Originally Posted by Sheep Shagger
From the diagram posted, it should only be the 2 wires that go to the multi function unit you need to test (black/yellow & dark blue&yellow ). Run the meter across those, spin the wheel slowly and you should get pulses of continuity and/or change in resistance. (This is from my experience with older KTM pickups). But the ones I have used before, only had 2 wires, I'm not sure why a third wire goes to the tach.
Gave it a try and no resistance or continuity. Looks like the speed sensor went bad.