I've got an 87 Moto 4 that's pretty much in mint condition. Therefore, thinking it might be any easy fix situation, I paid WAY too much for the bike. The bike will not fire and I am at my wits end because I cannot find a CDI box. What's more frustrating is that although I am a 12 volt "guy", a welder, and a general mechanic, I do not understand the bike ignition system. I understand the purpose and action of the CDI, but the wiring and function is throwing me off. I need help understand what is going on. The stator is stationary, and the ignition source coil has two wires, red and white. Are these two wires suppose to be 12v battery hot and chassis ground? The flywheel spins, separating the source coil from the TWO pickup coils. Why two on a single cylinder bike? So these two pickup coils are both two wires. Are two of the wires chassis ground and the other two send a 12 volt pulse to the CDI? With the flywheel separating the source from the pickup, exactly HOW does that work? I'm VERY sorry for the long post from a new guy, but I desperately need some help. I'm really hoping once I find out what does what, I can find another CDI that I might could retrofit. I've searched the web for WEEKS, with zero gained information. Thank you for your time.

 

Okay 1987 what size moto4?

When you say not fire you mean cranks and cranks and cranks and no start?
Or you mean you check for spark and there is none?

 

It is a 350. It cranks fine. No coil output from the CDI. The CDI is also not supplying the starter solenoid relay with ground.

My CDI is a 13 wire unit.
Black = chassis ground
Black w/ white = kill switch ground
Black w/ red = key switch ground
Green w/ yellow = ground input from front brake switch
Yellow w/ black = ground output to starter solenoid relay
White w/ black = ground input from neutral relay

Then there are four wires that come from the two pickup coils.

There are two wires that go to the source coil attached to the stator.

The only thing I know for sure is that the CDI is receiving everything it should, but it is not giving me a ground output to the starter solenoid relay.

 

okay so no coil out and no starter sol ground
Obviously you could supply the solenoid ground, but without a coil signal no spark

Any used CDI on Ebay? New look to be what $150-240 on ebay
Is there a universal CDI you can wire in? (cheaper)

just thinking out loud here

 

I'm with you. In three months I've seen one model specific CDI on eBay.

What I'm trying to get help with is the function of the ignition source coil and the two pickup coils. My source coil is wire into the CDI. If the two wires on the source coil are truly hot and ground, that can obviously be easily hard wired stand alone. It's what the pickup coils do. Why two? Why do they both have two wires? My thought is that power goes from the source to the pickup some how and then in to the CDI creating spark pulse to the coil.

 

see now Im lost, you are way over my head on that. I would have to have the bike in front of me to disect

I see some 13 wire CDI sets show up for your model around $80-90 online
New China parts

I am educating myself on your model I found this:
ATV Electronics series Part 1 - ignition systems: Off-Road.com

 

So the source coil I speak of is at 3 o clock. Reading the article you posted, I understand that this coil generates massive amounts of power to send to the CDI. The two pickup coils also at 3 o clock (wires were cut for testing) must be power in power out (two wire) and when the magnet in the flywheel passes the coil it tells the CDI to fire.

 

The CDI are pretty reliable. I would check the cheaper parts fist like a Ignition coil or try this video . The ATV is a Warrior but has the same 348cc motor that Yamaha has been using for 30 years .

 

If the CDI is suppose to supply the starter solenoid relay with ground and doesn't, is that a sign the CDI is bad?

 

If Yamaha did put the solenoid ground through the CDI, they would have a reason, such as the CDI needing a signal from the safety "lock outs" on brakes or gearbox before allowing the starter to get power. It could be that one of these lock outs, or a wire from it, isn't working so the CDI doesn't get the signal. A 13 wire CDI is so complex, you are best getting a workshop manual to check the system over properly, before buying new components.