I do admit that wiring up a motorcycle can be a bit daunting but I'm thankful for a good wiring diagram. If someone hasn't already cut the old harness up too badly it can be figured out.
A lot of the older diagrams are black and white so I make a copy and add color...much simpler that way.
With old motorcycle wiring the usual culprit is dirty or corroded connections. Clean every connection down to bare metal and apply dielectric grease when plugging the wire back in. All splices and new crimp connectors have to be carefully silver soldered together and covered with shrink wrap.
Even old Lucas, Prince of Darkness can function pretty well if you take your time.
My dad went to mechanics school back in the 1960's and he had an instructor that he called "clean and tight", I always think of that when doing wiring.
