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For Sale - Rewound Alternator Rotor

Discussion in 'Classifieds' started by Jim, Mar 15, 2019.

  1. Jim

    Jim Beyond the edge is the unknown. Here be Dragons XS650.com Supporter Top Contributor

    I'm hanging out my shingle....
    Band of Brothers Rewinding Service is open for business (thanks Bob:D)
    You can read here all the work that went into getting to this point.

    Send me your rotor. If it's a serviceable core, I'll rewind it with TEMCo MW0181 22 ga. wire. It's made in America wire. Run-out will be tested before and after rewind and the rotor will be static re-balanced. It's reassembled with new stainless screws, loctited in. The coil is epoxied in place with hi-temp JB Weld. Yamaha calls for 5.25 Ω +/- 10%.... So... 4.725 to 5.775 Ω. Your rotor will fall within that range. I'm getting 4.75 to 5.2 Ω on my rewinds with a nice strong magnetic pull.

    Here's what it costs... $105 and you pay shipping both ways. I now ship 'em in a flat rate envelope... $8.40 anywhere in the states.
    That's about 1/2 to 2/3 of the going rate for a rewind. Here's why.... first, I'm retired. I ain't doin' this to make a living. This gives me a little spending money while giving something of value back to this wonderful XS community.
    Second... I'm retired (did I mention that...:rolleyes:), I don't do anything in a rush anymore. If you're in a hurry, better go to an alternator shop... I'll be 'bout a week or two.
    Third, a shop that does this for a living can afford to absorb the loss of redoing your rotor for free if you burn up the rewind.... I can't. My guarantee is that when I ship it, it's passed my run-out test, it's balanced and it puts out a magnetic field that will snatch a large combination wrench out of your hand. Hell, I'll even send you a video of it. What I won't do is rewind it again on the house because you installed it in a faulty charging system and promptly burnt it up again.
    So... if you're running an old weak battery that burnt up you first rotor... it'll burn this one up too.
    If you're running the original antique mechanical regulator that's stuck at full charge and burnt up you original rotor.... it'll burn this one up too. If the iggy switch has a large voltage drop across it.... well, you get the point (I hope). I'll reserve a few comments below and add some useful links and stuff to check before you replace the rotor.
    One last thing, I'm not rewinding aftermarket rotors... OEM Yamaha's only. If you're not sure, PM me with a few pics and we'll sort it out. If you send me a repop, it's going in the trash.. and you're out the shipping. If it turns out your rotor is not rebuildable (rare, but it does happen), I'll split the cost to ship it back if you want it.
    This is on a first come, first serve basis. PM me and we'll go from there.

    Periodically I'll put a rotor up here for sale outright. They'll be $130. If you send me a rebuildable core, I'll refund a $25 core charge back to you.

    Question: Which rotor can I use on my bike? OK.... here's an easy way to remember it (for everyone... I get lots of PM's asking this)....
    If you're running Yamaha's original Transistor Controlled Ignition (TCI) system, you have to use an 80 or newer rotor with the trigger magnet. Other than that, any year bike can use any year rotor... be it the old or new style. Original points, Pamco... HHB, Boyer.... rolled your own from your Briggs and Stratton lawn mower:rolleyes:.... doesn't matter... ANY ROTOR will work. Yamaha TCI? You have to have the rotor with the magnet.

    PLEASE READ THIS!! Mikes XS sells a rotor puller for a very reasonable price. Amazon also carries 'em. Get one! I'm up to 3 cores now that failed the run-out tests. All 3 showed signs of being pulled off the crank with a 3 or 4 jaw puller... that or some pry-bars.:doh: They're bent.... well past the point of being usable. Send me a core with "pry-bar" marks on it and it's going in the trash. (Edited: 5/11/19)
    Because of gggGary's generosity, we now have a loaner puller. Send me a $20 deposit via Paypal and I'll send it to you to pull your old rotor. When I get it back (still serviceable), I'll refund it. (Edited: 1/1/2021)


    I'm now set up to rewind the Honda DOHC CB750, 900's and 1000's from 79 to 83. Cost is the same as the XS rotors. If you know of a Honda guy in need, point 'em this way. :D

    CB Rotor.jpg
    EDIT: 1/16/21
    Due to a recent misunderstanding :rolleyes:.... I need to reiterate that these are 40+ yr old rotors that have been rewound. If you're expecting to get a rotor that looks brand new, go look somewhere else... these ain't them. The slip rings have accumulated some dings over the years. I dress them down flush so they don't interfere with the brushes, but you can't just make 'em disappear. They are flush though... they won't hurt a thing. If you don't like that, don't buy one... simple as that.

