Alternator stator coil rewinding

My generator stator burned out, obviously shortly before the weekend, so the only way to fix it quickly was to rewind it my self. I couldn't find any info readily available so I post one now. Quick check in the box with my old tube amp building materials, copper wire is there, some isolation tube and fiberglass tape so I was ready to go. I've made a measurement of the winding and they where well out of spec, or better to say complete out of space. After dismantling alternator cover it was instantly clear (from the smell of it) that the winding insulation was gone. First step was to strip old wire of the stator poles and clean everything, also sanding down any sharp edges on the stator posts. The job is not very inviting but its got to be done, and of course counting the turns is vital. 37 turns pro post, wire thickness 0.9 mm without the insulating lacquer.



After that, is going to be easy. I've made some tools to do the job. On the late I turned down thick bolt and made the thread in it so I could attach my stator to it and fixed all together in the vice, because of this, you can pull hard on the wire when making turns so you can wind it “tight”, if you don't do it, will create different problems later.



Above, the tools needed for rewinding job and below the wire stand.



Than I mounted everything in the vice and started winding first of three sections. I'm using here 0.95 mm wire. Important is, that the inter connecting wire is long enough (picture below) so you can bend it towards outside so it want create problems later when mounting stator in the cover on to the supporting posts. Here, you see the side which is going in (down), towards the cover when assembling.



The green isolation paint has turned black because of the heat of windings being shorted and conducting electricity but I decided to leave it on, NOT PROPER JOB, if you doing it right it should look like this:



Above, picture is showing green protective paint layer so wire insulation won't get cut through on sharp stator edges. PROPER JOB.



Piece of hard wood helps “compressing” the winding turns, I press them every 4 to 5 turns. There is not a lot of space for the wires but probably enough even if you use 1mm wire which would give you some more current, probably only marginal, but you still moving generator output power towards more, instead of less, when using thinner wire.



And here all the windings are complete.



Next wires are being soldered together, three phase connection in star.



Measurement of the winding resistance, everything looks good.



The manual says, the resistance between two yellow wires suppose to be between 0.50 and 0.76 ohm.



After soldering job is done I started to impregnate the stator with epoxy. Normally this is done with help of the vacuum, so the epoxy stuff gets in between the layers of wire and inside the bobbin.





The next day everything was cured so I started reassembling generator together again.







Its also important to place the cables tight in the channel and also deep so it does not get cut by the protecting shield which has a tendency to stick too far out towards the rotor on the bottom and rub against it.



Now with everything in place I started the rectifier upgrade job. I got one before the alternator failure of off E-bay and it was listed as, from Yamaha MT-09 Year 04.2015 Rectifier Regulator. Its a Shindengen FH020AA.



This is only a quick job on fitting it because I'm planing on upgrading ignition system first. After that ill be needing a different mounting plate and probably the wiring too, but for now the target was to ride on coming weekend and so it happened.



Here the awaited effect 14.2 Volt rpm just above idle, light on, if I'm not mistaking, and the battery was “just normally charged” like when you ride the bike for a week or two, starting going stopping, next day again... etc.

And now for the tech part and some numbers:

The stator I rewound have 037000 1530 number stamped on it.
Its outer diameter is 93 mm, I believe its still original part.
The original wire was 0.9 mm thick without the insulation.
I have used wire 0.95 mm thick, and it did fit but I believe 1 mm would also fit.
Entire stator winding is made out of 3 sections, each divided between 6 posts.
Each post has 37 turns of wire (starting from inside to outside filling up the post, than toward inside, and again to outside, completing 37 turns, than moving to the next post starting from inside.)
To complete one section you need approximately 12.6 meter wire (times 3 for all sections, but this needs to be verified once again.)
All three sections are connected in star (one side of 3 wires together and the other 3 ends are going to the rectifier).
Resistance of two sections (from yellow cable --to the centre-- again to yellow cable) is 0.7 ohm.
Resistance from windings against the stator body, infinite.
Voltage between two phase, never measured. But it works.
The insulation tube used was fibreglass silicon type. (didn't have anything else)
I have impregnated windings with 2 component epoxy using brush, nothing fancy but it dos the job.
Output cable diameter (the yellow one) is 1.5 mm square. It barely fit in the holes in the rubber.
Time taken, no idea but I still rode the bike on that weekend.

Thanks.

I like your ambition. Good for you ! Looking forward to seeing the end result.

Edit note you just pushed the submit milliseconds before me HaHa

Hi Kawboy ! yeah i was still editing, because the first try got me nowhere, that's where my erratic clicking came from ha ha.

I remember doing the exact same thing almost 40 years ago on my 79 1300. At the time I was in school and coudln't afford the price of a replacement so I took it to a local alternator rewinder. The said they wouldn't touch it but the gave me some wire, told me to count off the loops, wind on new loops, bring it back and they'd epoxy and bake it for me which is exactly what I did. They didn't charge me anything and even gave me a few beers while waiting for the bake (gotta love that kind of local shop). I remember my fingers hurting a lot by the time the winding was complete and my wingdings didn't look anywhere near as good as yours do - that wooden wedge is a great idea.

Daro ! You took the long winding road and made it to the other end !
Outstanding work and ambition.
Your #'s closely match mine with the same V/R and an aftermarket stator. Charge on, dude !

Great work and inspiring! And a great walk through. Makes me feel like I want to build a whole bike from scratch!