well guys, it's this bike (93' gs)
http://gstwins.com/gsboard/index.php?topic=53881.0

as i said on the topic above (i think you'll understand why i opened a differnet thread instead of using that one; in a few words it's not a simple question any more - at least for me!) the bike was working properly (I thought). I took it for a ride 2up that night and everything looked ok . Of course I couldn't say whether the right cylinder was working at idle, i thought it was, and anyway i didn't have any other signs of malfunction as i am a new gs owner. The reason why i cleaned the carbs in the first place is described in the other thread. And that problem seemed to be solved that night. So the  bike seemed Ok. I left it for a month in place, i just started the engine for a while from time to time and it was working fine (still I can't say if the left cylinder was woring at idle - excuse me for mentioning that twice, I' ve searched in the forum and I saw that others had that kind of problem, for me the only thing i can say is that idle rpms were around 1200)

And 4 days ago i decided to take it for a ride. It started ok, the battery was fully charged and i hit the road. Everything was working ok but a little, just a little sluggishness between 2-3K rpm. After that it was good. I didn't pay much attention as I thought it must be a little "power hole" typical of the bike. When i getting close to my destination (after a 22km ride at highway speed 60-75mph) and went off the highway, the bike's rpm wouldn't fall bellow 3000 by themselves when i closed the throttle. That happend at first, after a while they would go down but the stayed for a while between 3000-2000 rpms.I managed to get them down by shifting down (another thing here, are the gs notorious of slow rpm dropping when you leave the throttle? I've ridden some other bikes and it's the first that is so slow at dropping the rpms, not tragically slow but enough to notice) and got where i wanted to go.
There i stopped the engine, started it again after a while and the rpms dropped normally without the logging at 3000-2000K.
I said it must have to do with the fact that it's the first long ride of the bike after a log long time and it will be ok... 

two days later i rode the bike back and it was Ok. Next day i did the same trip and I decided to gve it a go and reach 90mph. I did reach 85 (perhaps it could do faster with some patience). And then i relaxed and continued the trip at 75mph. After a while the bike started stumbling the way i described in the other thread (as i understand now, one cylinder, the right one, went on and off). I tried to keep driving but only one cylinder was working from a point on and that one couldn't keep the bike running, the speed was dropping (I tried to keep driving by revving up but it wouldn't rev up however hard i turned the throttle) and it finally stopped. I stayed put for a while and let the bike cool down a little and then I fired up again (after some attempts to start it without success). I continued driving to my destination and after a while it started stumbling again only to stop almost right where i was heading to (luckily not so much pushing for me this time).

At that point i had realised that something was wrong with the bike  . Next day i had to return. So i decided to try rinding the bike even on one cylinder back to my place, where i can work on it. I thought that if i went slowly i could do the trick.
But even on slow driving (50mph max) it started stumbling again and it stopped 15m away from my place. Now (a day ahead) it is still there waiting away from me. Only once did the good cylinder fire up, but it soon went off and the engine won't start again even if i discharge a battery on it. I took the battery out to charge it and the carbs to clean them.

Both carbs had enough fuel in the bowls, about the same amount, but i can not be totally sure about that.

Other Important hint: The bike has the coil that goes to the left spark plug (the one at the working cylinder) replaced with a non-suzuki one. It's totally different and it sits in a different place as the mounting bolts don't match. That was done from the PO. When me and my neighbor were trying  to make the right cylinder work (as i describe in the other thread) we swapped the coils to see if the right suzuki coil would start the left cylinder which was already running on the non-suzuki one. And it did (so we assumed that it was a fault of the carbs that only one cylinder was working and we thought that finally we had fixed th problem...

Anyway is there anybody couregeous enough (after reading such a huge post) to give me a hint?
Is it the carbs or the electric?

Pull the plugs one at a time and crank the engine to see if they're both sparking.  Then do a compression test.  If both those succeed with flying colors, then rebuild or buy a new set of carbs.

Quote from: 007brendan on November 10, 2010, 04:50:33 PM
Pull the plugs one at a time and crank the engine to see if they're both sparking.  Then do a compression test.  If both those succeed with flying colors, then rebuild or buy a new set of carbs.

Great advice 007brendan but don't do anything as drastic buying new carbs yet. If your not comfortable rebuilding yourself Buddha has a great mail in mail back rebuild service. Have never heard of an unsatisfied customer yet!

i think there is compression to both cylinders. And both spark plugs are sparking. I just don't know yet if the sparking is correct (as there is one after market coil). I will check the carbs, that's why i have pulled them out. But they are thoroughly cleaned and were working.
Can anybody see something to the bike's behavior that particularly shows that it's carbs and not electronics and vise versa? Please all answers are welcome, my bike is left alone out there and i need advice that would at least help me bring it home. Also i live in greece (that's for the difficulty in mail proceses)

I am answering your post to bump it. I know there are people here that have an idea what is wrong. Me myself..having an after market COIL I wouldn't do it. There are so many variables that could be causing this issue you need to start at one point that you know that works and go from there.

