Rebuild Your Bike's Expensive Stator


Introduction: 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.

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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    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

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

    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.

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

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

    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!

    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?

    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

    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!

    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.

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

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

    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.

    1 reply

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

    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!

    1 reply

    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.