I'm new to the forum and new to Yamaha as well, and recently acquired an '89 XVZ1300 with 18K miles. Have an issue with an intermittent electrical problem, and would like some experienced opinions regarding likely causes.
Initially when I tried to start it I got no response from the start button, yet all lights appeared to function, so I figured either the start button or relay. I jumped the positive battery terminal to the starter side of the relay and she fired right up, confirming the likelyhood of the start button being the culprit.
However, as I was pulling away (on a very bumpy gravel drieway) I hit a bump and the dash and headlight went out, bike still running. It was late at night, and I wasn't home, so I turned it around and headed back up the very bumpy driveway. I shut it down, turned the key off and back on, and tried the start button, but no response and no lights (bypassing the solenoid still worked though).
At the time I had only an owners manual for a 1200 (have since downloaded the service manual from this website, thank you very much) and noted the grounds for all the accessory lights in question are tied together to one grounding point. I removed several body panels and started rooting around looking for bad connections etceterra. Traced the ground to inside the left upper fairing, and it looked fine. In fact, all of the wiring connections looked pretty clean. This 23 year old machine must have spent most of its mostly dormant life indoors.
Anyway, after rooting around and not finding anything out of the ordinary (begging a ride home, getting some sleep and returning with some tools) I tried to start it again and it fired right up, but still no lights. I took the start button apart and it looked fine. I rechecked the wiring harness, fuses, etcetera and found only a couple of clues.
First, the fuse for the tail light was hot as hell (and has since melted), which seems to me must be a separate issue, probably a bad ground somewhere on the way to the tail, although I couldn't find anything.
Second, I noted a constant low current to the starter relay switch. Unfortunately all I had at the time is a test light (very dim light when voltage detected, not enough to throw the switch), and I haven't had an opportunity to get back into it to check it.
Now I figured I better get her home to work in the comfort of my garage, so I put it back together, and pressed start. To my surprise it fired right up, all accessories and lights working.
In addition, on the way home I received another clue. The lights and accessories were intermittenly shutting on and off, which seemed to coincide with progressively smaller bumps in the road.
I'll give the start button a more thorough examination, which may be the cause of the contant current to the starter relay switch. I'll also try to chase down what I feel is probably a faulty ground in the tail light wiring.
I'm thinking possibly the ignition switch.
Otherwise I was hoping someone with more experience with these machines might recognize the symptoms and point me in the right direction.