CDI Testing and Building...

[kb0nly]

So while the world went crazy this year i had time to tackle one problem that i keep having, crappy CDI modules from China. I've had a few replacements die, some that run but don't run well, and others that never even worked right out of the box. The biggest problem is most of the ones coming out of China that are on eBay and other ATV parts sites are unknown as to whether they are made for AC or DC ignition systems. The Honda ATC is an AC powered ignition system, the AC from the exciter coil is fed directly to the CDI module. The only one i found that was reliable was from Dr.ATV, its a good clone, only costs $20, and i highly recommend just buying one from him if you need one and spare the trouble of buying a few until you find one that works elsewhere.

After i had another one fail on my 200ES this year i started a journey into not only being able to test them, but also build them from scratch myself. Which included de-potting a half dozen OEM and aftermarket CDI units to reverse engineer them, find out what component values were being used in them, and then design and have manufactured my own PCB for reproducing them. And that is where i am at now, the testing stage!

First thing i did was build a tester, for not only testing the CDI units but also for testing ignition coils and even spark plugs. I still have to put a couple finishing touches on it, i'm machining a threaded mount for the spark plug to screw into that will have an acrylic cover over it for safety, but for now its completely functional, and replicates the CDI firing at 1000rpm. Why 1000? So i have an even number i can make calculations from when watching the output of the CDI modules on my scope, for testing design changes like capacitors and SCR's to see how it affects the spark length and time.



Then there is the new CDI PCB i designed and built, i have tested the prototype and the spark is great! I have yet to try it on my 200ES as i am waiting for my order of potting compound to arrive so i can pot it into a box. But its looking very good!





Unlike the originals or their clones i decided to pigtail the connector, the wires may still ingress water over many years like the original potted in place connector did but it gives extra harness length, especially for the ATC200ES, to cut off the original harness connector and replace it with a new one. I suspect that the wires potted in place compared to the original connector will leave a lot less open spaces, and the epoxy should bond well to the wire insulation. Even if the model its going on has the correct rectangular connector instead of the round one i end up replacing the connector on the harness because its corroded or someone had been scraping the pins or bending them hoping for a better connection. So the pigtail on the new CDI just gives some length for everything to reach.

After i get the finishing touches on this done if anyone is interested i can share the schematic of the tester box. I had a small run of PCB's made for the tester, i could possibly build a few more boards and sell them as a partial kit, or i can just share the PCB design and the schematic. I really don't want to get into selling these, it was a lot of work building it and making it look nice in a case. At the most i might sell the PCB and components as a kit and others can take it from there. Besides those parts all that's needed is a couple small transformers and various bits like a switch and some connectors. The transformers are wired back to back to form an isolation transformer, and the PCB pulses the output to generate not only the high frequency AC to simulate the exciter coil but it also creates the pulsed AC to simulate the pickup coil. Its a pretty simple circuit, i found some examples online and tested and prototyped until i got it to where i wanted it. Uses an old school 555 timer IC, no fancy microprocessors or anything complicated. Just connect everything flip on the power and watch the plug fire!

[wonderboy]

What an awesome project! I've wanted to do what you did for so long, but just never had the proper motivation. How did you accomplish the de-encapsulation? Chemical process or mechanical process?

Regardless if you sell completed kits, PCB's, assembled or unassembled, or just the schematic: I'M IN!

Are you interested in digging into other CDI's? ...like a 350x maybe? (hint, hint)

I'm totally interested in your bench tester as well. I was thinking of using a gutted bottom end of a 350x motor with no rod on the crank or gear in the trans. Just a flywheel, stator and pickup, and drive it with a variable speed electric motor. Then map out the spark curve versus RPM. Never got to that either. Are you using a function generator to generate your trigger pulses for the CDI on your bench tester?

EDIT: Re-read your post again, and you answered the tester questions already in your original post... guess I got too excited and quit reading the last part of your post...

[MrConcdid]

Man, ya'll are so far over my head, Here's what I read.
I took apart that magic box that makes it run and found out there is magic inside it.
You are willing to sell a magic kit but no hat and I must provide my own wand and rabbit.
Check on the wand and hat but icks-na on the abbit-a.

Awesome job, would love to see a video of it in action. I use DrATV modern square cdi boxes as an upgrade to the old round plug factory cdi.
thanks for sharing
MrC.

[ATC King]

If you could build a test unit that uses factory parts, like the stator and pulse coil, you could also test aftermarket versions of those. Should be simple enough with a variable motor, which you could include a RPM display for. A style with a degreed wheel, you could use a timing light with, for CDIs that have advance circuitry.

