Charging Issue: Help with Findings from Curly's Troubleshooting Guide

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browndawg

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Hi Guys,

I'm having a charging issue with my '81 XS650 Special. It began cutting out on me yesterday while riding. Came home and found the battery to be down to 8 volts, and the headlight is not brightening when bike is revved. I have begun going through Curly's charging tests (http://xs650temp.proboards.com/thread/3461), but I need a little help interpreting the results.

TROUBLESHOOTING STEPS:

1. First charge your battery to at least 12.5-12.7V. Charged battery up to 12.65V. Also had it load-tested at auto parts store and it checked out fine.

2. Slap-Test. Here things get strange. This morning it failed the test, no magnetism. A couple of hours later, it passed with flying colors, slapping wrench to case. Now, it is failing again. Don't know if this means something?

3. Bypass the regulator by jumping to ground. This caused no change in battery voltage when revving bike. When revved, battery stays at 12.4-5 volts. Also, headlight does not brighten.

4. Voltage at positive brush of alternator. Seems to be an acceptable voltage drop, still getting sufficient juice to positive brush: 12.65V (battery itself) --> 12.51V (red wire into keyswitch connector) --> 12.48V (brown wire coming out back of keyswitch connector) --> 12.51V (positive brush at alternator). These were measured key-on.

5-7. Stator Checks. About to continue with these, but had some questions first (below).

QUESTIONS:

1. Does my intermittent slap-test indicate anything important to you guys? It just seems like it might point to something obvious, but I'm not sure what.

2. For step 4, did I check the right wire to the right brush (see picture)? I couldn't find an actual brown or black wire, but what I checked looked close and gave me a logical reading of 12.51 volts.

3. The copper wires in my alternator are black with grime. You cannot even tell they're copper--that's how blacked they are. Could this be an obvious part of my issue?

4. At the end of Curly's troubleshooting guide, he says "dirty connections and worn brushes account for most of the charging system problems." However, nowhere in the trouble-shooting guide do I see a step saying to check the brushes. Is this something I should do?

Thank you guys so much. I'm learning as I go with this bike, and I know next-to-nothing when it comes to electrical stuff. I just wanted to check with you guys and make sure I'm not missing anything obvious with my findings so far. The only thing remaining in Curly's guide for me to do are the stator checks.

Thank you again!
 

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Thanks! I'll check the brushes tomorrow. Strange that this isn't it in the troubleshooting guide, right?

Anything else stand out to you in terms of the other questions?
 
In your pic you have an arrow pointing to the slip ring on the rotor, This can be cleaned off with very fine sand paper or 40 steel wool. Easiest if you remove the engine cover and stator.
This and old brushes may be why you get intermittent magnetism.
On the wires the one you have an arrow to is the brown wire. It may look a bit red. The other wire is green. The green wire is the one you jump to ground for the bypass test.
On the battery voltage Check it with the key and engine stop switch in the run positions. This will be your reference voltage.
If the voltage at the brown wire to the brush is much more than .2 or .3 below the battery reference voltage, you have to much voltage drop. Most often in the key switch or engine stop switch. Both can be taken apart and cleaned.
Most anytime a bike develops charging issues, the first thing to check is the brushes. They are a wear item. If worn, replace. The guide assumes you did this.
Leo
 
Don't sand off the alternator windings. Not sure what to clean them up with if they need to be cleaned at all. Seems all mine have a grunge look to them but no issue with performance. I believe they're dipped at the factory like the rotors windings. The sliprings that Leo is talking about is what your brushes make contact with.
 
Thank you so much for the advice, guys! I'm going to check those brushes first thing after I get home from work today. I like to start with the simplest thing first, and in this case I totally missed doing that!

As far as the voltage drop, it seems like I'm in an acceptable range. My reference voltage (at the battery) is 12.65V, and the voltage at the brown wire is 12.51V -- so only a .14 volt drop.

Regulator seems to be good. I'm getting no voltage increase at the battery when jumping the green wire to ground there where it goes into the back of the plug at the regulator itself.
 
