the 9 millionth "it won't charge" thread.....

[ClOckwOrk]

Hi there. I am new to the forum. I recieved a 1975 XS 650B from my father. he bought it new in 75 when he was 22 and gave it to me on my 22nd birthday. i am 26 now and just finally got around to getting it running. She is cherry and runs amazing (for the most part)

I'll throw some pics of her up later

on to the problems!

before i start i should say that i am mechanically inclined but electrical is not exactly my strong suit.

Here's the issues.

1. The bike charges, but draws from 12.6v to 11.7 or so with the keyswitch on.
2. The bike charges from the afore mentioned 11.7 volts up to about 12.3 volts at 3000rpm


I have checked/replaced the following.

Keyswitch: i saw some voltage drop at the keyswitch so i installed an extra i had here.

Alternator brushes: my dad immediately told me to do it because he suspected that. they were ok but i still replaced them.

I also had an issue with the handlebar switch on the left side. the blinkers didn't work so i bought a new one from mikes XS but it was not for the right year (for a 77') so i went back to the old one and just did away with the wiring for the turn signals. the horn and lights work as they should.

Cleaned the diode trio. At the red wire with the key on, i have 11.87 volts going to the diode trio

I also checked the resistance of the slip rings on the rotor. the numbers jumped from 6.2 down to 2.9 and stayed under 3 ohms when holding still as possible (with a cheap digital meter) i am told that i can't count on this being right with a cheap meter.

The positive wire on the rotor brushes only shows about 10v to 10.8v with the keyswitch on. I tried to bypass the rectifier and it seemed to help reduce the voltage draw with the keyswitch on. Tried the same with the regulator with no change in result.

So is the wiring from the regulator to the positive brush bad? i don't see how it could just suddenly go bad besides sitting covered in the garage for about 15 years. i really hate to tear apart the main harness to chase the wire, but i don't know what else to do. It seems foolish to start throwing parts at it if the charing system isn't getting the needed 12v supplied to it. Thanks for any help its greatly appreciated~!

 

[xjwmx]

Any meter is more likely to read high than low on the rotor. Touch the probes together; do you read less than about 0.5 ohms? If so the meter is good enough, and you should subtract what you read from the rotor reading, btw. I think you need to have the rotor re-wound. There are competent places that do it and there are hacks.

You "did away with" the turn signal wiring, and ordered a new switch, of the wrong year? You can fix switches. Anything that goes wrong with them you can learn how to fix. You need to calm down and step back and make your dad proud on this one.

 

[ClOckwOrk]

the new switch had 9 wires whereas the old one had 6. it was not compatible with a 75'so i went back to the original switch, and deleted the three wires for the turn signals. there is a plastic piece inside that holds the 3 wires where they meet at the switch. that piece was broken so the switch was not making contact. there was nothing i could do to fix it. i will source a used handlebar switch in due time. more importantly than that, i need to figure out the charging issue. I am aware that the rotor may need to be rewound but before i even get to that, i have to find out why i have almost a 2 volt draw at the rotor + brush with the keyswitch on. The alternator can't put out the voltage it should if it isn't getting enough in the first place, right?

 

[shotgunjoe]

when it comes to these types of issues, I like to try the simplest things first. Check your ground wire, clean the connections, maybe check resistance through the ground wire.

 

[xjwmx]

There's no such thing as "a 2 volt draw". A 2 volt drop might be what you mean. Dirty connections could account for it, where you're measuring. You have to take every connection apart, clean it, grease it and re-plug it. It's best if you take the connectors out of the housing, but not easy. If you have money to spend, I'd suggest a new harness, to simplify things, but it isn't necessary. I don't mean a simplified wiring harness. I mean to simplify your work on the wiring.

 

[XSLeo]

Ok lets do a few tests ok. Get the bike started. With it idling hook your meter to the battery, whats the voltage? Now using a jumper wire hook one end to the battery positive. While watching the meter hook the other end of the jumper to the green wire at the brushes. The battery voltage should climb. If so don't let it go over 15 volts, unhook the jumper wire. What happens when the jumper is hooked up?
On doing the rotor test try cleaning the crud off the slip rings. 600 grit sand paper works good. Then spray down with electrical contact cleaner.
A good cheap meter is sold by Harbor Freight, their item # 90899 can be bought for about $3 with the right coupon. It's as good as most $40 meters.
Leo

 

[ClOckwOrk]

I should add that i have spent a bit of time just cleaning up any connections i can find. everything so far has been fairly clean but i've taken them apart and cleaned them, and added a little di-electric grease. The battery ground wire was bolted to the battery box mount, which i noticed is rubber mounted. so i installed the ground wire to the frame (where it should be) somewhere along the line my dad changed the ground wire to suit whatever battery he was trying to use on it years ago.

