[Capt Frank]

I have fooled around with charging systems for a lifetime now and have learned a few things. In this forum, I have read many accounts of post mortems on stators complete with well done pictures and circles and arrows. All are focused on the result of stator failures and how it happened. Normally the insulation breaks down and a coil either shorts to ground or opens somewhere. Again, this is a result...not a cause. Want to know why stators fail?

Most charging systems fail for the same reason...trying to charge an old, or nearly dead battery.

Think about it. The battery gets worse and worse. The system works harder to charge it, voltages go down and amperages go up. Gassing boils water out, causing corrosion on the terminals. Voltages in the battery drop due to poor battery condition at the same time that terminal corrosion makes it ever harder to get power into or out of the battery. The stator works harder to charge until finally somewhere, at the weakest point, amperages get high enough to melt insulation or the coils just arc to ground.

The moral to this story? It's simple. Do not buy cheap batteries. Do not keep your battery more than a couple of years...three at the most depending on your climate. Do not keep your battery on a charger for more that a day a month, ever! If your starter is dragging, check the terminals. If they are tight and clean, check the battery with some type of stress tester. When in doubt... replace it. It's a lot cheaper than replacing the stator and the battery together. If you are jump starting your bike, you are going to get to know a lot more about the inside of your engine than you really want to.

Hope this helps,

Capt Frank

 

[Dana_h_acdc]

Excellent, Smithers. Excellent.



You said it better than anyone else has recently... but even with a good battery and a good connection why do the high speed windings fail as often as the charging windings? Or maybe more often? That Ignitech is a godsend! We would have been up the creek without paddles long ago if it wasn't for piece of magic!



My 2 rupies or yen or shillings or whereever your from!

 

[Cobram]

But would any of that hold true for a stator setup like our bikes have? The stator operates pretty much balls to the wall all the time, the higher the revs, the more output. Any extra the battery or systems doesn't use short-circuits to ground, so even with a bad battery, the load on the stator is the same. Or am I mistaken?



I think it's got a lot more to do with internal engine temps (same stator in a turbo lasts half as long as a NA bike), regularity of oil changes, and contaminants such as gas in the oil or other corrosives that can be generated in a crank case which attack the laquer.



The stator in my 32+ year old CX looked perfect when I had it apart, more than 35k miles. I bought it new and never let it go more than 1500 miles between oil changes.

 

[DaveF]

Our bikes use a shunt regulator system, so the load seen by the stator does not vary as long as the load does not increase to the point where the stator cannot keep up with it and the output voltage falls out of regulation.



One such case where this can happen is when the battery develops one or more shorted cells. Fortunately, this battery failure mode is not that common as compared to other failure modes.



That said, I did have a battery short out once while riding on a very rough road.

 

[CXPHREAK]

The stator in my custom failed the first time it was asked to recharge a flat battery [this, strangely enough caused by the exhaust system but that's another story].



The battery was near new and still performing strongly a year later.



I think there must be some merit to what Capt. Frank says but I think in my example the stator must have been about to fall over anyway.



I think the comments on oil changes and engine temperatures are also on the money as well as general engine condition allowing blowby of unburned fuel and combustion products adding to the hellish environment the stator lives in.

 

[ramprat06]

Good post Capt. And I agree with all the above. Keeping a good oil change regimen will save many hours down the line.



Three things. Heat, contaminates, and poor electrical systems.



Thankfully, there are means to fix most of those issues. And thus, keep these marvels on the road.



Joel in the Couve

 

[Shep]

I'm afraid some of this this information is incorrect.Stators are not an electrical load bearing device.They do NOT work harder if a battery is low.They are semi constant output device which continually provide current the excess of which is dumped as heat via the Regulator/Rectifier unit.

They are also for all intents and purposes electrically isolated from the rest of the electric system by the Regulator/Rectifier circuit.

The two most common causes of Stator failures in our design will be through not changing the oil+filter and coolant at the correct service points.Old oil slowly becomes acidic and abrasive and also causing the engine to rum warmer than needed this causing premature engine component wear.

There is of course a natural service life of components and depending the quality of the unit this will vary.

Peter's bike gives an idea of components being changed on a high mileage one owner CX,



http://globalcxglvtwins.hostingdelivered.com/viewtopic.php?f=20&t=289



Hi Shep,





Below is the list of work done on my 145 K machine. I should point out that in general I've changed the oil (and filter) every 3000 to 5000 Km, and I adjust the tappets every month or two. I also replace the air filter every couple of months.



stator replaced 70 K

cam chain replaced 70 k

valve seals and cleaning 70 k

Rectifier 100K



starter replaced 1X

Front forks oil replaced and seals 2X

Carb overhauled 145K

Rear Driver Overhauled 120K

Front brakes overhauled 3X

Rear brakes overhauled 3X

Rear Tires 5X

Front Tires 3X

Tachometer Replaced 143K

Clutch Cable 2X

Throttle Cable 2X

Front Stabilizer Brace 1X

Shifter 1X





I also added Zerk fitting to pivot area to stop squeaking around (70K)... and it works great.





