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Bad Coils?

  • Thread starter Thread starter Tertle_Power
  • Start date Start date
T

Tertle_Power

Guest
Hey guys,

I have a 1981 Gs 1000 that is currently not getting any spark to any of the four cylinders. I'm pretty positive it isn't the CDI because I hooked a test light up to the power for the CDI and the two separate grounds that are sent to the two coils and was able to get the light to flash on both. I have power coming up to the both coils. I tested the primary resistance on the coils and both were around 4 ohms (where they should be). I'm not sure how to test the secondary though since there are two spark plugs for each coil. I left one side of my volt meter in the pig tail for the coil and put the other one into the spark plug lead and got nothing. I tried hooking my volt meter up to both of the spark plug leads for the coil as well and still got nothing for resistance. Am I testing the secondary for my coils wrong or are they just bad coils? Why would both coils go bad at the exact same time too, because I know that's pretty unlikely? If the coils are bad what else could it be?
 
"I hooked a test light up to the power for the CDI and the two separate grounds that are sent to the two coils and was able to get the light to flash on both"

I doubt this means much as a test.... By the way, it's not a CDI, it's an ignitor - duplicates what points do, opens suddenly to break the current flowing to the coils to produce a spark (In two spark plugs simultaneously)
Ignition coils are very durable, test them by unscrewing the plug caps from a coil.. With your multimeter on 20kohm scale, stick one meter probe on one plug coil wireand other probe on other coil wire. Should see about 12000 ohms.
 
Found another thread that said to do that earlier, so I did. Both coils showed no ohms at all on the secondary. It seems kind of curious that both coils went bad at the exact same time, doesn't it?
 
Tertle_Power said:
Found another thread that said to do that earlier, so I did. Both coils showed no ohms at all on the secondary. It seems kind of curious that both coils went bad at the exact same time, doesn't it?
Click to expand...

yep, not likely but not impossible.
Make sure you have proper 12 volt on the other coil wires, if both coils fail to spark that may be the issue.

If you are up for quick and dirty, you can unplug the coil wire that normally goes to the ignition and rub/tap it against ground. That should produce a spark.

Principle demonstrated in this video :

 
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"Both coils showed no ohms at all on the secondary. "

This with the spark plug caps removed and meter probes stuck into spark plug wires?
 
With regard to the cause; either excessive load that has affected both coils (bad wires, water ingress, short circuit, bad spark plugs, ...) or simply old age and heat.
Any event causing the former can only be known by the person owning the bike at the time of the failure.
 
tom203 said:
"Both coils showed no ohms at all on the secondary. "

This with the spark plug caps removed and meter probes stuck into spark plug wires?
Click to expand...
"With regard to the cause"

I did remove the spark plug caps and stuck the probes into the spark plug wires. The bike ran fine (besides being a little bit rich because I have one to many spacers on the needles) the time I rode it before it died and then didn't even make it down the block the next time I tried to ride it. I was trying to go to work and I stalled it at a stop sign and it wouldn't start back up, so I pushed it home. I came back the next morning to see what was going on and it started up right away, but when I came back later that afternoon to go to work, it was dead for good. It rained a couple of days before the issues started occurring, but I had a water proof motorcycle cover on Suzzie, like I usually do. I'm thinking it might be some bad wires or connections somewhere on the bike, I've had plenty of wiring issues over the last few months and they only seem to be getting worse since I moved to the beach and the humidity is corroding my bike.
 
Oh, and I did make sure I had 12v at the coils. I have a significant drop from the battery to the ignitor (1V) and from the ignitor to the coils (another 1V). I have something like 10.3V (even if the bike was running there looks like it would still have a significant drop) at the coils. Since the ignitor works by switching the grounds on and off and not the power I jumped the battery power directly up to the coils with some wires and they still didn't work.
 
I'm not sure how to test the secondary though since there are two spark plugs for each coil
Click to expand...

Test resistance between the two High Tension leads of each coil.
(see manual)

oh, don't forget that there are resistors INSIDE the caps. these are about 5k ohms. there are tiny contact discs in there so if you want to undo the plugclip/screws that hold them in, do it over a large white piece of cloth...but usually these are ok so don't undo unless you suspect a problem. Be careful with the order of the these little partlets too.

SUM the the Voltage drops you are seeing ...coil+ignitor+ dirty contacts of kill and ignition switch = battery voltage
 
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I ended up replacing the coils and I have been getting good spark ever since. It was running a bit rich, so I leaned it out a little bit and it has been running fine except for a bad petcock.
 
I am doing the same thing and getting about 4.3 ohms on both coils, but when I to the secondary I get the same result of "0L" on the multimeter. I'm going to change the plug caps as they are old either way. But I don't think the coils are bad as the GS ran before, just seemed to have a miss past 60 or so...for which I blamed a bad plug cap on the #2 cylinder (corroded inside), which I hope will be resolved with the new plug caps.
 
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