Coils dying off

[schroedingersbaby]

I've had the bike for about two months, non-running while I clean it up and get it up to date with maintenance. From the beginning, it's turned over but hasn't started, which I figured out was from initially no fuel, and after I fixed the petcock it was a no spark thing. (Carburetors have been dipped, all o-rings replaced including intake boot rings).

I took the harness, cleaned it off, checked for burned out parts (there were none), tinned the big joints and put it back together. I also replaced the starter solenoid since when I took it apart it looked completely black. I replaced the R/R with a Honda one I incidentally had laying around for a bike that never materialized, I put that in and make a single ground point going to it as per suggestion. The coil relay mod was made at this point.

After all this, one of the coils started working (for two and three), and the other seemed dead, so I replaced with one from eBay. It still wouldn't start, and by testing it with the signal generator on BikeCliff's site, I determined my signal generator was dead because it gave an infinite reading. One of the users from this site, muzakstylee, helped me out by giving me a great deal on both the signal generator and an igniter unit, so I went ahead and replaced both. I tried starting at this point, and it was the 1+4 coil that I already replaced that stopped working.

So desperate, I went to the local salvage yard (great place, called the Rice Paddy) and grabbed one from them that tested as working, came back, put it on and the bike started right up. I rode it around for a day, realized that I wasn't quite done getting the bike up to speed (bad hanging idle), so I took the tank, and the carburetors off and started on a valve adjustment, and I sealed the airbox with weather stripping and I re-bench synced the carburetors.

Valve adjustment done, I put it all back together and boom, the 2+3 coils aren't sparking. I got a hold of muzakstylee and once again he came through with two stock coils that were tested working, at a great deal. I replaced that coil and it sparked. I tried starting it up again and now I wasn't getting spark from the 1+4 coils. I switched cables to test and nothing happened on that coil.

What's going on, do you think? Why are the coils dying off? Multimeter readings from the 2+3 coil are ~80ohms (this one is working) and the other one is reading about the same (but not working). Plug caps are new, all the other lights work, the horn works, all the fuses are new and unburnt out. The killswitch and starter button have been inspected, re-tinned and replaced (and they work). The battery is brand new. The clutch safety has been bypassed.

Tell me what to do and I'll test for it. Need pics? Well either way you'll get pics, but they might just be of a GS650GLX in the middle of a big bonfire . Anyone near Columbus, OH that would be kind enough to lend a hand?

[mike-s]

Silly question first, have you replaced and gapped the spark plugs? now that that's out of the way with an assumed yes, have you gotten hold of a timingstrobe light and actually checked the plugs were firing?

That would be the first/easy thing i would check, secondly i would check the leads going to the coils to make sure they had voltage there and work my way back towards the ignitor box and make sure the voltage was still present on the corresponding lead coming out of the box. Then check the inbound leads going to the sensors to ake sure they were generating the appropriate signal.

Other than that i have no idea where to go next,personally electrical demonds/problems can be a bigger pain in the butt than most other kinds.

[schroedingersbaby]

Silly question first, have you replaced and gapped the spark plugs? now that that's out of the way with an assumed yes, have you gotten hold of a timingstrobe light and actually checked the plugs were firing?

That would be the first/easy thing i would check, secondly i would check the leads going to the coils to make sure they had voltage there and work my way back towards the ignitor box and make sure the voltage was still present on the corresponding lead coming out of the box. Then check the inbound leads going to the sensors to ake sure they were generating the appropriate signal.

Other than that i have no idea where to go next,personally electrical demonds/problems can be a bigger pain in the butt than most other kinds.

Plugs are new, and they're gapped. As for the timing strobe light, I have not, how do you do that and what does it test for? The leads power the other coil when switched so I think those aren't the problem, but I definitely will check again.

[mike_of_bbg]

80 ohms for ignition coils? Or are you talking about the pickup coils? Stock EI coils should be ~3 ohms on the primary and 14k ohms + whatever the boots are (probably 10k if you replaced your boots with NGK 5k caps as is normal) on the secondary.

[tom203]

Another 650- wow, I didn't know they made so many! What's the mileage and any history? Hopefully, you dropped in on Basscliff's site and stole a readable wiring diagram. Let's get at it. Disconnected, the coils should show about 3-4 ohm primary resistance. With ignition and kill switch on, the coils receive positive juice all the time- the signal generators send a signal to ignitor, which then grounds out coils and makes spark at right time. Eating coils is strange behavior, but please no bonfires- it's 30 years old and probably just needs some good loving after years of neglect!

[mike-s]

I meant a ignition timing strobe light (i have one that looks exactly like that), but they are also handy for just plain verifying that the high tension coils are firing correctly. Alternatively if you don't have one just getting something like this or this will suffice as they merely use the induction fields to make the little light in them glow when the HT lead fires.

Tom is right, the coils recieve 12v (ish) all the time and when it is time for ignition the ignitor momentarily drops the 12v, which creates a pulse as the voltage stops flowing (i believe it is to do with the magnetic field collapsing or something) and a high voltage pulse is created on the HT circuit that goes off to the spark plug.

