2nd rotor in 2 years. Why? And how to make them last?

[jurgenkoppen]

Well, it seems a bummer to replace rotors so frequently.
I have a 78, with the mod on the charging system to a GM regulator and the home made rectifier using Radio Shack diodes. Worked great for 5000 miles, but now the rotor, which came from Tim Parrot (sp?), mysteriously went AWOL again .
Anybody have any clue where to look for the cause of the premature departure of my rotor? And are there any other sources for a replacement? Tim never reimbursed me for my core, he just did not answer my inquiries, so I am not to keen to give him more business. Looking forward to your input, Cheers

 

[retiredgentleman]

Well, it seems a bummer to replace rotors so frequently.
I have a 78, with the mod on the charging system to a GM regulator and the home made rectifier using Radio Shack diodes. Worked great for 5000 miles, but now the rotor, which came from Tim Parrot (sp?), mysteriously went AWOL again .
Anybody have any clue where to look for the cause of the premature departure of my rotor? And are there any other sources for a replacement? Tim never reimbursed me for my core, he just did not answer my inquiries, so I am not to keen to give him more business. Looking forward to your input, Cheers

I have some recommendations. Alternator rotors don't like heat and vibration. We can't do much about vibration, but we can reduce the heat. A few ways to reduce heat..............use spacers to open up the small cover plate for cooler air flow to the alternator..................reduce the alternator current load by installing an LED tail/brake light. The #1157 incadescent bulb is a current hog..............even worse on the 80 to 83 years that have two #1157 bulbs.

As part of reducing current load, use a 40 watt low beam headlight, not a 55 watt low beam. I use a 40/60 Halogen.

Also, make sure you have a good battery so that the alternator is not overloaded trying to charge a failing battery.

How is the rotor failing? Does it have low resistance from slip ring to slip ring, or is it open circuit. I have a spare rotor that I repaired. It came to me as a failed rotor, but on inspection, I found that the wire coming from the winding had broken off at the slip ring terminal.

Yes, you should try a different source for a rotor. www.customrewind.com in Alabama was known to do an excellent job on rewinding rotors.

I have been using the same alt. rotor that came on the bike 6 years ago, and also the same battery, with no problems at all. I use a VR-115 regulator, dual bridge rectifiers, and
always have about 14.2 volts, on my on board voltmeter, as I drive along the highway.

 

[jurgenkoppen]

Hey gentleman, thank you for your thorough reply. I will implement all your recommendations asap. Regarding your questions: The battery is fine and less then one year old, holding charge OK for weeks. The ohm reading between slip rings was infinite, ie open circuit. I just tried the test one more time with full voltage on brown, ground on green brush, but still, no charging, just... eeeks smoke and burning smell from the rotor/stator . Meanwhile my lights go of and on, the warning light ( oil/tail) goes off and on.I did all of Curly's tests, and the result points to the rotor. If yours is available, I am keenly interested. Since you are in canada, that would help with shipping as well. How much , and do you do paypal? Thanks again for your input, much appreciated. Cheers,J

 

[jurgenkoppen]

Also, where did you find your LED bulbs?

 

[retiredgentleman]

Hey gentleman, thank you for your thorough reply. I will implement all your recommendations asap. Regarding your questions: The battery is fine and less then one year old, holding charge OK for weeks. The ohm reading between slip rings was infinite, ie open circuit. I just tried the test one more time with full voltage on brown, ground on green brush, but still, no charging, just... eeeks smoke and burning smell from the rotor/stator . Meanwhile my lights go of and on, the warning light ( oil/tail) goes off and on.I did all of Curly's tests, and the result points to the rotor. If yours is available, I am keenly interested. Since you are in canada, that would help with shipping as well. How much , and do you do paypal? Thanks again for your input, much appreciated. Cheers,J

OK, well you have fallen into a trap that others have done too. Curly's test procedure where you ground the brush with the green wire, applys only for the 80 to 83 years. When you do that on your 78, you are puting a short circuit on your regulator, which is a very bad thing to do. Did you blow the main fuse by any chance? You may have damaged the regulator. Curly's procedure needs to be more clearly re-written.

You have misunderstood me. My spare rotor is not for sale. I only mentioned my spare rotor to point out to you that sometimes the wire from the coil is broken off and can be easily repaired.

Yes, you need a new or rewound rotor if yours is open circuit.

