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TW200 stator coils...

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Recently, I discovered that my CDI "source coil" had fried. My bike would not start - no spark - and the troubleshooting flowchart pointed me towards this coil.

Once I had the stator REMOVED from the casing (which was another tale of grief in itself) I metered the coil to find a VERY high resistance (over 1 million ohms, should be 600-900) and I had to order a new one.

Can anybody offer up an explanation as to how/why this particular part crapped out? I am suspecting that it had to do with some battery problems I had earlier this year, which may have created the right conditions for this coil to start cooking itself, but otherwise I hear this part is fairly bullet-proof.

Any other TW riders with similar tales?

Other than this problem, this little bike has been an absolutely indestructible work-horse!

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I'm not a TW rider, but have been in the electronics (and other) field since the sixties. They all work the same. Coils, or anything else electrical, for that matter, fries for only one reason: too much current draw through them. Too much juice=cooked stuff. if you aren't an electrical savvy guy, think of it this way: everything electrical, and I mean everything, runs on watts, which is not only a value of electrical consumption, but of work. That said, watts is described by the formula volts times amps. think of volts as PSI in a water system, and amps as gallons per minute. If you can't get the volts, you WILL get the watts, which overloads the system and something burns up. Fuses and circuit breakers are designed to either trip (CBs) or melt (fuses) and disconnect the load from the source. In your TWs case, the coil I figure you are talking about is the item number 2 on the Yamaha website parts list, PN 4WP-85510-10-00, which is the stator. Stator, as in stationary. (vice rotor as in rotating) If this fried, I would suggest that you look at several things.

1. will the battery take a charge and keep it. It should show 12.7 or thereabouts out of circuit about a half hour after being both fully charged and disconnected from the charger. Use a motorcycle charger, car ones will fry the battery.

2. If so, are there any frayed wiring that you can see? yamaha uses the color code red up to the mainswitch and then brown for 12volts after the switch. If there is a rubbed wire when you are continually dumping some amperage to ground (frame. etc) it will also do this. You may have to really look. The headlight circuit is dark blue or yellow, one being high, the other low. Taillights and instruments run off this as well.

3. The stator provides three phase AC to a bridge rectifier/regulator assembly, which not only converts it to DC for the battery and everything else, but regulates it at about 13.5 to 14volts DC max to charge the battery. If the battery is good, with good connections and in circuit, you should be able to start the engine, and read about 12.8-14 volts across a fully charged battery with the engine running and revved up a little bit. Easily seen with a meter hooked up. If not, something is loading down the system and will kill stator #2. Again, this assumes a known good fully charged battery. Unlike cars, motorcycle charging systems aren't designed to charge up a sick or dead battery, but to maintain a charge on a healthy one.

If I assumed wrong, and the part you need is #3 from the parts list, 4JG-85580-01-00 pulser coil, then your CDI box has killed it and is probably also dead. then you need the pulser coil, CDI box and I would throw in an ignition coil as well.

I know this was a bit involved, but that is how it works, and if you don't want to spend yourself into bankruptcy on electrical stuff, you need to know what killed what. I do this for a living, but not on motorcycles, but it all works the same, including your car and house.

If the first assumption, charging system, I'd say battery, rectifier/regulator, wiring (possible, but you'll have to look) in that order. Also, look for incorrectly attached accessories and such. Like the pigtail you leave on the bike for a battery tender. That system can't handle much more than stock, so take extras off. No chargers for other things with more power than a cell phone.

The starter is a load after the battery, so it wouldn't directly kill the charging system, but could drag the battery down so much that it kills off the charging system trying to keep up. Again, a good, properly charged battery will show about 12.7 to 12.9 volts unhooked after being fully charged, and unhooked for about a hour. 12.5 to 12.6 is ok, but 12.2 is not enough to properly run the ignition, which is a pretty heavy load on a lot of bikes other than the lights.

Ignition system, the second one, I'd put all three parts in, because you'll keep killing stuff off if you choose wrong.

Anything else, just ask. Hope this helps.

