Topic: How do coils wear, and what would indicate a bad coil?

[drumstyx]

I just checked my coils because I have an itch to get new ones (everything else ignition is new so I'm thinking why not). I get just about 4 ohms bang on between the input leads. Everything I've read says these are 5 ohm coils (78 750k). Does this indicate wear?

[Duanob]

Did you happen to check the leads themselves? They can draw a bit of resistance. You might be closer to 4.5 OHMS. Coils rarely go bad but if you just have to spend money, go for the Dyna 5 ohm coils, you can make and replace your own plug wires anytime you think you need to. Get some 7mm copper core wire in bulk, some NGK 5000ohm caps, some crimpers and connectors and covers from NAPA and your golden. That's what I liked about new coils.

decent price right here:

http://www.ebay.com/itm/Dynatek-DC8-1-5-0-ohm-Coils-Dual-Output-Honda-CB500-CB500-CB400-CB350-1969-78-/191681504263?_trksid=p2141725.m3641.l6368#rwid

[drumstyx]

Yep, the leads showed .4-.5 ohms, so I subtracted that from the reading, isn't that what I'm supposed to do?

[firebane]

Yep, the leads showed .4-.5 ohms, so I subtracted that from the reading, isn't that what I'm supposed to do?

.4 or .5 sounds like you didn't have the meter set to the right setting and need to change that. You may need to go to the 1k range or even higher.

[drumstyx]

Yep, the leads showed .4-.5 ohms, so I subtracted that from the reading, isn't that what I'm supposed to do?

.4 or .5 sounds like you didn't have the meter set to the right setting and need to change that. You may need to go to the 1k range or even higher.

I meant to say that the leads alone on the 200 ohm meter setting read 0.4-0.5 ohms. Then when testing the coils the meter read 4.4-4.5 ohms

[Deltarider]

Does this indicate wear?

No.

because I have an itch to get new ones (everything else ignition is new so I'm thinking why not).

Why not? Because it's money wasted, that's why.

[calj737]

Drum - to accurately measure your coils, remove the plug caps first. And measure their resistance too while you're at it.

As for spending/not spending/wasting money.... If guys like you didn't spend, where on earth would the economy be if everyone were a "Delta-esque Miser"? Go for it if you're inclined to do so. Sell your perhaps still good coils to another member who wants oringal gear, and  might need an inexpensive set. See, everyone wins! 

[PeWe]

If both coils have same data, they can be OK to use.
Dyna 5 ohms coils give stronger spark than old Honda std? It is called high output.....

If you have invested in new electronic ignition, it can be safe to go all the way with new parts.
Old points will not mind if coils are completely shorted

I have not compared since my bike had ignition problems when I parked it 1990. Next time I drove the bike was 2014 with new Dyna coils.

[drumstyx]

If both coils have same data, they can be OK to use.
Dyna 5 ohms coils give stronger spark than old Honda std? It is called high output.....

If you have invested in new electronic ignition, it can be safe to go all the way with new parts.
Old points will not mind if coils are completely shorted

I have not compared since my bike had ignition problems when I parked it 1990. Next time I drove the bike was 2014 with new Dyna coils.

I have points, but with transistorized firing, so I'm not actually sure where I stand on the spectrum.

Once I have things running reasonably, I'll see if I need to look into it. It's certainly possible and even probable that it's fine, but with permanent plug wires, it really seems these should be replaced for reliability considering they're 40 years old almost at this point. We'll see how she acts once she's going well though.

[b52bombardier1]

Coil wear occurs when a coil overheats (wrong dwell setting) and the enamel insulation on the wire cooks and breaks down.  Power then jumps between coil wire loops (primary and/or secondary) and the coil loses efficiency. The plug cap resistance can also wander, usually increase, and this is what happened for me on my CB500 - over 12,000 ohms is way too much.

 Coils rarely breakdown unless abused but after 40-45 years of use, who really knows.

Rick

[Duanob]

Why not? Because it's money wasted, that's why.

Isn't that his choice? I bought the whole Dyna ignition system on one of my bikes and never regretted it.

[Deltarider]

If guys like you didn't spend, where on earth would the economy be if everyone were a "Delta-esque Miser"? Go for it if you're inclined to do so. Sell your perhaps still good coils to another member who wants oringal gear, and  might need an inexpensive set. See, everyone wins!

Not so. Here are some figures (source: Scientific American). With not even 5 percent of the world population, the U.S. consumes 25% of the world's raw materials pie. For one that toures the country like I did, this buying frenzy can be seen everywhere in that typical phenomenon and symptom of bulimia: the garage sale.
Are we worried? You bet and I could say a lot more but that would bring me in conflict with rule #9 as somebody was kind enough to report me.
On growth, economy and our shortcoming of really understanding the exponential function, I could direct you to the books of excellent and nobelprice winning US economists like Paul Krugman and Joseph Stiglitz but for more fun, see the documentary "Two Raging Grannies" and you will have the full picture.
Forgive me my digression but I thought that question 'so why not' a bit ridiculously, didn't you? Back to the coils. When you go through the threads in this forum, it's striking how many suspect the coils. Maybe it has to do with the invisible (and hence mysterious?) way they work. Yes, they can go bad, but we don't see that often*. Far more are poor connections at the plugcaps or the caps themselves to blame.
* I still don't know why a Dyna coil after only 30.000 km gave up and my original Tec coils are still OK. Now there's a lot of copper in a coil...

[PeWe]

If both coils have same data, they can be OK to use.
Dyna 5 ohms coils give stronger spark than old Honda std? It is called high output.....

