Rebuild Your Bike's Expensive Stator

Here is how I've rebuilt the stator of my bike, a Yamaha yp250 scooter, branded here in Italy as Majesty 250. It might be also valid for other brands.
The original part is WAY too expensive here (more than 600$), so I HAD to invent ways to solve the problem. I drove the bike using this rebuilt stator for about 600 miles now and its still working. Im not sure that the insulating paint I've used will stand the eat from the engine motor oil as the original.
So far so good....
Step 5 has a picture with the complete schematic of the wiring.

Suggestions and criticism are welcome.

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Step 1: Original Stator.

This is the original faulty stator. It has all of its 3 windings shorted to the metal body.

Step 2: Uncoiling the Thing

This is a quite tedious job, as the epoxy is quite hard to remove. You might need the help of a screwdriver to lift up the wire inside and between the poles. Be careful while handling the copper wire as you unwind it. Some of its insulating paint bits, still attached, are sharp and might cut your skin.

Step 3: Preparing the Support

Before recoiling the stator, make sure to prepare its surface, smoothing out with a file (or a minidrill) all the sharp edges. In my case this step was absolutely required as I mistakenly removed the epoxy residuals (as you can see in the first picture below) with a paint removal gel. I had to prepare 36 small pieces of mylar cardboards (same used in transformers windings) cut in right size and cover with them all the poles.

Step 4: Coiling Up!

Get some awg (diameter) enameled copper wire (transformer wire) as the original. In my case that was 0.95 mm diameter. I got mine from an electric motors rewinding shop. While you ask for the wire get also some insulating paint. You'll need it later.
Highly recommended tip: while winding the stator, hook a digital multimeter to the metal body and to the fixed end of the phase you're winding. In case of shorts between the metal body and the wire on sharp edges the multimeter (set on diodes or continuity) will buzz and you can quickly unwind and take necessary action. (e.g. move the coil in a different position).

Step 5: Completing the Job

Once all the poles have been completed, the most is done. The whole stator need to be submersed into the insulating paint and put in oven to cure at 300F for 30 minutes. I did this twice to make sure a tick layer will form.
After the paint has cooled its just a matter of soldering the connector wires back.

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    69 Discussions

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    greenplanetev

    Question 8 months ago

    Hello,

    I am trying to modify the stator of Activa. Like what u explained above, there are 3 windings simply. But with Activa, there is only 1 wire coming out that goes to RR.There are 2 more wires for lights. How do i rewind it?

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    CharanN4

    Question 10 months ago on Introduction

    Sir.,am charan from india,, my 18.pole 5 wire magnet stator got shot.. , i had to rewind it.., and i will rewind it, i habe read u r article .those 5 steps are very clear to understand for every one.., but only one thing i need to get much more clear.., after the completing of coling the stator assembly,..,there will be six terminal coming out(both end of each coil),as its a star delta winding,.., but the coil connections which are getting out are just threee ..,there are total of six terminal , what shuld i do? ..how to do wiring fore those terminal after winding the coil.., can u please tell me

    2 answers
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    undinstructableCharanN4

    Answer 10 months ago

    Hi Charan, sorry for my late reply.
    You just connect together the wires at one end like in my drawing. The black dot is where they are connected together.

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    DadoB1CharanN4

    Answer 10 months ago

    You just twist 3 starting wires and put them between poles so they dont get in a way

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    anthonyl193

    12 months ago on Step 5

    I'll probably never do this job, but this is an excellent article, and I really like the idea that it is possible for a skilled enthusiast to tackle this. thanks

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    Antman24

    1 year ago

    I was wondering I only have one bad side on my stator could I use another set of coils to test the bike for spark. The bad line is my ignition side of my stator so I’m wanting to trade out with the charging side of the stator just to see if the bike will run since I’ve been dumping money and have yet to get it running since I bought it

    1 reply
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    undinstructableAntman24

    Reply 1 year ago

    Sorry Antman24, also fror my late reply. I'm not sure I've understood you correctly. The stator only generates AC current for the rectifier to convert it to 12V DC. If you need to test spark ignition coil, you could use the bike battery straight away. Just connect positive from battery to positive contact of the spark coil, and negative to chassis, of course. Then when you DISCONNECT positive contact from the spark coil you should see the spark at the plug.

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    undinstructableLiamD54

    Reply 1 year ago

    from the old winding, I've counted the turns at the time I've disassembled it

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    guds777

    2 years ago

    Cool thanks, i got 1,2 - 1,3 mm and no extra insulating paint, only the wires.

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    DanO32

    3 years ago

    Please accept my utmost appreciation for this. I just paid a fortune for some chap to do this. Next time I'll have courage to do it myself.

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    500thumper

    3 years ago

    Well written and easy to understand. Thank you. This may just have saved me a small fortune.

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    FstarockaB

    3 years ago

    fantastic, also think my mariner outboard stator has gone.. might be trying this sooner than later! gr8 writeup!

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    jam.tam.5

    4 years ago

    I bought a stator for my atv do i have to clean the copper before epoxy encapsulation? If so with what do i clean it with? Thankyou very much!

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    austin.silvers.50

    5 years ago

    Yea mines insulated by plastic but I scratched the wire in a few spots with a screwdriver, doesn't help that's they sold me the wrong gague wire either, gotta start all over, doesn't look too bad for first attempt tho what do you think?

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    austin.silvers.50

    5 years ago

    And my stator is 18 posts, if you start clockwise should you continue the same or go counter on the next? Also if you start start clock wise in phase one would you start opposite on phase two then back to clockwise on phase 3? Sorry for being a pain just a little confused

    2 replies

    Check out also this link

    http://www.bavaria-direct.co.za/info/images/Mini300_Winding_Instructions.gif

    taken from a link I published here 4 years ago

    As u can see from the picture in the last step, I've started counterclockwise (or ccw, as in the picture caption) and continued that way on every single pole and on every phase.
    Dont worry. I did know nothing about stator winding before doing this,
    but at the end (after one failed attempt which short circuit) I made it. The second stator has been doing his duties for 7 years now!

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    austin.silvers.50

    5 years ago

    Ok does it matter if the coating on the wire gets scratched while spooling?