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Old 12-18-2011, 08:43 PM   #136
JRWooden
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Random comments:

Gary: It might be the RPM at which the aftermarket stator is rated - 3500 RPM.
I would guess that max. output is not until much higher RPM, which is where BMW is getting the 400W max. output.

Cowboy: That sounds encouraging - how did you measure the temperature / temperature difference?

BudMore: Likely it will depend on the skidplate - note that the BMW version has some slots that let air pass thru, while some others do not have any slots. I'm not sure if the BMW design was an intensional addition for stator cooling or not... just my observation ... some skid plates pretty much block all airflow accross the engine covers... this can not be a good thing..........

a 10C degree temperature rise makes things happen roughly twice as fast...
http://www.chemguide.co.uk/physical/...mperature.html
e.g. insulation likely breaks down twice as fast for every 10 degrees C ..................

If oil were flowing into the stator area life would be much better ... alas, as Joel points out, there does not appear to be any provision for oil to circulate in that stator area ... thus ... it gets pretty damn hot when paired with a regulator design that runs the windings at 100% load.................

IMHO any and all methods that would reduce the average operating temperatue of the stator would pay huge dividends......

I gotta go now.............
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Old 12-18-2011, 09:18 PM   #137
ebrabaek
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I will make a CF/K shield...... It seems like good points have been passed on here.....enough for me to consider that radiant heat is at the very least a catalyst.

Erling
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Old 12-19-2011, 03:49 AM   #138
JoelWisman
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C5!

There is oil injected into the case at 2 points, just none directed directly onto the stator. It is cooled and in my opinion, not very well by splash only.

You will usually loose one coil only in the alternator, even if the problem is caused by external heat. The odds that all 3 phases age and fail at exactly the same time is remote and this particular alternator is wound with good separation between phases. Anyways when a phase finally fails, it does so by shorting at which point it cooks and turns black pretty instantly. At this point it may short to other phases and take them all, or if separation is good enough, only one phase will burn.

Just one phase being burnt is in NO way indicative that the voltage regulator has a problem, nor is it an indication that the voltage regulator doesn't.

Reducing the radiant heat directed at the stator cover can't hurt and should help, but I doubt it will help all that much.

No body is measuring the stators temperature but only the cover temperature and through various means. The stator is mostly hanging inside there and not in particularly good contact with the cover.

What would be REALLY interesting is if someone attached a thermocouple to the stator and read off temperatures. Hell, could add a gauge to the cluster and monitor it full time. "I ride a BMW, stator temperature is more important then coolant or oil pressure lol"

But seriously, I have a cheap digital candy thermometer. The sort u get at a grocery store. As it happens, It dropped into some carmel I was making and while I was tearing apart the kitchen looking for it, my carmel turned into hard candy. While chipping it out of the pan I found my digital candy thermometer but broken in half. The thermocouple, wire and display head all came out and still works. The wires are tiny and would squeeze under the rubber plug on the cover, RTV the junction to the magnet wire, tape the head to the cover and we would have real temperatures.

I.m in St Louis if anyone wants to come by and experiment :)
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Old 12-19-2011, 07:09 AM   #139
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Did you notice in the link that C5! sent about applications:

BMW Street Bikes
F650 (97-01)
F650CS (02-11)
F650GS (99-11)
F650ST (97-98)
G650X (07-11)
F800S (07-11)
F800ST (07-11)

SUZUKI Street Bikes
VS700 Intruder (85-87)
VS750GLP Intruder (88-91)

Wonder what the price is for the Suzuki parts :)

Never mind, Bike Bandit, Stator assembly for 1990 VS750GLP = $331.56 but none in stock.
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TowPro screwed with this post 12-19-2011 at 07:28 AM
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Old 12-19-2011, 07:39 AM   #140
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Quote:
Originally Posted by towpro View Post
Did you notice in the link that C5! sent about applications....
Yes, I had noticed that the F800GS is not listed.

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Old 12-19-2011, 08:21 AM   #141
JRWooden
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Quote:
Originally Posted by JoelWisman View Post
...No body is measuring the stators temperature but only the cover temperature and through various means. The stator is mostly hanging inside there and not in particularly good contact with the cover.

What would be REALLY interesting is if someone attached a thermocouple to the stator and read off temperatures. Hell, could add a gauge to the cluster and monitor it full time. "I ride a BMW, stator temperature is more important then coolant or oil pressure lol"

But seriously, I have a cheap digital candy thermometer. The sort u get at a grocery store. As it happens, It dropped into some carmel I was making and while I was tearing apart the kitchen looking for it, my carmel turned into hard candy. While chipping it out of the pan I found my digital candy thermometer but broken in half. The thermocouple, wire and display head all came out and still works. The wires are tiny and would squeeze under the rubber plug on the cover, RTV the junction to the magnet wire, tape the head to the cover and we would have real temperatures.