I bought the LED tail/brake light at Walmart for $19.95.

 

[jurgenkoppen]

Hmmm, the Curly trap.... Given that I had modified my 78 charging system set up using the Chrysler regulator (which regulates the ground, not the positive of the field brush) and given that my positive brown brush is isolated from ground, is my regulator still fried?
I am missing a few bits in my understanding here. I guess I need to do a regulator check of some sort now..... BTW, just bought a 79 rotor from another xs650.com member, so I can dissect the old rotor once I can get it off. Any tips on pulling it would also be appreciated,....Cheers, Jurgen

 

[weekendrider]

Jurgen the only sure fire way to pull it is with the rotor puller designed for that rotor.
If you want to dissect it follow the directions in this thread.
http://xs650forum.proboards.com/index.cgi?board=Electrical&action=display&thread=1373

My thoughts on the rotor failure.
Wet cell batteries were and are still common.
Not everybody takes a second look at them after installation. Till they get to the point it won't even kick start. By then it is so abused that the water refill and charge don't do anything but prolong the agony. By then they have learned if they pop the headlight fuse and kick or push start it they can limp home and put it on the charger.
In the morrow it will crank and the machine is reliable enough fire. By the next day your kicking again. So it is charged again.
The whole time this is happening the rotor is working harder never shutting off.
Getting hotter and hotter. The epoxy expands and breaks leaving a crack for the elements to get in.
The bike was desgned to run with it's stock headlight and tailights.
It was not designed to run with a battery that didn't allow a cooling period. Period.

Next is the brushes. I by no means understand electricity. But I do understand if something isn't generating a full charge and has to run all the time it isn't going to get a cooling period. Again overheating the rotor.

There are those that recieved decent treatment by the previous owners and don't have this problem. Retiregentlemans a fine example. He takes good care with his stuff and I'm betting it wasn't no rat bike when he bought it.
There are others. My '79 and an '83 still have the originals.
I recently bought one from another forum member that the epoxy is a clean ambered color with no cracks and lo and behold it ohm test at almost 6 (5.9 iirc)
I doubt 5twins has had to replace his. Grizld1 probably doesn't have problems or XSLeo and Pete's is probably better than new.

I do know I can post pictures of 4 bad ones and what they all have in common is black baked exopy with cracks. An ohm reading at 2 and below. And ya know those came from bikes people were still trying to limp along. Kick that sumbeech enough shell start.

OP I think your first rotor bit the dust from overheating.
The second failed cause Tim Parrot has sketchy feedback. Not really the rotors fault.

 

[retiredgentleman]

Hmmm, the Curly trap.... Given that I had modified my 78 charging system set up using the Chrysler regulator (which regulates the ground, not the positive of the field brush) and given that my positive brown brush is isolated from ground, is my regulator still fried?
I am missing a few bits in my understanding here. I guess I need to do a regulator check of some sort now..... BTW, just bought a 79 rotor from another xs650.com member, so I can dissect the old rotor once I can get it off. Any tips on pulling it would also be appreciated,....Cheers, Jurgen

OK, that's a different story. Since yours is modified which makes it similar to 80 to 83, you did not short out your regulator, and your regulator should not be in any different condition than it was before.

Yes, the correct puller that XS650direct sells is the best tool. That puller is very simple and the rotor will come off easily.

 

[retiredgentleman]

Jurgen the only sure fire way to pull it is with the rotor puller designed for that rotor.
If you want to dissect it follow the directions in this thread.
http://xs650forum.proboards.com/index.cgi?board=Electrical&action=display&thread=1373

My thoughts on the rotor failure.
Wet cell batteries were and are still common.
Not everybody takes a second look at them after installation. Till they get to the point it won't even kick start. By then it is so abused that the water refill and charge don't do anything but prolong the agony. By then they have learned if they pop the headlight fuse and kick or push start it they can limp home and put it on the charger.
In the morrow it will crank and the machine is reliable enough fire. By the next day your kicking again. So it is charged again.
The whole time this is happening the rotor is working harder never shutting off.
Getting hotter and hotter. The epoxy expands and breaks leaving a crack for the elements to get in.
The bike was desgned to run with it's stock headlight and tailights.
It was not designed to run with a battery that didn't allow a cooling period. Period.

