bad coils???

OK Gang, I've been chasing ghost's in the machine so to speak. After riding 60 miles and check the plugs they are wet somewhat. So I checked the coils tested them with the wires unhooked. The reading between the wire terminals is 0 ohms.
The reading between the spark towers is 12,000 ohms. I have a spare Green Dyna coils that tests out at .2 ohms on the wire terminals and the spark towers is 15,000 ohms. So I'm left to wonder are my coils bad/weak or is it something else I'm overlooking. I know that the Dyna coils are supposed to be @ 3 ohms so I'm wondering if in fact it is also bad. Any ideas??

If they were truly 0 ohms, they would be a dead short. You would get no spark out of them. Are you sure the meter is working properly?

Try this: with the tank removed at home, use a hair dryer and heat up the coils. The reading should be between 1.8 to 3.0 ohms on the primary(small wires) side.

On the secondary(sparkplug wire ports)side the readings will be between 10.4K to 15.6 k ohms.

Your coils may be failing from heat and/or insulation breakdown.

Actually O ohms does not necessarily mean a problem. A zero ohm reading always represents full continuity (no resistance), which is what you'd normally get between the two primary winding terminals. You will actually see anywhere from 1 to 3 ohms because the length and thickness of the windings themselves give some resistance. 1.8 to 3 ohms seems normal to me. If you nominally get the reading between the primary and secondary windings that MFolks mentioned, then the coils may be fine. But heat will sometimes cause worn primary windings (that are fine when cold) to short against each other, lowering the strength of the field they can build up. Heat also enhances resistance. Hence the hair dryer test.

The "zero Ohms" reading probably means his meter doesn't have a low enough range to get accurate readings in the 3 Ohm ballpark. Most meters do not.

Right, a false zero reading may not be a problem, but a "Truly 0" reading means he needs a new coil.

Yes, it's a matter of meter sensitivity. Even touching the meter probes together causes some resistance (there is minute resistance in the probe wires), but most meters are no where near sensitive enough to read this and you get a zero reading. Some digital meters will read this, and you adjust them back to zero.

If the windings are shorted together just beyond the terminals, you could get a zero reading, but it's also possible his meter is just off a tad. If bountyhunter's heat up test raises the resistance, then the coils are shot anyway.

Thanks for some suggestions. I have tried 3 different meters. 2 analog and 1 digital, all rat shack. The analog range is set to Rx10 I can't see why it wouldn't read 3 ohms. The spark appears to be very weak thus the reason for my test. I will check them with a digital Fluke meter @ work on Monday just to be sure. And I did check them both hot and cold same results give or take on the secondary readings.

If thier more than a few years old, just get new ones.

spudbudy wrote:

...The spark appears to be very weak....

What voltage is reaching the coil primary terminal?

Good Fortune!

OK here is the results of testing the two different coils with Fluke Meter. Both coils test out fine ! The old Andrews coils ohm out @ 3.2 and 11,500 and the Dyna ohm out @ 3.2 and 15,500. So my guess of bad/faulty coils was unfounded. I guess I will have to look elsewhere for my weak spark problem. On a side note does anyone know if makes any difference if the coil mounting bracket is grounded or not? I looked @ the wiring chart and didn't see any ground for the coils.

Well this has been all about coils, you never said what the plugs are "Wet" with? Fuel or oil. You can still have a electrical or spark issue, but is it possible you have another problem as in carbs or valve stem oil seals? As far as the spark goes they have a cheap spark checker at Harbor Freight that will go inline with your plug wire with the bike running, you can adjust the gap for the KV rating of your coil. Of course spark should remain constant and of good quality at all RPM.