I.m in St Louis if anyone wants to come by and experiment :)
I a prior job, a long long time ago in a galaxy far away, when I mounted up thermocouples for temperature monitoring we used a "thermal epoxy" ... its a two-part expoy like the regular stuff, but modified for better thermal conductivity.... good stuff - this would likely be OK:

http://www.newegg.com/Product/Produc...82E16835100013

Joel: You're right of course ... If we are going to get to the bottom of this .... getting some accurate baseline measurements, then comparing them to readings taking with bash plate, with heat shield, swapping regulators, etc. is really required.
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Old 12-19-2011, 08:48 AM   #142
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Quote:
Originally Posted by C5! View Post
Tks cowboy. looks like i should go this way as well. How much work did it require to do the wrap, did you have to remove the headers, etc... needed new gaskets? there are all kind of wraps, fiberglass, titanium, etc.. I have no experience whatsoever in exhaust wraps, anyone better than the other?
C5! I did not remove the headers. I got some heat wrap at the local auto parts store for $18.00. I used a couple of clamps to secure the tape at both ends. I started 1" forward of the foot peg and wrapped BOTH pipes all the way up just past where the Alternator cover stops, then single wrapped to finish at inlet.

You MUST start your wrap from the bottom - if not you leave room for water, sand, ect to enter the wrap. You will understand what I mean if you start from the top...... hahahaha.

I used a cheap-ass digital thermo. Yeh, I know they are not real accurate - I just wanted some kind of temp difference. I rode the bike for about 30 minutes without the tape - measured the alternator cover temp closest to the exhaust tube. Then I wrapped it, did a 100 mile hamburger ride and when I returned I measured at exact same place. It was much cooler... you could actually touch the cover without burning the hell out of your finger.

So... my pea-brain says to me - "look, if the cover temperature is lowered, the stator temperature inside the cover must be lowered too" - and lower temperature COULD mean longer stator life". Really, it said that to me.

Yes the stator area has a small oil bath. I would like to see a modified cover with some kind of cooling fins built in - because I REALLY think heat is the issue here...

"I COULD BE WRONG - BUT I DON'T THINK SO" quote by Sir Charles Barkley...

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Old 12-19-2011, 11:27 AM   #143
JoelWisman
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Cowboy, by "cheap ass digital thermo" Do you mean something you have to press against the cover? Or one of the infra red jobs that you just point at it?

If you used something that you have to place in contact with the cover to measure it, you used something far more accurate then the infra red units even if it was a toy :)

If those measurements were made with a direct contact thermometer then I'm convinced you are onto something!

I fully agree that the stator temperature is the most likely culprit.

What I am having a hard time guessing is how much the cover temperature is affecting the temperature of the magnet wire.

Only a lot of time or some serious measurements is going to tell.

I'm a little leery about heat taping the header near the engine. At higher throttles as well as anytime the bike is running lean, the first foot of the header sees flame on the inside. Pushing hard I've hotter the first foot of my header glowing red many times.

Insulating it may cause it to fail and could also increase the head temperature when the bike is pushed and especially when it's hot out.

I don't see any issue with insulating the exhaust where it passes under the stator cover nor insulating the side of the cover.

Fins on the outward facing portion of the cover would help as would using a thermally conductive substance to bond the stator to the cover.

The part that is complex is the magnet wire is a major source of heat itself. Copper is very thermally conductive but it can still have localized hotspots. It only takes one tiny bit of the magnet wire overheating to cause a short that immediately overheats the rest of the phase and even adjacent phases.

Since a failure anywhere in the magnet wire will cause a failure everywhere, and since the stator produces a tun of heat by itself, it could be that these stators are shorting where they face inward at the furthest place from the cover, perhaps somewhere they are getting little or no oil splash. Or perhaps they are failing in the closest place to the cover and heat conducted by the exhaust is the major contributor.

I simply don't know, but anything that lowers the cover temperature sure as hell can't hurt and absolutely should help!

If I still owned one of these bikes or still worked for a BMW dealer I'd be buying some digital candy thermometers, pulling them apart and measuring temperatures at a few places on the stator.

Sadly I don't so all I can do is empathize from afar and enjoy the fact that both my current bikes are known for long life stators :)

Good luck. I think you guys are on the right path and are bound to find it before BMW issues a fix, if they ever do.

P.S. Cowboy, some of your posts are showing you to have anything but a "pee-brain", but riding 100 miles in Minnesota during winter for a burger is insane :p
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Old 12-19-2011, 06:28 PM   #144
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Quote:
Originally Posted by FredRydr View Post
Yes, I had noticed that the F800GS is not listed.

Fred
Check Max parts catalog. It is the same part number for the alternator for the 800 S, ST and GS
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Old 12-22-2011, 07:05 PM   #145
TheCowboy
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Joel, I am using a point-at-it IR Termometer from Radio Shack. I use it when I am troubleshooting aircraft engines - looking for a cold cylinder. Rather than the old way - putting your hand on each cylinder head cover and which ever cover does not leave flesh on it is the bad cylinder. Now I can just point and click and see which one is the coldest - indicating which cylinder is not firing.

