Ignition troubles (GS450E) (SOLVED!)

[ChickenStorm]

Hi! I've just about finished up the bike for the quickly approaching riding season but I've stumbled into some ignition issues. The problem I'm having is one cylinder seems to run considerably worse at low rpm making it almost impossible to set the idle correctly, since when throttle is applied the sluggish cylinder wakes up and hangs the idle very high. I've been trying to tune the carburetors as I thought this was a fueling issue, in part because the bogging cylinder also keeps backfiring and sputtering out the corresponding carburetor. But after I tried switching the coils to the opposing sides the problem went away and the bike ran almost perfectly, revving high and settling back down nicely. Then after running for a while it shut off and upon restarting the same problem persisted only now on the other side which I expected. Now the big question I'm having is why did it run so well for a little while just after flipping the coils and then returning to the old issues. One thing to note is that I didn't have my fuel tank connected when this happened so the bike ran solely on what was left in the line and the floatbowls.

I'm running 130 main jets along with 47,5 pilots and the needle in the highest position (because I thought this was a lean idle/mid range)
I'm also now wondering if a bad coil could be the cause of my plugs constantly carbon fouling even though my mixture doesen't seem to be overly rich.
I tried my hand at balancing the carbs but only got them roughly close at idle, but on higher rpm the "good" side pulled a much higher vacuum.

Both coils primary resistance was 4 - 4.3 Ohms. Their secondaries varied a bit with the faulty one being 17.05 kOhm while the "good" one was 17.80 kOhm.

 

[Nessism]

You might want to check the Newbie Mistakes thread linked in my signature. If you can't see the link, be sure to turn on "view signatures" in your profile.

BTW, coils are blamed for far more faults than they cause...

 

[ChickenStorm]

If you're reffering to the part about the intake boot O-rings, I've got that covered. New boots and O-rings already on. I was very careful to check for any air leaks as I've been shamefully naive about it in the past.

I'm almost certain the fault is atleast in the ignition since the coughing and backfiring switched sides as I expected when I swapped the coils. I'm just a bit stumped as to why the issues disapeared temporarily, could be a contact fault within the base of the plug wire or in the wiring harness itself.

 

[LAB3]

If you're reffering to the part about the intake boot O-rings, I've got that covered. New boots and O-rings already on. I was very careful to check for any air leaks as I've been shamefully naive about it in the past.

I'm almost certain the fault is atleast in the ignition since the coughing and backfiring switched sides as I expected when I swapped the coils. I'm just a bit stumped as to why the issues disapeared temporarily, could be a contact fault within the base of the plug wire or in the wiring harness itself.

It could be that the problem is due to heat since it shows up after the bike has ran a bit and gets hot. It's common for electronic parts to fail when they get warm. Have you checked the primary and secondary resistance of the coils? How about the resistance of the spark plug caps?

 

[ChickenStorm]

I suspected the coils from the start since I may have tried welding the coil mounts to the frame while they were bolted on already :ghost:, so they might have gotten a bit toasty.

"Both coils primary resistance was 4 - 4.3 Ohms. Their secondaries varied a bit with the faulty one being 17.05 kOhm while the "good" one was 17.80 kOhm."

 

[ChickenStorm]

Now I'm wondering, are the coils interchangeable with some universal two pin models? As long as the resistance is the same any two pin would work?

 

[ChickenStorm]

UPDATE! I measured some old coils I have and also checked the voltage coming to the coils from the wires and one side is only gettin 0,11V. Is this the CDI:s doing or do I have a contact fault somewhere? I'm assuming the latter since when switching the coils it must've had a brief contact and that's why it ran so well.

 

[Grimly]

UPDATE! I measured some old coils I have and also checked the voltage coming to the coils from the wires and one side is only gettin 0,11V. Is this the CDI:s doing or do I have a contact fault somewhere? I'm assuming the latter since when switching the coils it must've had a brief contact and that's why it ran so well.

The voltage is coming from the ignition switch TO the coils and then to the ignitor, which in turn interrupts the circuit, thereby creating the spark.
If you're seeing a low voltage feeding one or both coils, there's a bad connection (or two, or three) in the supply.

