Weak charging system or mechanic with weak skills?

gruvola

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Greetings! I did a frame off resto on this about 5 years ago. Carbs and ignition run beautifully (both are original). But, been chasing charging system gremlins pretty much this bike's life before and after, able to ride 20-30 miles but battery drains. Embarrassed how many parts I've thrown at it. Here's the short version. Stator resistance 0.6 ohms on each of the three pairs, but showing only 20 ohms resistance on each wire to ground (which is weird - would have guessed either shorted or much more). Stator/charging test while running shows AC voltage consistent for each pair, starting below 10 volt AC at idle and climbing to 20 volt AC at 3k rpm (above 3k, it did the center stand scoot and I couldn't hold on to it!).

Battery is older but checks out with load test, etc. Voltage across battery is about 13 fully charged, drops to 12.75 with key and headlight on. Starts fine. Then sometimes, it will hold voltage about 12.5 at idle and then jump to 14 at 3k intermittently. But often voltage jumps badly or never climbs above 13. Importantly, I found I had a short in my negative battery cable which I replaced. Did this knock out the reg/rect?

So . . . Do I have a short between the stator and ground (all three stator wires to ground are only 20 ohm to ground)? Are the rotor and/or stator compromised? Do I spring for (yet) another reg/rect, suspecting I fried it due to the bad ground? Or, do I go all Hugh's hand built up on the deal?

Any help is appreciated. Be kind, I'm no genius.
 

Jim

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Nice lookin' bike... and welcome to the forum!

.6Ω 'tween the 3 stators leads is good. I'd suspect your 20Ω to ground reading, as you wouldn't get 20Vac on each lead revving it if you in fact had 20Ω to ground. You can double check, but I suspect your stator is good. The OEM ones are pretty well bullet proof.

Shorts are when power (inadvertently) goes to ground. So by definition your negative lead can't short to ground.... it is the ground.
With voltage jumping around like you describe, I'd suspect the regulator. You said you replaced it. Did you replace it with a stock mechanical regulator, or a newer solid state one?

And just to repeat.... nice bike!!
 

magoo66

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Greetings! I did a frame off resto on this about 5 years ago. Carbs and ignition run beautifully (both are original). But, been chasing charging system gremlins pretty much this bike's life before and after, able to ride 20-30 miles but battery drains. Embarrassed how many parts I've thrown at it. Here's the short version. Stator resistance 0.6 ohms on each of the three pairs, but showing only 20 ohms resistance on each wire to ground (which is weird - would have guessed either shorted or much more). Stator/charging test while running shows AC voltage consistent for each pair, starting below 10 volt AC at idle and climbing to 20 volt AC at 3k rpm (above 3k, it did the center stand scoot and I couldn't hold on to it!).

Battery is older but checks out with load test, etc. Voltage across battery is about 13 fully charged, drops to 12.75 with key and headlight on. Starts fine. Then sometimes, it will hold voltage about 12.5 at idle and then jump to 14 at 3k intermittently. But often voltage jumps badly or never climbs above 13. Importantly, I found I had a short in my negative battery cable which I replaced. Did this knock out the reg/rect?

So . . . Do I have a short between the stator and ground (all three stator wires to ground are only 20 ohm to ground)? Are the rotor and/or stator compromised? Do I spring for (yet) another reg/rect, suspecting I fried it due to the bad ground? Or, do I go all Hugh's hand built up on the deal?

Any help is appreciated. Be kind, I'm no genius.
What a fine looking motorcycle.No shame in wanting to learn at any age.Very knowledge sharing group here always very helpful. I’m not electrical savvy but Jim and others are.Welcome and best wishes solving your problem .
 

gruvola

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Thanks for the reply Jim! I replaced the original regulator and rectifier with a solid state one during my embarrassing barrage of parts buying. I've attempted to use the original 50 year old rectifier and regulator, but have similar results.

As for the bike, it is a long story. But I had a lot of help from some amazing friends when I lived in Minneapolis and River Falls, WI. A community effort for sure.
 

Jim

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Don't know what or where your reg/rec is from, but to be honest, I don't trust any of the aftermarkets.
Build your own and at least you'll know it's a good one. This is from TECH. Your bike uses a type B regulator, so you'll want to pick it up at comment# 2.
Not saying it'll fix your problem, but if it's built right, you can at least eliminate that as a cause.

https://www.xs650.com/threads/diy-reg-rec-5twins-and-jim.55842/
 

Melnic

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The stock regulator is a step regulator that puts a series resistance to the Rotor when the voltage to it exceeds a set voltage. It has a screw adjustment on it. Its possible that when it steps up the resistor is open circuit and thus when riding it will actually drain, But if that was the case, it should start to charge again when the voltage drops.