There's a guy on a motorcycle website that built an ignition test apparatus like that. He tests OE CDIs for people, and repairs them. Maybe you'd be open to testing ignition parts for people?

If you were to build some CDIs to sell, having something a little special may help. A simple A-B advance setup, triggered by a ground, would be good for more built engines and people wanting to switch between a 'torque' setting and 'rpm' setting, or stock-race. There are fully programmable CDIs already out there, but that's a little over the top unless for a really custom engine. No matter the CDI, total advance is mechanically limited.

[ironchop]

One of the most interesting threads I've read in awhile in here.

I totally understand your lack of desire to do these to sell, but disappointing nonetheless.

Nice work KB. I wish I had that particular skillset

[kb0nly]

Hey guys sorry for the delay and responding to the comments, things get crazy busy here in spurts and i just vanish for a while until i can get back to the computer!

Lets see if i can hit on all the questions...

As for de-potting them, i took them to a buddy of mine that does restorations of old audio gear, amps and stuff, he did it, i don't know how he did it, pretty sure its chemical based, but all i know is he removed it all in a day and the boards were pretty clean and came out with the silkscreening still on the PCB. He has a magical process that he uses for removing the potting material from old audio transformers or some such, i didn't pry, and if i did he wouldn't answer... LOL

I tried a test unit using factory parts, a pulse coil and rotor driven by a motor with a PWM controller, made a shaft to simulate the end of the camshaft and mount onto the DC motor, spent hours making the shaft and a housing and put it all together. The problem was doing it that way you have to also use that stator and flywheel to generate the pulsed AC input from it as well, if you just replace the stator output with AC from a transformer all you end up with is no spark or a blown SCR in the CDI.. Guess how i found that out!!

So what this unit does is pulse the AC output from the back to back transformers inside it, which form an isolation transformer, to generate the AC output that simulates the stator output. Its aprox 1000rpm that its simulating, the output is a pulsed 120v AC at aprox 16-17hz. I put the oscilloscope on a stator output to see what it was while watching the RPM with one of those inductive pickups wrapped on the plug wire. The reason for 1000RPM is just to do the math, if i want to adjust the timing i have an even number to work from, so if i wanted to go to 1500 RPM i just add half of what its currently at for the timing, etc.

My main goal was just to create a super simple tester that can be plugged in and connected to CDI's, ignition coils, and spark plugs, to test these parts when i am working on a stubborn trike or ATV. This really does the business!!

My plan is to post up the schematics, parts lists, PCB designs, everything one needs to build this. I just don't have near the time that would be involved to build these and sell them, and if i did they would probably be pretty expensive. I have around $60 in parts into mine including the case, and all the other wiring bits and pieces, not to mention probably 10-15 hours of building it over a week of evenings. I could do another one a bit quicker now but not that much quicker. However its a really easy build.

I've just been too tied up with everything work to get more info posted. I will quickly share the schematic and a picture of my first potted CDI tonight though! I salvaged the connector from one of the ones that i got de-potted. I haven't found a source for the PCB contacts for these connectors yet. I know they exist since all the Chinese CDI makers use them, but the few manufacturers of the connector shells i have contacted only were able to link me to or supply the crimps for wiring so far.

I won't take full credit for this design, i found a few websites, one from a German author that had very similar schematics for making a CDI tester. I just confirmed what their designs were doing and verified the design, then i designed a PCB to make a nice little compact unit to do this. I wasn't about to reinvent the wheel after finding out others built similar circuits to mine.

[kb0nly]

A quick update for the tester... I grabbed a scrap of aluminum and milled up a block to screw spark plugs into and mounted it to the top of the box.





And an inside shot of the box while i had it apart to add the plug holder..

[kb0nly]

Now for the CDI unit itself... I reverse engineered two of them that i had on hand, one was an OEM Honda CDI, it wasn't originally from a 200ES, it was from another model that used the square connector, and then i also went through a cheap chinese made replacement from eBay. The schematic for them is here..



Pay attention to the notes... The Chinese and Honda versions had different caps for C2, and resistors for R1, R2, R3. Testing the two variants i found very tiny differences in firing speed and length. Not enough that i think it really matters a whole lot, but there has to be a reason why they deviated. Or maybe it was just the cheap parts at the Shenzen market that week...

I have an OEM 200ES CDI module with the round connector on it, however, i don't feel like taking one that has a lot of value to it and destroying it just to see how the reverse interrupter circuit works on the original. If someone has a dead CDI from a 200ES thats an OEM original and they are willing to sacrifice it to destruction, let me know! I would like to get inside of one and find out what the sixth wire, the grey reverse wire, connected to. I had a 200ES CDI that i got apart and repaired in a post years ago, but that was an aftermarket replacement with no connection to the reverse wire pin and a round connector on it. You can buy the same basic CDI that are sold with the square 6 pin connector, with 5 contacts populated, from China with a the correct round connector that will plug directly into a 200ES and ignore the reverse wire. I have one! They are out there, i found them on AliExpress a few months ago for $9 each. However, some guys i know that bought them got them and they didn't work, presumably because as with the others they seem to mix and match whether its an AC or DC CDI. Or it could just be faulty units, who knows.

