Introduction: Rebuild Your Bike's Expensive Stator

Picture of 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.

Step 1: Original Stator.

Picture of 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

Picture of 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

Picture of 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!

Picture of 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

Picture of 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.


guds777 (author)2017-08-22

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

DanO32 (author)2016-06-30

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.

500thumper (author)2016-05-27

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

FstarockaB (author)2016-04-25

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

rush_elixir (author)2015-08-16


jam.tam.5 (author)2015-01-27

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!

austin.silvers.50 (author)2014-11-11

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?

austin.silvers.50 (author)2014-11-07

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

Check out also this link

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!

austin.silvers.50 (author)2014-11-07

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

Of course it does, as it insulates the copper wire from shorting on the metal cores. That's the reason ive used cardboard (mylar actually) on each pole to protect wires from being scratched on sharp corners.

undinstructable (author)2014-11-05

Can't remember right now, it's been a while since I published this instructable, but I'd say around 15-20 meters

austin.silvers.50 (author)2014-11-05

How much wire did you use?

jbest4 (author)2014-05-26

how far have you ridden now and is it still working like a champ?

jlilbrother (author)2013-12-21

I have to give you mad props for even attempting to do that job. I guess I should count myself lucky, the stator for my bike is only $65. But seriously, fantastic job man.

Thanks, man. Always a pleasure to get positive comments! Glad if it was of help to you

wanwnp (author)2012-04-14

nice tutorial!
very good on the warnings included, ie rough edges, etc..

however i wonder whether the cardboard melts inside your engine oil or not...

anyways, i think i wanna try your method, probably i can help others and earn some money out of it.. the shops that provide rewindings here are expensive!

undinstructable (author)wanwnp2012-04-17

Hi Wanwnp.
Actually the one described here is my first attempt. it worked for a while before a short made necessary to wind another one. This time though, instead of using the cardboard (which by the way is a special type made for transformers, and wont melt in hot oil) I cover the sharp edges with double component epoxy glue, my one stand 300° C, It is sometime called liquid metal. The stator is still working in my bike since I've built it this way.

danzar (author)2012-02-04

Very nice.

warar3 (author)2011-06-05

hey when connecting the wires to the regulator do they have to be in order

skamagedon (author)warar32011-08-21

they goto the rectifier

undinstructable (author)warar32011-06-06

No, they don't have to be in order, you can connect to the regulator in wichever order you like.
Good luck!

warar3 (author)undinstructable2011-07-02

Hi i havent been able to find any epoxy type paint any ideas i live in a kinda small town i got some hardware stores and some major ones like lowes/ home depo

undinstructable (author)warar32011-07-03

Hi there.
I don't know where do you live, but, in the States something quite popular is a product called JB-Weld:

I have used that in a second version Ive made, as the first one got shorted because the sharp edges of the metal core. Ive used the glue on the core to smooth the edges and on the wires at the end to seal the whole thing to get something similar to what you can see in the pictures of the original stator.

warar3 (author)undinstructable2011-06-13

one more thing you said you dipped the whole thing in the ins. paint and then in the oven. what about the top/surface metal dose that have to be sanded down for or did you just leve it // the very out side top with little metal lines//

thank you SL

undinstructable (author)warar32011-06-13

you dip the whole thing in the paint, then put in the oven. This shold be done a couple of times, for additional insulation. I suggest to have it done by a professional rebuilder like an electric transformer repair shop... Since the cooking is a rather long process, they do in batches, when they have several transformers or devices ready to be treated.

actionman72 (author)2010-11-05

Wonder, wonderful article, friend! People like you make do-it-yourself repairs a pleasure. If I had a spare daughter, I would give her to you.

actionman72 (author)actionman722010-11-30

I just rewound my 95 Bayou 300 4x4 stator using your guide. WOrked like a dream. Good stuff!

