor while it is running as well as moving engine parts in which clothing can get caught.

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