1980 XS650 Special II Charging problems.

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a197120

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Hey guys! I have been trying to get my 1980 xs650 II that was sitting around for a while and after some routine maintenance I have it mostly figured out except the charging system being low.

For the most part I have ran up and down the harness checking connectors and using contact cleaner on connections and making sure there's no raw wires at any bends.

So far I have replaced...
  • Old glass fuses with in-line fuse holders (main fuse was getting very warm, it still is getting warm but not nearly as badly).
  • Battery.
  • Brushes are also relatively new, I replaced them last time I was trying to diag this problem a few years ago.
Headlight turns on when the bike turns over.

I've lurked around for a bit so I did some preliminary testing and just wanted to see if anyone could help me decipher my results. I think the issue is going to be the rotor because of the low resistance across the rings but if anything else looks suspect or there are other tests that people know of I would greatly appreciate the help.



testreadingnotes
Battery voltage fresh off charger13.23V
Battery voltage with key on12.45V
Slap testworks, but not very strong.
Battery voltage with starter cranking10.70V
Battery Voltage @ low idle12.50V
Battery Voltage @ 3K RPM12.88V
Battery Voltage @ 5K RPM13.00V
Grounding left brush to groundno voltage increase
Voltage @ Left Brush (not running)5.11unsure if this is supposed to have voltage??
Voltage @ Right Brush (not running)11.45
Resistance across rings2.2Ω
Ring 1 to ground0L
Ring 2 to ground0L
AC Voltage White Wire 17.5V@3K RPM
AC Voltage White Wire 27.5V@3K RPM
AC Voltage White Wire 37.5V@3K RPM
Voltage drop tests starting voltage12.24VW/ key in on position, engine not runnning
Voltage at main fuse12.12V
Voltage at brown wire @ ign. switch11.72V
Voltage at red wire @ ign. switch11.88V
Voltage at brown wire @ wiring harness11.48V
 

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Yes, your charging output is very low, only about a half a volt, and the resistance between your slip rings is low as well. I'd say you need a new rotor. Contact Jim on the forum here about a rewind. If you're serious about keeping the bike then you might want to get a spare rotor. If you watch eBay, you can usually find one for less than $30 eventually. I've bought several and had pretty good luck (only one has been bad so far).
 
650Skull said:
Check the battery voltage at the ignition key before and after the switch. They are notorious for loosing voltage. May need to dismantle and clean contacts
Click to expand...
It drops about .16v from red to brown wire at the plug in the light box with the key turned on. Resistance with plug unhooked across is .6 ohms
 
Yes, I should have mentioned that, lol. You'll want to shop for an '80 or newer rotor, one that looks like this ......

$20RotorAfter.jpg


The pick-up magnet is sticking out from the outer slip ring at about the 4:30 position. What you don't want is a '79 or older rotor. It has no pick-up magnet .....

eBayRotor07-28-24$21.80.jpg
 
There is someone local who runs an eBay parts shop. I will see if he has any in stock to save some time.
 
a197120 said:
There is someone local who runs an eBay parts shop. I will see if he has any in stock to save some time.
Click to expand...

Even if it tests good, age is against it. Many a story of an original or good second hand one leaving one stranded on the side of the road. If it does work get yours rewound straight away and replace the other or carry it with you and the puller.

I wouldn't pay good money for a running one, prefer to buy a dud for nix then get it rewound.
Jim is the go to guy on here.

There are reputable rewinders about I am sure. Finding them with confidence and good reviews could take time.
 
a197120 said:
Hey guys! I have been trying to get my 1980 xs650 II that was sitting around for a while and after some routine maintenance I have it mostly figured out except the charging system being low.

For the most part I have ran up and down the harness checking connectors and using contact cleaner on connections and making sure there's no raw wires at any bends.

So far I have replaced...
  • Old glass fuses with in-line fuse holders (main fuse was getting very warm, it still is getting warm but not nearly as badly).
  • Battery.
  • Brushes are also relatively new, I replaced them last time I was trying to diag this problem a few years ago.
Headlight turns on when the bike turns over.

I've lurked around for a bit so I did some preliminary testing and just wanted to see if anyone could help me decipher my results. I think the issue is going to be the rotor because of the low resistance across the rings but if anything else looks suspect or there are other tests that people know of I would greatly appreciate the help.



testreadingnotes
Battery voltage fresh off charger13.23V
Battery voltage with key on12.45V
Slap testworks, but not very strong.
Battery voltage with starter cranking10.70V
Battery Voltage @ low idle12.50V
Battery Voltage @ 3K RPM12.88V
Battery Voltage @ 5K RPM13.00V
Grounding left brush to groundno voltage increase
Voltage @ Left Brush (not running)5.11unsure if this is supposed to have voltage??
Voltage @ Right Brush (not running)11.45
Resistance across rings2.2Ω
Ring 1 to ground0L
Ring 2 to ground0L
AC Voltage White Wire 17.5V@3K RPM
AC Voltage White Wire 27.5V@3K RPM
AC Voltage White Wire 37.5V@3K RPM
Voltage drop tests starting voltage12.24VW/ key in on position, engine not runnning
Voltage at main fuse12.12V
Voltage at brown wire @ ign. switch11.72V
Voltage at red wire @ ign. switch11.88V
Voltage at brown wire @ wiring harness11.48V
Click to expand...
Send your charging rotor to @Jim for a rewind. You won’t be sorry. I have at least three of his rotors.
 

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