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Discussion Starter · #1 ·
I have an 83 Honda Nighthawk with a bad stator. I was looking into rebuilding it myself... doesn't seem to be too overcomplicated with the wiring. Is there anyone who has successfully attacked something similar? I am looking for someone to provide a little guidance to the finer points of removal, cleanup, rewire, seal and bake. Not sure of suggested materials or process, but would like to give this a shot. Thanks in advance.
 

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Visionary
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I started out in the electrical field many years ago in an electric motor shop, rewinding electric motor and generator stators and rotors. It's been 35 years but I remember the process quite well.

We used to soak in a tank of very caustic material to eat the varnish but at home the easiest way to take it apart would probably be the other way we did it, heat it up, get the iron good and hot with a heat gun or torch and the varnish/ epoxy will soften and you can pull it apart. Remember you need to count the number of turns in each coil and figure out the internal connections, the pattern of how the phases are connected is very important.
You would line the slots or wrap the poles ( depending on how it's built) where the wire goes with insulating paper or fiberglass, then put the same number of coils of the same size varnished magnet wire in each slot, and then duplicate the connections (we used to braze them so they were reliable) and then you would be ready for the last step, epoxy or varnish. I'm not sure what the right material would be to run submerged in oil, we used an air dry then bake varnish, but I never did a anything that ran in oil so I'm not sure what to suggest.

I rewound generators and motors from automotive size up to a couple thousand KVA ( which is BIG), the process is the same but you probably wont need a crane to life the stator for your bike. The smallest I ever did was actually a vacuum cleaner motor, the size of a child's fist, it was my own.. a lunchtime project. I had it hanging on the 5 ton crane to drip off the excess varnish and took a picture that I wish I still had.


Either do all that or just buy one :)
 

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Discussion Starter · #3 ·
Mike721. That information is great. There was an instructable on rewiring a stator. That was the kind that was laid out more like a radial engine and looked like a painful exercise. The honda doesn't have the same "spoke" layout.
It followed along with what you said for the most part. Used enameled magnet wire of same gauge as original and some kind of insulating paper anywhere the coil could touch the stator metal core.

I don't know that the stator for this bike is in an oil bath.. Heard that was a thing for cooling, but when I took off the cover it looked very dry.... and I think vented. Maybe just heat is the enemy on this bike.

I don't know much about brazing connections, and insulating epoxy, but I am going to do some research and will respond here.

Yes, I could have someone else rewire this for me and probably do a pretty good job, but at $250+ it seems like it is worth investigating an alternative.
 

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Discussion Starter · #5 ·
Thanks Semifast. I have gotten positive feedback about Rick's before. The stator for my bike through them is $275 with a 1 year warranty. Not sure why it is on the top end of their price range for stators.
 

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Discussion Starter · #6 ·
Looks like I will try a used stator before I do anything crazy. Found a source that is local.

I also noticed that the model I have has a field coil winding in the center... just makes things a little more difficult.
 

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I also noticed that the model I have has a field coil winding in the center... just makes things a little more difficult.
A field coil requires sliding contacts to energize, using power output by the regulator; those contacts can wear out. Maybe your stator is fine?
 

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Discussion Starter · #8 ·
My resistance measurements on the three yellow wires as well as the field coil seemed to be off. Expected was .6 OHM on the pairs of three yellow stator wires, I had 1.1 to 1.2 Ohms on each set of wires. Field coil was I think in the neighborhood of 2 to 3 Ohm and expected I read was 6-8 Ohm. I am basing the failure of my stator on its inability to charge and these measurements. There are no apparent shorts and the bike mileage is low (6K). Stator visibly looks like new.

I don't know anything about the field coil, I assumed the regulator was regulating voltage to the field coil to "request" the proper amount of generated electricity based on demand.
 

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It is difficult for your average multi-meter to measure resistances that low; reading 1.1 instead of 0.6 is well within the typical error margin, and could be due to minor contact resistance built up between the probe and contacts, and the probes and meter inputs. There are also tiny offset Voltages generated by two dissimilar metals making contact. If the yellow wires read open to the engine, then it is probably good, as measured. Unless, of course, you are using a meter that implements 4-wire correction, which would be much more accurate.

You might want to also measure the field coil to engine case ground, as those numbers, while still in the margins for your average meter, do seem a bit low. There could also be worn spots in the slip ring the contacts ride on, or contamination diverting the current, reducing the average field current in the coil, or just dirty contacts in the connectors between the field coil and regulator. Yes, the regulator adjusts the current through the field coil, to increase or decrease the power out of the stator, but it assumes the current path is good. PM generators are a lot easier to verify.

While it is still possible the stator is bad, I would first measure the Voltage between the three yellow wires, with the field connected and motor running; I would expect something over 50VAC, probably much higher. If it wavers, the field connections are suspect.
 

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It is difficult for your average multi-meter to measure resistances that low; reading 1.1 instead of 0.6 is well within the typical error margin, and could be due to minor contact resistance built up between the probe and contacts, and the probes and meter inputs. There are also tiny offset Voltages generated by two dissimilar metals making contact. If the yellow wires read open to the engine, then it is probably good, as measured. Unless, of course, you are using a meter that implements 4-wire correction, which would be much more accurate.
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While it is still possible the stator is bad, I would first measure the Voltage between the three yellow wires, with the field connected and motor running; I would expect something over 50VAC, probably much higher. If it wavers, the field connections are suspect.
Also, measure the stator both cold, and after it's good and hot (30 minute ride should get it there and heat-soaked). A failing stator often gives WILDLY different readings (and failure modes) at typical road temps. Guess how I know that?
 

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Discussion Starter · #12 ·
RocketGeek. I have a 1983 550. Wish I had the 750. The stator I have is very pricey and not too easy to find.

WintrSol. I came across another post years ago. You answered on that post and the poster seemed to know how the stator worked after he removed it. Apparently the field coil produces a magnetic field and instead of a permanent or electromagnet spinning near the stator windings, this setup has a metal "bladed" cup setup that spins the blades between the field coil and stator windings breaking up the magnetic field and inducing an electrical charge in the stator windings.
 

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Looking at the parts diagram https://www.partzilla.com/catalog/honda/motorcycle/1983/cb550sc-a-nighthawk-550/alternator are the field and stator coils both part of #8 ? If so, that would explain the cost. But, an interesting way to avoid moving contacts. Also, if the stator and field are combined, it could be either coil causing the problem. Or, the moving rotor blades could have become magnetized, reducing the effectiveness; annealing them would remove any magnetism, but then, are they tempered? And, how much?
 

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I would get her running then, with alligator test leads by-pass regulator and put a head lamp in series with battery and run to brushes.
with the output from stator NOT going to R/R measure volts across and two yellow wires and from any wire to ground , meter of course
is set for A.C. volts say in 50 volt range. any voltage from ylw wire and ground, stator is bad.
I don't know what the a.c. voltage shoule be but the 3 sets of voltage readings from any 3 pair should be close to each other.

brazing is the best from what the motor winder says but I think slipping shrink tubing over a soldered connection could be pretty reliable.
 
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