coil test question

[Guest]

1981 GS850G orig coils, new Dyna resistor leads/caps put in last year. LT leads to coils spruced up & new connectors put on. About 2000 miles put on since.

1. Lost spark to #2 & #3 cylinders. #1 & #4 ok. Just did ohms test on the coils as easiest thing to try. Got 22,800 on 1 & 4 but coil for 2 &3 open. So barring a bad lead or bad connect to the coil pin (I believe either of those highly unlikely) does it seem like I luckily hit the prob on the first thing I checked? I had redone up the low tension leads to the coils last year with nice new connectors from vintage connectors & all there looks solid & clean & the connectors & wires were strapped down securely so no wiggling.

I still figure to pull off the coil, cut out the HT leads & retest directly thru the pins just to be certain.

2. If coil I can look up a used stock items or replace with pair of aftermarket (DynaTek???) any recommends there?


Thank you, as always,

DH

[eil]

Random thoughts:

Coils go bad, but it's usually rare.

The HT wires on plugs 2&3 form a circuit so a break on one side will result in neither plug firing.

Check and re-check your previous work to make sure a connector hasn't gone wonky, or that there's not a wire shorting to the frame. Clean and reseat the connectors.

Turn over the engine in the dark to see if one of the HT wires is shorting to the frame or engine somehow. I saw a video not too long ago where a guy had a crack in his spark plug porcelain and the spark was jumping from the boot, around the outside of the plug, and down to the base of the plug.

I believe you can test a coil by applying 12V to the primary and removing it. When you remove power, the plugs should spark (as long as the bases of the plugs are electrically connected to each other, simple wire or just laying them both on a piece of metal will work).

If all else fails and you do have a bad coil, a used one will probably work just fine indefinitely. Just make sure to test it before you install it and are able to return it if it's no good. New coils will definitely work, but they are not nearly as cheap. Check the resistance values in your service manual for which ones to get.

[suzukizone]

coil test question

Random thoughts:

Coils go bad, but it's usually rare.

The HT wires on plugs 2&3 form a circuit so a break on one side will result in neither plug firing.

Check and re-check your previous work to make sure a connector hasn't gone wonky, or that there's not a wire shorting to the frame. Clean and reseat the connectors.

Turn over the engine in the dark to see if one of the HT wires is shorting to the frame or engine somehow. I saw a video not too long ago where a guy had a crack in his spark plug porcelain and the spark was jumping from the boot, around the outside of the plug, and down to the base of the plug.

I believe you can test a coil by applying 12V to the primary and removing it. When you remove power, the plugs should spark (as long as the bases of the plugs are electrically connected to each other, simple wire or just laying them both on a piece of metal will work).

If all else fails and you do have a bad coil, a used one will probably work just fine indefinitely. Just make sure to test it before you install it and are able to return it if it's no good. New coils will definitely work, but they are not nearly as cheap. Check the resistance values in your service manual for which ones to get.

Thanks Charles. Will follow up on those tips!

DH

[Steve]

... does it seem like I luckily hit the prob on the first thing I checked?

Had to read that a couple of times to see what the shortened word meant. I wasn't sure if you hit the probe or the problem.

Have you tested the plug caps on the ends of the wires? They unscrew from the wires. Might take a bit of effort, you can squirt a bit of WD-40 around the junction to reduce some of the friction. Test the bare wires. If you get better readings (actually about 10k ohms less), your coil and wires are OK, your caps are bad. Look carefully up the end that goes over the plug, you will see a screwdriver slot. Remove that piece. There is usually a 5k ohm resistor there, it can go bad. You can replace that with a piece of solid wire or just go for broke and get new caps from Z1 Enterprise.

.

[suzukizone]

coil test question

Had to read that a couple of times to see what the shortened word meant. I wasn't sure if you hit the probe or the problem.