Cheers

Peter

 

[DaveF]

This topic was also discussed on the old forum, see here.

 

[stern-69]

Well, you guys are mostly right, but still a few inconsistancies that maybe I can shed a bit of light on.



The Stator is a simple 3 phase alternator that generates power when the engine is running (via rotating magnetic field being induced in a conductor. When the engine runs the stator can be looked at as a 3 phase transformer in its operation (as dealing only with the secondary coil). While the coil itself is somewhat isolated via the diodes in the regulator, it actuall IS what is considered a load bearing device. The regulators function is to "clip" the tops of the generated AC waveform and shunt it to ground, basically "limiting" the max voltage to the desired level. this is the reason the stator is wired 3 phase, as after full wave rectification the waveform itself is a pretty flat DC level (less "bumps as opposed to a standard bridge recification). As engine speed increases, so does the voltage generated by the stator, and the regulator keeps that in check by removing a larger amount of "top" from the waveform.



Now, the stator will produce "X" power based on engine speed up to the point of its maximum rating. Once this point is reached (well within the bikes operating RMP range) as the voltage increased, available current decreases. This is the main reason that the bikes are NOT supposed to be operated without a battery, as the battery acts as a large filter capacitor to keep a "min load" on the stator, thus limiting the voltage that can be produced (open circuit voltage). Without the battery, very little current would flow from the stator, but very large voltages (hundreds of volts) would be generated in the windings, leading to weak point arcing within the windings.



Now, currnet load on the stator is based on what is connected to the electrical system. A bad battery can draw a huge ammount of current, dropping the voltage the stator can deliver. The problem here is that heavey current loads cause the stator windings to heat up, and can lead to insulation breakdown causing shorts to ground, or open circuits within the weakest point of the winding. It is no different than if you were to take a transformer and short the output ... it would heat up and eventually short/open its secondary winding.



Now, batteries .... these things are antiquated technology but work well for their intended use. The main problem with batteries are the way they react to "charging". A normal good battery will start accepting a charge (known as a bulk charge) when they are low and begine to charge when the bikes running (as in after a high load like the starter motor). This charge drops quickly into its standby charge (trickle charge). This poses no issues for the stator as it is more than capable of these levels (bulk = 1/10 of AH max, and trickle = 1/30 AH). The problem comes with a bad battery (old, drained flat, damaged, low electrolite etc). A bad battery will do one of two things when you try to charge it. It will refuse to take a charge (will still draw whats equivilent to a bulk, but will not hold it), or it will suck a load (bad or shorted cell, total plate degredation, etc) which will see the battery suck many times the normal bulk level (can be as much a 1/2 AH rating). This is a huge load for the stator and will generate large amounts of heat in the windings. Some batteries in this condition will fail further into what is basically a dead short condition, which will either fry the stator or pop the rectifiers in the modual (not totally sure on the Imax of the diodes used, probably 20-30AMP min i would guess).



This does not mean that a new battery is OK, as I know my stator died when I tried to charge a 1 year old battery that was flat, and unfortunatly I neglected to notice it had lost over 1/2 its electrolite. when I added distilled water and tried, it was enough to kill the stator. Now this doesnt mean that it will happen all the time, as my stator was 30+ years old, and winding degridation happens over time, even if the bike is just sitting. The insulation and shellac on the windings DO degrade ith time and thats just a fact of nature. I would state that time is the biggest factor as opposed to bad oil or engine temp, as the insulation has a min breakdown temp of well over anything the engine can generate (300-600 deg C). This can further be validated by the poll someone started that compaired what failed when the stator died (in the pre 82 bikes using timing coils on the stator), where failure occured in the speed coils (which are NOT under load stresses) and not the charging coils.



So, how do you stop the stator from dying ? Well, you cant, but you CAN maybe give it some more time. An old stator is more "prone" to overvoltage and over currnet conditions than a new one, so keeping the battery good, changing fluids, general maintenance will all help. But as we all know, sometimes they just "POP" when we are riding. I would concur with post here that the single biggest way to prevent a stator failure (charging windings) would be to make sure the battery is good, and NEVER try to charge a bad battery. Also, jump starting a bike with a car is OK (you MUST leave the bike battery connected) BUT you must break the jumper connection once the bike is running.