I can build an airplane from scratch (I've built three of them - all aerobatic hot rods), but I am only a shade-tree mechanic when it comes to motorcycles - all though I did work in a BSA shop all through my high-school years - I sure loved my 441 Victor - and I still have the scars on my shins to prove it.

Like everyone else here, I am just guessing - shooting in the dark for some kind of answer to this puzzeling question of stator failures. I wish BMW would put one of there engineers on the problem.

I'll let you know in another 50,000 miles if this heat tape fixed the problem - or sooner if it don't.

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Old 12-22-2011, 08:03 PM   #146
JRWooden
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Quote:
Originally Posted by TheCowboy View Post
... I'll let you know in another 50,000 miles if this heat tape fixed the problem - or sooner if it don't.

TheCowboy
Thanks Cowboy ....


I'd like to try other things, but I look in my toolbox and sometimes all I see is a hammer...
Then I look at the problem and it doesn't seem much like it needs a nail.........................
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Old 12-23-2011, 06:21 AM   #147
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It is clear that stator windings are being chared and failing. Fact one. The question is why and what the root cause is.

Failures seem to come at 30,000 miles or more. Certainly not evenly distributed over time....ie the same rate of failures on new bikes and on the higher milage ones. Is this an important clue? Could this age related condition be fact two?

A first though logically it that it is too hot. Why?
Has the engine temp in the stator housing gone up over time? If so what would cause that?
A lot of talk about exhaust pipe temp contributing. Are exhaust temps hotter on older bikes. Are the exhaust headers closer or touching the case? Not enough info on this but the ad hoc info seems there is no change here.
Is there any real info to support the idea the stator housing gets hotter with the age of the bike? No?
So if the stator housing is not hotter with age, what would cause the stator it self to get hotter with age?
Is there more current flowing in "old" stators than new? If so what would cause this excess current?
Are the magnets on the rotor getting stronger with age? Are they rotating closer to the stator...higher flux density so more current is made? An area to think more about.
Could the regulator malfunction increase the currents in the stator? Most say no because of the design. Is that really true in all failure mods?
Does the copper winding in the stator age? Would this aging cause over heating? No?
Does the insulation on the stator winding age? Would this aging cause shorted windings and over heating? Would these shorts cause gradual output voltage reductions...that could be measured as a precursor symptom?
Why would the stator insulation age / fail? Poor material used? Some type of contaminations? Vibration cause cracking? All good things to think about and get more info.
Has anyone really analyzed a failed stator?
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Old 12-23-2011, 08:58 AM   #148
JRWooden
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Quote:
Originally Posted by vtbob View Post
...
Does the insulation on the stator winding age? Would this aging cause shorted windings and over heating? Would these shorts cause gradual output voltage reductions...that could be measured as a precursor symptom?
Why would the stator insulation age / fail? Poor material used? Some type of contaminations? Vibration cause cracking? All good things to think about and get more info.
Has anyone really analyzed a failed stator?
VTBob:

All good questions .... If I were a gambler I woulf vote for the quoted item above... but it's just a guess.
IMHO, yes, insulative qualities do degrate with time/heat so at some point when you get a short between ajacent windings the situation is agrivated and feeds on its self till it self destructs. The time it takes for this to happen would likely be a function of ambient temperature, average speed of bike (more convective cooling at higher speeds, but then also higher current in the stator at higher speeds ... not sure which would predominate.... ) and then if bash plate was installed this would reduce the convective cooling ....

With the stator sitting inside the "counterbored" flywheel and not getting much of any oil bath cooling and sitting on top of the exhaus header it is a less than ideal situation for the stator....

One of the other guys on the forum was going to send me his failed stator unit, but I have not hear back from him...
If I get it I will try to see what I can figure out... but it may be difficult to figure out wether the insulative failure was the result of the failure or the cause of the failure or ... both ...?

One thing I've mentioned before is that if the copper used in the windings is a lower grade it would have a higher bulk resistivity and thus create more heat.

In terms of predicting failure ... if all three stator windings are at the same voltage (the voltage will vary with RPM) then likely the stator is good - if on the other hand one of the windings is at a lower voltage then likely that winding is failing ... A device could be designed that would plug in-line with the harness from the stator that would monitor/compare the voltages of the three windings and post an alarm if one winding started acting up.... In truth I'm not sure how much better that would be than just a simple voltage monitor...

JRWooden screwed with this post 12-23-2011 at 09:57 AM
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Old 12-23-2011, 09:25 AM   #149
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Quote:
Originally Posted by JRWooden View Post
A device could be designed that would plug in-line with the harness from the stator that would monitor/compare the voltages of the three windings and post an alarm if one winding started acting up....
What about a regulator/rectifier that isn't running the stator at 100% capacity all the time.
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Old 12-23-2011, 10:08 AM   #150
JRWooden
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What about a regulator/rectifier that isn't running the stator at 100% capacity all the time.
Sorry to not be clear!
IMHO a non-shunt type R/R (that did not run the stator flat out all the time) would reduce heating in the stator and thus reduce (eliminate?) stator failures.

I was mostly trying to just respond to VTBob with regards to why the OEM design is failing prematurely ....
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