82 GS450L Hesitation/Breaking Up: Part II

[Ludeykrus]

The original thread can be found here:

http://www.thegsresources.com/_forum/showthread.php?t=88730

Basically, I've moved over the past few months and finally got settled in and had time to work on it.

I've been working through small bugs (mostly idle/carb issues) and am back to my original problem. The bike Will crank and idle up fine. It warms up good, but the problem is it breaks up around mid-RPM's. Regardless of how much throttle I give it, it will start breaking up around 3-3.5k and is breaking up hard at 5k. It will want to stay at 5k like a rev limiter, but with more throttle it can be coaxed to rev slowly higher, missing the entire time. I also am pretty sure it's popping upon deceleration.

I have cleaned the carbs out 2-3 times, replaced the spark plugs, cleaned the fuel tank, checked the fuel petcock for proper operation, replaced fuel line, and replaced intake boot o-rings. A compression test came out at 130psi and 140psi. When I first started on the bike, i had the stock airbox and filter. I ran it w/ no lid, no filter, and have currently installed some UNI pods, and no change. I checked the spark at the plugs, and it is firing everytime. It gets a blue spark, but to my experience w/ cars I expected a fatter spark. I don't think this is the problem, as I am fairly unexperienced with bikes. I tried tightening up the plug gap about .004" (I think....gotta recheck) but to no avail. I've ran it w/ the petcock on Prime, ON, the fuel lid removed...nothing.

Next problem, probably related: upon getting the bike good and warm from riding for about 5-10 minutes, it will start misfiring bad below 2k. It will misfire, and after 3-5 seconds of no throttle it will die out. It runs normally (aside from the first problem) above 2k. This also is independent of throttle position.

While I'm still working on the carbs a bit, I pulled the plugs during the higher-RPM misfires and see nothing extroardinary:



I no longer think it's a carb problem, and am leaning towards an ignition/electrical problem. My bike has the electronic ignition, and I don't think it's the coils (it doesn't seem isolated to one cylinder). I have recently been jumping it off my battery jumper box to get it started, due to a battery that went dead (a new one's in order).

Any ideas on what to try next? This is getting extremely frustrating! :x

[GS850_Coug]

I agree with your idea of suspect ignition. Running worse after warming up is generally due to a rich condition. Check to see that you have proper readings on your coils, wires, and caps. Also check to see that you have at least 12 volts to the coils. Do a test on your CDI/igniter (if so equipped) to make sure all is well there. If you have a points type ignition, the symptoms are classic condensor failure symptoms. Could also be a sticky advance mechanism. I'm sure others will chime in to help also.

[Nessism]

Ignition is likely source.

FYI, you will never get the bike to run right running pod air filters unless you rejet. Tons of info on this in the archives.

[nabrams]

FYI, you will never get the bike to run right running pod air filters unless you rejet. Tons of info on this in the archives.

Yeah, replace the pods with stock airbox and filter (make sure there are NO leaks!) before moving on to troubleshoot other areas. Unless, of course, you're the type who enjoys tearing your hair out from frustration, trying to get the jetting right.

[Ludeykrus]

Ignition is likely source.

FYI, you will never get the bike to run right running pod air filters unless you rejet. Tons of info on this in the archives.

Oh I know. I got a good deal on them, and w/ the number of times I've been removing the carbs (prob at 10 or so now...) I figured it would be worth it....even if only as a temporary means of making troubleshooting the main problems easier.

The pods didn't affect anything so far, and they aren't the main problem. Any suggestions? I think I got the idea, but could someone confirm on how I should check my coils?

[nabrams]

I don't understand how you're so sure that the non-stock pods and jetting are not the main problem.
Are you saying that you've run the bike with stock airbox/filter and jetting and still had the same problem?
It isn't clear from your other post.