Next is the brushes. I by no means understand electricity. But I do understand if something isn't generating a full charge and has to run all the time it isn't going to get a cooling period. Again overheating the rotor.

There are those that recieved decent treatment by the previous owners and don't have this problem. Retiregentlemans a fine example. He takes good care with his stuff and I'm betting it wasn't no rat bike when he bought it.
There are others. My '79 and an '83 still have the originals.
I recently bought one from another forum member that the epoxy is a clean ambered color with no cracks and lo and behold it ohm test at almost 6 (5.9 iirc)
I doubt 5twins has had to replace his. Grizld1 probably doesn't have problems or XSLeo and Pete's is probably better than new.

I do know I can post pictures of 4 bad ones and what they all have in common is black baked exopy with cracks. An ohm reading at 2 and below. And ya know those came from bikes people were still trying to limp along. Kick that sumbeech enough shell start.

OP I think your first rotor bit the dust from overheating.
The second failed cause Tim Parrot has sketchy feedback. Not really the rotors fault.

I think your understanding of electricity is quite good. You brought up some very good points.

The rotor can be doing its job either in a "light" duty mode or it can be doing it in a "heavy" duty mode. When the bike first starts up, the rpm is low and the battery voltage has been pulled down due to the starter motor. The result is the regulator puts about 2.2 amps into the rotor in a "heavy" mode. The rotor is working hard to produce a strong magnetic field. That 2.2 amps produces heat. How much heat? Power = current squared X resistance. So that is 4.84 X 6 = 29 watts.

Now on a bike that has a properly working alternator, a good battery, and no excessive loads, the voltage starts to rise ( reaching 14.1 volts in a perfect world) with rpm, until the regulator is only sending about 1 amp into the rotor. This is the "light" duty mode. The 1 amp produces heat. How much you might ask? Power = current squared X resistance. So that is 1 X 6 = 6 watts

If the battery is old, low in water, brushes are too short, slip rings oxidized, and the bikes electrical loads are high, such as #1157 tail light bulbs, running high beam 60 watts constantly; the voltage never increases (hangs around 13 volts maybe) and so the regulator keeps sending > 2 amps to the rotor. The poor rotor stays in "heavy" duty mode constantly.

Yes, rotors last a lot longer with only 6 watts as compared to 29 watts. Of course there is lots of heat that comes from the engine heat itself.

 

[pamcopete]

One part of the charging system that is usually overlooked is the rectifier. The original rectifier was made with earlier technology and has a higher resistance than a new silicon rectifier. The resistance of the older rectifiers does not get better over time, it gets worse, so to overcome the additional loss of the old rectifier, the regulator sends more current through the rotor windings which causes the rotor to run hotter and therefore shorten its life.

You can have a charging system that works just fine, with the battery voltage right where it should be and all of the electrical systems working just fine, but if you have the original rectifier, the rotor is working harder and getting hotter due to the voltage drop going through the diodes in the rectifier.

Even if you are going to keep that old relay type regulator, you should replace the rectifier for a longer rotor life. You can use two full wave bridge rectifiers from Radio Shack to do the job for less than $7.

 

[weekendrider]

Thanks RG but I really don't understand this stuff.
In my mind the rotor turns and makes electricity with the stator( fauking magic)
sends it to the rectifier to change it, then to the regulator to chop it up in pieces to be stored in the battery. But I'll keep reading and maybe some of it will stick.

Pete thanks for pointing this out. Couple of questions.
The test in the manuals have don't have a value?
Just good or bad? Any chance the little symbols got mixed up for the 82-83?
It seems to work jsut bardwacks for me when I check it?

 

[retiredgentleman]

One part of the charging system that is usually overlooked is the rectifier. The original rectifier was made with earlier technology and has a higher resistance than a new silicon rectifier. The resistance of the older rectifiers does not get better over time, it gets worse, so to overcome the additional loss of the old rectifier, the regulator sends more current through the rotor windings which causes the rotor to run hotter and therefore shorten its life.

You can have a charging system that works just fine, with the battery voltage right where it should be and all of the electrical systems working just fine, but if you have the original rectifier, the rotor is working harder and getting hotter due to the voltage drop going through the diodes in the rectifier.

Even if you are going to keep that old relay type regulator, you should replace the rectifier for a longer rotor life. You can use two full wave bridge rectifiers from Radio Shack to do the job for less than $7.

