Some info from my service manual
Tim
1. Remove the engine cover.
2. Connect a tachometer according to
manufacturer's instructions.
3. Start the engine and warm to normal operating
temperature.
4. Shift the engine into FORWARD gear and
note the idle speed on the tachometer. It should
be 750 rpm.
5. If idle speed requires adjustment, face the
steering handle and rotate the idle speed
adjustment knob clockwise (to increase) or
counterclockwise (to decrease) as required to
bring idle speed within specifications.
6. When idle speed adjustment is completed,
shut the engine off. Remove the tachometer and
install the engine cover.