I may price out a new harness. Price point is a little more of a concern than doing the work of putting it in, but if it will eliminate even half of my headaches i'd be happy to do it. I'm going to trace the wire from the rotor's (+) wire and see if there is anything wrong with it. thanks for the input so far guys. With enough poking around, i'm bound to find the issue eventually

 

[ClOckwOrk]

Ok lets do a few tests ok. Get the bike started. With it idling hook your meter to the battery, whats the voltage? Now using a jumper wire hook one end to the battery positive. While watching the meter hook the other end of the jumper to the green wire at the brushes. The battery voltage should climb. If so don't let it go over 15 volts, unhook the jumper wire. What happens when the jumper is hooked up?
On doing the rotor test try cleaning the crud off the slip rings. 600 grit sand paper works good. Then spray down with electrical contact cleaner.
A good cheap meter is sold by Harbor Freight, their item # 90899 can be bought for about $3 with the right coupon. It's as good as most $40 meters.
Leo

I have tried this a few times. I assume hooking the 12v wire from the battery will go to the positive wire for the brushes. it has a white insulating sleeve on it. the other is the ground and is just black. that is the only two wires on this bike (1975) Every time i try to hook the jumper up, i get a lot of sparks. i'd rather not start blowing fuses and bulbs.

P.S. the voltage while running is 11.87 volts almost religiously. when at 3000 rpm it is at 12.2-12.4 volts. the battery reads 12.6 volts with the key off, and is a brand new battery.

 

[xjwmx]

I think Leo's going to walk you through it by hand here. You should jump on it

 

[ClOckwOrk]

every time i try to put the jumper from battery + to rotor + the wire gets red hot and starts to smoke.

 

[ClOckwOrk]

checked yet again at the positive brush on the rotor and its showing 9.2 volts. according to curly's troubleshooting write-up, i should have no more than 0.3 volt drop across the wire. the keyswitch has been replaced. is there anything else in the line that can cause this drop? or just wiring......???

 

[xjwmx]

Do you have a wiring diagram for this year? You can probably find one on this site.

I would trace back up the wire from the brush through the connectors and see where the drop occurs, and the connection is probably bad there. If you're supposed to see 12V at positive brush. I don't know this year of rectifier and regulator, just '80 and up. I think Leo knows your year.

You can "back probe" the connectors, which just means stick the probe in the back side of the connector where the wire goes in. To find the bad connection. Be prepared for probing the connection to fix it temporarily and cause confusion

 

[shotgunjoe]

sounds like you have a short to ground!

 

[shotgunjoe]

to find a ground short, hook a test light between battery minus and the ground wire, if the light is on you have a short. pull the fuses one at a time till the light goes off, then go through that portion of the harness to find your short

 

[retiredgentleman]

If your VOM reads 3 ohms on the slip rings, you need to replace the rotor. If you don't trust your meter, buy a couple of 10 ohm resistors and twist the leads together in parallel (pamcopete tip) . Your meter should read 5 ohms for the 2 resistors.

www.customrewind.com will rewind the rotor.

 

[ClOckwOrk]

sounds like you have a short to ground!

this would make all the sense in the world as to why i can't put a jumper from the rotor positive wire to the battery positive to bypass the regulator.

i intend to get a rewound rotor but before i pick up the puller and rotor i need to trace back the wiring. it took me a few minutes to find where the wiring came out of the case. i'll try the light test on the battery cable and keep you guys posted. thanks again for all the help!

 

[shotgunjoe]

this would make all the sense in the world as to why i can't put a jumper from the rotor positive wire to the battery positive to bypass the regulator.

i intend to get a rewound rotor but before i pick up the puller and rotor i need to trace back the wiring. it took me a few minutes to find where the wiring came out of the case. i'll try the light test on the battery cable and keep you guys posted. thanks again for all the help!

Thinking about it again... I may have mis-spoke, I think maybe the test light goes on the positive side instead of ground. Makes more sense.

Been awhile since I had to find a ground short.

