Build your own SEM coil?

hondaguy · Mar 26, 2006

Hi all, i have a 1999 FC600 that has an electrical gremlin somewhere. It has no spark, and i read on here that 99% of the problems are the stator and flywheel. My resistances checked out fine but i saw that the coating on my flywheel was missing and cracked in places, figured that was my problem so i bought a new ignition and puller from my dealer($479 ouch). It gets here and the brand new flywheel also has some coating missing. My dealer says it normal. I found the hard start guide and tested my old one and the new one and they were both perfect.

Has anyone ever attempted to build (or rebuild) their own coil? I have heard numerous accounts of people building their own CDI's and i can't imagine this being any different. The actual coil of copper wires doesn't really go bad, so i would imagine is it just resistors,capacitors, diodes, SCR'S, and other common things in there that i can find at radio shack. Could i soak this in acetone to remove the coating? If my coil is bad, i am at least going to break into it and try to fix it before i shell out $430 for a new one.

I have checked every wire and ground on this thing and it looks like my plug cap has infinite resistance? Is this normal? Maybe it has so much my meters aren't reading? I am going to replace it tomorrow and see....

I might be interested in trading a brand new SEM stator, flywheel, and puller for a good coil....

Thanks for any help guys, i'm at the end of my rope with this bike.

ned37 · Mar 26, 2006

if i understand you correctly, your old stator ohmed out the same as your new one, right? then it is ok. you say your plug cap reads infinity? that aint right. is it a resistor cap? can you unscrew the inside to reveal a resistor and spring and discs? if you can't get a reading on either rx1 or rx100 from one side to the other, thats wrong. what about a reading thru your coil wire without the cap? what about a shorted kill switch? don't assume anything, just methodically start at one end and work your way to the other. write down your results. good luck.

ned

BundyBear · Mar 26, 2006

Do you definitely get no spark with the orange wire unplugged? You may have a fault in the kill circuit somewhere.

I have not heard of CDI/coil repairs being done yet but if it was mine I would certainly have a go. If the ignition coil inside the unit is defunct then I doubt you could fix it. You may have to go beyond Radio Shack to get some of the other components, but they are generally available from somewhere.

If the stator needs rewinding, it is definitely possible with patience and a few home-made tools. There should be no active components inside it, just four coils of copper wire each with about 3500 turns, that do fail and a fifth trigger pulse coil that is unlikely to have a problem. There is debate whether failure is due to time, water, heat or vibration but I think it might be a combination of all. You can get the potting off the stator by soaking it in acetone and CAREFULLY scraping the softened potting away, then soaking it again. You can probably get into the CDI/coil unit the same way.

Parsko · Mar 27, 2006

I can confirm Bundybear, Acetone will work okay on the epoxy, we use it at work all the time, but not for electrical, never tried.

I'm curious about this myself. I have been asking myself the same question about the ignition. The older ones have one curve, making it easier to "rebuild". The most important piece of info you would need to do this would be the input data of all the wires coming from the SEM, such as current, voltage, etc... You know the other end (wire (with resistance) and plug,) so you have all the data you need to determine what the guts need to be. The coil itself is simply a transformer, I think. The Doc covers some of this, but not the details nec. to design it. I too, do not have the knowledge to design a coil, but someone hear must (hinting to any EE in the house).

Also, if you managed to get through that last paragraph, I would suggest testing to make sure the acetone doesn't eat away at any housing, if there is one, if it's plastic.

...Parsko

Aspen · Mar 27, 2006

Hi folks!
IÃ‚Â´m not an EE, but half way...

BundyBear did this on a single sensor stator, right?
My research has shown that on my multiple sensor Ã‚Â´02 (and others), the sensing coils are not the ones that go out, but the ignition charge coil primarily. I do not know your year in particular.

If it is a single sensor, then using BundyBears method should work the same. Check his gallery. LOT of work though, and not for the faint hearted. I have a question whether the acetone couldnÃ‚Â´t dissolve the insulation on the remaining coil wires shorting the lot? Apparently that didnÃ‚Â´t happen to BundyBear, but still..??

Good luck!

And by the way, it does not seem like any company could do this economically, so why the hell not try it? You wouldnÃ‚Â´t loose or destroy anything of value as a core (but hold on...). I am determined to try myself, as everything points to the fact that these are not in production (ANY SEM) and will be in short supply eventually. At least HOLD ON TO IT!

As far as data goes, all you need is spec ohm data and the original wire diameter. The rest is just OhmÃ‚Â´s law. BUT, before you throw the old wire and get on with spinning 3500 turns of new one, MEASURE THE DIAMETER!

Again, Good Luck!

/Peter

doctorcorey · Mar 27, 2006

Pardon me for crashing the party, but I'd like to present a question. Has anyone ever contacted a stator company like RickyStator to see if they can repair these coils. Rewinding stators is their stock in trade. If they were made aware of an impending demand for this service, perhaps they would jump into it. Just an idea. I've used them for some time( gosh, I hope they're still in business!)

DC

hondaguy · Mar 27, 2006

Thanks for the quick replies everyone, but i believe i wasn't clear enough in my post. When i said i was wanting to rebuild my coil, i meant the actual ignition coil/cdi unit, not the coils on my stator (actually my stator is the SEM that is very flat and has a reflective black filament on the back side with no charging or lighting circuit, i think perhaps you guys were picturing the newer ones).

I think i am just going to dive into it and see what i find. I will try peeling back the epoxy coated side with an exacto before i try acetone.

On the plug cap, it turns out when i was testing it i was just using the continuity setting, and when i turned it to the other setting to test it, it tested 5,190 ohms and you can buy NGK caps in 5k and 10k, so it must be correct. I've disconnected the kill switch, checked all wires, sanded and retightened the grounds, but still not a thing.

I am going to break into my coil either way, but i am still VERY open to trading a new stator, flywheel, and flywheel puller for a coil....

hondaguy · Mar 27, 2006

Also, i took a class on DC circuits, but isn't this stator going to be putting out AC current? The spark plug would have to have DC, correct? This would mean that there has to be an inverter to convert it to DC in there as well, but would there have to be a second one also for hte trigger voltage?

Thanks

BundyBear · Mar 27, 2006

hondaguy said:
...i meant the actual ignition coil/cdi unit, not the coils on my stator ....

Check thru the electrical forums. There was a thread discussing what is in a CDI/coil unit and Dale even posted a pic of the insides of a newer digitally controlled jobbie, and I think there may have been posts on fixing them.

I undertand that this is not what hondaguy is after but there has also been lots of electrical threads on winding of stator coils. A couple of companies round the world have done them and members have left info on their experiences.

aspen said:
...not for the faint hearted.....

darn right! I would think twice whether I would attempt it again. I imigine getting into the stator would be easier than the CDI/coil unit.

kzoo · Mar 27, 2006

doctorcorey said:
Pardon me for crashing the party, but I'd like to present a question. Has anyone ever contacted a stator company like RickyStator to see if they can repair these coils. Rewinding stators is their stock in trade. If they were made aware of an impending demand for this service, perhaps they would jump into it. Just an idea. I've used them for some time( gosh, I hope they're still in business!) DC

http://www.rickystator.com/

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Build your own SEM coil?

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