Poll - How are your Stator rewinds holding up?

[maclariz]

Was interested to read various stuff in the Stator papers and in the posts about rewinding Stators. Was just wondering if you could do something for me and answer a couple of questions:

1) When did you rewind your stator?

2) Is it still working?

3) Did you coat with epoxy / similar or not?

This would help see whether home rewinds are working or not and whether epoxy coating has any effect on reliability or not.

 

[tfb]

1. On the Kat1100, rewound stator + new RR nearly 4 years ago. On the GS1000S, rewound stator + new RR just over a year ago.

2. Yes and Yes.

3. No and No.

 

[fgh]

1) When did you rewind your stator? Spring of 06

2) Is it still working? No! It shorted out after < 5,000 miles

3) Did you coat with epoxy / similar or not? Yes

 

[Guest]

1) When did you rewind your stator? This summer

2) Is it still working? Yup

3) Did you coat with epoxy / similar or not? Yup - baked varnish per rewind shop recommendation.

 

[Guest]

still running the original
95000 kms on the clock

 

[Nerobro]

1) When did you rewind your stator?

2) Is it still working?

3) Did you coat with epoxy / similar or not?

1) Two years ago now?

2) Yes, very well thankyou.

3) No. But I did use larger guage wire.

 

[maclariz]

1) When did you rewind your stator? Spring of 06

2) Is it still working? No! It shorted out after < 5,000 miles

3) Did you coat with epoxy / similar or not? Yes

Any idea why it fried?

 

[SPARKSS]

Was interested to read various stuff in the Stator papers and in the posts about rewinding Stators. Was just wondering if you could do something for me and answer a couple of questions:

1) When did you rewind your stator?

2) Is it still working?

3) Did you coat with epoxy / similar or not?

This would help see whether home rewinds are working or not and whether epoxy coating has any effect on reliability or not.

I've rewound 5 times now with varying results and I'm ok with that......I've been making notes and trying something a little different each time. My durability has been from a high of 20km to a low of 8500km and never with expoxy - really just using what I've had on hand - red insulator varnish or even high temp paint to help secure the windings. I've rewound a few motors over the years and quite a few transformers and have never had any fail until my attempts with the GS heheh. I've read quite a few theories about why they fail and outside of the obvious (shorted load) the following are my thoughts based on teardown (most times I've detected a slight change in charging voltage and tore down right away before it burned right up or left me walking).

- I think heat.....a combination of ambient and electrically generated is one factor. I haven't come up with a solution to the ambient heat prob yet but have been trying progressively less windings as a trade-off between keeping a system stable and generating excess heat from high power dissipation due to regulation and output current (which is high and tapers off right after startup).

- I think perhaps abrasion from small particles in the airgap between the stator and rotor AND chafing of windings - either to each other or to the core is a major cause of my own failures. Core covering prior to winding and winding movement would be helped big time with the right epoxy here. A heavy gauge wire sounds like the plan but it mechanically doesn't wind well much larger than 18ga (at least by my hands!). I can't help but wonder if trying to layer 2 or more layers/pole is doing more harm than good when hand wound based on voltage measurements and some observing of the waveform on a scope. At any rate, I'm no engineer - and my latest attempt is the one I'm most interested in. Instead of winding my 18 pole stator as 3phases x 6 poles I've tried 3 phases x 3 poles, leaving one bare pole between each wound one - an attempt at reducing heat in this area. In the same attempt I've reduced my winding to a mere single layer on each pole, crossing high to low on the backside (with insulator tubing). Results have been good so far but with just a few thousand km on it........generated AC waveform is good and consistent between phases and I have about 30Vrms available line-line. Rectified (DC) voltage holes at approx 13.8 under normal load and about 13.2 with two extra 4411 driving lights on. Time will tell.

Original rectifier and regulator here at 96500km still working fine.

 

[tfb]

Great post there sparkss; keep us posted (so to speak) :-D

Here's the question that I've been pondering for years now... maybe I should start another thread, but it does arise out of what folks have said earlier on this thread.

And that is, when our GS charging systems go belly-up, what has caused what?

From my reading over the years, some seem to be of the view that it is a faulty RR which causes the stator to toast itself.

Others seem to think that the stator goes first, then the RR.

Not to be ignored in all this, is the original Suzuki wiring arrangement (viz., the third phase only being engaged when the headlights are on) which -- it is alleged -- cooks a phase of the stator.