 

[ChickenStorm]

Yeah I checked that there is indeed a pulsing ground so atleast the ignitor is working, what worries me is that the coil wires only have a 10,8V potential even though the coil positive is 11,6V to ground. Battery voltage at this time was 12,7V so there must be something going on with these old wires... I'm getting decent spark at both coils though but it propably could be much better since I'm still getting a lot of coughing and starting issues at the moment.

 

[ChickenStorm]

UPDATE nr. 2: I replaced all connectors going to the coils and changed the plugs, tried starting and it made no difference. Then I tried out lowering the needle to the lowest position, lo and behold, it ran perfectly for a while. Then when it got warm enough it started backfiring out the exhaust and carb, and would bog terribly if I cracked the throttle even a little.
These CV carbs are so confusing since the changes I'm making trying to tune them yield almost the exact opposite reaction. I'm writing every change into my excel sheet so I'll try pasting it in here for reference :joyous:.
​ [TABLE="width: 1201"]
[TR]
[TD="bgcolor: #a5a5a5"]Main jet[/TD]
[TD="bgcolor: #a5a5a5"]Pilot jet[/TD]
[TD="bgcolor: #a5a5a5"]Needle clip position[/TD]
[TD="bgcolor: #a5a5a5"]Results[/TD]
[/TR]
[TR]
[TD="class: xl67, bgcolor: #ededed"](Stock) 120[/TD]
[TD="class: xl65, bgcolor: #ededed"](Stock) 45[/TD]
[TD="class: xl65, bgcolor: #ededed"]Middle[/TD]
[TD="class: xl68, bgcolor: #ededed"]Factory settings[/TD]
[/TR]
[TR]
[TD="align: right"]130[/TD]
[TD="class: xl65, align: right"]47,5[/TD]
[TD="class: xl66"]Middle[/TD]
[TD]Carbon fouling and stumbling at full throttle, uneven idle that hangs after high revs. Slow throttle response. Backfires when leaning pilot screw.[/TD]
[/TR]
[TR]
[TD="bgcolor: #ededed, align: right"]120[/TD]
[TD="class: xl65, bgcolor: #ededed, align: right"]47,5[/TD]
[TD="class: xl65, bgcolor: #ededed"]Middle[/TD]
[TD="class: xl65, bgcolor: #ededed"]Revs out very slowly, otherwise same.[/TD]
[/TR]
[TR]
[TD="align: right"]120[/TD]
[TD="class: xl65, align: right"]47,5[/TD]
[TD="class: xl65"]Bottom[/TD]
[TD="class: xl65"]No difference[/TD]
[/TR]
[TR]
[TD="bgcolor: #ededed, align: right"]130[/TD]
[TD="class: xl65, bgcolor: #ededed, align: right"]60[/TD]
[TD="class: xl65, bgcolor: #ededed"]Bottom[/TD]
[TD="class: xl65, bgcolor: #ededed"]A little better but still very bad, now considering an ignition issue.[/TD]
[/TR]
[TR]
[TD="align: right"]130[/TD]
[TD="class: xl65, align: right"]60[/TD]
[TD="class: xl65"]Bottom[/TD]
[TD="class: xl65"]Didn't want to start at all, when plugs were changed ran as bad as before.[/TD]
[/TR]
[TR]
[TD="bgcolor: #ededed, align: right"]130[/TD]
[TD="class: xl65, bgcolor: #ededed, align: right"]47,5[/TD]
[TD="class: xl65, bgcolor: #ededed"]Top[/TD]
[TD="class: xl65, bgcolor: #ededed"]Works perfectly when cold but coughs and backfires when coming down from revs. Bogs when given throttle when warm.[/TD]
[/TR]
[TR]
[TD="align: right"]130[/TD]
[TD="class: xl65, align: right"]47,5[/TD]
[TD="class: xl65"]Top[/TD]
[TD="class: xl65"]Runs good no problems, fuel starvation after revving caused by low spot in fuel line (easy fix). IDLE AIR SCREW ALL THE WAY SHUT![/TD]
[/TR]
[/TABLE]

 

[ChickenStorm]

SOLVED: Shut the idle mixture screw all the way and filled my gas tank all the way. There is a low spot in my fuel line which caused a lean sputter once it ran dry which I MISTAKED as leaning out when warming up. To summarize, too rich idle and needle position. hope someone with the same issue finds this thread helpful!