UPDATE:

I checked the brushes this evening:

--Right Brush: 10 mm
--Left Brush: 9 mm

So they're getting short, but not down to the 7 mm replacement minimum as yet. Here's the funny thing, though. Literally all I did was take the brushes out, measure them, then put them back in. And now the bike is charging! I'm reading 14+ volts off the battery when revving the bike!

Perhaps the brushes were not in there tight enough, or after reinstalling them they're making better contact? The Z brackets themselves seem a little weak/worn, the angles a little obtuse of 90 degrees, which may keep the brushes from fitting as close? In any case, I am going to order new ones.

Could this really be the issue, you think? Even with brushes at 10/9 mm length?
 
They maybe long enough but after 30 years under compression the springs maybe weak. This will keep them from pushing against the slip rings as well as new ones.
You might try stretching the springs a bit.
New ones don't cost much.
One thing some of us do is to unsolder the wire from the metal bracket. Drill a tiny hole just big enough for the wire then resolder the wire so it is below the metal bracket instead of on top. This makes it easier to install. While apart is a good time to stretch the springs a bit.
Also you can swap the brushes on the 80 up bikes inner to outer, and outer to inner. Do this every few thousand miles. This keeps them wearing at the same rate. The outer brush travels a longer path than the inner so it wears faster.
And yes this could be the issue. The brushes carry the current flow into and out of the rotor. If they are worn, weak or whatever they won't carry as much current. The current is what creates the magnetism. The stronger the current the stronger the magnetism.
That's why one of the tests is to find out if you have full voltage at the brushes. low voltage means low current.
Leo
 
TwoManyXS1Bs: wish I'd read that first thread before buying a new pair through Mikes!

Leo: thank you so much for the information. I may take out the old ones and stretch the springs while a wait for the new pair to come.
 
browndawg said:
2. Slap-Test. Here things get strange. This morning it failed the test, no magnetism. A couple of hours later, it passed with flying colors, slapping wrench to case. Now, it is failing again. Don't know if this means something?

QUESTIONS:

3. The copper wires in my alternative are black with grime. You cannot even tell they're copper--that's how blacked they are. Could this be an obvious part of my issue?
Click to expand...

To increase your research overload, and bump up the worry factor a notch, try a forum search on: "burnt rotor". It sounds like it may be going out.

You may want to remove the stator housing and view the rotor windings. Couple threads here (can't find them) give strong warning of impending failure if the rotor windings look burnt...
 
Oh boy, I better start looking into this, because my rotor windings look pretty damn toasted. TwoManyXS1Bs: no worries on adding to the "research overload"--I bought this bike largely as a learning platform!

If the bike quits charging on me in the meantime and I just need to limp home, I've read to disconnect the headlight and remove one of the brushes. Two questions:

1. Does it matter if I remove the left or right brush? Either is fine?
2. Why exactly does this help conserve battery power (sorry if this is a dumb question, just learning as I go)?
 
XSLeo said:
One thing some of us do is to unsolder the wire from the metal bracket.
Leo
Click to expand...

Leo what did you use to melt the solder? My 2 stage Weller wouldn't touch it.
I thought about one of those HF micro torches, but how much am I going to spend to save is a consideration for me.
 
browndawg said:
If the bike quits charging on me in the meantime and I just need to limp home, I've read to disconnect the headlight and remove one of the brushes. Two questions:

1. Does it matter if I remove the left or right brush? Either is fine?
2. Why exactly does this help conserve battery power (sorry if this is a dumb question, just learning as I go)?
Click to expand...

It's easier to just unplug the rectifier and regulator. This will explain why, or just give you a headache:

http://www.xs650.com/forum/showpost.php?p=363526&postcount=116

From this thread:

http://www.xs650.com/forum/showthread.php?t=1493
 
I use a regular soldering iron, I have two one 30 watt the other 40 watt. I do have a pistol grip one that is 40 watts with a button that lets it run at 100 watts for like 30 seconds then goes back to the 40 watts.
They worked fine. You might try a lighter. The kind that has the long stem, like for a bbq grill.
The metal strap acts a heat sink and can draw a lot of heat away from the solder.
Leo
 

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