winding sems

mattineildon said:

G'day men, I've stripped the charge and pulse coils out of a o2/03 sem stator, winding the coils wasn't too difficult but can anyone shed any light on reconnecting them?
there seems to be what looks like a diode connected between the earth and the charge coil windings, if it is a diode this one isn't working all that well! Also given that there are four charge coils this makes a start connection, three intercoil connections and a finish, problem is there only seems to be four terminals on the printed circuit board when it appears the should be five, any feed back would be greatly apreciated, cheers matt.

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Hi Matt,

Would love to spill the beans but unfortunately it's my living, but I can give you some words of advise check the connections as you strip it this puts you in good stead for when you rewind it.
It's not a case of just rewinding the coils that's the easy bit but it's like any job ground preparation is the key, if you have no winding skills this where you might come unglued,
like the originals.

Regards

Sparks.

Matt
Don't know if it is any help, but check my gallery (link below) for a scan of a handsketched page on how the SEM Husky stator was connected. It had the circuit board you mention, but it was just a connection point & did not have any passive components on it. It is obviously different to the Husey one you have as it has an extra wire coming from it.

if you are unsure then connect it as best you think. Paint it sparingly & temporarily in something easy to remove so you can change it if need be. When you are happy, do a good job of it.

I finally set mine in a stuff called isonel red, that they used for touching up wheel motor windings at work. I added about 10% more turns to the charge coils & it seemed to work fine without changing the timing noticeably.

Were there any markings you could see on the diode? If it is not a zener then any 400V or better 1A diode should do so long as it is connected the same way around. eg 1N4004 or 1N4007.

To get as far as you have you obviously have the will and skill to have a go!

mattineildon said:

Thanks again Brad, I cant see any markings on the diode but it just looks like a normal garden variety diode to me, in anycase its buggered so its been replaced! trouble is I could'nt scrounge any 0.71 mm wire and tried to use some that I unwound off a protection relay from work. too thick and I don't think I have enough turns on the coils to get the volts up to what I need, it was only a thou or two bigger but when the bloody stuffs only three thou to start with the new stuff may as well be welding cable! cheers matt

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Hi Matt,

I'm not shy about anything, can't understand what you mean about that.
The thing about people doing a bit of diy and it goes tits up then that is when the rewinding of ignitions starts to get a bad name.i've been winding this stuff for the last 32years give me some street cred.
Don't know what you mean about reversing the test meter leads to get the 3K ohms reading the diode has nothing to do with the final source coil resistance, what the diode does is ground a partial amount of the output voltage to stop it over voltageing the capacitor in the cdi, when this happens you will know this Bundy the voltage across the capacitor falls away and the performance of the ignition system drop dramatically.
To put it another way running a spark gap or 15mm at 5000rpm when it hits 8000rpm the spark either disappears or becomes intermittent lower the voltage and the performance returns.
So by putting your exrta10% is not necessary a good thing Bundy.
Oh and by the way the wire size is 0.071 for the charge coils and 0.09 for the trigger.
Regards

Sparks.

Hi, I’ve been away for a while but am a sucker for these SEM topics. May I ask what the fuss is all about? Here in the U.S. the Berg part number 250.125.12 retails for $225.00 and should be able to be had for around $190.00 without too much trouble. The KTM number that should interchange is 565.31.101.044 but would have to double check; retail $183.00. All of the lighting coil stators that I’ve seen have been the same except for the type of connectors and grommets on the wires; nothing that a bucks worth of solder and heat shrink can’t fix! (use your old wires and grommets – solder and insulate as required, we have used the old number on all of the later SEM digital ignitions through Kokusan using this method).
My old 1985 KX 125 is on its third stator and they only seemed to average about 100 hours lifespan. I’ve bought plenty of Suzuki stators in my career and currently sell a fair amount of KTM Kokusan ones here at work. At some point they just have to looked at as a wear item on dirt bikes; we as riders do have a tendency to treat them badly sometimes!

AlanNMS said:

Hi, I’ve been away for a while but am a sucker for these SEM topics. May I ask what the fuss is all about? Here in the U.S. the Berg part number 250.125.12 retails for $225.00 and should be able to be had for around $190.00 without too much trouble. The KTM number that should interchange is 565.31.101.044 but would have to double check; retail $183.00. All of the lighting coil stators that I’ve seen have been the same except for the type of connectors and grommets on the wires; nothing that a bucks worth of solder and heat shrink can’t fix! (use your old wires and grommets – solder and insulate as required, we have used the old number on all of the later SEM digital ignitions through Kokusan using this method).
My old 1985 KX 125 is on its third stator and they only seemed to average about 100 hours lifespan. I’ve bought plenty of Suzuki stators in my career and currently sell a fair amount of KTM Kokusan ones here at work. At some point they just have to looked at as a wear item on dirt bikes; we as riders do have a tendency to treat them badly sometimes!

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Hi Alan,

The KTM stator will only work on Bergs of pre 1999 era, from 1999 to 2003 there is no other model that used this type of SEM, the outputs for these years were a one off.
And for the above years I think the price is around $500.00.

Regards

Steve.