When looking at the big picture, blowing $100.00 on a new battery every few years is sure better than blowing $80.00 on a new stator (G8 anyway, more for the other) and having to do an engine out replacement (Stator cost + gaskets + down time + hastle + loss of riding season + etc).

 

[Cobram]

We've all said just about the same thing with a few nuances. The OP applies to an automotive charging system and not what's used on our beloved steeds.



Check the tars and change the earl.

 

[StormRider]

O.K. I understood everything FADM Stern said but Cobram I have to ask.......

"Check the tars and change the earl." WTF?

 

[Cobram]

O.K. I understood everything FADM Stern said but Cobram I have to ask.......

"Check the tars and change the earl." WTF?

South of the Mason Dixon line, y'all check the tar pressure and change the earl and filter.

 

[americanclassic]

O.K. I understood everything FADM Stern said but Cobram I have to ask.......

"Check the tars and change the earl." WTF?

tires and oil.

 

[StormRider]

Hah that was my guess. Really wasn't sure though.

 

[coffee_brake]

Wait, what?



I am a knowledge sponge regarding the charging system of the CX500, even though I don't comprehend some of the terminology.



As I understood it, the CX500 is such that, if the battery fails, it can be bump-started or jumped off with the dead battery still hooked up with no problem. Unlike more modern machines, which will burn up the R/R if the battery is too far gone while running.

Well-aware of the problems this might cause in other bikes, I was very careful to research this problem before making an offer on my CX500. Was I wrong?



'Cause I jumped my CX500 with a known stone-dead battery. Who knows how many times the PO did it, I did it to test-ride the thing, and again to get it started to prove to my hubby that it DID run and I was not insane to bring the rather crusty "vintage iron" home. Have I doomed the stator of my twisted twin? I haven't even put a tag on it yet, was gonna get that tomorrow!



I have never, ever heard of the oil condition having an effect on the charging system. Of course it's one of the first things I do and right up there on what the CX gets this week as I bring it to the street again...but considering the work to check it all out, I am still not giving up my place in line for an Ignitech unit.



Ya'll gotta keep it simple for me, I get Tahres and Ahl, but phases, volts and capacitors are a little beyond where I am now...

 

[Shep]

Oil doesn't affect the charging system as such but dirty/acidic oil can damage the Stator windings physically.Unlike most cars and motorcycles our stators are not,"Dry" and are splashed by oil.All mechanical and electron mechanical devices are designed to work with in certain temperatures so if the engine has been running over heated this will cause premature wear of many internal components.

As Cobram says change the oil earl(oil) regular and basically maintain the bike as it should be including the battery.The service points in the Manuals are there for a reason

 

[Casey Stangle]

This is an inherant problem with this bike. Does anyone know of another brand or model of motorcycle that this is a problem with? I have a 450 that is 41 years old and do not belive this is a problem with this model. Its stator is in oil and subjected to the same heat, maybe more because it is air cooled. I had an old 305 that the rectifier went out (one diode) and it would fry bateries. Never blew a stator. Are the newer stators that you replace it with more durable? Made differently?

 

[CXPHREAK]

I don't actually know the answer to your question but can say I have 3 CB 450s in the shed and all still charged when last run. I never had this sort of issue in many miles on the 450s 350s or the cb175s I had many years ago.



Having said that, many of those bikes charging was so marginal that many of them exhibit the "yellow wire mod" where the yellow wire to the regulator is disconncted to disable the regulator and running with the headlight on.



The CX charging system when functioning properly would far outperform those from those earlier bikes.



I believe the CX is worth just sucking it up as one of these bikes few flaws as it's not such a big deal if you can do the work yourself.



A good quality replacement stator, properly installed will last for many years and you'd be unlucky indeed if you ever had another problem with it.



The impression might be that these things fail all the time but really they don't. It is one of the more common failure modes of these bikes and maybe starts to seem a bit larger than life.

 

[DaveF]

I don't think the problem is that bad. It's not uncommon for a stator to die, but let's keep in mind we're talking about 30 year old bikes. How many car alternators last that long?



As CXPHREAK said, a high quality replacement stator should provide many additional years of service with no problems.



The newer stators are not necessarily more durable. There are differences between manufacturers, but most problems I am aware of from the newer stators are due to quality control problems (Electrex comes to mind) and not necessarily due to design variations.

 

[Shep]

I think if we put it in perspective over time if you get 50,000 miles+ from a Stator the cost penny-per-mile is negligible.Even less with the G8 Stators

There are many vehicles/motorcycles that have much more costly defects.A taxi drive pal of mine has just had to replace a fuel management unit for the 2nd time so that's another UK£ 250 = 402.32500 U.S. dollars

I haven't spent that much on both my Cx combined in the last four to five years except where I wanted to