GS750 Custom Build - no fire at the plugs

[Guest]

Hi everyone - I'm new to the forum. I'm working with a friend on a 82 GS750EZ Suzuki.

George has stripped the bike down to the frame, and cleaned, polished, and re-engineered about everything on the bike. It was
running when he purchased it. The Oil pressure light was on all the time when running - but the bike ran fine for 100s of miles, so
it is assumed that the sender was bad.....

Now, during re-assembly, George pulled any and all "un-neccessary" wires out of the harness and put it back together. He eliminated all
lights in the gauges, including neutral, kickstand, Oil pressure, turn signals, and the gear position indicator. The kickstand switch was long gone when he got the bike.

So.... I know that is a recipe for disaster, and we are in wiring hell now.

But... I've poured over the wiring diagrams - trying to figure out why we have no spark at the plugs. Here are the findings:
1. Ignition switch, kill switch work fine. flip either one off, and no voltage.
2. Bike will crank, but will not produce spark on any of the plugs.
3. We have 12v at the coils. 12v and ground at the Ignitor Unit.
4. Pick-up coils are wired in via L and Dg wires. we are certain the connections are good.
5. Re-gapped pickup coils at .006
6. No voltage received at the coil exciter wire when cranking.... (could we have the coil posts mixed up?)

We replaced the Ignitor unit with a "known good out of a running bike" module - no change.
the Pick-up coils Ohm out per spec in the CLYMER manual.
I cannot see how the oil pressure switch, clutch switch, neutral switch, and kickstand switch work to kill the ignition - and
not the starter motor.

Any ideas or suggestions would be greatly appreciated. George is about to dump this thing in the lake, and it would be a real
shame. It's going to be pretty cool if we can make it run.
Help?

[Redman]

.....
3. We have 12v at the coils. 12v and ground at the Ignitor Unit.
.....
.....
I cannot see how the oil pressure switch, clutch switch, neutral switch, and kickstand switch work to kill the ignition - and
not the starter motor. ..

Good observations.
The clutch switch is the only one that can have any effect on any of this, it can interrupt the starter solenoid (not the ignition).

You do have power at the coils, which is what I was going to tell you to check. So I dont know what else to tell you,....

Other than Welcome to GSR.

.

[steve murdoch]

[could we have the coil posts mixed up?].....
This is from a very recent post
left coil-o/w & w-cylinders 1&4
right coil-o/w & b/y-cylinders 2&3

o/w wires go to +ve terminal
b/y & w wires go to -ve terminal

Welcome to the site.

[George]

Thanks Steve

[could we have the coil posts mixed up?].....
This is from a very recent post
left coil-o/w & w-cylinders 1&4
right coil-o/w & b/y-cylinders 2&3

o/w wires go to +ve terminal
b/y & w wires go to -ve terminal

Welcome to the site.

The bike has yellow coils... I couldn't see a + or - on the coil body.
the o/w are on the outside... and the coils mount with the terminals to the rear.

[Pdyer1098]

1981 gs550 destroying coils

The bike has yellow coils... I couldn't see a + or - on the coil body.
the o/w are on the outside... and the coils mount with the terminals to the rear.

So this is my first post/question on here I have a gs550 with the cdi box I have replaced the coils 3 times now I've replaced the cdi box, the fuse panel, the plugs, the pick ups, and it still is blowing the coils after it starts and runs for a little bit

[George]

speaking of the clutch switch.... where is it? under the clutch cover?

Also, I want to confirm:
1. If (on a normal running bike) I start the bike with the kickstand down, bike must be in neutral, or clutch must be pulled in.
2. After starting - If I drop it in gear, and start to let out the clutch (kickstand still down) the motor will die.... right?
3. bike can be in gear, with kickstand down, and will only start (crank) if the clutch is pulled in.... right?

I'm assuming we or them have wired around some of these safety features... The neutral switch is out of the picture...

[George]

Wow... I did learn that these are ACCELL Coils. I don't know if they are better or worse.
Good luck

[mrbill5491]

Wow... I did learn that these are ACCELL Coils. I don't know if they are better or worse.
Good luck

Those are great coils, had them on my 750 for the past 30+ years. Strong as ever.