With the cheap abundance of CDI units now days i know this is nothing ground breaking anymore, but i wanted to be able to build them myself, regulate the quality of the components being use, and modify the design as i wish. The one that was in the picture that i potted with the brown connector i salvaged off a dead one is now on my 200ES, it runs PERFECTLY, and its going to stay there. I will build out a batch of them, stash them in my parts drawer, and always have CDI units when i need to repair one now. I tried various combos of capacitors, SCR's, etc. But with the limited energy produced by the OEM stator coil there isn't a lot of room for improvement for a hotter spark, but it does work well with a fresh CDI!

[kb0nly]

Been really busy with work but an update...

I've got a few hours of riding on my CDI that i designed and built and it's working great!! A lot healthier then the Chinese one i had on it originally, the plug isn't fouling anymore, i thought i had to go through the carb again but turns out it was just weak spark so problem solved! Reading the plug after a long ride everything looks perfect.

[ATC King]

Thanks for posting the OEM component values.

Chinese motorcycle and ATV CDIs are unquestionably hit or miss when bought by the single unit from places like Amazon and EBay. I think anyone not wanting to shell out the $$ for a new OEM CDI should buy from places like DR ATV that have units they know are compatible. New OEM CDIs for the 200ES are still available, for about $170. Really, they last a very long time, it's not something that's likely to go out again any time soon.

The CDI on these aren't complex, and as you pointed out, probably isn't much room for increased spark energy.

The simple design means they will operate under a wide range of conditions, but that doesn't mean optimally, like you pointed out with the Chinese versus OEM CDIs. I've ran across the exact same thing with my use of the Chinese units, which I why I prefer to cut losses and buy OEM if available. I have a BW200 that had a damaged OEM CDI, but still ran seemingly OK. When it got a new OEM CDI (was something over $200 years ago), it ran twice as well, but also started burning the oil instead of just pumping it out the exhaust. Smoked like it was on fire with the new CDI.

[coolpool]

Man, ya'll are so far over my head, Here's what I read.
I took apart that magic box that makes it run and found out there is magic inside it.
You are willing to sell a magic kit but no hat and I must provide my own wand and rabbit.
Check on the wand and hat but icks-na on the abbit-a.

Awesome job, would love to see a video of it in action. I use DrATV modern square cdi boxes as an upgrade to the old round plug factory cdi.
thanks for sharing
MrC.

Not to derail the thread but Mr Condid, I almost cried when I read your post laughing so hard.
This is quite a feat of ingenuity I must say. Being weak in the electrical department myself, I can only wish to be at this level of understanding one day.

I have a dead OEM 200es CDI with a round 6 pin connector you can have in the name of science. Let me know if you want it and I'll send it your way.

[kb0nly]

coolpool... I replied to your PM, sorry it took so long, its been crazy lately getting any free time.

The one i built and put on my 200ES has been working great, zero issues. I made a couple more, one went on a 125M and the other went to a 200, just guys that i was chatting with on Facebook groups that had CDI issues and i offered to build and sell them one. They could have just as easily bought one from Dr ATV but they didn't believe i had made a working repro of them and it was challenge accepted... LOL

I had a few guys with bad CDI's send them to check on my tester, sure enough they truly were bad units from 185/200's. Seems like everyone that has worked on these long enough has a stash of maybe bad maybe good CDI units in a box somewhere. I know i did, then i tested them and tossed the bad ones in the trash finally!

[Rangie]

Loving the reverse-engineered CDI. I'm going to build a couple to have a play with.

Resistor-wise, what rating did you go for? 1/4W?

Cheers,
Alec.

[Mr. NeverPlea]

Excellent job. A few years ago, I too struggled with the identity of Ayecee Deecee boxes. Luckily I had cousin with both the ac and dc scooters that he openly let us test with. It is a crapshoot, pile em up and take bets!

[85ATC250SX85]

Kbonly if your are still out there, please get in touch with me, dcrc620@gmail.com id like to build a cdi like yourself mainly just to say it to the man... but I do sell parts full-time and also have production soldering experience, and some circuit design, experience as well. ive got some 555 timers in stock thats what we used to deisgn our circuits... for modifying engine sensor signals atleast at the start..

Thanks Dan @
DHS-Moto