    Last edited: Jan 16, 2021
    Bjorn, Smuggy, spacetiger110 and 17 others like this.
  2. Jim

    Jim Beyond the edge is the unknown. Here be Dragons XS650.com Supporter Top Contributor

    Charging for Dummies

    In order to troubleshoot your charging system, you need, at least... a basic understanding of what's going on in a charging system and the components involved. Once you know how all this stuff works, it's actually pretty easy...

    Hundreds of years ago some very smart people discovered that if you wrap copper wires around a chunk of iron and give it some juice (volts), it creates a magnetic field. They also discovered that if you pass a magnet through a copper coil, you create electricity. So, knowing this, we can take a small voltage to create a magnetic field... spin that magnetic field inside some copper coils and generate stronger electricity. That's sent back to the battery for storage, to run other electrical systems and to supply power back to the rotor field to keep the cycle going.

    First up, the battery. Yes Virginia, as well as being a storage device, the battery is a component of the charging system on the XS650. We're using a 12V system.
    12V from the battery is sent to the voltage regulator (VR or reg.). The VR needs the battery voltage for 2 reasons. One, it has to know what the voltages is in order to regulate the amount of voltage going back to the battery to charge it. So, we can say the VR is a voltage sensing device. Second, it takes that battery voltage and sends it to the rotor's coil to create (and regulate) a magnetic field.
    The rotor consists of an iron core wrapped with about a half a pound of thin insulated copper wire. The ends of those wires are connected to slip rings so that we can keep it electrically connected to the reg. while we spin it. The iron core is arranged in "fingers" so that they alternate the magnetic field between north and south as it spins.
    Carbon brushes ride on the two slip rings as the rotor spins to provide power to the rotor. One brush supplies power (from the reg.) to the coil and the other supplies a return path commonly referred to as a ground to complete the electrical circuit. More on that in a bit.
    The stator consists of a series of iron cores wrapped with copper coils. These are arranged so that there are 3 outputs 120° from each other. When the rotor spins inside the stator, the coils are subjected to the alternating north/south magnetic field of the rotor. This generates an alternating, or AC voltage which is substantially stronger than the DC voltage we used to create the magnetic field. Furthermore, by controlling (regulating) the field strength of the rotor, we can control the output of the stator. Less power to the rotor means less voltage out the stator.... and more power in means more power out. Remember this quick jingle; rotors rotate, stators are stationary.
    Finally, the 3 phases of AC from the stator are sent to the rectifier (rec.). The rec. is simply a bridge diode network. The 6 diodes of the bridge allow only the positive half of the AC current to pass. So what's sent to the battery is what's called a "pulse (or ripple) DC."

    318px-3_phase_rectification_2.svg.png 6_pulse_bridge_without_inductance.png
    Image by Krishnavedala - https://commons.wikimedia.org/w/index.php?curid=15447198 Schematic by Clampower. Modified by me.

    So... to recap:
    Battery; stores energy from the alternator and supplies excitation to the rotor field windings (by way of the reg.).
    Regulator; senses battery voltage and sends power to the rotor accordingly.
    Brushes; electrically connect the reg. to the rotor thru the slip rings.
    Rotor; creates an alternating north/south magnetic field inside the stator.
    Stator; generates a 3 phase AC output based on the strength of the rotors magnetic field.
    Rectifier; converts AC to DC to charge the battery and to run ancillary electrical systems.

    Misc. Notes: There are two types of regulators... the type A reg. is used on 80 and newer bikes and the type B on 79 and older.
    The type A reg sends full power all the time to the rotor on the brown wire, and regulates the ground return wire (green). The newer combined reg/rec is a type A.

    A type reg.png
    Image from here.
    The type B regulator is permanently grounded and the green wire is regulated power from the reg. The older separate reg. is a type B.

    B type reg.png
    Image from here.
    (To be continued)
    Last edited: May 18, 2019
  3. Jim

    Jim Beyond the edge is the unknown. Here be Dragons XS650.com Supporter Top Contributor

    I'm not going to try to reinvent the wheel here....The following is from the charging system guide in the Tech section. Thanks @gggGary

    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?
    EDIT by me: A good battery will run the headlight on low beam for 20 min. with only about a volt - volt and a half drop.
    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"

    EDIT by me: Forum member @I am Carbon compiled some Youtube videos on how to use a multimeter into one thread. If you're shaky on using a meter, I suggest you have a look.

    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 JIS 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.

    EDIT by me: Here's a quick video on how to do the "slap test."

    3. On the solid state regulator models (1980 and newer) 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. Note* any more of a voltage drop could overcharge your battery... overheating the rotor in the process.

    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 togeter 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.

    EDIT by me: Here's a video on testing the rectifier.

    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.

    EDIT 5/31/21: @MaxPete was kind enough to turn this into a PDF. Thanks Pete!!


