Rewound Alternator Rotor gouges, trouble shooting charging system.

[75XSFLORIDA]

Replacing the rotor and 15.4 volts now prove 1 thing. The old rotor was bad.
15.4 volts at the battery also proves you are not regulating the rotor correctly. 15+ volts will cook a battery.
Sounds like you have a wiring problem also.

I would check what the voltage is between the brown and black wires are at the regulator and between the brown at the regulator and ground at the battery post when the bike is running at 3000.

I wonder what the voltage on the brown wire @ the regulator plug is

I just checked the brown and black wire with the regulator plugged in at the regulator and I’m getting the same voltage when revving, 15 to 15.3. I then checked the brown wire to the ground on the battery and I’m getting the same reading, low 15’s….where are we now?

 

[gggGary]

............That would cause my crazy voltage issue would it??.........

The handle bar ground won't change the charging voltage. It would affect electric start and horn buttons.

...................... did not take the ignition switch apart though.

Keep going...

 

[gggGary]

I just checked the brown and black wire with the regulator plugged in at the regulator and I’m getting the same voltage when revving, 15 to 15.3. I then checked the brown wire to the ground on the battery and I’m getting the same reading, low 15’s….where are we now?

Pointing at a failed regulator, try old mechanical one, you can leave the modern rectifier section (the plug with three white wires) in the circuit.

 

[75XSFLORIDA]

Pointing at a failed regulator, try old mechanical one, you can leave the modern rectifier section (the plug with three white wires) in the circuit.

Guess what? Exactly correct. With the old mechanical regulator plugged in and the old rectifier plugged in guess what my charging volts are now, 14.5 to 14.7v max and this is probably at 4000 RPMs….. so it looks like all components of the charging system were fine from the BEGINNING, and it was just a failed rotor!

 

[jpdevol]

And....you have a new regulator that is out of spec (bad)

 

[gggGary]

Send rotors to Jim and mail me a check.

 

[75XSFLORIDA]

Send rotors to Jim and mail me a check.

Love you Gary

 

[gggGary]

all components are the charging system were fine from the BEGINNING, and it was just a failed rotor!

Again; TWO rotors going open circuit is
(very) unusual.
Don't assume you are done yet. But hey it's working, so a ride while watching your handlebar mounted voltmeter should be fine to try.

 

[gggGary]

The rotor in the bike now is a 50 year old, used part. Old rotor coil insulation being brittle and failing from vibration/fretting is a known issue.

 

[75XSFLORIDA]

Again; TWO rotors going open circuit is
(very) unusual.
Don't assume you are done yet. But hey it's working, so a ride while watching your handlebar mounted voltmeter should be fine to try.

I agree!
I’m wondering if I should turn up the regulator a tad. At like 2500 to 3000 RPMs im probably 13.6 or 13.7 ….if I rev to roughly 40000 RPMs I’m a tad above 14…. My tach doesn’t work very well and is very sticky so I’m gauging all of this off of the engine sound. If I do need to turn it up I know I turn the screw in clockwise correct?? Can I do this with the regulator cover off with the bike running?

 

[jpdevol]

Note, this is just one opinion: given previous issues and the fact that you're getting variable readings from the old regulator - 13.8V was the reading you had before last failure - I would not run it long and monitor with onboard voltmeter until you get a solid state regulator that is in spec..

However, here's the drill from '75 Manual:

I'd want it as above, but with 14.2-14.5VDC (not 15)

 

[75XSFLORIDA]

Note, this is just one opinion: given previous issues and the fact that you're getting variable readings from the old regulator - 13.8V was the reading you had before last failure - I would not run it long and monitor with onboard voltmeter until you get a solid state regulator that is in spec..

However, here's the drill from '75 Manual:
View attachment 239132
I'd want it as above, but with 14.2-14.5VDC (not 15)

It’s just hard to say with the accurate voltagesare, and here are a couple reasons why. For one, the handlebar voltage meter is not instant, meaning, as soon as I snap the throttle back, it takes a few seconds for the volts to catch up with the actual reading. Two, If I stick probes on the battery terminals and rev the bike, it’s a little jumpy on the actual voltmeter thats in my hand as well. … three, my tach is not working very good so it’s hard to see what rpm im at…But what I do know is if I rev the bike very high probably around 4000rpms, the max volts i see is probably 14.5…And I think we all can agree that 4000rpms is about normal crusing speed on these. That being said, as long as I am in the 14v range (give or take .3-.5) at this RPM, I think the battery will charge ffine.