If you have invested in new electronic ignition, it can be safe to go all the way with new parts.
Old points will not mind if coils are completely shorted

I have not compared since my bike had ignition problems when I parked it 1990. Next time I drove the bike was 2014 with new Dyna coils.

I have points, but with transistorized firing, so I'm not actually sure where I stand on the spectrum.

Once I have things running reasonably, I'll see if I need to look into it. It's certainly possible and even probable that it's fine, but with permanent plug wires, it really seems these should be replaced for reliability considering they're 40 years old almost at this point. We'll see how she acts once she's going well though.

Points with Hondaman ign module?

I installed new points and got recomendation from Mark to use the points old style for a while before installing the ign module. This to burn the connection points clean from a protective layer.
Run the points only with old coils and no electronic box and you'll see how it works. No meaning to install the ign module when something is wrong. Then fault trace and check if coils are bad. One thing to replace is the caps. Wire lenghts must be ok to cut 5mm before assemble the new NGK caps, right.

I replaced the wires on my old CB750 coils. Cut the wire max 1" from the coils and crimped new wire here. Covered with shrink hose. I had good tools for it from my job back then.

[calj737]

If guys like you didn't spend, where on earth would the economy be if everyone were a "Delta-esque Miser"? Go for it if you're inclined to do so. Sell your perhaps still good coils to another member who wants oringal gear, and  might need an inexpensive set. See, everyone wins!

Not so.

Will too.

[Deltarider]

I installed new points and got recomendation from Mark to use the points old style for a while before installing the ign module. This to burn the connection points clean from a protective layer.

This is good advice for new breakerpoints. If your points have done some miles already, you can install the transistor ignition module rightaway. You do not necessarily need new points btw.

No meaning to install the ign module when something is wrong. Then fault trace and check if coils are bad.

Right so. This is not so difficult. For a start here is a simple test you can do yourself. Just shove a piece of transparent vinyl tube over both HTleads thus that the ends face eachother (like in the pic below). Mark a minimal distance of 7mm on the outside of the tube and align the ends of the HTleads with those marks. Operate the coil by interrupting the 12V on the primary leads, best done with a condensor connected ofcourse. This is a simple static test to check if the coil is capable to jump a minimal distance of 7mm as Honda prescribes. When in doubt - for instance when 'misses' (is that the correct word?) only occur when coils are warm - you can have them checked at a workshop. They won't charge much. Some make their own testbench.

One thing to replace is the caps.

I even remember socalled 10.000 km servicepacks specially composed for our bikes that had not only 4 new sparkplugs in it but new NGK plugcaps as well.
Arcing between HTleads and or plugcaps and the engine (ground) is often seen on CB500/550 models (maybe the other models too) which will result in misses. This is best seen in the dark. If you listen closeby, you can even hear the cracks. Some spray watermist to detect it. The stock coil HTleads have a thin extra hose around the leads. You can try to clean them with a little bit of alcohol or, when you've removed the caps, replace them. Many OEM coils give the impression HTleads have become loose. They rarely are however and will function OK.
Some mistake a bad condenser for a faulty coil. At the breakerpoints a tiny bit of sparking is normal, excessive sparking is not good and indicates a bad condenser. See

Left condensor (1+4) is bad, right condensor (2+3) is good.
Another thing to be aware of is that the spadeconnectors at the back of the breakerpoints are not intermittently (because of vibrations) grounding. When installing make sure these spade connectors do not touch the baseplate (especially 2+3 can touch easily!).

[drumstyx]

I installed new points and got recomendation from Mark to use the points old style for a while before installing the ign module. This to burn the connection points clean from a protective layer.

This is good advice for new breakerpoints. If your points have done some miles already, you can install the transistor ignition module rightaway. You do not necessarily need new points btw.

No meaning to install the ign module when something is wrong. Then fault trace and check if coils are bad.

Right so. This is not so difficult. For a start here is a simple test you can do yourself. Just shove a piece of transparent vinyl tube over both HTleads thus that the ends face eachother (like in the pic below). Mark a minimal distance of 7mm on the outside of the tube and align the ends of the HTleads with those marks. Operate the coil by interrupting the 12V on the primary leads, best done with a condensor connected ofcourse. This is a simple static test to check if the coil is capable to jump a minimal distance of 7mm as Honda prescribes. When in doubt - for instance when 'misses' (is that the correct word?) only occur when coils are warm - you can have them checked at a workshop. They won't charge much. Some make their own testbench.

One thing to replace is the caps.

I even remember socalled 10.000 km servicepacks specially composed for our bikes that had not only 4 new sparkplugs in it but new NGK plugcaps as well.
Arcing between HTleads and or plugcaps and the engine (ground) is often seen on CB500/550 models (maybe the other models too) which will result in misses. This is best seen in the dark. If you listen closeby, you can even hear the cracks. Some spray watermist to detect it. The stock coil HTleads have a thin extra hose around the leads. You can try to clean them with a little bit of alcohol or, when you've removed the caps, replace them. Many OEM coils give the impression HTleads have become loose. They rarely are however and will function OK.
Some mistake a bad condenser for a faulty coil. At the breakerpoints a tiny bit of sparking is normal, excessive sparking is not good and indicates a bad condenser. See

Left condensor (1+4) is bad, right condensor (2+3) is good.
Another thing to be aware of is that the spadeconnectors at the back of the breakerpoints are not intermittently (because of vibrations) grounding. When installing make sure these spade connectors do not touch the baseplate (especially 2+3 can touch easily!).

My biggest concern, perhaps unfounded, is that the wire comes loose at the top. It's soldered, but who knows how much jostling around they've gone through over 40 years.