(BTW, in both my bikes I have removed that original wiring, and have simply wired all three wires from the stator straight into the RR. So maclariz, maybe we need to add a fourth question to your three above: is the wiring arrangement wrt the headlight switch bypassed?)

Does anyone have a logical explanation for how things typically happen in the cascade of depressing electrical events? :-s

 

[SqDancerLynn1]

Heat is a big problem, even a low oil level can cause stator to overheat.
The third leg- eliminating the switch= less wiring=less resistance=less heat. You do ride with the headlight ON. Bad connections, bad grounds cause excessive heat. Anything you can do to minimise it will prolong it's life

 

[SPARKSS]

Well (chuckling here)....Part of the answers to your questions I touched on in my post (re heat and electrical load) but some more specifics could be mentioned. The stator is ONE source of electrical power in the bike.......the battery is the other. By itself the stator generates AC which by itself would be ok for powering lights but not the ignition, nor for performing it's more important role, charging the battery, so a rectifier assembly must be used. To make most efficient use of the AC power, we don't use not a simple 1 diode/phase setup (halfwave) but 2 diodes/phase which rectifies both the postive going half AND the negative going half of that AC wave......we call this full wave rectification and this particular arrangement of diodes is a fullwave rectifier bridge (there is another fullwave setup but requires a differently wound source). The rectifier and everything that it supplies is therefore the LOAD for the stator.......shorted diodes in this rectifier may cause excessive load to the stator just like a short or abnormal heavy load elsewhere in the bike. Because the battery is charged by the stator/rectifier IT is a LOAD ultimately to the stator also.....one or more shorted cells in the battery keeps the charging current high as the stator/rectifier tries to bring the battery voltage up - and can never do so. This is one common failure that causes excess heat in the rectifier and stator. Now we'll turn our attention to voltage regulation. Because the stator generates more voltage as the engine speeds up, and the loads on the bike (resistances) are basically fixed, any increase in voltage over the nominal design voltage of things like lights and the ignition cause increased current to flow through and out of, the stator which results in more power being generated AND dissipated by the stator....power = heat and is the product of voltage x current....thus we have to regulate the voltage to prevent both the loads burning out AND the stator from destroying itself. The battery as a load (while it's charging) also will draw more current as the voltage increases but can only be easily pulled UP so far after which increased charging current causes battery destruction due to gassing and plate warping due to heat - ruining it. The regulator circuit the bike uses is a "shunt" type circuit typically using whats known as a zener diode (there are many methods however). This basically acts as a short circuit across the stator output ONLY WHEN THE AC VOLTAGE RISES HIGH ENOUGH......because this (should) happen for just a part of the waveform, normally the extra heat generated isn't significant and in fact, the usual operating loads of the bike (battery, lights, igniton) tend to pull down the voltage just enough to not require much regulation at idle and lower engine speeds. Reason for mentioning all this is that should part of the bikes loads (battery, lights etc) open up, the voltage can soar in the stator which MAY cause insulation to break down (along with the high ambient engine heat - remember!) and/or cause the rectifier diodes to exceed their rating - which MAY cause them to short.....and so the downward spiral starts. The reason the GROUND LEAD is often mentioned as a culprit is that, if missing, it causes the stator to become unloaded (problems as above).

Now think about WHY the engineers put a switch in to lift one phase, except when the headlights were turned on - an attempt to drop the generated voltage BEING RECTIFIED thus stabilizing system voltage when the extra load (power) of the headlights wasn't required. If you'll notice, only 2 of the phases typically have shunt regulation applied to them.....for system protection when electrical loading is slight. Many of us wire this phase directly, bypassing the switch but keep lights on (or they're wired on) and running like this, day and night increases the dissipation of the stator......what can I say.

On my own bike I have the 3 phases wired, but have reduced the generated voltage to compensate.......and have that headlight switch available to turn 'em off should I have to conserve or boost charging current a little.

Another point often brought up is "why even have a battery.....my GS550 has a kick starter" for example. Although used primarily to power the starter motor, the battery does an excellent job of moderating system voltage just because it can't easily be pulled high (it just charges heavier!). Thus in a system designed for use with a battery, WITHOUT one, the simple permanent magnet/stator charging system will cause the voltage to skyrocket......heating the regulator (which is not designed for this heavy continuous use) and heating other loads such as lights and ignition excessively......and burning them out (this I can attest to!).