What color are the plugs? If they are white, then I want to say your tank vacuum is plugged and starving the engine. Hope this isn't the case.....

And just a thought, if the coils are old the first symptom of them going bad is that they will shut off when heated. After they cool down for 20 minutes or so they'll spark again.

thank you guys for the answers! The plugs are not white or so i remember. I'll check that of course.
By the way the carbs are opened, cleaned again - they seemed fine anyway. Let's hope i'm not doing something wrong here...

As for the coils, Big Rich's idea gives a good hint, it seems to be something that has to do with the bike getting warm. Do you think that i will be able to figure out the coil's fitness  using a multimeter? (If that might be the case I'll better get myself one before my long ride to the bike - thank god i also have a moped).

Quote from: gsdox on November 10, 2010, 10:32:01 PM
i think there is compression to both cylinders. ...

How did you check compression ?

Do you have access to a compression gauge like this :

http://www.amazon.com/Actron-CP7828-Professional-Compression-Storage/dp/B00020BM28

?

no. (since i do not have a cover for the pulse generator coils) i crank the engine using a wrench. And it takes a proper amount of pressure to do so, so i think there is compression. Of course I can be wrong. If you think that I should try to check that with special equipment please say so, as i'm out of ideas anyway, as you 'll see below.

I went to the bike again with re-cleaned carbs, a multimeter and a fully charged battery. The coils are in specs; the old one (not the aftermarket one), that on the cylinder that doesn't work, gives primary resistance 5.9 Ohms when the specs are 3-6. The aftermarket one gives 5.1 Ohms. And as for the secondary they are again different but both in specs and not at the limit this time. The pulse generator coils are in specs too.. Any ideas? Perhaps I should stop blaming the coils?

The thing is that i can't get the engine running (if i could i would drive it  to my place on half cylinder and just let it rot in my yard and cool down. But now it's in the middle of nowhere). I totally discharged the battery spinning the crank and played with throttle and choke the same time and it was only after the battery was almost out that i could get the engine turn a few times - one cylindered most probably. But it couldn't keep running and it stopped the next moment. Till the battery died again.

I'm getting mad thinking that unless i find a solution at least to start it, i'm going to have to pay 100euros for towing a bike that worths 300... Please any ideas welcome...  

Quote from: gsdox on November 11, 2010, 11:10:15 AM
no. (since i do not have a cover for the pulse generator coils) i crank the engine using a wrench. And it takes a proper amount of pressure to do so, so i think there is compression. Of course I can be wrong. If you think that I should try to check that with special equipment please say so, as i'm out of ideas anyway, as you 'll see below.

I went to the bike again with re-cleaned carbs, a multimeter and a fully charged battery. The coils are in specs; the old one (not the aftermarket one), that on the cylinder that doesn't work, gives primary resistance 5.9 Ohms when the specs are 3-6. The aftermarket one gives 5.1 Ohms. And as for the secondary they are again different but both in specs and not at the limit this time. The pulse generator coils are in specs too.. Any ideas? Perhaps I should stop blaming the coils?

The thing is that i can't get the engine running (if i could i would drive it  to my place on half cylinder and just let it rot in my yard and cool down. But now it's in the middle of nowhere). I totally discharged the battery spinning the crank and played with throttle and choke the same time and it was only after the battery was almost out that i could get the engine turn a few times - one cylindered most probably. But it couldn't keep running and it stopped the next moment. Till the battery died again.

I'm getting mad thinking that unless i find a solution at least to start it, i'm going to have to pay 100euros for towing a bike that worths 300... Please any ideas welcome...  

Another way is to plug the spark plug hole with a rag or even your finger (carefully) while cranking, should feel a good amount of pressure if engine compression good.

Since you said you see good spark for your spark test, and you possibly have adequate compression, the engine should fire with fuel present in the cylinders.

I would try a small amount of fuel squirted into the plug holes ( like a teaspoon each side), re-install the plugs and crank. Should fire at least briefly.

If it fires then that would indicate adequate spark to at least crank it, and that possibly you're not getting fuel to the cylinders otherwise.

If it doesn't fire, then I would think ignition problems.

(btw, how do the plugs look after your many failed attempts to crank ?     Wet or dry ?)

i didn't take them out this time to see, but recalling form the last time  (other thread) that i had the same problem, the spark plugs looked wet.

I will do as you say and check if the engine starts with fuel from plug holes... Anything else to notice?

Quote from: gsdox on November 11, 2010, 04:48:52 PM
i didn't take them out this time to see, but recalling form the last time  (other thread) that i had the same problem, the spark plugs looked wet.

I will do as you say and check if the engine starts with fuel from plug holes... Anything else to notice?

Wet plugs are not likely to fire - maybe because of carb fault flooding the motor, or maybe because of ignition fault, you just keep cranking adding more fuel which doesn't get burned off = wet plugs. 

Or if wet with oil then probably  a worn out engine.