Just another guy with charging issues

Monster Rat

Monster Rat

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I don't think I have ever joined a forum where everyone is so friendly, especially given the amount of repeated questions. The number of threads started on charging problems is staggering. Welp, I am joining that list.

I have an issue that as I ride the bike it discharges the battery to the point that the headlight consumes enough juice that it will eventually kill the engine. If I turn off the headlight and kick start, and keep the rpm's up enough I can limp it home. Here are some details -

1974 with stock charging and ignition components still intact. Rotor ohms were 5.3 The stator ohms are confusing me. I checked it off the bike and resistance readings are different than when on the bike. OFF - .9-1.0 between white wires and open between the other wires. ON - .5 between white wires and I have a reading on the black wire of 20.0 ohms, that should be open correct? The brushes are in good shape, probably 3/8" longer than the wear mark. When the key is on I show 12.2v at the green wire 6pin alt connector when it is separated from the alt. When connected the green wire at the brush, and the 6 pin connector (both sides) is right at 4.5v Should it drop that much across the rotor? Sounds like the stator is shorted. Am I correct in this thought?
 
This sounds like the classic XS650 alternator brushes are worn out thingy. Nearly every XS650 chews up a set of brushes at some point in time. They are cheap (check out Jack's Small Engines - $3.22 per brush and there are two of them - slightly different) - and easy to replace - IF you have the correct JIS screwdriver.

Here are the two part numbers you need to search for:
  • 256-81611-11-00
  • 256-81612-11-00
Changing the brushes takes about 15 minutes - in the rain, beside a dirt road, in the middle of friggin' nowhere - with an angry girlfriend standing beside you.

Don't ask.

Pete
 
That 4.5 volts makes be suspect that your rotor has a ground on it. The rotor winding may still measure 5.3 ohms, but the winding may be touching the rotor frame somewhere.
Remove both brushes, and use your ohmmeter to measure from either slip ring to the rotor frame. That should be a very high resistance (infinity).
If its not a very high resistance, then you have a rotor problem.
 
My brushes measure INNER - .520" OUTER - .550" are the due for replacement at that length?

I have both brushes removed and went from outer slip ring to stator housing infinity - inner slip to stator housing infinity.

Thanks for the help guys!
 
The brush lengths are good. The stator resistance readings are acceptable. Its very difficult to measure these low resistances, because the resistance of your meter leads can vary between 0 and 0.7 ohms.
Your voltage regulator is old and it may be causing a voltage drop between the brown and green wires.
Unplug the regulator. Now with the VR unplugged, measure the resistance from the brown to the green terminals of the VR itself.
That should measure 0 ohms. Subtract any ohms reading that you see when the 2 meter leads are shorted together.
 
if your rotor creates a magnetic field when you switch the ignition on then the fault must lie with your stator or regulator or the associated wirng..
The early models should have a direct ground connection to the chassis from the inner rotor brush via the stator body to the crankcase so if your engine is grounded to the frame and the frame is connected to the battery negative that part of the charging system is ok.

Test your stator windings and leads are not shorted somewhere or trapped under the stator body and you get continuity on the white wires from stator to regulator connector.If that checks out then you should substitute a good regulator if you cannot test your own

Have you read through this guide in the Yech section? http://www.xs650.com/threads/expanded-charging-system-guide-in-progress.10561/
 
Last edited:
Monster Rat said:
My brushes measure INNER - .520" OUTER - .550" are the due for replacement at that length?

I have both brushes removed and went from outer slip ring to stator housing infinity - inner slip to stator housing infinity.

Thanks for the help guys!
Click to expand...

Agreed - the brush wear limit is (I think) 7.0mm and yours are more than 12.7mm long - so they should be fine.

Pete
 
Monster Rat said:
Leads touching 000 across the green and brown 10.4 ohms
Click to expand...
Your old stock regulator has failed internally and its time to retire it to the trash bin.
I recommend you buy an automotive nos regulator. The VR-115 (or equivalent) was used on cars in the 1970's.
I use the VR-115 on my 1978 XS650 SE, and it works amazingly well. It will give you around 14 to 14.3 volts when you drive down the road.
Probably find them on E-bay for $30 to $50 dollars so shop around. You'll need to rewire the VR-115, but its easy to do.
Here is a link with the info:
http://www.xs650.com/threads/regulator-rectifier.21485/
 
I looked earlier today for the vr-115 but none of my local stores had one on the shelf. I can have next day, and will order tomorrow. $26 I did try one of these off of an old Jeep out in the pasture, but didn't make any difference. May be defective. Of course I may not have wired it correctly.
reg.jpg
 
Last edited:
Alrighty guys, I picked up my new R292 VR. Last night while looking at the condition of the other wiring I found that the black wire to the rectifier was melted in the main harness side of the connector. I removed the rectifier and performed the test I have seen others outline in other threads. I appears to test ok. I am going to run dedicated grounds to the frame from both my rectifier and regulator. Anyone see a problem with doing that? I am going remove the melted black wire from the harness. and search further for an explanation on why that happened in the first place.

Thanks for all the guidance thus far!
 
well done findin the burnt ground wire.
Take a look in the Tech section you'll find the electrical schematic for your year.
You;ll see that the inner rotor ring is grounded via the inner brush and brush holder and stator body to the frame so the rotor is always grounded as per my previous post.

The regulator and rectifier are grounded via the black ground wires so you'll need to find out why and where the black wire got shorted out in the loom and run a fresh ground wire.
 
Last edited:
650Skull said:
http://www.xs650.com/threads/electrical-problems.50316/#post-520642 Same problem......Maybe some info here that will help
Click to expand...
I hadn't read that one before. Some how I missed it. Good read.

Well folks, it seems to be working like a champ! I figured I would also pony up for a new AGM battery from the local CARQUEST. The BWD R292 voltage regulator is doing it's job, and the rectifier is as well. Kicked the bike over, fired right up and even at idle it is right at 14.2 I had hooked a Sunpro volt meter to my battery and zip tied it to my bars and it stayed 14v+ for the short ride I took it on. Last night I got on Radio Shacks web site and ordered the stuff to make a new rectifier so I believe I will still follow through with that plan once the components arrive.

Once again all the help you guys have provided me and MANY others has gotten a 40+ yr old bike back up and going. Without the high cost of a PMA.
Thank You All! Now it's onto carb tuning, fork seals, turn signals, OH MY!
 

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