    Attached Files:

    Last edited: May 31, 2021
  4. 2XSive

    2XSive At least one screw loose behind the handle bars XS650.com Supporter Top Contributor

    Just got a pair of rotors back from Jim. Look at this beauty! Nicely done, Jim!!!

    Attached Files:

  5. YamadudeXS650C

    YamadudeXS650C Central New York XS650 XS650.com Supporter Top Contributor

    Great offering of service, Jim !
    I will know where to turn for future needs.
    Thank you.
    gggGary, Jim and Mailman like this.
  6. DogBunny

    DogBunny Motorcychologist Top Contributor

    Thank you Jim for your most excellent rotor. It looks and works great. Holding it in your hands, you can see how conscientious Jim is and how much care and thought went in to it.

    Here it is installed. Attached to my stator is a permanently mounted LED timing light that I made with much appreciated help from TwoManyXS1Bs, which he thought and wrote up in this thread:

    And here is one of member artek's clear stator covers which allows me to check my timing and admire Jim's rotor without having to remove anything. The stator covers are for sale here:
    I've had that stator cover on for about 2-1/2 years. I've done zero maintenance to it in all that time, and it still looks new. Likewise with the LED timing light which still works great. The rest of my bike may not look like much, but my stator is a show-stopper.
  7. Jim

    Jim Beyond the edge is the unknown. Here be Dragons XS650.com Supporter Top Contributor

    Oooooh... I like that timing light.:)
    MaxPete, gggGary, tzimmerm and 3 others like this.
  8. Mailman

    Mailman Hardly a Guru Top Contributor

    Wow! I didn’t know anyone but 2M had that patented built in timing light, AND with a glass stator cover! That is so cool!
  9. MaxPete

    MaxPete Lucille, Betty, Demi & Gretel: I ask, THEY decide. XS650.com Supporter Top Contributor

    Jim’s rotors are really beautifully made!

    Last edited: Apr 25, 2019
  10. YamadudeXS650C

    YamadudeXS650C Central New York XS650 XS650.com Supporter Top Contributor

    A technical exposition and light show all in one !
    I love it.
  11. 2XSive

    2XSive At least one screw loose behind the handle bars XS650.com Supporter Top Contributor

    Can only imagine what that would look like going down the freeway at night. The XS650 Plutonium Powered Time Machine. Very cool.....

    Attached Files:

  12. Jim

    Jim Beyond the edge is the unknown. Here be Dragons XS650.com Supporter Top Contributor

    Got another one ready to go. Slip rings have a few minor dings.... nothing that will affect operation though. Will work for all years. SOLD.

    Last edited: Apr 29, 2019
  13. Jim

    Jim Beyond the edge is the unknown. Here be Dragons XS650.com Supporter Top Contributor

    I have another rotor ready to ship. Early style without the TCI magnet. Will fit any year as long as you're not running the TCI (ignition) system. SOLD

    Last edited: May 16, 2019
  14. MaxPete

    MaxPete Lucille, Betty, Demi & Gretel: I ask, THEY decide. XS650.com Supporter Top Contributor

    If you’ve got a pre-80 model XS650 with charging system issues, this is your best bet folks. It’s a much more solid solution than a PMA or one of those wonky battery-less setups.

  15. Beags64

    Beags64 XS650 Junkie Top Contributor

    Scuttlebutt 'round the water cooler is the guy in the QC dept has stage 4 OCD.:D
  16. azman857

    azman857 '80 XS 650SG Rider XS650.com Supporter Top Contributor

    I've been running one of Jim's rewinds. NO issues. NO regrets. Just get one. Nuf said.
    madmax-im, tzimmerm, Mailman and 5 others like this.
  17. 2XSive

    2XSive At least one screw loose behind the handle bars XS650.com Supporter Top Contributor

    Likewise. My 81 xs voltmeter hooked into the switched wire in headlamp bucket would never register above 13.8 or 13.9 and would intermittently drop to 10.5 at 3000 rpm. I knew my rotor was about shot. Installed the new rotor from Jim and now have constant 14.1 volts, which I know is .3 -.4 volts low on cheap Chinese voltmeter. Levels out at constant 14 volts even. No question about it. Order from Jim.
  18. Jim

    Jim Beyond the edge is the unknown. Here be Dragons XS650.com Supporter Top Contributor

    Laughing Minions.gif
    MaxPete, thuban and gggGary like this.
  19. gggGary

    gggGary When a whole one is just too much. XS650.com Supporter Top Contributor

    One on the way! Don't really need it right now but might put it on madness, just cuz!
    Mikey, MaxPete, Mailman and 1 other person like this.
  20. Machine

    Machine Race the wind Top Contributor

    Rotor coming your way Jim.
    No hurry at all !
    -Randy, Vancouver WA, USA
    Mailman and Jim like this.

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