Bang My Head on the "Spark"

[neimad]

1980 GS750L
vance & hines headers/can
motion pro drag bars
sport bike brake lever
custom seat
bags

New stator & R/R couple years ago... Rarely ride it, 20k miles. Took it out for a jog the other day, 30min ride. As i was getting home, it acted like it fouled a plug. Come to find out cylinder 2&3 are dead, no spark.

I was dumb and replaced the coil for 2 &3 (left side when sitting on the seat) to find out the old wasnt bad. After ohms test, all 3 coils are good. Stator tests in spec. I swapped power leads to replaced coil.. it sparks.

I also did the test with a 1.5v power source, in which i was able to get the ignitor to spark 1 & 4 upon connecting power, when disconnect - nothing (should of fired 2 & 3??). I just want to make sure im not missing anything - you get to a point where you just dont want to throw any more moola its way. Another thing i noticed... With the ignition key "on", testing for power at coils... At the left coil (2&3) i have + power on both leads.. 11v. Is that normal? I don't mean the volts, but rather both leads... When i test the right side coil (1&4, the one that fires), only one lead has juice.

If i have read right, the ignitor grounds the coils when triggered, causing spark. So does this just help confirm that the ignitor is toast? I am tired of fighting this old boy.

Lastly, replacing this with a Dyna S replaces the ignitor and spark generator, correct? Should work with my existing mech advance?

Please advise... (this site is great btw...)

[67fire]

I don't believe that anyone is allowed to answer your question without first posting a picture of your bike. J/K!
Welcome to the greatest place to find anything that you ever needed or wanted to know about your GS!

Just wait for it...

Eric

[chef1366]

If both wires going into a coil are showing voltage than you're deduction is correct.
Either that or a shorted wire.

[67fire]

BassCliff, will be along shortly with your "official" welcome!
The picture, no worky.

Eric

[neimad]

I don't believe that anyone is allowed to answer your question without first posting a picture of your bike. J/K!
Welcome to the greatest place to find anything that you ever needed or wanted to know about your GS!

Just wait for it...

Eric

http://helpshelter.net/photo.jpg

They won't mind if i borrow their site to host a pic...

[BassCliff]

Hi Mr. neimad,

I'm glad you found us. Your bike looks lean and mean. Nice.



I've seen several used ignitors on ebay lately for pretty cheap. I know it's taking a chance buying old electrical parts, so you may want to go ahead and upgrade. That way you won't have to worry about it. Anyway, I just stopped by to say, "HOooooowwDY!"

Here is your very own magical, mystical, mythical, mind-expanding "mega-welcome". Please take notice of the "Top 10 Common Issues", the Carb Rebuild Series, and the Stator Papers. Now let me roll out the welcome mat for you...

Please click here for your mega-welcome, chock full of tips, suggestions, links to vendors, and other information. Then feel free to visit my little BikeCliff website where I've been collecting the wisdom of this generous community. Don't forget, we like pictures! Not you, your bike!

Thanks for joining us. Keep us informed.

Thank you for your indulgence,

BassCliff

[posplayr]

1980 GS750L
Another thing i noticed... With the ignition key "on", testing for power at coils... At the left coil (2&3) i have + power on both leads.. 11v. Is that normal? I don't mean the volts, but rather both leads... When i test the right side coil (1&4, the one that fires), only one lead has juice.

If i have read right, the igniter grounds the coils when triggered, causing spark. So does this just help confirm that the igniter is toast? I am tired of fighting this old boy.

)

IIRC the positive side of both coils is common with the igniter and is colored Orange and White . When the key is on you will see +12V on the O/W wire. Depending upon how crappy your connections are in the ignition and ON switch and fusebox, the voltage at the coils will drop when they are energized or when the ignition has the negative leg of that particular coil grounded. +10V is kinda the point of no return for poor starting based on low voltage.

What you are seeing where there is the same voltage at both ends of the coil is when the igniter leg is not grounding the negative side of the coil,; it is open circuit and not pulling current so you see the same voltage at both sides. This is normal.

You may not be doing a coil relay mod, but there is an overview schematic here that shows how current flows from battery to ignition back to fuse then to ON switch. It might help you to compare/interpret against the schematic specific to your bike. I see you have a GS750L; nice bike. From what I remember the above is true.

http://www.posplayr.100megsfree3.com/FH012AA_Charging/DynaS_Coil_RelayMod.pdf

[chef1366]

I was under the impression he was testing the coil leads off the coils and not the coils themselves.

[neimad]

Sorry for the delay...

Sorry, so many things going on this summer... The bad part is i havent touched the bike since! And i was testing the leads with them disconnected from the coils, so does that change anything? I disconnect the plug with two wires from the coils. Im testing each wire with my volt meter grounded else where on the bike. On the side that does not fire, both leads have + volts. So if the ignitor leg isnt grounded, i would see power there?


Thanks again.

[rustybronco]

On the side that does not fire, both leads have + volts. So if the ignitor leg isnt grounded, i would see power there?

Yes.
also the inverse is true, if the igniter has grounded the coil, the wire going to the igniter would be at near 0 volts.

[neimad]

thanks for the reply

so would you agree with me that the ignitor is at fault?

[rustybronco]

No...

I would check the continuity of the wire from the 2-3 coil to the igniter. If that appeared to be good, then I would take the igniter apart.

***pm me your e-mail addy***

[pdqford]

I disconnect the plug with two wires from the coils.

Oki-doki. So you are testing the coil primary circuit.

Im testing each wire with my volt meter grounded else where on the bike.

And you are probing the harness side of the connector, not the coil side of the connector. Correct?

On the side that does not fire, both leads have + volts. So if the ignitor leg isnt grounded, i would see power there?

With the connector disconnected, the ignition switch "on" and the kill switch "on" (irregardless if the ignition box is pulling it to ground) you should only see battery voltage on the O/W wire on the harness side of the connector. If you are seeing voltage on the other wire in the harness side of the disconnected connector (B/Y if for cylinder 2 & 3, W if for cylinder 1 & 4), I would think that it is shorted to vehicle power somewhere.

When the ignition box turns the coil "on" it connects the B/Y or W wire to ground. When its time for the coil to fire, the ignition box "ungrounds" the B/Y or W wire. So with the connector unplugged the B/Y or W wire in the harness side of the connector is either connected to ground or to nothing and would not have voltage.

[rustybronco]

And i was testing the leads with them disconnected from the coils, so does that change anything? I disconnect the plug with two wires from the coils. Im testing each wire with my volt meter grounded else where on the bike. On the side that does not fire, both leads have + volts. So if the ignitor leg isnt grounded, i would see power there?

I guess I should have read it correctly.

If there is power on the ignitor side of the coil, you have a wire shorted to power, or the ignitor is allowing power to reach the negative side of the coil.

Thanks pdqford, for opening my eyes to what he "really" was saying.

[neimad]

sorry

not enough details in my descriptions... pdqford, you are correct. I am testing the harness side of the plug, otherwise i would be testing the coil circuit. I ground the neg lead off the volt meter on the frame, and probe each pin on the connector with the positive lead from volt meter, that leads to the harness. O/W and B/Y i think... Ignition key "On", however i dont remember if the kill switch was on or off. I never use it, just use the key.

And with that test as described, i get + volts on each wire, and by that i mean 10+v or more. SO, either a shorted wire, or a faulty ignitor? A bad ignitor could allow voltage on the wire that is supposed to be dead or grounded, correct?

Same test on the good firing side, 1&4, one has positive volts and other wire is dead or grounded.

I can take the ignitor apart tonight if it is something that can be repaired?