There's lots of other points and details to much of this but it ought to give you an idea.

 

[maclariz]

One thing I also saw on my wiring diagram for the GS400 is that the Zener diode regulator is attached to the yellow wire from the stator. This means excess voltage on the yellow wire (once the battery has reached capacity) dissappears nicely down the regulator. Unfortunately, excess voltage on the other two wires (phases) from the stator cannot go the same way straight to earth. Instead, this excess voltage will need to go back through the stator to get to the yellow wire and then out to the regulator. Thus, once the system is producing too much voltage bringing the regulator into action, current will feed through the stator to regulate it. This could be one phase of current if lights are off or two phases if lights are on but you get the idea. Whatever, do this for a long time and the stator is going to get nice and toasty. So a nice long trip at high revs could well fry your stator good and proper. Sounds to me like refitting a better regulator/rectifier unit is pretty much essential for good stator life.

Haven't seen the wiring diagram for the Electrex units, but it would seem that a separate regulator for each phase would make more sense.

 

[SPARKSS]

One thing I also saw on my wiring diagram for the GS400 is that the Zener diode regulator is attached to the yellow wire from the stator. This means excess voltage on the yellow wire (once the battery has reached capacity) dissappears nicely down the regulator. Unfortunately, excess voltage on the other two wires (phases) from the stator cannot go the same way straight to earth. Instead, this excess voltage will need to go back through the stator to get to the yellow wire and then out to the regulator. Thus, once the system is producing too much voltage bringing the regulator into action, current will feed through the stator to regulate it. This could be one phase of current if lights are off or two phases if lights are on but you get the idea.

Great discussion here. You're a little off base on your theory however with respect to how that single regulating zener works on your GS400 (and indeed what the current flow path takes within the rectifier and beyond). First of all, voltage doesn't flow.......voltage is only seen because there's a difference of potential between one point and another (one point more negative with respect to the other which we therefore may call positive). It's this difference that causes CURRENT (which we measure in amperes) to flow IF there's a complete circuit. You likely know this but the terms are often misused leading to confusion.

The next information needed is that current only flows one way* or not at all. My training followed the electron theory of current flow which describes current flowing from negative to positive (This bothers many people and there's a reciprocal theory describing positive to negative......but the same exact rules apply in either case except with polarities reversed). The reason I say this is so that you know that current can not be generated by the stator and then flow through itself (this requires an external complete circuit!) - thus your single regulator on the GS400 acts on just the one "phase". Tracing current flow at any instant in time will show this to be the case.

NOTE - We often refer to a phase and mean the source between any 2 of these 3 wires. With the WYE wound stator, each of these pairs of wires actually has 2 phases in series (though not with voltage at exactly the same time).....each phase is the physical winding. More correctly this is called line-to-line voltage between any 2 wires here. Should you be looking at a stator wound DELTA (3 in a triangle!).....then each pair of wires indeed looks at a "phase".

What does happen, which confirms your suspicion that the stator keeps working, is that two of the phases, not regulated merely continue to charge the battery and keep system voltage up.......whereas the 3rd also contributes but is limited (and loaded!) by the regulator should the voltage tend to rise above the regulators "zener voltage" (trip point if you will). Overall the contribution by the 3 "phases" is moderated and we say it is regulated.

Hopefully you're still awake there Wishing the snow away here already so that I can get back riding.

 

[maclariz]

Great discussion here. You're a little off base on your theory however with respect to how that single regulating zener works on your GS400 (and indeed what the current flow path takes within the rectifier and beyond). First of all, voltage doesn't flow.......voltage is only seen because there's a difference of potential between one point and another (one point more negative with respect to the other which we therefore may call positive). It's this difference that causes CURRENT (which we measure in amperes) to flow IF there's a complete circuit. You likely know this but the terms are often misused leading to confusion.

The next information needed is that current only flows one way* or not at all. My training followed the electron theory of current flow which describes current flowing from negative to positive (This bothers many people and there's a reciprocal theory describing positive to negative......but the same exact rules apply in either case except with polarities reversed). The reason I say this is so that you know that current can not be generated by the stator and then flow through itself (this requires an external complete circuit!) - thus your single regulator on the GS400 acts on just the one "phase". Tracing current flow at any instant in time will show this to be the case.

