Help! 78' cb 750k melted wire

[stevewag]

Before everyone jumps down my throat- I have researched this! I get lost in the technichal jargon of it all so please go easy on me. As you can see in the pics the green wire between my rectifier through the square connection, all the way along the wiring harness to where it splits near the coils, is melted. The pigtail that connects to the frame looked like it was starting to melt too. The other green wire that came off it to the headlight bucket was fine. Now, does this lead you to assume the rectifier itself is bad or maybe that length of green wire just had a short or both? I haven't had the bike for long, and only ran it a bit, but it did appear that when I put a volt meter across the battery terminals the voltage stayed the same at idle and when revs increased, so not charging. Would that play into this melted green wire?

My feeling is that I should replace the rotten green wire, then do more testing of stator/ rotor/ field coil. But should that rectifier be replaced too?

 

[my-79-750-k]

That green wire should absolutely be replaced. As far as the rectifier goes, I wouldn't doubt it's bad. You can probably pick up a replacement for a few dollars, I can't imagine them being too much money.

 

[Mopower93]

Same thing happened to me a few years ago. Ended up being a broken wire from the alternator. I would re-wire from there, and replace the rectifier and regulator with an all in one solid state unit. Less hassle, and reliable.

 

[Tune-A-Fish]

This is common with any older bike that uses a single ground strap for most of the electrical and why I segregated mine into three mini harnesses one for lights, ignition and charging system even added a fused hot for accessories.

Seems a daunting task but I would open up the entire harness and replace the ground and any shorted or burnt wires with soldered connections sheathed with shrink tube. You can make an exact replica of the ground loom with soldering and shrink tube. If you want I have a stock regulator and rectifier that are good you can have for the ride, but I highly recommend you get hold of Spark Moto... (banner link on the left of this page) Buy a new solid states reg rec and carefully wire it in.

 

[Sonreir]

Obviously my case is a bit different than most, seeing as how I always have the parts laying around, but all of my bikes get new R/Rs as a matter of course. The new technology is so superior to the old that it's not something I would skimp on.

All the advice in this thread is solid. Get all the wires replaced, not the just the green one. Once the wire gets hot enough to melt through the insulation, it almost definitely damaged the other wires in the same run. If you need a new run from the alternator to the rectifier, let me know. We can eliminate the sub-harness for you, entirely. It slims things up quite a bit.

 

[stevewag]

thanks for all the help. Looked into the rec/rel unit and seems like a no brainer. I may rewire that gound, plug it all back together, retest the charging sysytem thoroughly before I buy the single unit. I have a tendancy to buy before I'm sure its needed, which at the end of the project = $hundreds.