Ignition Coils Need Replacement

Unfortunately the manuals aren't specific about the caps and their resistance. However, they show the caps in place when the coil's secondary winding resistance is being measured, so I wouldn't measure the resistance without the caps on. One other note - the specs for the ignition coil resistance, especially the secondary winding, are not consistent in the different revisions of thee manuals (see images below). Ed

April 1977 Manual:


July 1979 Manual:

krayneeum wrote:

bountyhunter wrote:

krayneeum wrote: Hi all,

Right Coil
Primary - 6.0 ohms
Secondary - 14.7K ohms

Left Coil
Primary - 5.8 ohms
Secondary - 14.5K ohms

I'm confused as to why my primary ohms are HIGHER than normal,

Can your meter read low Ohms accurately? Connect the meter leads together and see what the 'zero" reading is then subtract that value from the test reading.

Good idea! Apparently my meter is off. It reads 1.3 ohms when I touch the leads together. With that said, my revised readings are:

Right Coil
Primary - 4.7 ohms
Secondary - 13.4K ohms

Left Coil
Primary - 4.5 ohms
Secondary - 13.2K ohms

Does that change anything as far as the condition of these coils go?

No, but as somebody else may have mentioned: it is IMPOSSIBLE to test a defective coil with an Ohm meter. The coil is actually a high voltage flyback transformer similar to what old CRT type TV's used to use. It is the high voltage windings that fail over time when the insulation between the windings breaks down and the HV starts arcing across winds. A bench tester won't pick it up because it doesn't apply that kind of stress.

BTW: the failure is accelerated by oxygen which is why transformers and coils are potted (molded in plastic or something similar like hard rubber) is because it keeps out air. If they get old and develop cracks so air and moisture penetrate, they are dead coils walking.

Dead coils walking, very true. I'm wondering if the figures quoted where the spec offered to the factory

I think coils could be bench tested but it would need 'drop testing' with something like a high voltage 'megger ' resistance tester.

I suppose a coil having both an inductive as well as resistive load, measuring just the resistance would be flawed anyway.

Complex and imaginary numbers and the J operator maths are a bit out of scope of the manual anyway; beside the numbers don't seem to be too critical. I'm wondering if the manual figures came from the spec for the suppliers , rather than a tolerance and no-one really knows what the acceptable range is.

Tyrell Corp wrote: ........... and no-one really knows what the acceptable range is.

That's my guess too. Looking at the secondary winding specs in the first image vs the second image makes the specs seem dubious at best since the two ranges are totally contradictory. Ed

Hey all,

Thanks for the great responses!

Finally got a battery charger and charged my battery fully. Unfortunately, it didn't help.

After many failed attempts to start it, it finally started up-- but barely. It ran for a less than a minute and sounded very rough.

loudhvx wrote: Coils often do appear to fail at the same time. I had two go bad within 50 miles of each other. What happens is both coils develop small cracks over time. They can still work fine for years that way as long as they stay dry, but if the bike is then ridden in heavy rain, and the water works its way in, both coils can then fail suddenly. This usually happens when you are on a long trip, of course.

Welp, I think this might just be the case. I inspected my coils more closely, and found this:

imgur.com/a/TlpAU

Both cracking. The bike (unfortunately) has been spending the summers outside. While I usually try to cover it with a tarp when it rains, I don't always get to it in time. There have been some bad rainstorms lately as well.

Thoughts?

My thought: any suspect (OLD) coil should get booted. That's because of the grief mine gave me.

Z1 sells (or SOLD) a really good replacement for $36 which is what I replaced mine with and it is great.

Unfortunately, they have been out of stock for months and I don't see them anywhere on the net so they may be history.

www.z1enterprises.com/ItemDetails.aspx?i...zuki&item=EM24-72451

No eBay APP ID and/or Cert ID defined in Kunena configuration

bountyhunter wrote: My thought: any suspect (OLD) coil should get booted. That's because of the grief mine gave me.

Z1 sells (or SOLD) a really good replacement for $36 which is what I replaced mine with and it is great.

Unfortunately, they have been out of stock for months and I don't see them anywhere on the net so they may be history.

www.z1enterprises.com/ItemDetails.aspx?i...zuki&item=EM24-72451

Looks like this one is an equivalent OEM: 33410-45012



Might pull the trigger on two of these, and find some caps to go with them.

Hell of a deal if it's a good coil. It does look like the ones that Z1 was selling which work pretty well.

Those look like the ones. $35 and free shipping. That is hard to beat.

Awesome! Ordering two.

Anyone know if these caps will pair well? Not sure if I need resistor caps or not. My plugs are B8ES non-resistor type.

www.z1enterprises.com/ItemDetails.aspx?i...LB05F&item=TU38-1001

Thanks a lot for the help!
-Stephen

The NGK spark plug caps from Z1 will work fine with these coil wires. Caps will screw right in the ends of the wires.