I have a 90cc Baja Chinese quad with no spark. The spark plug is fine, since I tested it in my other Chinese quads that runs great. The "ignition" voltage from the stator to the CDI measures about 54VAC and the timing trigger signal from the stator measures about 0.2VAC, both being nearly equivalent to my other quad. So now I wonder if the kill switch circuit is causing the issue. In the attached photos of the CDI, can anyone tell me which wire would be the kill switch circuit? Yes, I can tear apart the wiring harness to figure it out myself, but I'm trying to avoid dismantling more than I have to. So I thought someone here might readily know.

Thanks in advance!
M Ridzon

 

The kill switch wire is the black/white and goes to both ignition switch and kill switch, also wireless kill switch (or "sink plug" type) if it has one. Some are wired earth to kill, some earth to run, so these switches can be in series or parallel, depending on type. Easy way to test circuit, disconnect plugs at CDI put a 12v test lamp between live battery post and black/white wire at this wiring plug, switch on ignition, if lamp goes out when ignition is on, or t'other way round, the switch is working. If nothing happens, either lamp stays on or doesn't light at all, one of the switches, or wires to them, is faulty.

 

Update: I tested the kill switch wire (black/white) after disconnecting from the CDI. It seems functional. When the kill switches (i.e., key, kill switch, rear parental tether) are in "run", the circuit shows nothing at the CDI. When one of them is toggled (i.e., to kill the machine), the circuit shows ground at the CDI. Any thoughts on where to go from here?

 

Update again:

On my good quad that runs, with the CDI plugged in, I measured VAC on the ignition wire (black/yellow going to ign. coil). It outputs roughly 0.15VAC when running. If I instead crank it with the kill switch triggered (i.e., rider has killed the engine), the same wire outputs roughly 0.04VAC when cranking (but it obviously doesn't start).

Lo and behold, on the bad quad that doesn't run, the same wire outputs roughly 0.04VAC no matter what. And the grounds (two green wires are ground at CDI) to the CDI are good. So I'm pretty sure the CDI is bad.

 

What is the difference between the CDIs for VIN prefix LE8S and LUAH? Mine is the latter. I see tons of cheap CDIs on eBay for the former, but they all explicitly say "VIN Prefix LE8S." From the Baja parts catalog HERE, it looks like my CDIs part number is WD90S-463, which doesn't show up on eBay. On Google, a couple sites show up with that CDI, but are several hundred dollars. Ouch! My CDI has the rev limiter, but I don't know if the replacement needs to have that.

Is there really any difference between the two CDIs?

 

CDIs are a nightmare as, although most use a 6pin configuration, the pins go to different wires on different models. Your CDI is odd as it has a longer two pin plug than most, note the unused hole in the middle for another wire, most don't have this. I would guess that many cheap AC CDIs would work if you altered which wire went to which pin, and fitted a smaller two pin plug to the black/red and black/white wires. Be very sure it is the CDI at fault if you do go for the correct one, 0.2v from the trigger coil isn't a lot, though some bikes do run with a voltage this low.

 

Update: I called Baja. From what they said, Scooter Outlet in El Paso, TX is their main distributor for old parts for these ATVs. I called them and ordered a CDI and ignition coil ($30ea). I installed the CDI only, last night. Lo and behold, the bike started!! Yay! So it looks like my diagnosis was correct. I'm also going to install the ignition coil since the old one has cracked rubber and plastic (i.e., dry rot from old age), and I'll keep the old one as a spare.

Thanks for the feedback here!

 

So I bought a used 90cc Baja 4 stroke but it needs a new wiring harness, it has a 8 or 7 coil stator but I don’t know where to find a wiring harness that will fit the motor because most of them have a two or six stator on amazon but I don’t want to take the risk of losing 50 bucks

 

You can try Scooter Outlet, which I mentioned in my previous post. For your Baja, check out HERE to see if you can find your parts catalog and part numbers.

Otherwise, I shop eBay and Amazon for parts on these Chinese bikes. Many parts on these Chinese bikes are interchangeable (I own two, Baja and TaoTao) and I've found that you can usually do okay just visually comparing them before purchase. Unfortunately a lot of times, that's the only recourse I have, is to visually compare the pictures on the retail site, to the part in my hand, since part numbers aren't always available or jiving properly (e.g., they may advertise it with a TaoTao part number, but it fits your Baja too).

 

Yeah so I took a look and I couldn’t find anything with a 8 coil stator. The wires that are coming out of the current one at 2 yellows 1 green/white 1 blue/white 1 black/red do you know what they do