 

[75XSFLORIDA]

Note, this is just one opinion: given previous issues and the fact that you're getting variable readings from the old regulator - 13.8V was the reading you had before last failure - I would not run it long and monitor with onboard voltmeter until you get a solid state regulator that is in spec..

However, here's the drill from '75 Manual:
View attachment 239132
I'd want it as above, but with 14.2-14.5VDC (not 15)

Maybe the reason it’s not at 14 V at 2000 and 3000 RPMs is because I need to turn the screw in. That’s what I was asking on my last post. Maybe I should do this a tad and see what happens. You didnt address that with your response.

 

[joebgd]

Wow!
I didn't read the entire thing after ab pg idk 5 or 8 I skipped to last pages.
Also, I don't think I ever known of so many people knowing how to communicate so well. All of government should have an xs650. We seem to act like adults on an average way above the general public. Lol

 

[gggGary]

If it goes above 14 volts at higher RPM then my best guess is it's putting out AS MUCH AS IT CAN at lower RPM so adjusting the screw won't have an effect.
The laternator cannot put out more than IIRC 200 watts. Loads; ignition, the rotor, charging thre battery, lights all are drawing against the output.
Go for a ride around the area see how it does I suspect it will stabilize over 10 to 15 minutes of riding. You are using lots of battery charge with starting shutting off restarting etc. Go ride for a bit. Report back.

What headlight bulb to you have? The wattage is stamped on the back of the reflector. Many bulbs are higher watts than the original 40 watt on low 50 watt on high bulb. This would have an effect on voltage at lower RPM.

 

[75XSFLORIDA]

Note, this is just one opinion: given previous issues and the fact that you're getting variable readings from the old regulator - 13.8V was the reading you had before last failure - I would not run it long and monitor with onboard voltmeter until you get a solid state regulator that is in spec..

However, here's the drill from '75 Manual:
View attachment 239132
I'd want it as above, but with 14.2-14.5VDC (not 15)

Well, I just turned the adjustment screw about slightly less than a quarter turn in and everything looks beautiful now as far as the volts. Right at about 13.8 to about 14.6 when revving as high as I can pretty much, probably close to 5000rpms…. When at about about 3000. I’m right at about 14 V… also, it’s just as accurate to hold probes on the multimeter when I’m revving the bike, correct?? Dont have alligator clips at the moment

 

[75XSFLORIDA]

If it goes above 14 volts at higher RPM then my best guess is it's putting out AS MUCH AS IT CAN at lower RPM so adjusting the screw won't have an effect.
The laternator cannot put out more than IIRC 200 watts. Loads; ignition, the rotor, charging thre battery, lights all are drawing against the output.
Go for a ride around the area see how it does I suspect it will stabilize over 10 to 15 minutes of riding. You are using lots of battery charge with starting shutting off restarting etc. Go ride for a bit. Report back.

What headlight bulb to you have? The wattage is stamped on the back of the reflector. Many bulbs are higher watts than the original 40 watt on low 50 watt on high bulb. This would have an effect on voltage at lower RPM.

Original 40w…. but the thing is I don’t even ever cut the headlight on and I never ride at night so that’s pretty much a moot point.

 

[gggGary]

Yes those digital volt meters do a have a bit of lag designed in. That's normal.
If you can keep the VOM probes in contact by hand that's fine.
Cleaning your ignition switch contacts inside should remain on your todo list. Water gets in at the key slot and goes down to the contacts, any origianl grease is now old and dirty the copper gets corroded 'specially in Fla. The switch is not super hard to R&R work over a cookie sheet so any small parts don't get lost while you're working.
A how to;
https://www.xs650.com/threads/ignition-switch-overhaul.46712/
your 75 will be very similar inside

 

[gggGary]

is I don’t even ever cut the headlight on

You actually should use it, unless doing extended low speed/ idling. The headlight is a constant load, helps keep voltage steady, especially with those mechanical regulators, and being seen ('specially in FLA!) is kinda important.
Good luck.

 

[Rasputin]

Havent checked ohms on slip rings yet. Yea maybe from washin bike water sits in there and corrodes over time. The thing is when I rev the bike till about 3000 RPMs or even more, the battery voltage never goes higher than 12.4. To me that seems like a bad rectifier. If the rectifier was good it would be charging the battery upon revving the bike right??

Acid test. Turn on the headlight and observe, does it get brighter when you raise the RPM? If so it’s charging.