Expanded charging system guide (In progress)


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Baraboo, WI, USA
Here's a start on an updated charging system guide. Let me know good bad different.

Here is the curly's guide: I have some additions, changes, pictures below
1. First charge your battery to at least 12.5-12.7V.
Is the battery Good?
Will it hold voltage overnight or longer?
Will it light a turn signal or other bulb for 15 or 20 minutes and still have 12 volts?
Is the fluid at the correct level? Use ONLY distilled water to refill if needed.
If the battery is questionable buy a new one. A too small battery can be a problem, while idling the charging system will not keep up to the load of a headlight, tail light, ignition etc and the battery will slowly discharge. Small batteries discharge faster. Yamaha calls for a 1200 RPM idle speed is to keep the battery charging, a too slow idle won't keep a battery charged.
A good charging system won't fix a bad battery, and a bad battery will break a GOOD charging system.
A VOM (Volt Ohm Meter) is needed, It doesn't have to be fancy. One can often found at the hardware store, home center, farm store, auto store, electronics store for less than $10.00 Either analog (a meter with a needle) or digital will work. The digital are easier to read and they auto range so you don't need to pick a range You just need to know what you want to measure, DC volts and Ohms are the functions we will use most.
A diode test function is nice but not a "must have".
A jumper wire is nice to have. About 3 foot long, 16 gauge wire or more (14 is heavier than 16 in wire gauge) two alligator clips or a solderless lug U and an alligator clip are handy ends to have on it.
Normal hand tools. Flat and good philips screw drivers, wrenches etc. When loosening screws push firmly in, then apply torque. Do not strip the heads. Some of the screws may have been machine tightened 3 decades ago.

If you don't have one a hand impact driver is a real time and money saver.
Does my charging system work?
Start the bike, shady area is nice, point the headlight at a garage door or wall, rev the engine, does the light get brighter and then dim a bit as the engine goes back to idle? If it does you have at least SOME charging.
Stock, 1980 or later, and the headlight doesn't light at all?
You may not have any charging, the headlight is controlled by a relay that is powered directly from the stator, no charging, the relay won't close, no headlight.

2. Find a really thin feeler gauge like 0.010" or 0.015" or a wrench, steel ruler, a putty knife, or any chunk of steel that can be lightly held near the alternator cover works too, see picture) and hold it pointed down about a half inch away from your generator cover on the engine. Now turn the key on. If your regulator and rotor are working the feeler gauge should slap the case when the magnetic field is created in the rotor. If nothing happens or the magnetic effect seems really weak then go on to the next test.


XS650charging 031.JPG

3. On the solid state regulator models all you need to do is locate the green wire at the regulator plug and make a jump from it to ground. That bypasses the regulator and allows full battery current to flow through the brushes out of the rotor through the green wire to ground. That causes the rotor to make a stronger magnetic field which in turn causes more current to flow in the stator. If your battery terminal charge voltage jumps up to 14.5VDC when you rev the engine then the regulator or the ground connection for the regulator is your problem.

4. If nothing changes then it's time to check the voltage on the brown wire (It may be black on your bike) at the positive brush with the key on. It should be very close to battery voltage. The brown wire that feeds the brush gets its power from the brown wire at the keyswitch. If you don't have battery voltage at the brush then check the voltage at the switch connector while it's plugged in, by probing from the backside of the connector with the key on. Again you should see the same voltage as the battery. If you do get full battery voltage there then repair the brown wire circuit between the switch and the positive brush. If not then the switch is either bad or the red wire from the battery is not passing the full current like it should. If that's the case then keep going back along the red wire, through the main fuse until you find the source of the voltage drop. No more than 0.3 VDC drop is acceptable.

5. Once you have full voltage to the positive brush re-check the charging voltage to see if you're getting 14.5 VDC or better at the battery when revved to about 3,000 rpm. If you still don't have a charge then do the feeler gauge test again. If it slaps the case your rotor and regulator are working and you can go on to stator checks. If not then pull the brushes out of their holder and use an ohm meter to test the rotor. Measure the rotor first by touching the tester leads to the brass slip rings. Then take one lead and touch anywhere on the engine that's not painted. For the first test you should see between 5 and 5.5 ohms between the slip rings. On the second test between one slip ring and the engine you should see infinity on the meter. Any reading lower than 5 ohms on the first test or less than infinity on the second test means you have a bad rotor. Replace it. If it tests good then go on to the stator checks.