Yes Pete, the old selenium rectifiers got the job done, but had a higher forward voltage drop. Probably dropped about 1 volt, whereas the modern silicon diodes only drop about 0.6 volts. Since the voltage drop increases with age, anyone using the OEM rectifier, likely has quite a bit more drop than 1 volt.

 

[xjwmx]

Well, nobody else is using a rotor per year, so something is broken. If the rect is killing your rotor, it isn't happening to a lot of other people. We really don't know what the rotor can handle. We just feel we do.

But it could be that the first was real old and the second was real crap and that the third one will be the charm. Meanwhile I'd check all my wiring and understand everything. At the subatomic level.

At any rate, I thought I read you saying you had a new rectifier anyway.

 

[retiredgentleman]

Thanks RG but I really don't understand this stuff.
In my mind the rotor turns and makes electricity with the stator( fauking magic)
sends it to the rectifier to change it, then to the regulator to chop it up in pieces to be stored in the battery. But I'll keep reading and maybe some of it will stick.

Pete thanks for pointing this out. Couple of questions.
The test in the manuals have don't have a value?
Just good or bad? Any chance the little symbols got mixed up for the 82-83?
It seems to work jsut bardwacks for me when I check it?

If measuring a diode (rectifier), an ohmmeter will show about 6 or 7 ohms, when using the lowest scale. Reversing the probes will show very high (open circuit). On my analog meter, the red probe + connects to the cathode (band) of the diode, to get the forward conduction (6 or 7 ohms). That just means that the VOM battery is supplying a negative voltage on the red probe, and a positive voltage on the black probe.

With my digital meter, I select the "diode" symbol, and it will show about 580 to 700 millivolts forward voltage drop, which is normal. In this case, my black probe (com) is connected to the cathode (band) of the diode.

 

[jurgenkoppen]

Thank you all for your input. Gathering all the information, it seems that my first rotor fried due to age and low battery.
I make it my job to tweak my old machines until they are just humming. I do seek to understand them on a "subatomic level", and lavish them with TLC.
The second rotor had a new battery, the Chrysler regulator, and the Radio shack diode pack rectifier. The only reason for earlier departure left according to my still limited understanding could be still 1) the load of the lights, as RG pointed out,2) the iffy work ethics of my rewind expert Tim, or 3) a sneaky short somewhere in the ignition circuit.
At this point I recall that I had the colorful charging indicator sold by Mike's XS wired into my system. One fiber of that meter connection in the headlight bucket had found its way out of the junction in the circuit and apparently occasionally touched the headlight bucket inside on my bumpy logging road. Perhaps that was enough to fry or jeopardize my charging system.
At any rate, thank you all for adding to my understanding. I will bend over backwards to make my lady 650 purr and hum. Dynamo Humm, (FZ) one of my favorite sounds...

 

[pamcopete]

Thanks RG but I really don't understand this stuff.
In my mind the rotor turns and makes electricity with the stator( fauking magic)
sends it to the rectifier to change it, then to the regulator to chop it up in pieces to be stored in the battery. But I'll keep reading and maybe some of it will stick.

Pete thanks for pointing this out. Couple of questions.
The test in the manuals have don't have a value?
Just good or bad? Any chance the little symbols got mixed up for the 82-83?
It seems to work jsut bardwacks for me when I check it?

Don't bother testing the rectifier. It will probably test good, but that is meaningless. It's like checking the tire pressure on a bald tire. If it is the original rectifier, just replace it. It's like $7 for the rectifier vs $125 for the rotor.

 

[cra-z1]

Good read. Great info and everyone very professional sounding.

 

[jurgenkoppen]

Thanks RG but I really don't understand this stuff.
In my mind the rotor turns and makes electricity with the stator( fauking magic)
sends it to the rectifier to change it, then to the regulator to chop it up in pieces to be stored in the battery. But I'll keep reading and maybe some of it will stick.

Hey weekender, maybe I can play the role of the guru for a moment.
You have it right that the rotor and stator makes the AC power which then is turned into DC by the rectifier.
The regulator however, just senses how much voltage is going to the battery, and if there is too much coming in, turns down the electrical field generated by the rotor, thereby lowering the output of the stator/rotor combo. That way there will be no overcharge. Once the voltage drops below a set point, the regulator allows again a stronger field, and the combo is cranking out more juice again. I am pretty sure that is how it goes.