Coil Ohms Readings

[alexbrown64]

Well, i have absolutely no spark whatsoever on my little YZ80E.
It has the outer rotor style magneto assembly.
The Yamaha book i have for the year says the  Primary coil should be 1.0 Ohms
The secondary coil should be 5.9K Ohms.  And it doesnt mention a value for the tiny pulser coil.

I have uploaded a pic (below).

The exploded view diagrams online refer to both the larger coils as source coils.
I am getting about 359 Ohms through the brown wire which leads to the biggest coil.
I am getting nothing through the smaller coil which has a red lead. No Ohms and it seems to test as an open circuit.
I am getting about 9.9 Ohms through the pulser coil which is a white lead with an orange stripe.
I have tested the smaller coil lead right back from the plug to the coil, and i get a reading that the cable is OK.

So, my questions to all you guru's is... Which coil is primary and which is secondary?
I could replace the smaller coil with the red wire, but do the other values sound correct?



Cheers,

Alex

[sleepy]

That is the resistance value for the top coil, the one hooked to the spark plug.
Ignition coils have 2 windings inside , primary or low tension and secondary or high tension.

[alexbrown64]

Hi Sleepy, that figures..

I have seen that value of 1 Ohm mentioned for the coil that goes to the spark plug.
But that is still confusing as to what the two coil values on the stator plate should be.
I guess the one that is open is definitely knackered as its not returning any value at all.

Cheers,
Alex

[sleepy]

This may help if I can get it to work, IT175 diagram could be similar.
Can't workout how to load a PDF image. PM me an email address and I'll send it to you.

[alexbrown64]

Thanks Sleepy,

Got your diagram and i have converted it to a jpeg and uploaded it.
I also talked to an ignition shop that deals with these all the time.. (Betta Bikes in Adelaide, thanks Steve).

Looks like my manual was quoting the coil that goes to the spark plug only.  No mention of values for the other three coils on the stator plate.

So, using Sleepy's IT175 diagram as a rough base, it looks like i am in the ball park with the largest and smallest coils.  Its the mid sized source coil part number 2J5-85511-20 that is the problem.  Luckily, there are a heap of NOS ones on Ebay, so i can get a brand new one and solder it in.

Here is the IT175 wiring and values..



and here is the little 80 diagram...



My Ohm values are very close to the IT values.. i think enough to get a ball park figure. Hopefully problem soldered.

Cheers,

[OverTheHill]

https://www.partzilla.com/catalog/yamaha/motorcycle/1978/yz80e/c-d-i-magneto-yz80e
Wouldn't have thought only 2 coils in the flywheel unless there's a lighting coil left in there but looks like i'm wrong looking at a cdi box on ebay but if i was stuck & you're getting ound 350 ohms out of the brown to earth then a simple cdi box off a yamy scooter would work where by [did it on my 490] i happened to have a passola scooter typical simple box & think i hooked the brown from source coil to the black/red in the box. White/red [not white/orange think you said so must be a faded red stripe] from stator goes to 'that' in the box. Orange to plug coil. Don't think there'll be a black but if there is then earth it but don't earth any black/white as will be kill switch--stops it when earthed. Worked for me. Plus another trick that worked was simply using the source coil [brown in your case] & hook it to an RG50 or LT50 JR50 plug coil which is a cdi box combined. No trigger coil needed. Only two terminals on the coil & one is the kill wire terminal. Did that on a DT125LC with a destroyed pulser coil when screws fell out of lighting i think. In 'that' case i didn't even have to alter anything as timing was ok & ran faultless till kids grew out of it. YZ490 never suffered but probably without the brown & two coil set up maybe the timing doesn't advance or retard as much as it does originally--or does the extra coil boost the spark at high revs, i don't know--just ran like a normal arm stretching 490 & retarded for starting so all good. Looks like maybe only one terminal in so there'll be a branch off that for kill switch just to short the source coil.
https://www.ebay.com/itm/Ignition-Coil-With-CDI-for-Suzuki-JR50-JR-50-/221913131546
Funny thing is--looking at the YZ80E stator on partzilla it looks like the second coil has no windings but shows a wire going to it. Anyway, if you have a red then it's got windings. Resistance won't be anything like the 350ohn coil & maybe 100 or so guessing. Hope that's not too confusing but sure confused me trying to proof read it--gave up lol, keyboard misses letters.