Rewound Alternator Rotor gouges, trouble shooting charging system.

[75XSFLORIDA]

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

Got it!
So I just took her on a 10 minute ride and no matter how high revved the engine, no matter what gear I was in, the most I would see across the voltmeter was 14.9. That’s with the headlight OFF….So it looks like everything is spot on now.

 

[75XSFLORIDA]

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

Shes resting now and outta surgery!

Heres my lil 66 S65 that i fully rebuilt a month ago! Runs like a dream. One kick bike.

 

[magoo66]

Are you going back to original wheels and exhaust on your 75b or leaving those mags and exhaust on it?Just curious.

 

[75XSFLORIDA]

Are you going back to original wheels and exhaust on your 75b or leaving those mags and exhaust on it?Just curious.

Well if I had the original I may. But I don’t. These are Morris mags. Period correct for the mid 70s and this is a hooker exhaust, headers and muffler. A lot of people confuse these wheels with the XS special wheels, but they are not…. I’ve never seen Morris mags with a rear disc on an XS… the rear caliper bracket is for the Yamaha STAR wheel that they made back then so everything is OEM in the rear.

 

[75XSFLORIDA]

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

Yep. Aware of that test and yes it does!

 

[magoo66]

Well if I had the original I may. But I don’t. These are Morris mags. Period correct for the mid 70s and this is a hooker exhaust, headers and muffler. A lot of people confuse these wheels with the XS special wheels, but they are not…. I’ve never seen Morris mags with a rear disc on an XS… the rear caliper bracket is for the Yamaha STAR wheel that they made back then so everything is OEM in the rear.

Thank you

 

[Jan_P]

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)

AMEN and a rectifier also .recommendation given 3 x by 3 different Senior Enthusiasts ( Or more )

 

[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)

JP,

I contacted the company that makes this solid state unit i was using that we all agreed is bad and this is what they said below…didnt you have me do this test already? Can you explain how to do this brown wire test again without buke running?? I want to see this .08v difference between brown wire at regular and voltage at battery like this guy is saying exists.

Heres what he said:

“The mid-15s you see in charging is too high, but is not due to a broken reg/rect. If the regulation circuit were to break the voltage would be unchecked and should go up into to 18+ range. What you have is a working regulator that is getting bad information from the bikes wiring harness. If you go and turn the ignition key on, keep the motor off, and measure the voltage at your battery and then compare to voltage present on the brown wire going into the reg/rect you will find about a 0.8v difference. This should not exist and if left unaddressed will lead to your electrical system failing. The brown wire carries power into the reg/rect but that power's function is not to run anything but give information to the reg/rect on what the voltage at the battery currently is. Because of the voltage drop the reg/rect see the battery at about .8v lower than it really is, and thus overcharges by .8v. You have to fix the voltage drop or you will ruin your electrical system, the OEM mechanical unit will soon overcharge also if this is left in addressed.

Thank you,

Kyle Wood - Sales Manager”

 

[75XSFLORIDA]

Yep, I only had half the question - GLJ has the complete question: overcharging can be low voltage on the brown (from drop at the switch (etc) per Gary) but also can be a bad ground to the regulator. It's not well discussed in newer manuals, but here's two references to "excessively high voltage" in older manuals relating to the "black wire"
View attachment 239104
3) Hook up an ohmmeter, (U,-.,LU onms1, one prooe

attached to the black wire and one probe to the regulator base. It must read zero ohms resistance.

Several ohms resistance indicates a frayed or broken black wire.

NOTE: Voltage output will be excessively high if this black wire is broken anywhere between the

regulator and the stator.

OR.....it could just be a junk new regulator

I think i have this ohms test correct that you had me do at one point and that that guy is also saying to do…ignition on bike not running, one probe touching brown on regulator and the other probe touching ground on the battery….i get 11.67v.
Then just a simple battery voltage test showed 12.25v….. they should be almost the same correct? This is a huge difference. See pics

 

[75XSFLORIDA]

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

This is where i am now.
This is with old mechanical regulator

 

[75XSFLORIDA]

View attachment 239103
Do this test and lets see if the regulator is seeing the same voltage as the battery has.

Test WITHOUT bike (switch on, bike not running) running shows regulator does not see same voltage as battery. See pics

 

[GLJ]

Test at the regulator again this time move the black probe to the black wire going to regulator.
Keep red probe on the brown wire.

 

[75XSFLORIDA]

Test at the regulator again this time move the black probe to the black wire going to regulator.
Keep red probe on the brown wire.
View attachment 239181

With key still on correct??
So what about the last test, explain the variance.

 

[75XSFLORIDA]

Test at the regulator again this time move the black probe to the black wire going to regulator.
Keep red probe on the brown wire.
View attachment 239181

Ok here we are….black probe to black wire, red probe to brown wire….11.63v

 

[gggGary]

Hate to be an echo, but; there's a good chance that voltage drop you are seeing is occurring in the ignition switch.
What the tech says is EXACTLY why I was TRYING to get you to R&R your ignition switch.
But I'm just a dummy.
You can check the voltage drop directly; With the switch on, put the probes on the red and brown wires at the ignition switch (or it's connector inside the headlight bucket). The reading will be the voltage drop across the switch contacts.

With it running connect a jumper wire from battery +12 terminal to the brown wire at the voltage regualator connector, see what the output is then. if it's now below 15 volts go look at the iggy switch, if its still high the problem is the regulator.
@75XSFLORIDA

 

[75XSFLORIDA]

Hate to be an echo, but; there's a good chance that voltage drop you are seeing is occurring in the ignition switch.
What the tech says is EXACTLY why I was TRYING to get you to R&R your ignition switch.
But I'm just a dummy.
You can check the voltage drop directly; With the switch on, put the probes on the red and brown wires at the ignition switch (or it's connector inside the headlight bucket). The reading will be the voltage drop across the switch contacts

Ill do that, but is a 0.58 voltage drop all that significant?

 

[75XSFLORIDA]

Hate to be an echo, but; there's a good chance that voltage drop you are seeing is occurring in the ignition switch.
What the tech says is EXACTLY why I was TRYING to get you to R&R your ignition switch.
But I'm just a dummy.
You can check the voltage drop directly; With the switch on, put the probes on the red and brown wires at the ignition switch (or it's connector inside the headlight bucket). The reading will be the voltage drop across the switch contacts

So however large the drop is, is equal to how large the overcharging margin is right? So when i see voltmeter at 14.5v when revving hard and riding, that really is15v cause my drop is 0.5 correct??

 

[GLJ]

Ok here we are….black probe to black wire, red probe to brown wire….11.63v

That checks to see if there is any volt drop on the ground side of the circuit. Ground looks ok.

 

[gggGary]

There will be some drop. It's a long wire carrying a load, the rotor winding draws 27 watts the coils and taillight are on that circuit too. so maybe 5 amps total.

 

[gggGary]

When testing OEM solid state rectifier/regulators by plugging several into the harness of one bike and checking output at 3,000RPM I would find outputs ranged from ~ 13.5 to ~14.8 volts on different "working" regulators.