2013 Drake Smith - Please do not use or reproduce this elsewhere.  Feel free to link to it though.

1986 & Later Fuel Level Sender

Wiring:

Brown

Ground

Green/White

12V+ to Fuel Pump

White

Low Fuel Lamp in Instrument Cluster

Yellow

Optional Round Fuel Gauge

How It Works:

Fuel Pump Power - K75 & K100: The fuel pump only receives power when the engine is turning.

Fuel Pump Power - 4V K Bikes: When the ignition is initially turned on, the Motronic runs the fuel pump for a second to two to pre-pressurize the fuel system prior to starting.  After that, the fuel pump will run when the Motronic senses that the engine is turning. (from the Hall Effect sensor)

Low Fuel Indicator: The low fuel indicator comes on when you have approximately 4 liters of fuel remaining.  There is delay circuitry built into the instrument cluster so that it doesn't go on and off as the fuel level float bobs up and down in the tank while you're riding.

Fuel Gauge: As the fuel level float goes up and down, the yellow wire sends out variable resistance (from ground) to the fuel gauge.

Flaky Connector:

As these bikes age, it is not unheard of for the connector from the main wiring harness to the fuel level sender to deteriorate and cause the fuel pump to get intermittent or no power.

Click here for one way to fix that.

2013 Drake Smith - Please do not use or reproduce this elsewhere.  Feel free to link to it though.