Well I've been poking around China CDI's a bit and figured I'd find my findings, atleast for using them on an ATC350X.
First thing first, they are all wired based on the 350x pin out, so it's a nice stright plug in and test vs stock. My stock CDI works great, so I can do ABA testing. These reviews are purely based on listening to my engine and basically dry reving it. The stock CDI revs out the full rpm range well, but I do know the top end is a bit on the lean side (need to rejet for the DG exhaust I put on it).
First one up is the most expensive China CDI I bought a "Racing CDI", still stupid cheap compared to even used CDI's. This fancy blue housing CDI looks to be built fairly well. The red LED light blinks per spark, after a little bit of RPM it appears to be solid on, probably just blinking faster than my eyes can see. It started the engine and idled well. Low to mid range it ran just like stock. Had high hopes, but high rpm it doesn't rev out fully. I suspect the timing is too far off from what the 350x engine demands. If you never get above around 3/4 throttle, this CDI could be a cheap alternative if you're in a pinch. China part number on this one is H048-014.
Second CDI is this ornage housing one. I've read people were having luck with them working out well. The China part number on them is H048-016. This one ran the same as the above CDI for idle and mid range. The high rpm was even worse though, not a huge difference but probably 500-1000 less rpm (I need to get a tach to be more scientific lol).
Both of the above CDI's made the high rpm sound like it was leaner than the stock CDI, maybe it's just from a stronger spark and retuning would fix the problem? I'll have the CDI's around when I rejet the engine some day.
The last CDI is the typical black one that looks similar to the stock one. Looks exactly the same as the orange one, but the plastic housing is black and the epoxy fill was done horribly (not flat at all). This one wouldn't fire up the engine. I gave it a little gas and it puffed a nice ball of smoke out of the carb. I guess this is a 2 stroke CDI or something. The China part number for this one is H048-024.
Bonus CDI, in the past I bought this one with high hopes, but like the ones above, it falled short. It was hard starting, but I could get it going with a little throttle. It advanced the timing WAY too fast, at around 2500-3000 rpm it would hit a wall and not rev any higher. I don't have the part number for this one sadly. It's slightly smaller than the above one though.
Bonus #2!
Stock 1999-2004 TRX400EX CDI part number 30410-HN1-003. One of the replies to this thread suggested this was a suitable replacement. The 400ex is just a tiny bit smaller than the 350x CDI, I can get measurements if someone needs/wants them. I warmed up the engine with the stock CDI again, double checked it revs out well and all is good and smooth. Popped on the 400ex CDI (service manual calls it a ICM [Ignition Control Module] btw) and it fired up exactly like OEM. Low to mid range seems to be a perfect match. However once again, top end it's not quite right. I had a couple back fires though the exhaust, nice flame effect but not running perfect. I'm wondering if it's hitting a rev limiter or something. So once again stock OEM seems to be the thing to stick to.
Mikes ATV Fix CDI
Took me forever to get my carb cleaned, reassembled and reinstalled, but I'm back at it again. My machine is an 85 350x with what we suspect is the "low voltage" stator design, so we pretty much expected there to be running issues since other's have had issues too. From my understanding the 86 stator's exciter coil puts out more power and runs this CDI just fine but I don't have the newer stator on hand to test the theory out. Anyway, as normal, fired up the 350x and warmed it up with the stock one to make sure all is running fine, carb is a lot better now that it's been though an ultra sonic cleaner. It's a tiny bit lean so likely need to raise the main jet a little, but it's pretty close to being right. I popped on Mike's CDI and tested the "easy start" feature which seems to work well, I can hear the timing change after the first fire, just took enough rpm to get a spark. Stock takes a tiny bit more rpm, but not much more when warm at least. Low to mid rpm sounded the same as stock, however high rpm it seems to hit a wall like spark just dies right out, almost like a rev limiter but it doesn't fire at all till I let off the throttle. If I bring the RPM up very slowly I can get it almost as high as stock before it starts to break up.
I built myself a special adapter so I can tap into the CDI wires while it's running to take readings. This test isn't standardized at all, but might show a bit of what's going on. Probably best to take this section with a grain of salt since it's only one metric to base things on. The idea is I can use my home built peak voltage tester to take a reading of the input voltage from the exciter coil and compare to the output voltage to see how efficent the CDI is at passing though voltage. Amps/current is the other half of this and I'm not sure how to read that matric with this kind of setup. I performed the test at idle, but the idle was a bit high, roughly 1600-1800rpm.
Anyway, base line reading with the stock CDI was as follows:
Exciter (CDI input power) - 207v
Ignition Coil wire (CDI output power) - 92v
Note: Output voltage increased with higher rpm till higher rpm then it dropped a little. Not going to red line my engine long enough to get actual numbers though.
Mike's CDI tested as follows:
Exciter (CDI input power) - 76v
Ignition Coil wire (CDI output power) - 29v
Note: Output voltage dropped with more rpm
Orange CDI from above:
Exciter (CDI input power) - 79v
Ignition Coil wire (CDI output power) - 29v
Note: Output voltage dropped with more rpm
I think the next step is to buy an ignition test light and check what the spark curve looks like for each CDI that makes the engine run at least ok.