Weird Results; ever experience this?

[Red Fthr]

I'm trying to resolve some electrical issues on a little cb 125 s2.

I noticed there was an issue when I started plugging in instruments, the batter almost immediately died.

After unplugging everything and Runnin the bare minimum, I noticed the yellow, and white/yellow wires (that come from the stator and connect in the headlight bucket) were hot and burning the plastic at the connection.

So, I busted out my multimeter to test the charging system. With the bike idling, I started at the battery and my readings were all over the place, it was like my multimeter couldn't compute; spitting out and flashing random numbers. Next I checked my rectifier, same odd/weird results for both AC and DC.

Anyone ever experienced this? Know what it means? And yes, my multimeter is working fine.

It's a simple system: generator, rectifier, battery, main switch (toggle), and coil

 

[Red Fthr]

Next I need to check the stator itself. Going to recharge the battery and try this hopefully tomorrow. I'll keep posting.

 

[crazypj]

You must have something either shorting or connected wrong. I would remove the sprocket cover and make sure none of the cable guides are missing or cutting through wires or the sprocket cover itself hasn't trapped something. I've also seen engine mounting bolts or plates crushing wiring harness under tank around head steady. Rectifier isn't damaged? It's probably the old orange plate type, get a newer style solid state, more efficient than the old selenium ones.
Haven't worked in a Honda dealers since around 1980 though so forgotten a load of stuff

 

[Red Fthr]

I'll keep an eye out for that when checking the stator, hopefully today. Thanks!

 

[Maritime]

Check all the wires for split/missing/damaged insulation as well. sounds to me like a short going to ground and causing all the weird readings.

 

[irk miller]

Agreed. Especially check under something like the seat if you rerouted anything. It could be cutting through insulation.

 

[Sonreir]

This could also occur if the AC wires don't properly match up to the rectifier.

 

[Red Fthr]

In the garage now. Which one is the A/C again? red/white? ???

 

[Sonreir]

Pink, yellow, and white coming from the alternator.

Pink should go straight to rectifier. Yellow goes to the headlight switch and to the rectifier. White becomes white/yellow toward the head of the harness and also connects to the headlight switch.

 

[Red Fthr]

That is correct.

 

[Sonreir]

I'd look for grounding issues, clean up all the connectors, and replace anything that's been cooked. Might not hurt to replace the rectifier, too.

 

[Red Fthr]

I tested the resistance of the alternator:

Bike off:

yellow=.002 ohm
White =.001 ohm

Bike on (alternator not connected):

Yellow = all over the place
White = all over the place

I guess that was to be expected.

So, bad connection somewhere/ short/ bad ground?

 

[Sonreir]

Those are very weird readings on the alternator wires.

You should be getting about 1.5Ω between each of the wires (varies about .5Ω depending on the circuit, but should definitely be over one Ohm).

Also, be sure you're getting no continuity between any of the alternator wires and ground.

 

[crazypj]

Weird readings on alternator output leads show a short circuited rectifier.
It wouldn't happen if rectifier was open circuit.
Battery has been fitted backwards at some point

 

[Red Fthr]

What do you mean, "fitted backwards"

Probably going to get in the garage today to try out some stuff.

 

[Sonreir]

Positive to negative and vice versa.

 

[Red Fthr]

Unless the person before me weird the positive and negative with the wrong cables. Couldn't hurt to reverse it. Haven't had a chance to get back in the garage but I'll be there tomorrow.

 

[crazypj]

Doesn't need any 're-wiring', battery will fit either way round and cables will be forced to fit.
I've seen it happen way too many times.
You need to test rectifier

 

[Red Fthr]

My positive terminal leads to the fuse, to the main switch (red) which is a toggle switch, and to the rectifier (red and white). I had tested at the rectifier and it was the same weird results.

 

[crazypj]

Test rectifier out of circuit (disconnect all the wires and test as per manual)