One Coil Losing Voltage/Bike Cranks Won't Start (Pics + Videos)

[Legionnaire]

Okay so I have a 1981 GS450E and I have gotten tons of help from this forum so I thank you all so much. I just got my carbs professionally cleaned by Rick at Old Skool Carbs so they look and are basically brand new!

My bike attempting to start: http://youtu.be/c99vCc35IuI

The other day it actually turned on right away and idled totally fine...

My gas flow does not seem to be the problem because my petcock and all that jazz flows perfectly.

So this is how my gas is setup right now to make sure it flows in to my carbs and the carbs also have gas in the bowls:

I tested my spark and here are some videos, I know you should have a fat blue spark, but I am not sure how fat it really should be.

My coils don't fit exactly right this is how they are attached, does it matter that just one is touching the frame? I usually put something rubber over the other one so the mtetal doesn't touch the frame:

Spark Test

(Watch full screen to see the spark)

Left Side Spark: http://youtu.be/gVZbXDxUb48

Right Side Spark: http://youtu.be/ft02sfxrhMc

Testing The Coils:

They are brand new coils barely ridden at all and they end up passing all the tests...

Right Coil:

They are 5.0 coils, and it jumped between 4.8-5.1 ish so it checks out

Here is the boot:

Here is the voltage of the plug that the coil plugs into:

I do believe 12v is exactly what it should be, right? The left side is where things get weird.

Left Coil:

Exactly at 5.0

Seems just about the same as the other:

THIS IS WHERE I THINK MY PROBLEM LIES:

So I took a video to try to explain this the other coil plug is at 12v which is totally normal. This one starts near 12v and just drops drastically down to pretty much zero or near it:

Important video: http://youtu.be/EMBlqCMr3Hg

So is this a short or something that is sucking my coil down, where should I look first? What would this effect? The starting of the bike? Is my spark too weak, thanks everyone who can give me any sort of insight. Means a lot!!

 

[BigD_83]

Have you done the coil relay mod?

The O/W wire just beside the connector looks burnt in the photo in your OP. Seems like a good place to start looking for a short

 

[BigD_83]

The reason I asked about the coil relay mod.

http://www.thegsresources.com/_forum/showthread.php?t=185193&page=7#post1782525

Your short could be deep in the harness, too.

 

[tkent02]

It started and idled fine the other day.
Both sides are still sparking.
Why are you chasing ignition problems?

 

[Legionnaire]

@BigD: Thanks for that, definitely worth running through everthing and checking out what is up. I feel like this has been like this since day one, after I replaced the coils I rode around for quite a bit couple weeks the carbs sucked during that time, but the bike would start... sort of weird it's a problem now.

Also does the spark look weak, cause in my head when I hear fat spark I imagined like a damn tesla coil!

It started and idled fine the other day.
Both sides are still sparking.
Why are you chasing ignition problems?

Just because the carbs got completely overhauled and the gas is flowing, so I assume the last thing that is the electric. Plus the voltage on one coil completely drops off at a point.

It started and idled for the time I let it and shut it off and now it's won't at all. I don't really know why I just thought it was good to investigate the lack of coil voltage.

Good point about the spark though I mean if there is spark it should start, where do you advise looking? Double checking my gas flow maybe?

 

[tkent02]

The carburetors are the most likely thing to change without being messed with...
By fat blue spark we mean a tiny blue spark, but a bright and solid one. It only looks fat when compared to a tiny yellow spark. It should be easy to see against a dark background. Some bikes run fine with a spark so small you can't really see it. Those in your video looked good although background lighting and the camera itself makes it hard to tell.

 

[Legionnaire]

The carburetors are the most likely thing to change without being messed with...
By fat blue spark we mean a tiny blue spark, but a bright and solid one. It only looks fat when compared to a tiny yellow spark. It should be easy to see against a dark background. Some bikes run fine with a spark so small you can't really see it. Those in your video looked good although background lighting and the camera itself makes it hard to tell.

Okay well I will check them out... I just got them cleaned so they are probably fine, but I feel like I always had some fuel delivery problems... the new petcock I got faces the opposite direction and the tube has to go quite the distance in a weird way to get to the fuel tee. I did take it all off and run it straight down to test though.

What would one coil getting almost no voltage/having a short cause me if my spark is fine?

Thanks!

 

[tkent02]

Are you sure it's not just one coil has it's points open and the other has them closed?

Actually your bike probably has electronic ignition, but are you sure it's not reading differently due to the crankshaft position? One coil getting ready to fire while the other just fired? I haven't played with an electronic ignition for a while but both coils will only read the same voltage if it's running.

 

[Legionnaire]

Are you sure it's not just one coil has it's points open and the other has them closed?