Testing bridge rectifier

another good video , Regulator test @ 9:56
 

Jan_P

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CSF rule --- cheapest simplest first
Service the connectors and brushes charging circuit. Scrape clean and contact grease at connectors
Check so pins are sitting right
Right screws at the right place n brush holder
Check so the fuse sits properly.
Then wires in charging circuit.
I assume there is a Voltmeter installed so the jumping Voltage is out on the Road .If Not I would install one at least temporarily

The stock regulator and rectifier in my view has the advantage that there exist routines for testing them in Service Manuals to be found online
And are more robust should something else be a problem.The regulator can be adjusted.
So when looking for problems I would use them ( With a Voltmeter installed so it don't go to high )
And then go electronic when the problem is found and corrected which have a better regulating capability
Since you have tried 2 setup Reg / Rec first assumption it is not there

Stator can go bad but rotor is much more common i guess 5--10 x 1
If i recall right there are Service instruction s for both rotor and stator .Which can be measured Cold at the same time when the connectors are serviced .
Perhaps it is possible to verify stator via those service instructions --that was how i Foumd my defect stator .
And rotor 3 times slip ring resistance
 

gruvola

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Update: Well, I've had an adventure the past few days afterwork. I found several things.
- the rotor was indeed bad, but it wasn't just resistance (about 2 ohms). It appears the brush mounting screws on the new OEM style stator were slightly too long and dug a groove in the new OEM style rotor!!! I had the original 50 year old rotor (measures 5+ ohms) and new brushes. So I replaced those, grinding down the brush mounting screws a bit and checking for clearance on the rotor.
- the new stator is fine. although resistance is 0.7 instead of 0.8, it's very consistent between pairs and the manual shows 0.8-1.0 in one place and 0.6 in another - so . . . I agree with Jim and Jan, it's probably fine
- I tested the rectifiers, both in the new reg/rec unit I bought and the original one, and was surprised to find both spec'd out fine. (thanks for the video link Melnic)
- I tested the original regulator and found the resistance in all three positions to be spot on. I cleaned it up good with contact cleaner.
- After reinstalling the rotor, stator, and brushes, decided to try the new solid stat reg/rec and it shot up to about to about 15 volts on idle and 18 volts at 3k rpm. it was reasonably stable, but too high.
- I took a shot and put on the old regulator and and rectifier and it sat at 12.5 volts at idle and 3k rpm. But, I remembered it had a screw to set voltage. I turned it about 1-1.5 turns and bam, it was 13.4 at 1k and sits at 15.2 at 3k!

So, I think everyone who gave advice was right about something. Stator is good, rotor was bad, both rectifiers were good, both regulators weren't working right. But, I could clean and adjust the old regulator. I reinstalled three 50 year old electronic parts and now it works. Wow.

The only remaining question I have is this. Voltage does jump around a bit, ranging from 13.1 to 13.6 or so at idle and 14.5 to 15.4 or so at 3 k rpm. But it doesn't exceed 15.5 even when I rev it. It bothers me a little because I'm used to my modern bikes holding voltage at 14.2 like a rock. Am I expecting too much? Or could I still have a loose connection? (by the way, the entire wiring harness is new . . . but new isn't everything)
 

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Jim

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The only remaining question I have is this. Voltage does jump around a bit, ranging from 13.1 to 13.6 or so at idle and 14.5 to 15.4 or so at 3 k rpm. But it doesn't exceed 15.5 even when I rev it. It bothers me a little because I'm used to my modern bikes holding voltage at 14.2 like a rock. Am I expecting too much? Or could I still have a loose connection? (by the way, the entire wiring harness is new . . . but new isn't everything)
You turned the screw in too far. 15.4v is about a volt too much. You went in a turn and a half, so turn it back out half that and see where you're at.
 

Jim

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because I'm used to my modern bikes holding voltage at 14.2 like a rock. Am I expecting too much?
Sorry, just noticed this question....
Yes, you are. At idle, a perfectly good XS can actually discharge the battery slightly. For example, I can show 12.7 on the battery with the bike off. At idle that will be about 12.3.... 12.5v. It's just it's nature, the rotor magnet isn't strong enough to give any more than that at low rev's.
 
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Jan_P

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You turned the screw in too far. 15.4v is about a volt too much. You went in a turn and a half, so turn it back out half that and see where you're at.

