Topic: melted green ground wire?

[falconhockey]

I recently picked up a new 77 cb550k. It was in GREAT condition except for the fact that the electrical system was screwed up and the owner just quit riding instead of every fixing it. I figured i already have one completed bike that will be a good blue print to put back together this one. What i found yesterday was the green wire that connects the rectifier to the frame was melted and fried. What would cause this?

[bryanj]

The main ground wire from the motor/frame to the battery not having a good contact at the frame end OR the battery fitted backwards

[Bodi]

The rectifier ground is only for the rectifier and will not melt due to a problem with the main battery "-" frame ground. Reversing the battery polarity - connecting "-" to the red wire and "+" to the ground cable - will melt that wire very very quickly, and almost certainly ruin the rectifier itself. If a diode in the rectifier (there are six) fails by "going short" then that wire can melt. Diodes fail either by going open - no connection between the leads, or going short - like a plain wire between the leads.
I think you will need a new rectifier, but you can test yours anyway. The procedure is posted here a lot of times. You should have a decent digital electrical test meter with a "diode test" function or a decent analog VOM: the digital one makes it slightly easier.

[falconhockey]

thanks alot! thats what i thought but i just wanted to make sure. The rectifier seems to be good yet, so we will see after i get the rest of the new wireing harnest hooked up. The previous owner wasnt the smartest and decieded that the bike had no power so he would rip off all of the wireing without ever checking for any specific problems... and never replace it. genius i tell ya!

[Spanner 1]

This is possibly a good example of not using a car type battery charger on your bike... a 10 or 20A charger will supply too high a voltage when only loaded with a little'ole bike battery and the rectifier is very overvoltage sensitive = shorted rect. = melted green  wire, and not caused by wrong polarity charge leads to the battery in this case. If your stuck an have to use a high amperage charger, unplug the rect. before connecting the battery to the charger leads

[Gordon]

The rectifier seems to be good yet, so we will see after i get the rest of the new wireing harnest hooked up.

I'd be surprised if it is.  It takes longer to melt the ground wire than it does to kill the rectifier.