NOTE - We often refer to a phase and mean the source between any 2 of these 3 wires. With the WYE wound stator, each of these pairs of wires actually has 2 phases in series (though not with voltage at exactly the same time).....each phase is the physical winding. More correctly this is called line-to-line voltage between any 2 wires here. Should you be looking at a stator wound DELTA (3 in a triangle!).....then each pair of wires indeed looks at a "phase".

What does happen, which confirms your suspicion that the stator keeps working, is that two of the phases, not regulated merely continue to charge the battery and keep system voltage up.......whereas the 3rd also contributes but is limited (and loaded!) by the regulator should the voltage tend to rise above the regulators "zener voltage" (trip point if you will). Overall the contribution by the 3 "phases" is moderated and we say it is regulated.

Hopefully you're still awake there Wishing the snow away here already so that I can get back riding.

Okay, some fuzzy stuff in my description, but still the two wires without direct connection to the Zener will have voltage on them and if the battery is full, then the only way for the current to go is back to earth via the stator. Surely this will make the stator hot. If not, what is wrong with this R/R design and why does it cause all the problems?

 

[SPARKSS]

Okay, some fuzzy stuff in my description, but still the two wires without direct connection to the Zener will have voltage on them and if the battery is full, then the only way for the current to go is back to earth via the stator. Surely this will make the stator hot. If not, what is wrong with this R/R design and why does it cause all the problems?

Nothing wrong with dragging fuzzy out now 'n then! I still read a misunderstanding here. You're entirely correct that, on your bike, only 1 phase is limited providing some regulation. However the other 2 are not. As long as the charging source (stator+rectifier) has a voltage higher than the battery, the battery will continue to try to charge.......once the chemical process has completed (battery fully charged), additional charging current just serves to heat and hydrogen is gassed off (typical flooded lead-acid battery). Because the engine with this type of generating system has low output @ low rpm and high output @ high rpm, a compromise must be struck between the size of the battery, anticipated normal engine operating range and loads........with a regulator thrown in to moderate the voltage at the mid to higher rpm end. Long story short (no pun intended!), the reason your stator heats, is simply because extra current is being output to the battery and other loads as the voltage rises with rpm. On the phase (or phases) being regulated, the current also rises but in the form of a temporary short-circuit (shunt) across that phase, by that simple regulator......and the battery and other bike loads don't experience an increase in voltage as a result. All this is possible because ALL of our wiring has resistance - and this relationship to voltage, current and power is what our friendly ohms law describes so well. Power can do work or be dissipated as heat (sometimes desired and sometimes not).

An observed waveform of this is not pretty under light or no load......2 of 3 phases (in your case) are somewhat a sine wave and 1 is cropped. In the case of 2 regulated legs, 1 is somewhat sine and 2 are cropped.

Make sense? In your description (if I've interpreted it correctly), if you disconnected 1 stator lead (either one that doesn't have the regulator lead attached) from the rectifier, you'd expect it to still heat due to being regulated - and this can't happen......a source must have 2 terminals and a complete circuit for current to flow.

 

[hp1000s]

OK...so having said that(LOL)...is it considered wise to eliminate the stator wiring loop that runs all the way to the left handlebar control-and back, if the headlight load will always be present? Oh yeah...tech-talk is kewl!

 

[SPARKSS]

If the headlight will always be on then you'll need that wire connected......so you could eliminate the "loop to the headlight switch". It'll likely shorten the life of the stator somewhat.......which is a marginal item working in a terrible environment at the best of times - they'll run for a heck of a long time but with no room for extra engine heat or electrical load - in my opinion.

 

[Matchless]

Here is quite an interesting take on the subject: http://www.shadowriders.org/faq/jumpstarting.html