Actually your bike probably has electronic ignition, but are you sure it's not reading differently due to the crankshaft position? One coil getting ready to fire while the other just fired? I haven't played with an electronic ignition for a while but both coils will only read the same voltage if it's running.

Yeah it's an electronic ignition

Well it's not the coil, but its the plug coming from the wiring harness that plugs into the coil that is reading no voltage/drops in voltage. (That might be what you are talking about too) I just find it weird that there is spark but one of the plugs is reading so strange. I will definitely investigate my wiring harness maybe there is an obvious wire that's loose.

I used to have a short where my battery would drain pretty quick even with the lights off, it seems to have gone as of now

 

[barnbiketom]

the two wires to each coil:
one should always have battery voltage.

the other is TOGGLED to ground by the electronic ignitor, so one or the other may read funny depending on crankshaft/pulse coil position....

with key on engine off, the orange/white wires should always have battery voltage. the other wire depends on ???

If you have spark on both plugs, I doubt you have an ignition problem

 

[Legionnaire]

the two wires to each coil:
one should always have battery voltage.

the other is TOGGLED to ground by the electronic ignitor, so one or the other may read funny depending on crankshaft/pulse coil position....

with key on engine off, the orange/white wires should always have battery voltage. the other wire depends on ???

If you have spark on both plugs, I doubt you have an ignition problem

Ah I see because I would text each set of wires against eachother, positive on orange wire and negative on black wire and one was good and the other one was crazy. Did you see the video of the second reading?

Either way yeah the spark pretty much rules that out then... I will definitely make sure all my gas flow is working

 

[barnbiketom]

yep.. i test it with orange TO GROUND..

if no spark then test the ignitor/pulser/wiring.


We here have all seen many many many carbs professionally done that still wouldn't flow gas on the idle circuits.. just my thinking.

Also I know it has been rejetted because of the pods, but perhaps you need more than just mainjet changes to make it run properly??

 

[Legionnaire]

yep.. i test it with orange TO GROUND..

if no spark then test the ignitor/pulser/wiring.


We here have all seen many many many carbs professionally done that still wouldn't flow gas on the idle circuits.. just my thinking.

Also I know it has been rejetted because of the pods, but perhaps you need more than just mainjet changes to make it run properly??

Orange to ground, I thought it was black to ground?

Yeah well the bike is jetted at least close because it used to run and idle fine. I haven't had much time to look at it ... but I will.

 

[Guest]

For one get rid of those old funky connections at the coils.
Either wire them directly or buy a new pair of plugs.
I chased a problem for awhile and was dropping a coil. That was my problem.
They are old and worn out!

 

[Legionnaire]

For one get red of those old funky connections at the coils.
Either wire them directly or buy a new pair of plugs.
I chased a problem for awhile and was dropping a coil. That was my problem.
They are old and worn out!

Molex are so neat though!!

But yeah good idea they are oldddd so it's time to refresh it all.

 

[BigD_83]

I just noticed the position of your fuel filter in the OP. TO ME it looks like it is positioned in a way that would require the gasoline to flow uphill when the tank is in place.

Do you move it when you finally put the tank back in place or leave it where you have it in that photo. Are you having starting problems both with the tank off AND on?

just to reiterate: that O/W wire is your hot, and it does look burnt, so it wouldn't hurt to sort that out, but likely not your issue as you were getting okay spark in your video.

 

[Legionnaire]

I just noticed the position of your fuel filter in the OP. TO ME it looks like it is positioned in a way that would require the gasoline to flow uphill when the tank is in place.

Do you move it when you finally put the tank back in place or leave it where you have it in that photo. Are you having starting problems both with the tank off AND on?

just to reiterate: that O/W wire is your hot, and it does look burnt, so it wouldn't hurt to sort that out, but likely not your issue as you were getting okay spark in your video.

Oh god... did I really put it on backwards... wow. I really hope that's my problem that would be amazing. I feel dumb but this is def something to check!

Yeah I am having starting problems with the tank off and on that has got to be it.

Thanks for the clarrification I will check out the fuel filter then check out the wires!

 

[Guest]

He said your fuel needs to flow downhill and not uphill at any time.

 

[Legionnaire]

The bike turns on here and there now after I crank the bike over a bunch it will eventually turn on and after that it'll turn on automatically every single time. But once I let it cool down say the next day I still have heaps of trouble getting it to turn on again.

 

[JayWB]

"My coils don't fit exactly right this is how they are attached, does it matter that just one is touching the frame? I usually put something rubber over the other one so the mtetal doesn't touch the frame:"

Yes, it matters. The coils have to be well grounded or they cannot produce a spark.