The idle mixture screw setting not only influences the idle but also midrange performance. Consumption depends mainly on it. Takes about five minutes. Buy yourself a little mirror on a telescope stick. To turn the adjustment screw you can use a small rachet with a blade bit.
Motor has to be warmed up well.
Drop the idle speed down to a still smooth running minimum by turning the stopper bolt of the throttle valve. Use the mirror to check the actual position of the idle mixture screw. Turn the screw slowly half a turn out, then half a turn in and watch where the motor speed reaches its maximum. Leave the screw in the maximum position and readjust the motor speed to about 1300rpm. I use to take it apart together with the fuel pump.