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I'm not a TW rider, but have been in the electronics (and other) field since the sixties. They all work the same. Coils, or anything else electrical, for that matter, fries for only one reason: too much current draw through them. Too much juice=cooked stuff. if you aren't an electrical savvy guy, think of it this way: everything electrical, and I mean everything, runs on watts, which is not only a value of electrical consumption, but of work. That said, watts is described by the formula volts times amps. think of volts as PSI in a water system, and amps as gallons per minute. If you can't get the volts, you WILL get the watts, which overloads the system and something burns up. Fuses and circuit breakers are designed to either trip (CBs) or melt (fuses) and disconnect the load from the source. In your TWs case, the coil I figure you are talking about is the item number 2 on the Yamaha website parts list, PN 4WP-85510-10-00, which is the stator. Stator, as in stationary. (vice rotor as in rotating) If this fried, I would suggest that you look at several things.

1. will the battery take a charge and keep it. It should show 12.7 or thereabouts out of circuit about a half hour after being both fully charged and disconnected from the charger. Use a motorcycle charger, car ones will fry the battery.

2. If so, are there any frayed wiring that you can see? yamaha uses the color code red up to the mainswitch and then brown for 12volts after the switch. If there is a rubbed wire when you are continually dumping some amperage to ground (frame. etc) it will also do this. You may have to really look. The headlight circuit is dark blue or yellow, one being high, the other low. Taillights and instruments run off this as well.

3. The stator provides three phase AC to a bridge rectifier/regulator assembly, which not only converts it to DC for the battery and everything else, but regulates it at about 13.5 to 14volts DC max to charge the battery. If the battery is good, with good connections and in circuit, you should be able to start the engine, and read about 12.8-14 volts across a fully charged battery with the engine running and revved up a little bit. Easily seen with a meter hooked up. If not, something is loading down the system and will kill stator #2. Again, this assumes a known good fully charged battery. Unlike cars, motorcycle charging systems aren't designed to charge up a sick or dead battery, but to maintain a charge on a healthy one.

If I assumed wrong, and the part you need is #3 from the parts list, 4JG-85580-01-00 pulser coil, then your CDI box has killed it and is probably also dead. then you need the pulser coil, CDI box and I would throw in an ignition coil as well.

I know this was a bit involved, but that is how it works, and if you don't want to spend yourself into bankruptcy on electrical stuff, you need to know what killed what. I do this for a living, but not on motorcycles, but it all works the same, including your car and house.

If the first assumption, charging system, I'd say battery, rectifier/regulator, wiring (possible, but you'll have to look) in that order. Also, look for incorrectly attached accessories and such. Like the pigtail you leave on the bike for a battery tender. That system can't handle much more than stock, so take extras off. No chargers for other things with more power than a cell phone.

The starter is a load after the battery, so it wouldn't directly kill the charging system, but could drag the battery down so much that it kills off the charging system trying to keep up. Again, a good, properly charged battery will show about 12.7 to 12.9 volts unhooked after being fully charged, and unhooked for about a hour. 12.5 to 12.6 is ok, but 12.2 is not enough to properly run the ignition, which is a pretty heavy load on a lot of bikes other than the lights.

Ignition system, the second one, I'd put all three parts in, because you'll keep killing stuff off if you choose wrong.

Anything else, just ask. Hope this helps.

Everything you offered is helpful however, it was not the stator coil itself that was fried, but the larger "source coil" that is built onto the stator (although I assume that everything you said can relate to this item as well). This coil is clearly visible on Part #2 that you referred to...and is WELDED in place so it cannot be replaced as a single item.

Thanks.

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Well, you have lost me, as the stator is a three phase alternator, just like your car. There is no separate coil that I'm aware of on these. In years past, magnetos had a separate source coil for the ignition, and another for lights and charging system, but modern bikes use a three phase alternator just like a car, which is converted to DC by the rectifier and regulated by the regulator (both of these are as one unit). They then use the regulated DC to run everything from your headlights to your ignition, and keep the battery charged. Are you saying these are two completely separate systems within the stator of your bike? I see the plug on the factory drawing Is it the smaller one of the pair/ because if it truly is the source for your CDI, then my original statement stands: your CDI box killed it, as it is the load for this. Or the wiring to the CDI box.

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Sorry, had a call to answer; I forgot to ask, look at the diagram and tell me if it is item number 2 or 3 that fried. If it is part of #2, then I'll say I'm surprised they have a separate power supply for the CDI, but I guess it makes sense. The old magnetos were that way, but all of my recent Yamahas are not. Learn something new every day...even us old goats.