Hi Steve,
We've had success here interchanging the earlier and later model stators as long as the number and colors of the wires were the same. We are a large dealer here in Nevada and (in the spirit of customer service) couldn't tolerate the long backorders during the "transitions" in distributors that we all have suffered through in the past. It took some skill shimming the flywheel to stator clearance but the bikes all ran fine this way. The Swedish produced bikes seemed to vary quite a bit from bike to bike and the stators might have been a production variation too? In any case I would encourage the owners of the digital SEM electric start bikes to try the interchange if their wires match and they’re in a pinch. I don’t doubt that your remade stators are of the highest quality and would guarantee fitment if the customer has the time and access to them.
To you specifically; give me a call at 775-358-4388, 9-6 PST. I stumbled across a way to extend the life of these by quite a bit and think you could market it. It’s free to you to produce but think it a little too ambitious for the average owner to do himself.
Best Regards, Alan

Hi there bear with me this is my first time typing on any thing like this. First of all I wanted to do the same thing this time last summer so I did. It all started with Y wont my bike start the night before a once in a year trail ride that was pre payed 3 months prier. So I found no spark, that led me to a sick stator. Very simple I have the FC501 which only has 3 wires (Green) (Red) and (Black) with a multimeter I Had a reading coming out of black and green but nothing from black and red. So what to do next ah. Off to a bike shop to see what was available. Very helpful sourced a new one with a price crazy like $650. So that led me to my shed for a tinker. I thought what have I got to lose. So to my under standing my stator has 4 charging windings and apposite them is the sucker that tells my coil to fire. So how does one get in to this thing that is very clearly not to be gotten in to. Ha. started with a knife slowly digging away at what i thought the windings are because. That is the one place on the hole thing I'm wanting to rebuild. And can get away with putting a knife into. Worked well got every thing exposed. In till I came to the circuit board. That was a surprise. What to do now I thought you cant carry on with a knife. So then started with a soldiering iron wasn't even touching that hard plastic resin stuff. But it did make it malleable. Man that's a big word it means bendy. So that lead me to how do i heat the hole thing up to controlled temp? Water was my answer water boils at 100 degrees center-grade. So i went on to thinking cant hurt, the bike would get up to that kind of temp. So off to the kitchen with my stator. Sing out to the wife if she has a old pot she doesn't use much. And she says what for. Any way long story short boil stator on Hi for 5-10 mins always moving so wires wouldn't touch bottom of pot taking of the heat every so often to see if some resin could come off and walla. Very cool chuffed as with myself started thinking of my next step. Before i went any further I really needed to try and understand this thing. So drew a drawing of the inside of the stator and got my vernier caliper out. remember when i started i had no values so this was my only way of getting it close to what it may have been. Measured each winding every one was different. But gave me a really good goal to work to. Still measuring things I had to find out what kind of wire and where it get it. Went to a locale rewind place and they were so unhelpful. Wasn't Evan able to tell were I mite find the rite wire. So that sent me home to jump on google with a copper wire that is .06 of a mm to find which lead me to Remington Industries. The wire i got was only $15 US but still cost me anther $50 in shipping joke I know. Oh yea that reminds me I also got a price for a rewound stator out of UK from Taffmeisters. Very helpful was David. Gave me a price of $200+post GBP thats if I send him my old one. I translated that to about $450 nz . Fear price i thought but im still gunna give it a go my self So with my wire im in to it. Pulled plastic windings out and start plucking them of all the old wire. once i have the plastic bits the wire winds around had to find a way to wind it back on. Cut a wooden skewer in 3 bits taped them together and that gave me some thing that will nicely slide up inside the plastic bits and that i can put in my hand-held hi speed drill. Made a jig that holds my drill and holds my roll of wire. So with my two hands one is guiding the wire and the other is on the trigger for the drill. With nothing else on my mind i could wind 2 windings a night after work. Using the measurements id taken before I plucked them. Another good tip was getting some glasses for this.Ha I don't normally wear glasses but i found some x1 reading glasses really helped and my wife made me really nice soft cotton forefinger and thumb slippers for guiding the wire in to its new home. Thats the easy part done. next was to put it all back together. And then some how you need to seal it. Witch is why Im here mine failed after a year. I used a 2pac epoxy resin. but i didn't cover the hole thing so it was the steel center and the ali that let in the corrosion. So the things ill do different next time is get the proper values for winding and seal with some kind of clear coat before epoxy. as for the rewind it was mean, bike started easy went hard rode trough creeks up to the seat and the part that fails when its sitting in the shed its just not rite. Well take from that what you like but it worked for me. Good luck if you do take on the challenge.

Excellent post!! thank you for that, opened my eyes

Hello there,
heres one for those who want to think outside the circle !
I have an FC600 its had nothing but trouble with the ignition system. i had a go and rewound my stator and the bike fired up first kick and now runs great. Out of interest, I gerry rigged an ignition system off one of my model airplanes to the bike. The cdi/coil unit is powered by 4.5 volts and runs a 50cc two stroke engine on a tiny NGK CM6 plug and timed by a hall effect sensor. So I fitted a magnet to the outside of the flywheel at 33 deg btdc and all the rest of the bits were zip tied and once again the bike fired up after a couple kicks and ran perfectly under load and revved freely running on a different system.
parts are getting hard to find , think ouside the circle .

BTW.....,Rewinding the sem stators is not difficult , take your time ,do some research and you will save a bunch of dollars cause your time is free.
Cheers
Ricksta