Great catch, my Escapade is a flat four. The research continues. Thanks for the heads up, Twolandrider!
You'll still have to account for the differences in how the bike and the trailer are wired. Somewhere/somehow.
If there's a four wire connector on the trailer that means the trailer has been wired the way trailers are wired for most cars. One wire is a ground. One wire is tail light. One wire right turn and brake. One wire is left turn and brake.
Some bikes do it that way at the rear. So the trailer was previously ran behind something else. Harley does it different. Out the ass end of your Harley you'll have wires that separate turn signal and brake light. So you'll have:
One wire for ground
One for tail light
One for brake light
One for left turn
One for right turn
The sixth wire on a Bushtec harness is for a separate hot wire that can be used to power an internal light (or wire a phone charger or whatever else you might wish to hook up.
The extra wires are there behind a Harley because the turn signal and brake light don't exist in the same bulb/housing on our bikes the way they do on cars or some other bikes.