Topic: 1980 CB650 charging issues

[Mentch171]

Hello. First post here looking for some help. I’m currently working on a neighbor’s CB650 with an electrical issue. I’ve Googled, read, searched and completed some of the recommended tasks but I’m thinking I still have a problem with this bike. The bike is in incredible condition, well cared for and ridden occasionally. Recently the battery has been dying on the owner during rides and won’t start without a jump or fresh charge on the battery.  The owner replaced the battery with a new lithium battery but it still dies after awhile.  I read about the common rotor problem, tested it to only 1 ohm and replaced it with a new unit and had him try it for a bit before going further. Same results, died after not too long. I got a new regulator and before replacing I tested voltage at the battery. Key on 12.8 v, running at idle 12.7 and 13.1 at 5000rpm. I have pretty much the same results with the new regulator installed. The stator tests continuous across the yellow leads and open to any ground. What can I do next?  Thanks in advance.

[Mentch171]

Update.
Key off 13.1v key on, 12.8-12.9v, idle 12.7v at idle 13.1v at 5000rpm with new regulator installed. Going to test voltage on three yellow wires while running next.

[Mentch171]

Update #2
No voltage from any yellow leads with the bike running. Stator tests ok according to Honda shop manual procedure though. Stator looks a little burned out to me.

[TwoTired]

Can you confirm the brushes are actually delivering voltage to the rotor.  Should do so even if not spinning.
The rotor makes the magnetic field.  No magnetic field and the stator won't make any voltage.

Cheers,

[Mentch171]

I didn’t think of that. How do you test power in the brushes?

[Bodi]

Easiest quick test is to hold a steel tool against the alternator cover, you should feel some magnetic pull towards the cover with key on.
- Measure voltage at the brush wires. They should be easy to find but I haven't looked at an '80 650 in many years. They will go from the engine plug to the alternator: it has 3 yellow wires (output) and two others, probably white, to the brushes and eventually to rotor.

[Mentch171]

I have 0.6v on one brush and 12.6v on the other.

[TwoTired]

So, you have 12v being delivered by the vreg to brushes.
And, 0.6v error in your battery neg green wire distribution?  I can only guess as you don't explain where you've placed the meter probes.

Disconnect the vreg, and measure the rotor resistance at the disconnected vreg terminal wires.

If you apply 12v to a known good rotor resistance, current must flow and thereby create a magnetic field in the alternator.

Cheers,

[Mentch171]

Negative probe on negative battery terminal positive probe to each brush one at a time. 12.6v on one brush, 0.6 on the other.

[TwoTired]

Negative probe on negative battery terminal positive probe to each brush one at a time. 12.6v on one brush, 0.6 on the other.

Kinda figured that was the case.
Makes you wonder where the 0.6v went.  ( wiring/ connector corrosion)
It's not a show stopper though.
Measure the rotor resistance from the viewpoint of the vreg.

Cheers,

[scottly]

Kinda figured that was the case.
Makes you wonder where the 0.6v went.  ( wiring/ connector corrosion)

Lloyd, remember that the 650 solid-state regulator controls the negative side of the field coil, and that solid-state regulators always have some voltage drop.

[TwoTired]

Thanks for the reminder.

Cheers,

[Mentch171]

Measure the rotor resistance from the viewpoint of the vreg.

Cheers,

8.8 ohms at the vreg 5 pin plug, measured across the black and white wires.

After a little bit of warm up I see 10.0 ohms measured the same way.

[Mentch171]

I have 12.2v on the black wire out of the vreg. What should I see in the white wire?  I only have 0.69v. These are the two wires sending voltage to the brushes, correct?

[TwoTired]

8.8 ohms is a little high.
Did you subtract out the meter's test lead resistance?

Has your rotor's slip rings been cleaned?

To your question, the vreg varies the white wire voltage when it wants to turn down the alternator power out.  The white wire voltage will raise to that closer to the black wire voltage.  When both wires are the same voltage the alternator output would be nil.  When the two black and white wires are the most different in value, the alternator output should be at maximum.


