hey everyone i have a 1988 k100 and i’m converting to a scrambler. i’m trying to wire a custom led tail light to mount on the frame, and i’ve wired up the ground wire and running light and it’s not coming on, i’ve checked all the fuses on the side (the 7 that are closest to the air box) and they’re all fine. i previously wired up the same tail light and fried it accidentally so i purchased a second one and now it isn’t wanting to work with me. any help?

Take it off the bike and test it on a battery. That will give you a go/no-go for the next stage.

The BMU controls power to the rear marker light.  Is your BMU remaining lit all the time even though you've engaged the front and back brake levers at least once since turning on the ignition?  If so, you might need to mod the BMU.  See Duck's instructions here: http://www.kbikeparts.com/classickbikes.com/ckb.tech/0.ckb.tech.files/bmu/bmu.htm

If you're making a scrambler and using LEDs you can just ditch the BMU and wire as follows:

Gray/White wire from BMU connector to 12V+ of tail LED.

Gray/Green (front brake switch) and Grey/Red (rear brake switch) from BMU connector to 12V+ of brake light.