No power unless tank grounds on frame

[Guest]

So to start this odd mess off, my bike (1982 GS850GL) was shorting out and turning off whenever I held my left turn signal down. It was fine on the right signal, but hold the left in and the bike would just lose power and turn off. I replaced the entire left hand control unit, thinking 36 years was decent from the first.

This weekend, I put on new rubber and upgraded my suspension and when I put it back on the ground, no power. The neutral and oil lights come on though, but no power to the headlight, signals, or starter. However, during my trouble shooting, I discovered that everything worked fine when my tank rubbed against the frame - but only when the fuel gauge connections are plugged in. (although it sparks a little where it makes contact)

So I'm thinking there's an issue with a ground? It's mostly stock wiring, although I wired in a new stator and SH775 R/R (which grounds directly to the negative terminal on the battery) I've checked the chassis ground and all the signal rings , I've cleaned every contact, I've had the headlight apart to check the connections, and have had no luck...

I have:

-cleaned ground / chassis bolt
-checked ground / battery box bolt
-cleaned contacts throughout harness
-checked all signals ground rings are secure and grounded
-checked signal and ground connections in headlight
-cleaned ground / battery connectors


I'm out of ideas...any you could provide would be greatly appreciated!

[dorkburger]

Fun... I would start by checking whetever wiring is under / near the tank. It sounds like there may be a damaged wire somewhere, and yes, bad or missing grounds cause odd behaviors.
Last summer I found that my front brake light switch wire was broken inside of the wire covering, preventing it from working. Not sure of your electrical skills, but you may need to become friendly with a wiring diagram and test meter. I would start with a close and thorough visual inspection first.

Edit. Did the bike run ok aftet the r/r and stator install?

[Redman]

................., I discovered that everything worked fine when my tank rubbed against the frame..............
.....
So I'm thinking there's an issue with a ground? .............

Interesting observation.
Good conclusion.


On the battery negative, do you have the thick black cable to back of engine, and do you have a black/white wire from the bike wiring harness?

Do you have a meter that you can check continuity.....? If so, I have some test that I can describe to you.

[mnferwerda]

I would second what Glen said. I had a short under the tank inside the wire covering. What I found once I uncovered the bundle of wires was that the covering of some of the ground wires had melted off due to the R&R/stator issues. This was further evidenced by a melted connection in the headlight wire nest.

[Guest]

The bike goes work since the r/r and stator were changed. Wiring isn't my best skill but I do have a meter and know some basics...

I already have the tank off. Nothing open or that would be connecting from what I can tell. Interestingly, the bike is in it's "dead" state without the tank, and I know I had it running without the tank doing carbs last summer..

Yes, I have the thick black wire that leads to the frame connected to the battery. The harness is connected directly to the battery box.

[Guest]

...a quick victory. I disconnected the ground from the battery box and connected it directly to the negative terminal and BINGO, back in business. Thank you gentleman!

[Steve]

Nice to see you have THAT part resolved, but be aware that there also needs to be a ground wire going to the battery box. The starter solenoid needs a ground to operate, and it is mounted on a rubber-isolated battery box, so there needs to be a wire connected to ground it.

General rule regarding electrics (especially vehicle wiring): when you have some really screwy symptoms, it's a bad ground.

.

[dorkburger]

Interesting. Sounds like it may have been grounding thru the fuel circuit.
Years ago I had a car that when the headlights were on the gauges went wacky and the dadh lights went out. I ended up grounding the gauge cluster and it was fixed......
Grounds......

[Redman]

...a quick victory. I disconnected the ground from the battery box and connected it directly to the negative terminal and BINGO, back in business. Thank you gentleman!

Good to hear of the success.
But before you get too far (and bike die on side of road because is not charging) let’s verify a couple things.

you need the blk/wht wire on battery negative (sounds like that was what was missing) , and you need a blk/wht wire on battery box (typically solenoid mounting bolt) ..... those and all the other blk/wht wires all need to be connected to each other in the wiring harness — that is what I was going to have you check with meter continuity checker. And one of those boo/wht Aires needs to be connected to the bike frame so the bike frame is also grounded. And the r/r black wire also needs to be connected to all this for the r/r to function, typically is connected to the solenoid mounting bolt along with blk/wht wire. Many folks run the r/r black wire direct to battery negative and that is better in many ways (but not related to your problem at the moment).

The blk/wht wire on battery box (solenoid bolt) is TO ground the battery box because the battery box is not grounding by any mounting to the frame.