Air Flow Sensor
The airflow sensor, in most types of K-jet is located on the air filter housing and measures the amount of air entering the engine. The sensor housing is conical in shape into which the airflow sensor plate is fitted. The airflow sensor plate lifts as the throttle is opened by the incoming air.
The amount of lift is proportional to the volume of air entering the engine. The shape and angle of the cone will determine this ratio.
A neutral plate position is normally level with the bottom of the cone, this is adjustable by bending a small clip / spring that acts as a stop at the bottom of the unit. The purpose of this spring is to allow the flap to move beyond its neutral position to allow excessive pressure to escape if the engine was to backfire passing a large volume of air back into the air filter housing.
If the system did not have this, the pressure could split or blow off the rubber air pipe bizzo. Any splits or ill fitting air hoses that allow unmonitored air into the engine require fixing!!!..... been there!!.....
As the airflow lifts the sensor plate this lifts the control plunger - the higher the lift the greater the amount of fuel fed to the injectors.

To adjust the fuel mixture a small 3 mm Allen screw is located within the airflow sensor; this alters the relationship between the sensor arm and the control plunger. Turning the screw clockwise enriches the mixture and vice-versa. It should be noted that the screw should be turned in very small increments and the Allen key should be removed before the engine speed is raised.

Failure to remove the Allen key, before starting the engine, can result in damage to the airflow sensing unit.....so take it out!!!!