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Wiring help

  • Thread starter Thread starter musicman
  • Start date Start date
M

musicman

Guest
So I'm not one to post "help" threads on forums usually, as I myself hate trying to diagnose stuff via interwebernets, but figure since you guys have been there done that with these bikes that I better ask. Bike in question is a '79 550e.

Been toying around with this little Suzuki for a few months, so far doing simple stuff, i.e. wheel bearings, tires, headlight, playing around with the stock seat pan, working on the carbs, etc. I haven't really done anything electrical, say for a battery replacement. Though now I guess I get to, haven't even ridden this thing yet.

Went to start the bike today to adjust the carbs some more, and it was turning over slower than usual. Smoke started pouring out from under the tank in the midst of this all, killed the key lifted the seat and started hunting for the smoke source. There appears to be a ground wire that runs front to rear on the bike, black with a white line, near the air box 2 jumpers come off it spliced into said wire, both seem to go to frame points. One was bolted to the battery box, the other to the front mounting point for the solenoid. Both of these jumper wires burned up and let all their magic smoke out, and as we all know, you let the magic smoke out of the wire and it don't work no more.

First thing I did was tear into the main harness praying the other wires were in tact, and prayers were answered, they didn't get fused together and the insulation appears perfectly intact. But these 2 ground leads burned clear up to their splice point, after that everything appears well.

Any idea what happened? My two thoughts were a.) the starter has had enough after 33 years of service and was drawing too much juice, and b.) one of these wires wasn't bolted to the correct location. As a side note no fuses blew, all correct ratings and such. Don't really care if the starter is done, no problem kicking such a tiny engine over.

Thanks for any advice, appreciate it :cool:
 
I have Two suspects:
1) Was this release of smoke while running the starter motor? If so, then I suspect a bad connection of the big negitive cable to the engine (top/back of transmission), at either the engine end or battery end. This would cause some of the starter motor current to go thru that ground wire in the wiring harness. So all that current that is intneed for that big thick wire ends up going thru the regular size black/white wire.

2) R/R failed and dumping lots of current down its ground wire. And the R/R ground wire is "grounded" to the solenoid bolt on the battery box, where ther is also a ground wire from the wiring harness. But if the baterry box is not well grounded to the frame then that current from the failed R/R goes thru that ground wire in wiring harness to get to the battery negitive and/or the frame.
Unplug the R/R. If that wire smokes some more when plug the R/R back in, well, then you know that is the problem.
I had the R/R fail and it burnt that black/white wire right off that frame ground by battery box and did melt insulation in the wiring harness.
THis is one reason why folks recommend adding your own ground wire to the R/R negitive so not depending on that blk/wht wire in the wiring harness.

Both case 1 and 2 are enough current heat up that black/white wire in the wiring harness like a toaster heater element.
 
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I think you nailed it on number one, appears the connector on the larger ground wire at the battery post is a bit corroded, so I guess I know roughly what happened. And yeah, it did burn up while cranking, all the dots seem to line up there. Just for peace of mind though I'm going to replace the original r/r with a honda one next as well. Thanks for the reply!
 
Yep, one of the joys of GS (or just about any electrical system)...

TROUBLESHOOTING!

1) The wire that burns is often not the cause, something else fails causing the path of least resistance to change. When this happens, and the new path is not able to handle the load, the smoke escapes! The problem is figuring out what changed!

2) The resistance of the path can change, if the current has no other path, it will create heat. Heat will allow the smoke escape.

3) Sometimes, the smoke gets clostrophobic, and escapes just because it's sick and tired of being cooped up in the same damn wire for thirty effing years.

4) The current being fed into the path has changed and thus allowed the smoke to escape.
 
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