Given the readings you've reported, the rotor should be making a magnetic field.  When the rotor spins, the mag field alternates north and south poles, and any wires in the vicinity (stator), should have a voltage induced in them, allowing voltage and current to be available on the three yellow wires.  This will be AC voltage that the rectifier will convert to DC for use by the bike's battery and systems.

The AC voltage will not be reference to any bike ground for measurement purposes.  Measure AC voltage between the yellow stator wires with meter probes.

Have you tested the rectifier diodes yet?  If these are open or otherwise damaged, the AC to DC conversion can't properly occur.

Cheers,

[Mentch171]

8.8 ohms is a little high.
Did you subtract out the meter's test lead resistance?

Has your rotor's slip rings been cleaned?

To your question, the vreg varies the white wire voltage when it wants to turn down the alternator power out.  The white wire voltage will raise to that closer to the black wire voltage.  When both wires are the same voltage the alternator output would be nil.  When the two black and white wires are the most different in value, the alternator output should be at maximum.


Given the readings you've reported, the rotor should be making a magnetic field.  When the rotor spins, the mag field alternates north and south poles, and any wires in the vicinity (stator), should have a voltage induced in them, allowing voltage and current to be available on the three yellow wires.  This will be AC voltage that the rectifier will convert to DC for use by the bike's battery and systems.

The AC voltage will not be reference to any bike ground for measurement purposes.  Measure AC voltage between the yellow stator wires with meter probes.

Have you tested the rectifier diodes yet?  If these are open or otherwise damaged, the AC to DC conversion can't properly occur.

Cheers,

I did not subtract the test lead resistance.

New rotor so the slip rings should be clean.

I'm only seeing 12v ac on the yellow wires.

I'll check the rectifier. I have the original, which I assumed was bad after changing the bad rotor, and a brand new one.

[TwoTired]

Do you know if the new rotor had a protectant applied to the rings for storage or shipment?

Did you clean it before installation?

Cheers,

[Mentch171]

Just sanded the slip rings and also cleaned with a bit of brake cleaner. No change of AC voltage on the yellow wires. Still about 12.5 v AC.

Can you give me a rundown on testing the regulator/rectifier?  The manual I have and my test results aren’t jiving. Maybe I’m testing wrong.

[TwoTired]

There are six diodes between each yellow and red and green respectively.
Use the diode test function on your multimeter, and probe each yellow to green, and then each yellow to red.  Repeat the testing with the probe leads reversed.
12 tests.  One polarity should show no conduction, the opposite polarity should show conduction.  Depending on the meter design specifics, it may show the actual forward bias voltage drop in the range of 0.6 to 0.7 V.  The opposite polarity ought to show infinity indication.

Cheers,

[Mentch171]

Ok. Both R/R’s test the same.

Black probe on green, red probe on yellows.
No conduction.

Black probe on red, red probe on yellows.
0.547
0.523
0.530

Red probe on green, black probe on yellows.
0.536
0.534
0.536

Red probe on red, black probe on yellows.
No conduction.

[TwoTired]

If i interpret your report correctly, six tests no conduction six tests with conduction is the result desired for a three phase rectifier.

Cheers,

[Mentch171]

That’s what I thought too but this is out of my usual area of expertise. That’s why I appreciate all your help here so far. What’s next?  The new rotor tests good. Could it be bad?  The stator also tests good but could it be bad? 

[bryanj]

If you can bypass all the reg wiring and put 12v direct to the brushes and you then get AC out on each pair of yellows both rotor and stator are good

[TwoTired]

How did you "test" the Stator?

If all the major charging system components are indeed "good".  That only leaves the interconnect wiring.

Cheers,

[Mentch171]

If you can bypass all the reg wiring and put 12v direct to the brushes and you then get AC out on each pair of yellows both rotor and stator are good

I do have 12v at the brushes but I have little AC voltage coming back out to the rectifier.