Looking for electrical advice

1982 XJ 750, so here's my problem, I'll start the bike and the gauge lights will illuminate but not stay on while riding, or a running tail light for night riding? I'm very new to owning this bike and am slowly learning more and more please forgive my ignorance if it's something simple. I have the manual with the wiring diagrams and can't seem to figure it out. Any help would be appreciated.

 

do you mean the speedo and tach lights?
or does the computer center go blank?

when bike is running the tail light should be on and the back lights to the speedo and tach.

the computer tests the functions abd the black bars go out unless there is a problem and the fuel indicator shos the level as a bar graph

 

this is what you should see. neutral light on, brak indicator, my float does not work, the batt light , my sensor is disconnected. fuel

 

The spedo and tach lights, they'll illuminate when I turn the key to on then go out.

 

They should be staying on. I would suspect either the keyswitch contacts, or possibly the fusebox.
If you have the original fusebox and the fuse clip for the instruments is cracked it would carry current intermittantly. It's possible that the crack is growing as the current warms the clips.

Does the tailioght go out as well, or does it stay on?

Do you have a Maxim (XJ550H pictured the Maxim dash) or a Seca?
There are some wiring differences between the two.

 

So it's an aftermarket fuse box, and the seca dash. I pulled the headlight to see if anything was unplugged and someone got in there and did some aftermarket wiring. As far as the tail light it works when I use the brakes but that's all. Heres the current fuze box situation and I pulled the headlight and I've got 3 wires that aren't plugged in and I think they came out with the light.

 

check the 5 amp fuse in the headlight bucket your meter(speedo/tach) and license plate light get power from that fuse.
could be contacts in ignition switch could also be the connectors used by prev. owner his crimps could be bad

Clean and lube the ignition switch
does that brown wire in your fingers connect to the brown wire above your fingers

 

Hello all, finally got enough time to really dive into the bike, turns out it was the ignition. The ignition would create a gap and wouldn't maintain contact to keep the bulbs lit!