TOPIC:

Hi again. Im new. The PO of my 79 reported that it may have a suspect coil. Something about a miss fire when the bike is warm. I picked up two NOS coils in lieu of this.
I want to test each of the current coils to see which one is the problem.
I have tested primary resistance on the replacments and get 2 which from what I read is OK.
How do I test the secondary circuit? I read somewhere you attach a multimeter from one of the poles to the spark plug hole but I get nothing?
Am I doing it wrong?

The secondary circuit would be from one high voltage terminal to the other.

Bill

KZQ wrote: The secondary circuit would be from one high voltage terminal to the other.

Bill

I measured from one blade terminal on the coil to the other and got the 2 Ohm resistance.
There is another test I believe for the other circuit which is what I need to know how to do.
Any help?

There are 2 high voltage terminals/towers. You test between these on the Z13 type coils. Not sure now what the resistance should but 10000 ohms is a reasonable figure. All 3 should be within about 10% of each other and also check for a resistance reading from each tower to the core (the laminated steel centre piece) you should not get a reading but a digital meter will give a OL which means Outside Limits of the range of the meter.
An OL reading does not mean there is no leakage to the core/earth but that there is not one that can be measured by an ordinary meter.
Also it pays to test for leakage from primary to secondary coils by attaching one lead of the meter to the 12v input and the other to the High Tension Tower you should also get an OL reading there.
None of these tests will give you a definitive answer because the meter can't produce a high voltage which will break down the insulation and make it conduct but you will get a good idea of the condition of the coil.

To test your factory coils

1: The most accurate way to test a coil is by arcing distance. Should be 7MM or more. There are some simple ways to build your own indicator, with a 7MM gap. Also the coil can behave differently while under a load, i.e. with fuel and compression under dynamic cylinder conditions. (While running)

2: To test the Primary side (Low voltage side.) (On each coil, Pink Lead TO Green/ Black/ and then Blue Leads.) Set meter to 1ohm. Meter should read 1.2 to 1.9 Ohms. detached from the resistor.

3: To test the secondary side (High Voltage side.) Meter leads on each high tension lead, without the resistor caps. Set the meter to 1k ohms, it should read from 12K to 18K Ohms.

4: Don't forget to test the Resistor Caps. They should read around 5K Ohms.

Hope this helps and keep us posted.

T.

Oh I forgot:

To test the resistor.

Ohm meter to 1ohm scale

One meter lead to Yellow, the other to pink. Value should be 1.5 to 1.9.

It is this resistor that brings your low voltage side of the ignition near the 3ohm value, for your coils to work properly.