I'm glad my instructable helped you.
Pity you don't have a spare daughter! ;-)


MatrixRage (author)2010-10-21

You sir, are a freaking genious. Great instructable, very clear to read, great diagram at the end of the article. thanks

jimjutte (author)2010-08-20

Your article goes well beyond what I was looking for, but certainly gives me something to think about for the future. I have a Majesty 400. At the risk of asking a stupid question... because I did something stupid.... the wires that come off of the stator and go into a connector... is there a particular order that they MUST go into the connector. I wasn't paying attention while moving my bike and somehow manage to pull the connector plastic off of the three wires... now, I don't know the order that they need to go back in. :( Cheers

undinstructable (author)jimjutte2010-08-21

Your question is actually very pertinent, :-) especially if you're not into electronics. The order the wires are in the plastic connector doesn't matter, so you can insert the wires in whichever order you like. Make sure the voltage regulator is okay, also. It should have a connector with 3 plus 2 contacts, the 3 on one side and the 2 at the corners at the opposite side. The 2 contacts are where the + and - comes from. The 3 contact on one side is where the actual wires from stator go and this is the "input" side of the regulator. Have fun

jimjutte (author)undinstructable2010-08-21

Thanks very much. Indeed there are two others, a white and red. Thankfully, they were part of a separate connector. Cheers

hectortito (author)2010-03-26

is there a machine coiling ? For this case

Well, I think there is a machine, but not where I live or not that I know about...
That's why I had to do by hand! Also its cheaper.

shteef (author)2010-02-03

 great ible mate, the stator on my outboard motor is buggered and Mercury want $639 for a new one!! i will be following your instructions Very closely this weekend.

undinstructable (author)shteef2010-02-04

No problem man,
Just  a few tips:
Make sure to file or sandpaper the edges as its very easy to scratch the wire enamel and short the winding.
I've used a bit of heat resistant metal epoxy, standing up to 230 F°,because my stator works submersed in the motor oil, . The epoxy  makes edges rounder and lessen the occurrence of a short.
Check anyway with a multimeter after each pole is completed.
Here's a very handy web page about motor winding for electric powered airplane models:
Have fun and good luck!

Dr.Bill (author)2009-04-12

A star wound generator. You have given me an idea! What kind of amperage does this thing put out? At what voltage?

undinstructable (author)Dr.Bill2009-04-13

Can't remember what amperage is the thing, now. But it would provide enough for battery charging and services, (e.g. lamps, horns) Hope it was helpful. Cheers- A

Dr.Bill (author)undinstructable2009-04-13

I need enough power to runHam equipment so I guess if it charges batts it'll be ok. Thank you.

JerryMopar (author)Dr.Bill2009-11-19

most tri-pole cycle stators usually can put out 200+ Watts  @ approx 13.5 volts

Dr.Bill (author)JerryMopar2009-12-22


JerryMopar (author)2009-11-19

WOW, very simply done/very effective 'ible. Maybe Ill try this when/if I even fry one of my cycle's stators. VERY well done my friend!

Thanks Jerry....It was tough, but it worked at the end! And very rewarding!

mattccc (author)2009-11-17

can i have some meserments of the stator

Adri_66 (author)2009-04-04

Very good guide, I have understood everything! Good job

undinstructable (author)Adri_662009-04-05

Thanks Adri. Hope this will help repair you bike or whatever it is! Have a nice day. A

vespatim (author)2008-09-25

Great instructable! I was wondering if there was an easy way to test if a stator will work before installing it using a multimeter.

undinstructable (author)vespatim2008-09-26

Of course there is a way, but it is not always practical, especially if the windings are under a thick layer of resin.... First check) First you should check that none of the three wires coming out of it is shorted to the metal part... Sometimes, especially due to high temperatures involved, the wires lose their insulation, especially on sharp edges, so they short to the metal body of the stator. Put the multimeter in "Diode" mode, the one that buzz when you short the probes, then one probe on the metal body, (make sure the resin is not insulating the probe), the other probe on each of the wires, in turn.... if you got the buzzer buzzing, then the stator is shorted. Second check) Even if the wires are okay respect to the body, the stator could still be faulty because the wires are shorting between them.... As you can see from my diagram, the wires are tied together at one end... To check for this kind of fault, you should untie the wires at the common end and check if each one if electrically insulated from the other two. In both cases, if the stator turns out to be faulty, it must be rewinded, as I've showed in my instructable. I hope this helps you. Ciao

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