But if it truly is the source coil for the ignition, then I'd say the CDI box is on the way out, if not already out. They sometimes have poor enough connections that extra current is drawn to overcome resistive connections and that causes trouble, but I've never seen it kill off coils in the generator/magneto/alternator.

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The link doesn't work for me...don't know why, but I am familiar with the parts-drawing that you are referencing and #2 is indeed the stator coil.

Mounted on the circular ring is one LARGER coil, it's near the 7 o'clock position on the stator - this is the one that is fried and as I mentioned before, it is NOT repairable or replaceable; you have to replace the ENTIRE stator assembly!

246nex2.jpg

If the manual is right (and I sure hope it is) this IS the faulty part and my measurements concur...I just hope it's the ONLY faulty part.

(Why is the word "manual" hyper-linked? I didn't do that!)

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I looked again at your diagram, and sure enough, there it is. I was initially amazed that it was that way until I thought about it and the TW is basically the same since it came out in the 80s. If you look at the XT350 generator (magneto), it shows the same thing, only broken into a source coil for the ignition and two lighting/charge coils. Like I said, learn something every day. All of my current bikes just have alternators that feed the system like a car, then the various stuff gets its power from there. The price you pay for electric start and fuel injection. Can't run those without a good electrical system.

If that coil fried, and it wasn't due to a bad wiring harness from it to the junction to the rest of the wiring, then the question asks: what did it in? Is the insulation just tired? (that varnish looking stuff) Or is the CDI box starting to go and this is how it showed up.

In the old days, the magneto coils would sometimes open due to to all of the heat and vibration, but if they fried it was due to rubbed/shorted wiring or a bad ignition coil (pre CDI box). You have additional stuff in your circuit, kill switch, sidestand interlock switch, CDI box, plus the wiring and the coil. Anything is possible, but I'd look at the entire circuit to be sure nothing was messed up. If you have a wiring diagram: the kill switch on the handlebar: does it interrupt the source of juice for the CDI from the source coil, or is it just grounding a line to the CDI box? Same question for the sidestand switch. The only other things in the circuit that I'm aware of (remember, I don't have one and I'm doing this out of my empty hollow head) is the ignition switch and the CDI box, coil and spark plug, and the wiring between. Wiring should be relatively easy to check: it will be visual if messed up, although could be hidden behind other things. Switches and other, not so easy, but findable. If you have access to another TW, then use a ohmmeter to check between the wiring harness where your source coil plugs in to ground. With switches off and on. You'll find something, I would guess. If nothing else, you will know it ISN'T messed up.

The potting material they used on the coils: can you tell if the source coil portion was vibration cracked before the failure? Sometimes age and all of the heat cycles kill off the insulation and do them in, but I haven't see that recently. I still have some 70s stuff that works just fine. You've done well so far, I can guess that you have the factory manual and you're not afraid to try out your hunches.

These bikes are famous for anvil like reliability. I take it it runs now, after the coil change? I'm not attempting to induce paranoia, just caution: the coil could have been all there was, but it doesn't seem like that is all that is involved.

The funny little highlights/underlines, etc, are part of this site, and others as well. This site has a parts/goodies sales component that I believe they are attempting to link to.

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what did it in? Is the insulation just tired? (that varnish looking stuff) Or is the CDI box starting to go and this is how it showed up.

THAT is the Million Dollar question, but as I said earlier: I believe that my troubles started earlier this year when my battery was dying (not holding a charge due to a bad cell) and I kept pushing it while I was waiting for the new battery to arrive - 5 days later (ordered it on a Friday afternoon).

Last year, I'd had another problem with the battery when I changed the sprocket and had laid the bike on its side to do the work...I didn't realize it at the time, but the battery was spilling out the overflow while it was laid over. A week later, it was dead because half the cells had no liquid in them!

I'm hoping that it was this sort of stupidity on MY part that led to the demise of this coil, rather than some internal short or parasitic draw that will take days to diagnose and correct!

I take it it runs now, after the coil change?

I haven't changed the asembly yet. It is on backorder from the dealer right now and should be another week or so out of Japan.

In hindsight, I probably should have ordered it online from Stadium Yamaha or Boats.net but it was one of those split-second decisions I had to make...

