Bad coil?

[Americanrider]

I'm losing fire on my '53 while riding and it's very hard to start, I'm running 12 volts / cycle elect gennie, brand new C plugs & wires. I think my coil might be shot, but the only testing I know is for late 50's Chevy's, not Indians.

1. With a multimeter on 200 ohm setting, red on POS and black on NEG teminals of the coil I get 0.0 reading, [Chevy should be 1.5 to 1.7 would be a good reading].
2. With the meter set on 20K ohm and black in the center post hole, red on POS terminal it reads 8.5, [Chevy should be a 11.00 to 13.5 is a good reading] any less than 11.00 is a bad inner coil winding.

So is there a different test I should run?
Anyone have recommendations on replacment (or hotter) coil that could make kicking a 80 inch any easier?

Thanks in advance!

[BoschZEV]

1. With a multimeter on 200 ohm setting, red on POS and black on NEG teminals of the coil I get 0.0 reading, [Chevy should be 1.5 to 1.7 would be a good reading].
2. With the meter set on 20K ohm and black in the center post hole, red on POS terminal it reads 8.5, [Chevy should be a 11.00 to 13.5 is a good reading] any less than 11.00 is a bad inner coil winding.

So is there a different test I should run?

An ohmmeter only can be used for the most superficial test. There are two problems. First, the primary resistance of any coil is so low that most common ohmmeters don't let you distinguish between the ~1 ohm (or sometimes less) of a good coil and the 0 ohms of a short. However, a more fundamental problem is that even if the coil has the proper primary and secondary resistance when measured at dc, they can develop internal shorts during operation that only can be tested for with an appropriate AC tester.

You say you made the measurement on the 200 Ohm scale and the reading was 0.0, so I will assume here that you are using a digital meter that reads to a tenth of an ohm (i.e. the max. reading on this scale is 199.9 ohms). With one lead of your ohmmeter attached to one of the terminals of the coil, hold the other on it and zero the ohmmeter (or confirm that it reads 0.0). Note that an inexpensive ohmmeter won't let you zero the output so with the leads shorted together it might read, say, 0.3 ohms. If this is the case you are looking for differences between that reading and the reading when the leads are across the primary of the coil. After zeroing the meter, move the lead to the other terminal and see if there is any perceptible difference in the reading. Repeat this several times. If it truly is reading 0.0 ohms (or, say, 0.3 ohms both when shorted and when across the coil, i.e. no difference in reading) your coil definitely is bad and it shouldn't work at all. In other words, taken at face value some of the information in your post is inconsistent which is why I'm suggesting you redo the test.

[rustforsale]

Hi. I'm having some possible coil issue as well. 6 volt coil and when I zero out and then put both probes on each terminal I get a 1 ohm resistance. And then when I test the high coil by having the meter probe on the coil terminal and the other on the spark plug wires and set at 20k ohms I get 0. Faulty correct? I saw a YouTube video that says there should be 3-5ohms for the primary coil an 14k for the secondary.

What are the numbers that would indicate the ohms are in the proper usage specs? My service manual for my wl doesn't give those numbers.
Thanks

An ohmmeter only can be used for the most superficial test. There are two problems. First, the primary resistance of any coil is so low that most common ohmmeters don't let you distinguish between the ~1 ohm (or sometimes less) of a good coil and the 0 ohms of a short. However, a more fundamental problem is that even if the coil has the proper primary and secondary resistance when measured at dc, they can develop internal shorts during operation that only can be tested for with an appropriate AC tester.

You say you made the measurement on the 200 Ohm scale and the reading was 0.0, so I will assume here that you are using a digital meter that reads to a tenth of an ohm (i.e. the max. reading on this scale is 199.9 ohms). With one lead of your ohmmeter attached to one of the terminals of the coil, hold the other on it and zero the ohmmeter (or confirm that it reads 0.0). Note that an inexpensive ohmmeter won't let you zero the output so with the leads shorted together it might read, say, 0.3 ohms. If this is the case you are looking for differences between that reading and the reading when the leads are across the primary of the coil. After zeroing the meter, move the lead to the other terminal and see if there is any perceptible difference in the reading. Repeat this several times. If it truly is reading 0.0 ohms (or, say, 0.3 ohms both when shorted and when across the coil, i.e. no difference in reading) your coil definitely is bad and it shouldn't work at all. In other words, taken at face value some of the information in your post is inconsistent which is why I'm suggesting you redo the test.

[fillibuster]

I'm losing fire on my '53 while riding and it's very hard to start, I'm running 12 volts / cycle elect gennie, brand new C plugs & wires. I think my coil might be shot, but the only testing I know is for late 50's Chevy's, not Indians.

1. With a multimeter on 200 ohm setting, red on POS and black on NEG teminals of the coil I get 0.0 reading, [Chevy should be 1.5 to 1.7 would be a good reading].
2. With the meter set on 20K ohm and black in the center post hole, red on POS terminal it reads 8.5, [Chevy should be a 11.00 to 13.5 is a good reading] any less than 11.00 is a bad inner coil winding.

So is there a different test I should run?
Anyone have recommendations on replacment (or hotter) coil that could make kicking a 80 inch any easier?

Thanks in advance!

Install new points and condenser, get a new coil with internal resistor and install it, and .... oh, by the way, was your coil HOT to the touch right after it quit? My electrics expert told me that they get really hot when they're failing, and they aren't that spend-ey. ... as compared to a 53 Chief.....