Have you tested the plug caps on the ends of the wires? They unscrew from the wires. Might take a bit of effort, you can squirt a bit of WD-40 around the junction to reduce some of the friction. Test the bare wires. If you get better readings (actually about 10k ohms less), your coil and wires are OK, your caps are bad. Look carefully up the end that goes over the plug, you will see a screwdriver slot. Remove that piece. There is usually a 5k ohm resistor there, it can go bad. You can replace that with a piece of solid wire or just go for broke and get new caps from Z1 Enterprise.

.

Sorry Steve, as a lazy guy, I subbed "prob" for "Problem". Actually I just subbed, "subbed" for substituted. Jus 2 laz, I gess.

Last year, I replaced the HT leads & caps, which had gotten grody, with a nice new set of Dynatek resistor leads with the factory attached "clamp on the plug tip" style rubber caps. It could be one of the leads is bad but no visible sign & is that more likely than the rare but possible chance the 35 year old coil gave it up? Dunno but plan to pull the coil & leads & test the coil directly on the pins the leads attach to so I know I am getting a solid reading/non-reading. Charles also gave me some specific homework, Just have to hide from my wife & the list she may be preparing for me at this very moment.

Thanks to all for advice!

DH

[Steve]

Sorry Steve, as a lazy guy, I subbed "prob" for "Problem". Actually I just subbed, "subbed" for substituted. Jus 2 laz, I gess.

Don't kid yourself, I am one of the "laziest" around here, but if I can't read what the problem is, I just pull out the "lazy" card and don't even bother to reply.

I also don't respond when there are "texting" shortcuts used. I am just enough of an old fogey to not know what a lot of them are, and dang it, I'm just too lazy to look them up, so I will just ignore them.

.

[suzukizone]

Don't kid yourself, I am one of the "laziest" around here, but if I can't read what the problem is, I just pull out the "lazy" card and don't even bother to reply.

I also don't respond when there are "texting" shortcuts used. I am just enough of an old fogey to not know what a lot of them are, and dang it, I'm just too lazy to look them up, so I will just ignore them.

.

OK sorry for the misleading absence of letters. I use "prob" in everyday language, was just sort of talking.

As to "texting" never did it in my life, I text by grabbing a piece of paper and a pencil and writing text on it. So it was, apparently, a mis-aimed joke about abbreviating. I will try to self-edit in the future.

DH

[Steve]

Sorry, that was not aimed directly at you, but at many of the newer members here who are apparently younger than my youngest child, and might even be young enough to be a grandchild of mine.
They come here and start throwing alphabet soup all over the place as if we are supposed to know what they are 'talking' about.

I realize that your reply was in jest, the humor was not lost on me.

We also have a few members here whose native language is NOT English. Sadly, I can understand their broken English much better than some who DO claim English as their primary (only?) language.

Feel free to write and speak any way you wish on the forum, but be aware that there are "nanny" filters that will bleep out some rather inoccuous words. Most of us aren't impressed by that kind of language anyway.

.

[suzukizone]

"some who DO claim English as their primary (only?) language."

I do believe a quick check with our brethren & sistren of the UK persuasion might reveal whatever we are using here ain't english.

But I digress. In pulling the 2/3 coil, last night to investigate futher, I found the orangish wire of the primary coil was snapped off at the coil. Luckily after busting out the odd yellow glue where it entered the coil body I was able to get a good re-solder job on it. The coil is now firing. Lots of GOOP applied where needed to secure all wire wiggles has been applied.

Still don't get a "cap-to-cap" reading from this coil but the spark is nice & fat. Found, on a wee bit of left over HT lead from the Dynatek set I had, that the inner run of what looks like polyester core (?) shows NO continuity but the black plasticy stuff that surrounds it does. Not sure what weird since this is but I got good spark so whether science or black magic I'll take it & run.

Thanks for all mechanical & grammatical input. It is always appreciated out here in the boonies. There are no local shops with any help for us cavemen since the one I worked for closed down in 2010. Even the cows ride Harleys out here.

DH