Jump Starting ? NOT from a Running Car​

Submitted by Radford, B Davis​

The issue is that cars (and 'wings and a very few other bikes) have a different type of alternator than our Shadows (and most other motorcycles) have.
Basic theory idea, for those who came in late: Generators of all types make electricity by moving a magnetic field relative to a coil of wire. The stronger the magnetic field and the faster it moves, the more electricity is generated. The moving part is usually called an armature or rotor. The stationary part is called a stator.
The typical car alternator is an excited field type. The magnetic field is created by an electromagnet in the rotor. Supply voltage is controlled by the amount of current going through the electromagnet. Most big AC generators are made this way. If an external power source is applied of a higher voltage than the regulator setpoint is applied to the system, the regulator will recognize the system voltage as being above setpoint and turn the field magnet (usually rotor) off. Result: No problem, as long as the applied voltage isn't so high as to damage anything (typically 25 V or higher on a 12V system). So you can (usually) jump start a car with another car, or a GoldWing without any problems.
Now the bad news:
Most motorcycles don't use an electromagnet to create the magnetic field. Instead ,we have a drum-shaped rotor (usually on the crankshaft) with several permanent magnets placed inside (a magneto). These magnets moving past the stator coils create the electricity we need to run the lights, charge the battery, etc. But you can't change the strength of a permanent magnet. So regulating the generator output is not a straightforward issue of turning the field magnet strength up or down.
The motorcycle voltage regulators I've seen all take the approach of shunting excess generated power to ground. This has the advantage of making sure that the voltage is the same everywhere in the system, but the disadvantage of meaning that the stator is always flowing its maximum rated supply current. This, I think, is why many motorcycles have a reputation for frying stators.
So the design of one of these regulators is completely different from a cage regulator. It has a voltage detection part, like the other regulators, but the big resistor/power transistor package has to be strong enough to carry all the possible excess power generation to ground. It handles a lot more power than the car regulator has to. It generates a lot of heat as it does this, which is why the regulator on my '85 VT1100 is finned and out in the open air--to carry off the heat before it cooks something in or around the regulator. A typical bike magneto makes 30-50 amps at max power. So the regulator is designed to dissipate a maximum of about 700 watts for short periods (this would be full power and no loads on the bike--the battery and lights are all missing). In practice, this cooks the regulator pretty fast--they don't like to dissipate more than about 200 watts for any length of time.
Now consider what happens when your moto regulator is doing a good job keeping the system at a nominal 14.1 volts when running, but the battery is weak, so you have to jump-start it on cold mornings. You hook up the bike to your Toyota with a 95 amp alternator (max output about 1400 watts). The Toyota's voltage regulator keeps *its* system at a cozy 14.3 volts when the engine is running. We now have a problem.
The cage's alternator and regulator want to maintain the system at 14.3 volts. Your bike's regulator, the instant the system is turned on, is going to try to bleed off excess voltage from the system to keep it at 14.1 volts. The car's alternator is rated for 1400 watts. The bike's regulator can dissipate a maximum of 700 for (very) short periods before it cooks itself. It's a tug of war, and the bike regulator ALWAYS loses.
Moral of the story--jump-start your bike from a non-running cage. The quiescent voltage of a car (or bike) battery is in the 13.2-13.8 volt range. The only result of this is that the full output of the bike's magneto will go into the cage and moto batteries once the bike starts. This actually reduces the load on the regulator to near zero, so it's quite happy with this state of affairs.
Corrolary: Want to reduce the load on your bike's voltage regulator? Install MORE (or brighter) lights. No kidding. Since the regulator only handles power output beyond the bike's demands, installing more demands means that the regulator does less (and is happier). The stator does the same amount of work in either case, so no problem there. Be forewarned, though, that Honda didn't exactly break the bank on copper for the wire in our bikes. It's sized to work just right with no corroded connectors and the stock loads. You need to run larger/more supply wires from the battery if you intend to use significantly more power than does the stock system.

 

[Matchless]

My stator was rewound by an old hand in the trade who told me that he used the specs from a newer model as the OEM stator was very prone to failing on the 1980 GS bikes. He used heavier gauge wire and definitely fewer turns, which gives out about 40 volts AC per phase instead of the 70 - 90 volts quoted by some people. I recall not seeing any voltage change on the battery above about 2000 rpm, voltage stays just under 14 volts on a full battery, nothing changes when lights are switched on and off. My 3rd winding is permanently connected. I have not noticed any charging problems and drive with lights on in town a lot.
I recall my old beach buggy days and the only good test on those old 6 volt bugs was to wire an ammeter to the battery and see if the charge with and without load is positive and that a low current flow goes to the battery when full and higher when discharged and that it does not show any negative flow except maybe when idling.
I should do a quick check of this on my GS.

 

[SPARKSS]

My stator was rewound by an old hand in the trade who told me that he used the specs from a newer model as the OEM stator was very prone to failing on the 1980 GS bikes. He used heavier gauge wire and definitely fewer turns, which gives out about 40 volts AC per phase instead of the 70 - 90 volts quoted by some people. /QUOTE]

Hi there Matchless.......Your "old hand" understands the problem exactly.