[schroedingersbaby]

80 ohms for ignition coils? Or are you talking about the pickup coils? Stock EI coils should be ~3 ohms on the primary and 14k ohms + whatever the boots are (probably 10k if you replaced your boots with NGK 5k caps as is normal) on the secondary.

Walk me through the jargon. I put my multimeter on the two top posts where the wires from the igniter come from like so :



and got ~80ohms on both sides. It is entirely possible my multimeter is on the wrong setting since I've never used this one before. Through the boots I got about 30k with NGK caps.

[mike_of_bbg]

The focus isn't strong on the dial, but it looks like you have it on your lowest ohmmeter reading (200 ohms), which is correct for testing the primary. That reading looks like 5.8 ohms to me. What bike were these coils from? Did I read correct that you have a GS650LX (as in 1981)? The pre-80 bikes used points and the coils were about 5 ohms. The 80+ bikes used electronic ignition (where I said "EI" coils) and those are 3 ohms. The extra resistance on points ignition helps to keep the points from burning out.

[schroedingersbaby]

Another 650- wow, I didn't know they made so many! What's the mileage and any history? Hopefully, you dropped in on Basscliff's site and stole a readable wiring diagram. Let's get at it. Disconnected, the coils should show about 3-4 ohm primary resistance. With ignition and kill switch on, the coils receive positive juice all the time- the signal generators send a signal to ignitor, which then grounds out coils and makes spark at right time. Eating coils is strange behavior, but please no bonfires- it's 30 years old and probably just needs some good loving after years of neglect!

It has about 30,000 miles, and as far as history, all I know is that the previous owner had it running like a top up until two years ago when he moved to Columbus, OH from Wisconsin and it stayed in his garage for two years. When he finally got around to retitling it he found that it wouldn't start, so he took it over to a scooter store to repair where it stayed for about six months before I walked in and talked the scooter guying into selling it to me.

I have the exact same wring diagram in my Clymer Manual, but nontheless it's easier to read on my 24" monitor. Unless I'm not seting the multimeter right, they both read at about 80ohms (and just now when I went out to recheck they both gave infinite readings even though 2+3 is sparking. Anyway to have 'em both spark like a Harley dual fire system does and just waste spark? It'd save a lot of trouble

[schroedingersbaby]

The focus isn't strong on the dial, but it looks like you have it on your lowest ohmmeter reading (200 ohms), which is correct for testing the primary. That reading looks like 5.8 ohms to me. What bike were these coils from? Did I read correct that you have a GS650LX (as in 1981)? The pre-80 bikes used points and the coils were about 5 ohms. The 80+ bikes used electronic ignition (where I said "EI" coils) and those are 3 ohms. The extra resistance on points ignition helps to keep the points from burning out.

That's not the coil I'm using on the bike, that's the extra I have from the four! extra I have, used to illustrate what I did. Lighting in the grage isn't that great at 7pm That's correct, it's a 1981. What would that mean then to my EI ignition? The eBay coils were from a 1981 GS650, the ones from the Salvage yard were from an 1983 GS750 and the two from muzakstylee is from an 1982 GS650.

Glad I read the instructions right, since I don't seem to get the correct readings on anything I try, except resistance on a human body (about 100ohms if you were curious)

[mike_of_bbg]

You should be way more resistive than that!

Are you testing the primaries with the coils connected or not? They should be disconnected!

[schroedingersbaby]

You should be way more resistive than that!

Are you testing the primaries with the coils connected or not? They should be disconnected!

Going off the internets here. Apparently internal and skin resistance give way different readings, and that's not factoring in at idle or in movement. The more you know...

I tested them disconnected, since connected would fry the multimeter with the igntion and killswitch on (I think?).

[mike_of_bbg]

80 ohms is way too high on the primaries. Any way you can verify that your DMM is operating properly? I wonder if your voltage is running too high and frying stuff? Was there a reason you replaced your R/R with the Honda? Did you check voltages after replacement?

[schroedingersbaby]

80 ohms is way too high on the primaries. Any way you can verify that your DMM is operating properly? I wonder if your voltage is running too high and frying stuff? Was there a reason you replaced your R/R with the Honda? Did you check voltages after replacement?

Well R/R works fine I think, it read 12.4 off, 13.6 at about 2k rpm and 14.5 at about 5k rpm. I only replaced it because it's a known problem that'll eventually happen, and I already had one lying around mocking me for paying $90 dollars for a useless part .

I have no idea how to tell if my multimeter is working right, besides that it still reads the battery OK. I've been chalking the wrong numbers up to my inexperience with this multimeter. This is why if I could find one of you guys that's remotely local it'd be awesome.

[tom203]

Well R/R works fine I think, it read 12.4 off, 13.6 at about 2k rpm and 14.5 at about 5k rpm. I only replaced it because it's a known problem that'll eventually happen, and I already had one lying around mocking me for paying $90 dollars for a useless part .

I have no idea how to tell if my multimeter is working right, besides that it still reads the battery OK. I've been chalking the wrong numbers up to my inexperience with this multimeter. This is why if I could find one of you guys that's remotely local it'd be awesome.

Your pic shows correct way to test primary coil resistance,assuming you put meter on lowest "OHM" setting (probably 200 ohm). Seems weird that you have a bunch of coils with high resistance. Go to Radio Shack and buy a 100 ohm resistor and test your meter.