 

[ClOckwOrk]

well i tried the test light again and there was no ground short. however i did step back and take a deep breath..... and started checking voltages again. I found that the brown wire from the key switch had good voltage until i plugged everything into the 4 wire connector. i chased the brown wire back to the voltage regulator and found that it had 12v to the connector when not plugged in. so the wiring through the harness was fine. Next i unplugged the pins from the connector, and plugged in only the brown wire. had a strong 12v, and less than the acceptable 0.3 volt drop. However once i plugged in the green wire for the regulator, i saw the 2 volt drop that i have been chasing. I also realized that while running the bike, the regulator adjuster screw changes nothing, wether it is in all the way or totally out. With the regulator unplugged and the bike running, it sits at proper battery voltage (obviously not charging this way)

with the regulator plugged in, it sits at 11.2 volts and climbs slightly when revved to 3000 rpm.

so i believe i have pinpointed the problem down to the regulator. So i guess the next piece of advice i would need is what should i replace it with? i'd rather not hack the wiring too much so if there is anything plug and play available that would be best for me. any suggestions? thanks again guys

 

[xjwmx]

^There is a Pamco Pete thing you can build using a car regulator, search the sites. Make sure you choose the right version for your year bike.

Here is a link to some Ken Maxwell stuff. He's been on here and is also really sharp on xs650 electricals. I think you have a mechanical regulator. This might be a useful starting point. You know I'd try to bust into the mechanical regulator and try to rebuild it Not a better solution than replacing it, but funner.

http://www.mikesxs.net/ken_maxwell/ChargingSystem.html

 

[XSLeo]

Ok, I think your problem on the voltage drop is a bad rotor. When you put the jumper on this shows that. If you check the ohms from the rotor slip rings to ground, I'm sure you'll find continuity.
The regulator may be ok. When you turn the key on power flows out on the brown wire to the regulator.
If the voltage on the brown wire is less than the preset voltage of 14.5 volts it sends power out on the green wire to the positive brush. At the brush power flows into the rotor, out of the rotor on the black wire brush. The black wire brush is grounded at the brush holder and on the black wire back into the wiring harness.
This power flow creates a magnetic feild around the rotor. As the rotor spins this feild passes around the windings of the stator. This causes AC power to flow in the windings of the stator. This AC power flows out on the three white wires to the rectifier where the AC gets converted to DC where it flows out on the red wire to charge the battery. The black wire goes to ground.
When you start the bike the alternator starts making voltage. As this voltage climbs, when it reaches 14.5 volts the regulator stops the power flowing to the rotor. When this happens the alternator stops making voltage.
When the voltage stops the battery starts to drop, when it reaches 14.5 volts the reg turns the rotor back on.
The reg keeps doing this on/off switching several hunderd times a minute to keep the battery charged.
On your bike when the reg sends power to the rotor, your shorted rotor sends part of this power to ground. This power being bled away keeps the alternator from making much electricity. Thats why your battery won't stay charged.
I think replacing you stock reg with a Chrysler reg is the best option. I did on my 75. One of the best thing I ever did for it.
I'll post some pics to show how to wire the reg and the three nylon screws you will need to do the mod.
You can cut the wires off your old reg and wire them to the new reg so it will be a straight up plug in.
In the pic where it shows the wires to the reg hook the green wire from the plug to green wire on the reg, brown to brown. The black wire to the case of the reg.
This reg needs the black wire brush ungrounded from the stator, the three nylon screws will do this.
You also need to hook power to the black wire brush. The best way to do this is up at the 6 wire plug where the stator wires plug into the harness. The black wire on the harness side of the plug, cut it off an inch or two from the plug. Cap off the black wire in the harness.
Hook the short black wire from the plug to a length of brown wire. Run this brown wire to the brown wire after the switch.
The new reg is set up turn the rotor on and off after the rotor not before like the stock mechanical reg.
The new reg when you turn the key on power flows on the brown wire to reg and the brush thru the rotor out on the green wire to the reg. The reg reads battery voltage on the brown wire. If the battery voltage is low the reg turns on and grounds the green wire to power the rotor. Then does the same as the stock reg, being solid state it turns the rotor off/onn much faster than the mechanical reg. Thousands of times a minute instead of hundereds. This does a much better job of keeping the battery at the proper charge.
There is also a rectifier mod that can be done for About $10. It takes two Radio Shack rectifiers, some wire and an aluminum plate. I'll post up some pics on that too.
Leo