These bikes are famous for anvil like reliability.

Indeed. I bought it from a guy when it had less than 5000km on it and other than batteries that I keep killing, I've had to spend little on breakdown maintenance. I've gone through a set of tires, but that's understandable...check and adjust valves as needed...nothing but synthetic oil...she's been bomb-proof up till now.

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Since it is the source coil for the CDI, then batteries or no batteries should have nothing to do with it. The rest of the stator charges the battery, provides the juice for the lights, etc. So what we're dealing with here is a AC generator whose sole purpose is to charge up the CDI to provide spark, and nothing else. So that, unless the insulation just said enough, then where to look for stuff, if anything at all? It could be just that, Bad/old/whatever insulation/potting on the coil. Perhaps not. Again, shorts in kill switch, wiring or main ignition switch, plus the actual CDI box is pretty much it. there is nothing else in the circuit. So eliminate one by one until you're sure.

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Yamaguy 55

As you seem to understand this system my Question is if I disconnect the headlight load ( turn off headlight will it overcharge my battery

 

    Thanks in advance

    Norm in Arkansas

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Sorry, been super busy and haven't been here in quite a while.

 

I answered this as a PM, but having been reminded of this previous conversation, I'm posting here too. So, I have to come back up to speed.

 

I'm not sure I'm in the know or not, but thanks anyway.

 

Firsticon1.png: modern motorcycles tend to have good electrics, unlike those of the past.

Exampleicon1.png:

In the not-so-good old days of the AT-CT-DT-RT series two stroke Enduros, if you pulled the battery, then started the engineicon1.png and ran the headlight, it would blow the bulb. The battery was needed as a load to help regulate the magneto charge/lighting output. The surges normally "damped" by the battery's presence would be free to spike and kill the bulb.

 

The TW is one of Yamaha's oldest designs, coming from the 80s essentially unchanged. However, I'd think it would have an advanced enough charging systemicon1.png to handle having the headlight off while still maintaining the battery. 

 

You could go to electronics supply house and get a tab regulator and addicon1.png it to the circuit, but there's always a chance of incorrect installation or a wiring problem, which could murder the entire charging system. 

 

The next option would be a high wattage ballast resistor to mimic the load the bulb has. But this has the same pitfall the first option has.

 

Then, you could always just leave the headlight on.

 

The running voltage measured across the battery is similar to that on autos: anywhere from 13.5 to 15 VDC while the engine is running, measured across the battery. You probably should check this after the bike has run for a bit and the charging system has had a chance to top off the battery after starting. In theoryicon1.png, if the headlight is off or on, it should be roughly the same. In theory.

 

But if I were doing this, I'd start by getting a good voltmeter, an accurate and trusted one (lucky me: I have several due to my job). Then I'd first measure the battery voltage first thing in the day, before i started the bike. If you have a battery tender, the access for the measurements already exists in the harness that you installed for that. I leave my bikes and John Deere on float charge all of the time I'm not using them, and the JD has a battery from 2002.

 

Get a pad, write down the voltage. A healthy battery that sat overnight should be 12.6-12.9 VDC. 12.7-12.8 is about where mine are. This is before you turn it on and run it. After use, with the headlight in the circuit, check it again, write it down too. Wait about a half hour after turning it off before  you check it. Do this five or so times to get a good average. So we're talking maybe a week or so of daily use. If used infrequently, maybe make ten checks to be sure you have a good average.

 

Now do the same thing with the headlight out of the circuit. If the battery "after" voltage is notably higher, then you are more heavily charging the battery. If it is .25 or more higher every time, then you may want to add a zener diode or something else to the positive lead. But if it were in the range stated above, I'd just monitor it and deal with it if I had problems. Any really good electronics supply house can provide you with whatever you need. Buy several, although modern electronics are very durable. Remember that anything getting rid of excess voltage is doing it by converting it to heat, so provide suitable cooling.

 

I don't have particon1.png numbers as that would assume I have a TW as well, which I don't. Every application doesn't necessarily use the same thing.

 

Let me know howicon1.png it works out. I'd also be interested in how the OP did in this topic. Those XT225s and TWs are everywhere, and run forever, so anything to add the the knowledge base is a plus.

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