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.
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.
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.
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.
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.
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.
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.
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.