6v magneto CDI system, head scratcher.

Alright so I have this scooter I've been messing with, and I just can't get the darn thing to fire up. Currently trying to sort out this harness and get spark, but I'm used to the regular old 4stroke motors with points and such.

The harness has cut/unused wires everywhere and the 2 diagrams I have don't line up with what's there. It's a 6v magneto system with a CDI unit, currently running no lights at all and no battery.

This is a diagram from an earlier model (FZ50, I have the FA50), but the colors in the harness all line up with it and they didn't match up at all to the FA diagram.



Disregarding all the lighting circuits and keeping all the necessary bits for running. I have the engine and harness grounded properly to frame. It seems as though I'm missing a Y/R wire from the magneto to the ignition switch. The rest of the wires from the magneto are connected to their matching colors.



The main switch has the correct color wires from the switch (matching the diagram) but the wires from the harness aren't the right colors.



Switch side:

Harness side:


The 2 red wires coming out of the junction to the switch go to the tail, one would lead to the battery and one goes to the rectifier.


If I'm not running a battery, do I need to jump the POS/neg wires that would normally be connected to the batt?

I bypassed the kill switch on the right hand controls by grounding the B/R wire back to the harness earth.

What am I doing wrong here?

Yes, you'll need the battery. In this case, it acts as a regulator. Make sure to use a flooded cell and not AGM or LI-ION.

When you said "I bypassed the kill switch on the right hand controls by grounding the B/R wire back to the harness earth", did you mean that the B/R is now grounded? That appears to be the KILL wire and grounding it via the switch or kill switch means no spark. To get it to run, connect just the magneto to CDI wires and leave the Y/R and W/R wires safely taped off for now.

teazer said:

When you said "I bypassed the kill switch on the right hand controls by grounding the B/R wire back to the harness earth.
" did you mean that the B/R is now grounded? That appears to be the KILL wire and grounding it via the switch or kill switch means no spark. To get it to run, connect just the magneto to CDI wires and leave the Y/R and W/R wires safely taped off for now.

Click to expand...

Lol... I missed that part.

If the black/red wire is grounded then the bike will not fire!

Ah, ok. So the B/R is grounded out when the handlebar switch is switched to off, not on. Got it.

I had spark on this thing without the battery installed when I first got it, but I found later that the coil wire/engine ground were shoddy connections. I'll fiddle with it and report back. Thanks


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Alright so "KILL" wire no longer grounded, disconnected Y/R and W/R, and have the B/R, R/B and W/B plugged into the harness, and I'm still not getting spark.

The main switch (keyed ignition) tested good on the main circuit with a multimeter, but I unplugged it and tested for spark anyways. Still nothing.

I have a battery I can borrow to troubleshoot this thing, but I was hoping to avoid buying one. Like I said though, right after I bought it I HAD spark for a while, but now I got nothing.


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adventurco said:

Alright so "KILL" wire no longer grounded, disconnected Y/R and W/R, and have the B/R, R/B and W/B plugged into the harness, and I'm still not getting spark.

The main switch (keyed ignition) tested good on the main circuit with a multimeter, but I unplugged it and tested for spark anyways. Still nothing.

I have a battery I can borrow to troubleshoot this thing, but I was hoping to avoid buying one. Like I said though, right after I bought it I HAD spark for a while, but now I got nothing.


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Click to expand...

Have you tested the coil just to make sure it didn't burn up since you began putting power to it?

deviant said:

Have you tested the coil just to make sure it didn't burn up since you began putting power to it?

Click to expand...

Yeah, the orig was good but the connection between the plug wire and coil was failing so I put a new coil in.


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adventurco said:

Yeah, the orig was good but the connection between the plug wire and coil was failing so I put a new coil in.


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Click to expand...

AC coil or DC coil?

