Measuring secondary winding resistance

When measuring the secondary winding resistance of the ignition coil, my manual says to connect one ohmmeter lead to each spark plug lead.

The accompanying picture shows them doing this with the spark plug caps in place.

The manual then says I should get a reading of 10.4-15.6.

My reading is more like 23.7.

My question is: Is this due to the resistors in the plug caps or is my coil bad?

Did these bikes come with resistors in the plug caps in 1979 or is that a more modern thing?

I think mine did come with resistor caps.

As to question:

"My question is: Is this due to the resistors in the plug caps or is my coil bad?"

If it's the original coil, the answer is likely YES.

Topper wrote: When measuring the secondary winding resistance of the ignition coil, my manual says to connect one ohmmeter lead to each spark plug lead.

The accompanying picture shows them doing this with the spark plug caps in place.

The manual then says I should get a reading of 10.4-15.6.

My reading is more like 23.7.

My question is: Is this due to the resistors in the plug caps or is my coil bad?

Did these bikes come with resistors in the plug caps in 1979 or is that a more modern thing?

Resistor Caps would be 500 Ohms each, no where near the 10,000 ohms difference in your measurement.
Post a picture of coil and wires/ caps.
Sounds like Coil is Fubar to me.

Motor Head wrote: Resistor Caps would be 500 Ohms each, no where near the 10,000 ohms difference in your measurement.
Post a picture of coil and wires/ caps.
Sounds like Coil is Fubar to me.

DOH! That's right, for some reason I was thinking 5k ohms each for the plug caps.

Well at least I know what to do next. Many thanks to both Motor Head and Bounty Hunter for the help!

I would measure without the caps. If the coil checks out; if fine get non-resistor caps. Ed

Topper wrote:

Motor Head wrote: Resistor Caps would be 500 Ohms each, no where near the 10,000 ohms difference in your measurement.
Post a picture of coil and wires/ caps.
Sounds like Coil is Fubar to me.

DOH! That's right, for some reason I was thinking 5k ohms each for the plug caps.

Well at least I know what to do next. Many thanks to both Motor Head and Bounty Hunter for the help!

:blush: Well i was wrong on the resistance of the plug caps, went and posted in your other thread too. Here is the correct info from NGK: www.ngksparkplugs.com/docs/Resistor_Covers.pdf

Yeah, looks like we both figured that out about the same time.

So the specs in the manual assume no resistor in the caps.

I had time to do more testing today and sure enough, with no caps I'm getting 13k ohms and with them I get about 24k ohms.

Got an EMGO from Z1 and measured it with essentially the same results.

Only problem is this EMGO doesn't fit my bike. The mounting studs are too close together. I must have picked the wrong one. I guess I'll be returning it.

Thanks for helping to answer this question for me.