[Yellow53Chief]

Hi,
One quick and reliable test for a coil, is to shake it. If you hear fluid sloshing around, the coil is either shot or will soon be shot. If you don't hear sloshing it doesn't mean that the coil is good, but it does tell you that the coil's fluid seal is still intact. If the fluid seal is compromised, moisture can enter the coil and ruin it.
Hard starting can sometimes be cured by greasing the kickstarter arm pivot. This point needs lubrication as often as the chain - about every 500 miles. Hard starting can also be caused by blown head gaskets. If there is oil around the head bolt washers, or oil at the head bolt threads that are open to the air at the bottom, the gaskets are likely shot.

[hairynob24]

i have kill 2 coils of late on my 50 chief ,today with help from a mate who does auto electrics for a living , we went through the battery ,ok ,than coil no good ,found that the spark plugs had to much resistence 1.2ohm these were Auto light 303,installed NGK BP7ES resistence .2ohm ,he belives this caused the coil to **** itself ,got a new non resistor coil stated a bit better but could not get far ,pulled the carby bowl off ,all good ,through i would change the rotor and bang fine took it for a good run ,great , so check your plug resistence and look at the rotor ,the rotor that works great has a hammerhead tit on it,see how you go ,cheers Rob

[BoschZEV]

i have kill 2 coils of late on my 50 chief ... ,found that the spark plugs had to much resistence 1.2ohm these were Auto light 303,installed NGK BP7ES resistence .2ohm ,he belives this caused the coil to **** itself ...

There a a few possible causes of coil failure, but resistance of 1.2 ohms vs. 0.2 Ohms isn't one of them. The secondary of the coil is several thousand Ohms so the difference of an Ohm here or there when it discharges is totally negligible.

If you've experienced more than one failure, or a failure a fairly short time after you installed a new coil, likely possibilities include:

-- A coil that is incorrect for the application. For example, a coil with a low primary resistance draws greater current. This is useful when starting but such a coil requires the use of a ballast resistor in operation. These coils are fine for use with a ballast resistor, but easily can overheat without one because the internal heat generated goes as the square of current (i.e. I = V/R so the current doubles if the resistance is cut in half, and Power = I^2R so cutting the resistance in half doubles the power dissipation)

-- Incorrect circuit wiring that has inadvertently bypassed the ballast resistor (if it has one).

-- Use of an automobile coil with internals not designed to withstand the vibration it will experience when used on a motorcycle. Imagine two cans on a paint mixer, one with something inside it that is surrounded by tight packing material and the other without packing material at all. The contents of both would be fine in a low-vibration environment, but the latter will be quickly destroyed on a Harley... er, I mean, paint mixer.

-- Incorrect installation by the user. For example, if the mounting clamp is overtightened so it partially compresses the outer shell of the coil to make contact with the internals, or it is mounted in an alternative location where it is subjected to much greater vibration that in the stock location, or it has a smaller OD than the stock coil so the clamp allows it to move, etc.

[hairynob24]

BoschZeV what coil would be a good choice ,when i have an electronic igition ,alternator ,an electric stater ,12v i still have no confordence in the bike , sorry American Rider not cutting in on your post ,cheers Rob.

[BoschZEV]

BoschZeV what coil would be a good choice ,

Unfortunately, with so many bikes, and so many models, and so many years, I only can wish I were able to make recommendations like this from memory.

[Northup87]

Hi,
One quick and reliable test for a coil, is to shake it. If you hear fluid sloshing around, the coil is either shot or will soon be shot. If you don't hear sloshing it doesn't mean that the coil is good, but it does tell you that the coil's fluid seal is still intact. If the fluid seal is compromised, moisture can enter the coil and ruin it.
Hard starting can sometimes be cured by greasing the kickstarter arm pivot. This point needs lubrication as often as the chain - about every 500 miles. Hard starting can also be caused by blown head gaskets. If there is oil around the head bolt washers, or oil at the head bolt threads that are open to the air at the bottom, the gaskets are likely shot.

I just bought a brand new 6V coil from Jerry Greers and when shaken I can hear considerable sloshing. Is this an indicator my new coil is going to go bad?

A.J.

[Yellow53Chief]

Hi,
A coil with sloshing fluid in it is usually a sign that the coil is 'breathing'. This 'breathing' is often caused by a leaking hermetic seal which normally keeps any atmospheric gases (including moisture) out of the coil windings. When the coil gets hot - gases move out. When the coil cools - gases move in. In severe leakage instances, fluid can be seen leaking around the coil's secondary center terminal connection or around the primary wire terminals or case-to-top seal. Typically a coil is completely filled with fluid before the factory hermetic seal is created. A completely filled coil cannot slosh, and if the seal is good - it cannot leak or 'breath'. Atmospheric gases (including moisture) can be injurious to the coil windings, thus the possible premature failure. A good idea would be to check with Jerry Greer and see if the other coils they stock have any sloshing sound. Maybe you got a coil that wasn't 100% perfect. Maybe they are selling a coil that has some inert gas installed into the coil body before it is sealed. Sorry I can't be more specific about your particular coil.

[BoschZEV]

"Sloshing" isn't a very precise term. If your coil sloshes because it's only 3/4 filled with oil, there's a problem, but if it made no sloshing noise at all, there also would be a problem. Beer cans (and cans and bottles of every liquid) slosh because air has been deliberately left inside. This is done not (only) because the manufacturers want to cheat you out of a fraction of an ounce, but because liquids are incompressible. If no air was left inside to take up the slack, thermal expansion of the liquid would burst the cans -- or your coil -- at the seams.