The idle mixture screw is located at the very bottom of the carburetor.
- Turn the screw until it is all the way in. Do not force the screw in any further because it is very easy to damage the needle valve and its seat by screwing the adjusting screw in too tightly.
- Turn the screw out 3 / 4 to 1 3 / 4 turns. This should be the normal adjustment setting. For a richer mixture, turn the screw out. The ideal setting for the mixture adjustment screw results in the maximum engine rpm.
Limiter caps are installed on some engines. These caps limit the amount of adjustment that can be made and should not be removed, if possible.
On engines equipped with limiter caps, if a satisfactory idle cannot be obtained perform the following:
- Remove the caps by installing a sheet metal screw in the center of the screw and turning clockwise.
- After removing the caps, adjust the carburetor in the same manner as described without the caps.
- There are special service limiter caps available to replace the ones removed. Install the service limiter caps with the ears positioned against the full rich stops.
Be careful not to disturb the idle setting while installing the caps.
- Press the caps squarely and firmly into place.