6. At the stator wire connector locate the three white wires. Use a voltmeter set on the AC scale to test the three possible connections between the white wires by probing from the backside of the connector. (The connector should be plugged together for this test) With the engine running at idle you should see about 10.5 to 11 AC volts (Not DC) on each of the three combinations of white to white that you make. If you get a very low reading on one or two legs then something is grounding your stator. If you have high readings on any of the legs (i.e. 16-18VDC) then your rectifier is bad.

7. If you got low readings on any of the stator voltage checks then unplug the connector and use your ohm meter to check the stator windings. Check the resistance between the three fabric covered wires (stator side) on the side of the connector. On each white to white connection you should read about 0.4 to 0.5 Ohms. If you get a very low reading on all of the three combinations find the single Yellow wire connector and disconnect it. Re-check your stator resistance. If the readings are now good then the yellow wire or safety relay are shorted. If there is one or more that still read low after disconnecting the yellow then check those legs by touching one lead to ground with the other on the white wire. You should see a very high Kilo ohm or infinite reading. If you get a low resistance check the stator lead pigtail to see if it is pinched by the cases or rubbed through on the frame. If that looks ok then your stator is shorted and needs to be replaced.

And that's about it except to say that dirty connections and worn brushes account for most of the charging system problems. Good Luck you'll find the problem.

Do these things first, we want to eliminate common problem areas that often cause grief on old motorcycles.
Remove clean and replace the ground strap from the battery to the frame, BOTH ends, wiggle the end connectors is there gray dust falling out, are the wires breaking or corroded looking?

XS650charging 025.JPG

If so Replace the wire. It needs to be a heavy gauge wire, all electricity from the battery has to go through this wire including the electric starter draw. Now check the red wire that goes from the + battery terminal to the starter solenoid it is heavy and about 6" long.

XS650charging 026.JPG

At the solenoid end of this big red wire a smaller red wire heads back up towards the fuse box, ALL battery current except the starter draw goes through this wire. The other big wire on a bolt next to the first wire goes to the starter. check that connection while you are here.
Basic charging test #2 you will need a wrench and a screw driver. Set them up like this. Get the wrench as close as you can to the alternator cover. turn on the ignition switch, the wrench should tap the cover and stay there. turn the switch off the wrench should fall back away. repeat if you are not sure or just think this is fun. IF the wrench moves your regulator brushes and rotor all work!

XS650charging 031.JPG

Now lets check the battery.

#1 a good a battery that is completely charged.
You want to see about 12.6 volts on your Volt ohm meter.

XS650charging 021.JPG

XS650charging 020.JPG

XS650charging 019.JPG
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Gary, this is a great idea. I can't see the pics at work, but this kind of illustrated procedural treatment of this subject will be a boon for folks like me who are... well... challenged in this area. Off to a great and helpful start! Thank you for your time and trouble, sir!

Before you dig in.
If you have charging system issues, you need to test and confirm all the parts. Do not just test till you find a "broken" part and order "just that part". It is common for more than one problem to be present, often because a PO kept running a bike with issues, like running with a bad battery, wiring or fuse box, causing other parts to fail. Or wrecked more parts while "testing" the system, or made mistakes like jump starting the bike with a running car. This is especially true now that the PMA replacement system is available as a "kit". If the system has $everal failed component$ it might be better to go to a new system, just a couple of years ago this was not an option.
It is an unfortunate fact that sometimes old bikes are no DEAL and can suck up more money in repairs than they are worth. The good news with the XS650 is that parts ARE available at reasonable prices. A lot of old bikes are toast if major charging or ignition components fail, the only option being untested used parts from the occasional FleaBay seller.

Some slip ring, stator pics.

late rotor.jpg early stator.JPG chargingii 002.JPG late stator.jpg late brushes 001.JPG chargingii 004.JPG early stator brushes.jpg chargingii 003.JPG XS650charging 009.JPG XS650charging 010.JPG XS650charging 004.JPG XS650charging 007.JPG
I will do a testing the components series of pics.

