Coil secondary ohm testing

Greets all.
I been working on a '78 KZ650D-1, and I am at the point that I need to verify the correct function of the electrical system.
According to the manual, I should get 4ohms across the primary coil, and 23Kohms across the secondary.
Two questions:
1) One of the coils shows 4.4ohm across the primary. Is it time to replace that coil? Will the extra .4 cause issues?

2) I can not get any reading at all across either secondary (testing across both plug wires). Multimeter is functioning correctly, I am making definate contact with the plug wires metal connectors.

Advice? Tips?
Thanks,
-Al

OLTIMER wrote:

Greets all.
I been working on a '78 KZ650D-1, and I am at the point that I need to verify the correct function of the electrical system.
According to the manual, I should get 4ohms across the primary coil, and 23Kohms across the secondary.
Two questions:
1) One of the coils shows 4.4ohm across the primary. Is it time to replace that coil? Will the extra .4 cause issues?

2) I can not get any reading at all across either secondary (testing across both plug wires). Multimeter is functioning correctly, I am making definate contact with the plug wires metal connectors.

Advice? Tips?
Thanks,
-Al

4.4 ohms primary winding resistance is just fine. No problem there.

Best method to measure ohms on secondary winding is at the coil outputs with plug wires removed from coil. But where the wires aren't removeable from coil, next best method is to remove the plug caps with contacts between the internal plug wires, thus removing the caps from the equation. That said, it should be possible to measure between the caps themselves (between the clips inside the caps), and sometimes resistor style caps will cause an increased ohm reading. But there is a fairly wide range of acceptable ohm readings for the secondary windings. A break in the windings of either primary or secondary will likely show zero continuity.

Seems doubtful that both coils would have faulty secondary windings.

If not already done, would remove plugs, hold plug bases against engine, and spin engine over with ignition turned on, to visually inspect spark quality. Remember to simultaneously ground both plugs from the same coil during this exercise. As both plugs must be grounded to complete the secondary high tension loop whereby the coil fires both plugs simultaneously. In short, both plugs from the same coil (with both plugs held grounded) should both produce simultaneous good fat blue sparks.

And of course, lack of spark could result from other reasons, even with perfect coils.

Best to use brand new plugs. Some fuel fouled plugs can look perfect, but never fire, regardless of time used.

Good Luck!

plug wires removed from coil.

Can't. Moulded @ factory.

and sometimes resistor style caps will cause an increased ohm reading

Ahh . will try eliminating caps.

A break in the windings of either primary or secondary will likely show zero continuity.

Not likely. Bike ran for the 6 blocks I rode it around 2 months ago, and the parts were removed almost right away.

Seems doubtful that both coils would have faulty secondary windings.

Agreed.

and spin engine over

Can't. Still too many parts disassembled, and no battery yet.

I will try the remove caps route, I just hope I don't break them in the process. Coils look to be original equipment.

Thanks for the quick reply!

Results:

Coil 1:
Secondary ohms = 14,660
Plug caps a) 1.2 million b) infinite.

Coil 2:
Secondary ohms = 12,040
Plug caps are both infinite.

Recommendations?

OLTIMER wrote:

Results:

Coil 1:
Secondary ohms = 14,660
Plug caps a) 1.2 million b) infinite.

Coil 2:
Secondary ohms = 12,040
Plug caps are both infinite.

Recommendations?

Coils sound OK to me. Z1 sells 4 Ohm OEM replacement coils for $36 if you need a coil.

My recommendation is to purchase new plug caps, the coils should work fine.

Just for grins one day, I checked all the plug caps in my spares collection. Think I checked a dozen or so, and there wasn't a single good one in the bunch.

Z1 sells 4 Ohm OEM replacement coils for $36 if you need a coil.

That is an awesome price! Too bad I can't find the part you are referring to ...

Here are the ignition parts available for my make / model. I only see 3.0 ohm and less, and they are all way more expensive than that.
Perhaps can you post a link to the item?
THanks,
-Al

unless you are restoring this bike do your self a favour and buy your self a complete dyna ignition complete with coils you will never experience any more ignition problems again irun them on all of my bikes.I have 3 ignitions that i have run since the early 90's one of them has been on my drag bike since i started racing in 1994 never had a problem since. one other reason to update is your dealing with 30 year old electrical components. thats what i would do if i was in your situation. good luck and have fun with that bike. one thing to remember is it will want to rev up alot quicker. so i would recomend installing a drl300 rev-limiter as well

bountyhunter wrote:

OLTIMER wrote:

Results:

Coil 1:
Secondary ohms = 14,660
Plug caps a) 1.2 million b) infinite.

Coil 2:
Secondary ohms = 12,040
Plug caps are both infinite.

Recommendations?

Coils sound OK to me. Z1 sells 4 Ohm OEM replacement coils for $36 if you need a coil.

What am I missing? Why are the coils ok when the manual calls for 23k ohms on the secondary , and he has about half that?
And aren't most of our plug caps supposed to be 5k ohms? I would think he needs new coils, wires and caps, yes?

These are the $36 coils.

OKC_Kent wrote:

These are the $36 coils .

You sir, are my Hero today!
I have wanted to replace both coils since I got the bike, because the plug wires are weather-checked and stiff, but the high price of the ones I could find put me off.
bountyhunter wrote:

Z1 sells 4 Ohm OEM replacement coils for $36 if you need a coil.

And my thanks also go out to you, for letting me know that these parts existed on Z1!

With this, I think I am within $500 of getting the bike in ridable condition (plus artwork / paint, but that is 'decoration', not mechanical soundness)

I may yet get to ride this year before the snow flies ...

EDIT: w00t!! I just added it all up, and I only need to spend about $230.00 to get the rest of my parts!
Then I need to either get a set of carb sync gauges, or have it done at a shop, and I need to paint the fenders/tank/covers ...

OKC_Kent wrote:

bountyhunter wrote:

OLTIMER wrote:

Results:

Coil 1:
Secondary ohms = 14,660
Plug caps a) 1.2 million b) infinite.

Coil 2:
Secondary ohms = 12,040
Plug caps are both infinite.

Recommendations?

Coils sound OK to me. Z1 sells 4 Ohm OEM replacement coils for $36 if you need a coil.

What am I missing? Why are the coils ok when the manual calls for 23k ohms on the secondary , and he has about half that?
And aren't most of our plug caps supposed to be 5k ohms?

I was allowing a bit of measurement error in the resistance. Caps can have very high resistance if they are "silencers" which is to say, quiet down EMI so your radio won't howl as you tach up the engine.