At this point, I'd probably run wires directly from the magneto to CDI and avoid any potentially bad connections in the loom and see if spark appears. Don't forget that the magento and CDI have B/W ground leads that do need to be connected to ground.

teazer said:

At this point, I'd probably run wires directly from the magneto to CDI and avoid any potentially bad connections in the loom and see if spark appears. Don't forget that the magento and CDI have B/W ground leads that do need to be connected to ground.

Click to expand...

It's already set up that way. The switch just grounds the system out in the off position. It can run with no battery or switches of any kind, because removing the on/off switch just takes away your ability to shut it off without pulling a wire..

deviant said:

AC coil or DC coil?

Click to expand...

I haven't a clue, and apparently neither does emgo. its this : https://www.amazon.com/Emgo-Universal-Ignition-Coil---/dp/B002EC389W/ref=sr_1_1?ie=UTF8&qid=1473365527&sr=8-1&keywords=6v+motorcycle+coil

So both of the on/off switches essentially provide a second ground to the CDI in order to kill it, is that what i'm understanding?

The B/W wire has a bunch of crimped Y connections (all are good, I inspected the whole harness), so its all basically one wire that I have grounded via a clean loop connection/screw to the frame. So when the B/R wire is grounded out, that disables the spark.

Sort of. The ignition needs a ground on one side of the generation to complete the circuit. Those are B/W wires and are needed to make spark.

In addition, the way to "kill" the system is to ground out the CDI and the magneto so that they produce no power when that side of the circuit is grounded out. That's the B/R wire which kills it when grounded.

On a magneto or stator powered CDI, you have an AC coil. If it's battery powered, then it's going to be a DC coil. I'd be willing to bet that Emgo coil is DC and it's the reason your bike won't produce spark.

IIRC, your XL350 is set up like my XL250, so they use an AC coil. Try hooking that coil up and see if it fires up.

deviant said:

On a magneto or stator powered CDI, you have an AC coil. If it's battery powered, then it's going to be a DC coil. I'd be willing to bet that Emgo coil is DC and it's the reason your bike won't produce spark.

IIRC, your XL350 is set up like my XL250, so they use an AC coil. Try hooking that coil up and see if it fires up.

Click to expand...

That is the coil I'd bought for the XL. I can put the old coil back in the scooter maybe I can tape it up so the wire doesn't spin in the connection near the coil. That one tested good too but I think that I had spark when the plug was out and then I'd put the plug in and because of the awkward angle the plug wire is at it screws with that connection.

XL350 definitely uses an AC coil. Have you run it on that bike yet, or did you buy it for when the rebuild is complete?

deviant said:

XL350 definitely uses an AC coil. Have you run it on that bike yet, or did you buy it for when the rebuild is complete?

Click to expand...

The XL hasn't been run yet. Next week or so hopefully. So I don't know if that coil will work or not.

I swapped the original coil back in, tested it again to make sure it's good, but still no spark.

I am gonna get a working FA50 over here this weekend and use it to see what the hell im doing wrong.

Tomorrow I'll run some fresh wires directly from the magneto to the CDI and see if sparks fly.


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I have a running FA50 in the shop this weekend that's helping me troubleshoot. I did some part swapping and here's what I can confirm:

-main switch = good
-CDI unit = good
-coil = good (also the Amazon coil works fine as well)
-no battery required to run
-bike will run without Y/R and W/R hooked up.

So I'm convinced I have something botched up in the wiring. The jacket on the wires coming from the magneto was torn up a bit so I pulled it, all the wires look like new underneath. I really doubt that the magneto itself is gone. The loom is unwrapped and all crucial wires seem to be fine. I'm thinking I should run some new copper for the ignition circuit.




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To follow up that third to last sentence, I pulled out the multimeter and tested for continuity on the stator. All circuits passed with the exception of the main line, the R/B. I performed all tests and showed open circuits between R/B-B/W and R/B-B/R



This was performed with the multimeter at the following setting.



I am still flat out confused though. If the stator was bad from the get go, how did I have spark initially? What could cause the stator to just die after kicking the bike over a handful of times?


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