Rebuild Your Bike's Expensive Stator

Intro: 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.

Comments

[CharanN4]

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

[subhashmsit]

3 wire should be connected togather and the other 3 terminal will be phase 1,2,3....it will be star connected stator coil...if want to do delta then reply me

[undinstructable]

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.

[DadoB1]

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

[greenplanetev]

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?

[subhashmsit]

The positive wire comes out from stator coil and the negative wire is connected with the body......so U can take the whole body of ur veicle as negative port.

[lambchop1965]

Guys does anyone have a diagram of the pattern for rewinding a Suzuki GSXR stator please

[gregnokes]

What if the stator on my old bike is too weak from the manufacturer just the way the built or wound it, is there a way I can increase its out put? Can I increase the wire diameter or number of wraps? Also does the wire need to be one long continuous strand or can you slice the wire together while wrapping the stator to make the wire long enough to complete all the necessary wraps or does the wire need to be 1 long continuous wire for each phase wrap? Last question instead of the paper could you dip the leg in epoxy to seal the metal from the wire winding, then just sand the surface back down of each leg so the metal is exposed and can make the connections with the magnet as it spins? Thanks i advance for you help.

[brianhoskins460]

Great job.Makes me brave enough to do mine.I have a couple questions.I assume you do all the winding for the 1st phase,then the 2nd phase and onto the 3rd phase. 1) Are the poles numbered or can I start winding on any pole making sure I wind each phase onto every 3rd pole? 2) Does it matter if the wires from each phase touch each other as I work my way around the stator? It looks to me like there is no way to avoid this but I thought I'd ask in case I'm missing something. 3) What if I do something wrong? 4) What if the insulation or the paint or the seal isn't good enough or for whatever reason it doesn't work the way it should...5) Is there any possibility,at all,that I could damage my bike in any way? And for my last question...You've done this a few times so you know what to expect might happen,how careful or forceful you can be and so you'll be a lot faster at this than I will be as a first timer.My question to you is this...6) How long did it take you to do this your first time? 7) How much did the materials add up to? I know our situations are not the same I'm just trying to get a rough idea so I can weigh the time and materials against the price of a new stator.
Thank you again for the very thorough instructional tutorial. I've read some of the other questions so I know it's been a long time since you put this up so if you don't get to my questions right away I totally understand.But summer's almost here and I'm getting the itch to ride so I'll buy one if it comes down to it.I'd rather try your way first.
Thanks again.Great job.Keep you and yours safe and healthy.
Take care.
Brian Hoskins

[undinstructable]

Hi Brian, thank for stopping by.
As per your questions: 1) I think you can start winding on any pole, although, since there is a sensor that feels the pulses (the black block in the pictures), its better to respect the originar order of poles as much as you can. 2) I don't understand you question. The wires are insulated by a thin layer of enamel, so it doesn't matter if they touch each other during winding. 3) Just make sure the enamel doesn't get scratched on sharp corners of armature. That would make a short and would make the whole process a waste of time. My suggestion is try to be as much as tidy as you can, and make winding as much as tight as you can. And, after you complete a pole, with a multimeter set to ohm, verify that the wire is not shorted to the body.
4) see n.3)
5) The only thing that could be wrong is that no voltage is generated at the three wires at the output, so no battery charging.
Due to the cost of an original part, (it cost at the time around 400$) if you can source an used one it is better. I choose to do it manually because the cost of a replacement and no chance to find it used.
Be prepared though, as the whole job requires a lot of time and patience.

ANOTHER TIP. Before taking apart the original wire, try to separate the three windings, ie disconnect the end where all three wires comes togheter. If you are lucky, only one of the windings will be shorted to the body, and you can only rewind that one, although I think that because of the epoxy resin it will be a difficult task to take off that winding alone.
SECOND TIP:The shop where I go when I need an electric motor rewinded, gave me the tip to cut the original winding with a dremel, so you can count the number of windings.
NOTE: always check water and oil level in your engine. Heat building in the engine is what cause damage in the stator epoxy/insulation, and replacement will be needed.

Good luck, have fun and stay safe!
Cheers
Angelo

[anthonyl193]

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

[Antman24]

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

[undinstructable]

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.

[LiamD54]

How do you work out how many turns you need?

[undinstructable]

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

[guds777]

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

[DanO32]

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]

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

[FstarockaB]

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

[rush_elixir]

awesome