Yes to that .. A bit to high ... I Would adjust + Consider a new electronic setup with separate Regulator and Rectifier as per advice here on the forum.
Not expensive and gets the charging spot on.
I Have had the stock regulator ..showing fine specs cold and charging right cold But go ballistic at warm days high temperature upsetting the Boyer Bransden ignition ( Or shorting somewhere )
 

wildav

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Update: Well, I've had an adventure the past few days afterwork. I found several things.
- the rotor was indeed bad, but it wasn't just resistance (about 2 ohms). It appears the brush mounting screws on the new OEM style stator were slightly too long and dug a groove in the new OEM style rotor!!! I had the original 50 year old rotor (measures 5+ ohms) and new brushes. So I replaced those, grinding down the brush mounting screws a bit and checking for clearance on the rotor.
- the new stator is fine. although resistance is 0.7 instead of 0.8, it's very consistent between pairs and the manual shows 0.8-1.0 in one place and 0.6 in another - so . . . I agree with Jim and Jan, it's probably fine
- I tested the rectifiers, both in the new reg/rec unit I bought and the original one, and was surprised to find both spec'd out fine. (thanks for the video link Melnic)
- I tested the original regulator and found the resistance in all three positions to be spot on. I cleaned it up good with contact cleaner.
- After reinstalling the rotor, stator, and brushes, decided to try the new solid stat reg/rec and it shot up to about to about 15 volts on idle and 18 volts at 3k rpm. it was reasonably stable, but too high.
- I took a shot and put on the old regulator and and rectifier and it sat at 12.5 volts at idle and 3k rpm. But, I remembered it had a screw to set voltage. I turned it about 1-1.5 turns and bam, it was 13.4 at 1k and sits at 15.2 at 3k!

So, I think everyone who gave advice was right about something. Stator is good, rotor was bad, both rectifiers were good, both regulators weren't working right. But, I could clean and adjust the old regulator. I reinstalled three 50 year old electronic parts and now it works. Wow.

The only remaining question I have is this. Voltage does jump around a bit, ranging from 13.1 to 13.6 or so at idle and 14.5 to 15.4 or so at 3 k rpm. But it doesn't exceed 15.5 even when I rev it. It bothers me a little because I'm used to my modern bikes holding voltage at 14.2 like a rock. Am I expecting too much? Or could I still have a loose connection? (by the way, the entire wiring harness is new . . . but new isn't everything)
As a mechanic friend commented one day after returning bad parts to the store,"New means new, it doesn't necessarily mean good". Beautiful bike btw.
 

Melnic

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Yes to that .. A bit to high ... I Would adjust + Consider a new electronic setup with separate Regulator and Rectifier as per advice here on the forum.
Not expensive and gets the charging spot on.
I Have had the stock regulator ..showing fine specs cold and charging right cold But go ballistic at warm days high temperature upsetting the Boyer Bransden ignition ( Or shorting somewhere )
This is what pushed me to the VR115 because the regulator is a coil and spring (the adjustment screw sets spring tension). When I found that out and noticed mine was set to switch fully at 16.5V, I ditched it for the VR115 cause I knew coils can weaken over time and the temperature sensitivity would affect the spring. Im sure new, Yamaha set them at a level on the bench before installing that would be safe across a wide temperature range. Who knows what that level was and likely only setting it on a bench w/ a variable power supply would be the way to do it (like I did when I figured out my switching voltage was too high). The VR115 I "think" monitors the battery voltage output in order to keep the rotor coil at the proper voltage to limit the output. Well, that is how I would have done it. the Original Regulators only switched to add more resistance when the voltage was high enough and that is a step function, not a variable function. I'd even look at what the battery voltage is at 5K rpm if you like to highway ride.
 

5twins

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The VR115 is definitely the way to go. If you have an on-board voltmeter you can watch while riding, you would probably discover, as I did, that the output from that old mechanical regulator isn't as steady as you think, lol. Mine would randomly drop off at higher RPMs where it should have been giving me full output. I came to the conclusion that the vibration levels at certain higher RPMs were effecting the contacts inside that old mechanical unit and throwing it's output off. I figured this unnecessary ramping up and down of the charging output was working the alternator harder than need be and was the big reason I switched. The VR115 gives me a nice, steady 14.2 or 14.3 output, maybe a couple tenths higher in cold weather. But the other thing I like about the VR115 is it reduces the output a little once the battery is charged up. After electric starting and I've ridden a few miles, enough to replenish the battery, the output drops a few tenths, to around 14 or the high 13s.

Since you're sticking with the original regulator for the time being and aren't in a rush, watch eBay for a VR115 or it's equivalent. So far, that's where I've gotten all mine, and for a good price, like $10 to $15.
 

Melnic

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Now that you made that adjustment, what is the battery voltage at 3K, 4K RPM? What RPM will you cruise at?
 

gruvola

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Hey Melnic, It's running right around 13.5 at idle to 14.5 at 4k. and reasonably consistent. I bought everything I need for described reg/rectifier y'all described. Haven't had time to put them together yet. But, I'm feeling pretty good about it all.
 

Kevin Werner

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Did you installa volt meter on the bike? I have seen them at $8 but captured this quickly. They are light weight, attach with tape or velcro and let you know your system is working. You can wire it ino your headlight shell easily.
1703346687315.png
VM.jpg
 
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