Here's a how to add a magnet to an early rotor so you can use it on a late 80-84 TCI ignition bike.
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What you call TDC is better described as crankshaft position indicater.TDC postion is shown on the stator. Other than that minor detail, great stuff!
went an looked at multimeters today. There is quite a price range. What do I need for the bike. Looks like they run from $12 (seemed to be more for computers) to $80. Is there any specifics I need it to be capable of. I have decided I want to go digital. The entry level ones seem to be around $20-$25

went an looked at multimeters today. There is quite a price range. What do I need for the bike. Looks like they run from $12 (seemed to be more for computers) to $80. Is there any specifics I need it to be capable of. I have decided I want to go digital. The entry level ones seem to be around $20-$25


Just get one that is from a reputable manufacturer. I usually buy Craftsman and have good luck with the quality of them. Don't buy the cheap ones, like Harbor Freight unless you want one to pack with you for emergency use.
hey all. this mite seem like a redundant question, but i have lost all patience with this charging system and need all the help i can get. i have a 1980 with the stock TCI ignition. will the stator from a 79 or earlier (points ignition) work on an 80 or newer model? i got one from a 76 for cheap but am still not getting any voltage. any help would be great
I don't think an auto ranging meter can be bought at a reasonable price that does well with the low ohm readings needed on this bike.
Those who condem the Harbor Freight Meters, like item number 90899 have not used one. I have found them the be easy to use and very accurate. This meter can often be bought with a coupon for less than $3 and works every bit as good as a $50 meter. I have one of each.
In your pics in post #4 the first pic is an older 70-79 stator. The second pic showing the inside is a later 80 up stator. Possibly get pics of both older and later from both inside and out and clarify the differences in the brush holders.
In the last pic you show the wires and colors, no red wire in that pic, it's a brown wire.
The text is good. I never had much trouble with that part. Getting pics that show how to do the test and getting them to go with each step is a great idea.
80XS I think this should have it's own thread. This thread is more a evleopment thread for improving Curly's cgarging guide.
The main problem of using the 70-79 stator on an 80 up bike is the way the brushes are grounded. The 70-79 are grounded and the 80 up are not.
Mounting the TCI pick up on the older stators might be problematic. Not get it rigt and the bike will run pooorly.
That is a great format and helps heaps............WHY DIDN'T YOU DO THIS A MONTH AGO??????:cussing:

As a complete newbie going through this Curly's list was essential and the upgrade is a great next gen asset!

Good on you for taking the initiative to do it.
I started another thread asking questions, based on this thread I made it pretty far down the line. History.

1980 XS650SG, stock ignition etc.

I passed the slap test and moved on down the line. I started the bike and grounded the green wire off the regulator and at idle my voltage started climbing. But I get lost after that test. Is my regulator shot, can I fix it or does it need some sort of ground that I'm missing after taking the bike apart?

I guess what's next after I get this far. Any help would be great, I got her licensed and all my Mikes parts get here tomorrow.
My eyes are bleading. That is..... awesome. I may have missed it but I don't see how to test the solid state regulator. I see how to test and adjust the older style, I did find the additional info about the S/SG but nothing that helps me out. Thanks a ton for that link, I will be doing some huge downloading soon but I have tunnel vision right now. I want to ride!
My bad, the solid state regulator test is in the G SG suppliment. It's a bit obtuse but you are looking to see if current flows from each white wire to black in one current direction and to red in the other. i.e. you check that the six diodes pass current only in one direction. It does not however give a procedure to check the IC regulator which from your green wire ground test is the likely culprit.

Here's a copy
i would like to know what is most likely to stop first? my wifes bike stopped running cause the battery drained down and its a brand new battery and we were only about 14 miles from home. i charged the battery and started the bike, it appears to be charging then it looks like its not. then I reved it up to about 3,000 rpm and the voltage fluxuates all over. at first it seems to go to the 14volt range then as time goes by it drops to like 9 or so. i at first thopught it was the regulator but now am thinkin the stator is the prob. anyway what do ya think?? thanks btw for the info u posted it will help me to do some checks before i purchase a regulator or stator... :)
inkman, Welcome to the board.
The early bikes work differently than the later bikes. If you tell us the year and model, and any mods to the bike we can help you better. Lots of us put the info in the signature. This way that info is there each time you post, and we won't need to ask.
The first thing to look at is the brushes. Are they at least 3/8 inch long? The book calls for 1/4 inch but they usually get bad before they are that short.
If that won't fix it start at the beginning of this thread and work the steps.
We can't see your bike to well from here. Your going to have to do the testing. Then get back with us for possible solutions.
sorry:) its an 81 xs650s totally stock. my brother bought it for 100, and shipped it to us for her first bike as a wedding gift. its in great condition and alkl ive done is install a new battery and clean her up. the guy who had it let it sit for over a year and when i cranked her she purred really sweet. i own a 2000 harley but man i love this bike. :) thanks for your help . I will do some checks on her tomorrow and let yall know what i find.