[George]

thanks MrBill.... Do you know how to tell the positive from the negative post?.... Mine don't seem to be marked.

George has also changed forks, polished the rear swing arm, and everything else on the scooter....
I'll attach a picture when I get one.

[Redman]

speaking of the clutch switch.... where is it? under the clutch cover?

Also, I want to confirm:
1. If (on a normal running bike) I start the bike with the kickstand down, bike must be in neutral NO , or clutch must be pulled in YES- regardless of netural.
2. After starting - If I drop it in gear, and start to let out the clutch (kickstand still down) the motor will die.... right? NO
3. bike can be in gear, with kickstand down, and will only start (crank) if the clutch is pulled in.... right? Yes & No. Clutch has to be pulled in regardless of gear and/or kickstand.

I'm assuming we or them have wired around some of these safety features... The neutral switch is out of the picture...

Clutch switch (as we call it, on schematic it is called "interlock" with no description of what or where) is on the clutch lever. Is in the starter solenoid circuit in series with the starter button. That is its only function, interrupts the starter solenoid. Its only function. And it is the clutch switch only in that circuit (well, the circuit is: the kill swtich, the clutch swtich and the starter button, and the solenoid.).
Note: the clutch switch wears out and quits working. Most folks just bypass it. Some people (me) make a haphazard repair and then find a replacement.

The clutch switch, and the oil pressure switch , and the neutral switch, and the sidestand switch are not at all in the circuit to the ignition system.
(hey, I am repeating myself here, I said that in previous response a couple days ago.)


>> later note:
Okay, I see that I was not very clear before.

Clutch swtich: In starter solenoid circuit ONLY. Effects nothing else.

Netural swtich: Lights the netural light. Effects nothing else.

Sidestand swtich: Lights the sidestand light when sidestand not completly up: Effects nothing else.

Oil pressure swtich: Lights the Oil Light AND the sidestand light (yes, both): Effects nothing else.

Only thing that cuts power to the ignition is the Kill Switch. With GSes were are talking about the 70s and 80s, you know.
Was not untill in the 90s that started to see such logic on kickstand and gear and clutch to kill the ignition if this-but-not-that-with-exception-of-blah-blah.

Other Note: The Netural swtich, and the gear position swtiches, and the sidestand swtich and the oil pressure switch... each of them is the type of switch that connects to the ground, it completes the ground.


But this is getting way off track of your "no spark" situation.

.

[George]

Breaking news... (no, it still wont spark).
We have Accell 140403 coils. They are installed right next to each other, side by side.

There are two small posts - but no marking as to + or -.
We presently have the Orange/White wire connected to the outside posts of each coil, and the
yellow/black on the inside of one... and the White wire on the inside of the other.
Unless it doesn't matter on plus / minus, we have one coil wired backwards.
That said, did we fry the Ignitor Unit the first time we cranked it?
I've searched the web for diagrams on the Accell 140403, but no indication of positive or negative terminals....

We tested the coils this afternoon. One coil - no continuity 0 ohms. Second coil, .5 ohms post to post, 0 ohms post to
spark plug lead. So, apparently two bad coils, worked before wiring modifications...
Are these easy to distroy? Can't understand why they would go bad.

[steve murdoch]

A search shows a lot of site members have used those coils.

http://www.thegsresources.com/_forum/archive/index.php/t-76392.html

[George]

Thanks Steve. On another note, I'm watching a local 83 Suzuki 650 4 cyl bike that runs, being parted out.
Any chance that we could use the coils, Igniter module (if it has one?). If nothing else. We could test out
a running bike.

I appreciate your help

[George]

We have checked out the coils. One coil has about 4ohms between the small posts. Nothing from a small post to a plug wire post.
the second coil has nothing on either the primarys or secondary posts.

We are shopping for new or used coils.

we have a GS750E.... is that significant?

[steve murdoch]

Here is some testing coils info.

http://www.thegsresources.com/_forum/showthread.php?72924-How-to-test-the-ignition-coils

A GS750E does not require any sort of special size or output coil.