[Dragonfly]

OK I am having a VERY simular issue with my Gs450sx. And after nearly a month of tinkering and working on the bike I have it narrowed down to the coils.
On mine I am loosing spark in the left cylander due to old crappy wires. I have trimmed the ends off of the wires and replaced the plug boot, for it to only be a temporary fix.
It sounds to me like this might be your problem as well.
I am trying to track down a used coil, and as soon as I get it replaced ill let you know what i find.
I do think though, that once you get this one problem fixed, the pod filters are going to be a thorn in your side.... You will probobly want to reinstall your airbox and try to tune the pods later...
Micah

[Ludeykrus]

I don't understand how you're so sure that the non-stock pods and jetting are not the main problem.
Are you saying that you've run the bike with stock airbox/filter and jetting and still had the same problem?
It isn't clear from your other post.

Yes, I tore down the carbs twice and tinkered on the bike for a month or two while the stock airbox was on. I just recently replaced the airbox for pods to make troubleshooting much easier.

The bike is stock aside from pods, and I am SURE the pods and jetting are not the problem!

[Ludeykrus]

..........

I think I got the idea, but could someone confirm on how I should check my coils?

[DickV]

Coil check

Coils need to be tested under load on a coil tester. Checking resistance only does not reveal what happens when the high voltage occurs for the spark; if the insulation on the secondary side is not in good shape the resistance will be close or within spec but when the high voltage occurs it can jump across the poor insulation. I suggest taking the coils to a shop that has a coil tester and is willing to conduct the relative quick and easy test. Good luck.
DickV

[Ludeykrus]

Quick update:

Coils are within spec on the resistance test. I can't find a place anywhere near me that has a coil tester machine, but I don't think it's the coils: I can run the bike on one cylinder at a time, rev it, and it will misfire on both cylinders. I really doubt both coils went out at the same time.

I have my Clymer manual and am trying to check the igniter and signal generator. The manual says to check the signal generator by checking resistance between the signal wires and ground on the frame. This was done very quickly between classes, but I got resistance in spec if I grounded to the black wire in the signal generator housing, but not when grounding to the frame/battery terminal! Hmmm.....gotta try that test again before assuming anything.

I also can't figure out how to check the ignitor. The manual's picture says to disconnect both signal generator wires at the left side cover. The signal generator wires run as a bundle with two connectors along the way, but there is no way to disconnect just the two signal wires without also disconnecting the ground wire (and the oil pressure sensor wire? the 4th one, green/yellow). Also, I don't see an easy way to connect my multimeter to the ignitor to perform the test......How should I go about doing these tests?

Thanks in advance.

[Ludeykrus]

Update #2:
I read up on some older posts on here about checking the ignitor and figured it out.

Went home and dragged out the multimeter again. The signal generator gives me about 60 ohms when testing between the signal wires and the ground wire that's inside the actual signal generator housing on the side of the engine casing. However, it did not register anything when I grounded between the signal wires and a ground on the engine or the neg. terminal of the battery!

I also checked the ignitor by pulling the 4-wire signal generator wire plug going into the ignitor. Used both the multimeter and a AA battery to try to get a plug to fire, and couldn't do it. I hooked the wires up again and turned the motor over and the plugs sparked! Hmmmm........

So do you think that my ignitor is out-of-service? The bike runs decent otherwise, but sputters out in the mid-high RPM's.

BTW: the low-RPM misfire I detailed earlier in this thread was caused by the dead battery. Apparently the stock alternators don't make much juice until around 2k.

[chef1366]

I would change the igniter, check cam lobes and degree in the cams.

[Ludeykrus]

But generally doesn't the ignitor stop all spark when it goes out? It seems like an intermittant spark at higher RPM's is odd for an ignitor failure....

I may pull it out tonight, pull it apart and check the solder connections.

[Ludeykrus]

Final update:

Replaced the igniter and the bike now runs the best it has ever run. Everything I've read on here indictated a faulty igniter will shut the bike down all at once, but apparently mine had a bad solder connection or something making it run decent up to around 5k.

Problem solved!