Question about coils

I have a 79 kz650 that's got under 2000 miles on it, it sat in a garage for about 30 years. I can't seem to get a strong spark even with 12 volts going to the coils, each coil is cracked in 2 places. I looked through the forums, but im still confused as to how properly test the coils.

Welcome.

You'll want to test the primary and secondary coil resistance values.
Disconnect the coil wires before testing.
Measure the coil primary resistance, using an ohmmeter set at R x 1; measure the resistance between the yellow/red lead and the green or black lead. The value should be 4.0 ohms.
Measure the secondary resistance, changing the ohmmeter setting to R x 100 and measure the resistance between the two spark plug leads (from the same coil). The value should be 23K ohms.
If the coil resistance values do not meet these specifications, the coil(s) must be replaced.

Cracks in the coils are not good. You may be able to get away with spraying an electrical sealer on the cracks, but if the cracks are large, you may just want to source some used or new coils.

Do find a service manual. All the test procedures will be in there.

This shows the coil testing for the 1981 and ON 650s, so the values are different, but gives you an idea on how to hook it up:


img.photobucket.com/albums/v494/rstnick/...itertestingsteps.jpg

Search for the WG Coil mod info too.
It uses a relay, and some re-wiring, to bring power more dirrectly to the coils, bypassing the kill switch etc.

if the coils are cracked dont waste much time with them save your self a bunch of trouble and grief and get yourself some new ones. either stock replacement or my own personal favorites dyna tek green 3 ohm coils

Thanks for the info guys

Cracks may also be an indication the regulator on the bike is not working correctly. The cracks are caused by excessive heat - something excessive voltage can cause.

With the bike running, you need to check the voltage across the battery terminals. At idle you should get 12.5v-13v. As you bring the rpm up, the voltage should rise and cap at around 14v. If the reading climbs much past 15v, your regulator is toast.

emaxxima wrote:

I have a 79 kz650 that's got under 2000 miles on it, it sat in a garage for about 30 years. I can't seem to get a strong spark even with 12 volts going to the coils, each coil is cracked in 2 places. I looked through the forums, but im still confused as to how properly test the coils.

You can't test them properly because you don't have a high voltage arc down test apparatus. They may Ohm out fine but have arcing through the insulation. You can get new EMGO four Ohm replacement coils from Z1 for $36. I wouldn't screw around with a cracked coil.

Junk them coils and save yourself the headache as mentioned by others...

While your at it, spend the additional $120 and get yourself the Dyna-S ignition module from Jeff @ Z1... Worth every penny for once it's adjusted for timing, static and dynamic, forget about it, no point adjustments or condensers to go out on you or no PM required on it...

As for the coil mod...DOH! :dry: With a properly charged battery, if you already have +12Vdc at the coils @ idle and up to ~ 14Vdc at 3Krpm then this mod isn't going to do a damn thing for you... And it definitely isn't going to change/correct for the cracked coil...

Oh no... Not this MOD debate again... :laugh:

OMR

get yourself the Dyna-S ignition module & forget about it,

I've had a Dyna fail on me. Lasted a good 7 years or so, but not forever.

Good point for nothing and I mean nothing electrical is going to last forever but in most cases will last a reasonably long time...

bountyhunter wrote:

emaxxima wrote:

I have a 79 kz650 that's got under 2000 miles on it, it sat in a garage for about 30 years. I can't seem to get a strong spark even with 12 volts going to the coils, each coil is cracked in 2 places. I looked through the forums, but im still confused as to how properly test the coils.

You can't test them properly because you don't have a high voltage arc down test apparatus. They may Ohm out fine but have arcing through the insulation. You can get new EMGO four Ohm replacement coils from Z1 for $36. I wouldn't screw around with a cracked coil.

Do you know the output of the emgo coils?

Old Man Rock wrote:

As for the coil mod...DOH!... Oh no... Not this MOD debate again... :laugh:

OMR

I didn't start the coil mod debate... this time. :blink: :laugh: :laugh: :laugh: :laugh:

At least we always agree on the virtue of good clean contacts and switches.

But FYI, this is how I did mine:

With Points .

With Dyna S .

S Details .

More S details

Best of success,
Bill