Suzuki GS1100L ignition problem

[Anonymous]

I have a 1982 GS1100L and it run extremely well for about twenty miles and then it starts to miss and it begins to run on 3 cylinders. Number 4 cylinder is always the culprit. As soon as this happens, I immediately change the spark plug on number 4 cylinder and the bike straigtens out immediately. I thought it might be the coil, but number 1 cylinder always runs fine. The plug is always black and sooty when this happens. I suspect that the problem is in the number 4 plug wire. I have replaced 3 new plugs and this happens every time. Any suggestions would be appreciated. I am leaning towards a new coil as they come with new plug wires.

[Anonymous]

Could be oil fouling.

Could be oil fouling. If the rings on that cylinder are to blame they would couse the plug to get black like that and foul.

[Anonymous]

Although you stated immediately, How long between fouling #4 and replace spark plug? if the bike cool down by the time you replaced also cool down the coil and here the cycle goes again....most likely coil; wire either work or don't

[SqDancerLynn1]

swap the # 1 & 4 Plug wires and retest

[Anonymous]

I sure hope it is not oil fouling. If so, I guess a compression check of # 4 would be in order. Wouldn't there be some evidence of blue smoke if that was true. The time between fouling and the replacement of #4 plug is about 2 minutes. I like SqDancerLynn1's theory of swapping plug wires but I just won an auction for a set of coils, so I think I will wait till they are delivered and replace the old one. I will post with the results. Thank you for all replies.

[SqDancerLynn1]

Plugs 1 & 4 are fired by the same coil so it would be just a mater of pluging the plug wires into the other plug

[Anonymous]

Had same problem.

I had the same problem just this week on my 82 Gs-1100 Gl and I found it to actually be the fuels lines of all things. If your fuel line is too long then because the placement of the petcock being in such an odd spot it creates an air bubble like the trap under your sink that prevents enough fuel getting through. Wierd but true. As for why it only affected the one cylinder since the t sits between the middle carb's is still a mystery too me. The fuel line should literaly have to be removed and put back on when the tank is sitting on the bike. That's how you know it's short enough. Another thing to check is the resistance of the wire heads they should be i believe between 7-9 ohms although I am not completely sure, check all of them. If your resistance has gotten too high it will make for a cold spark which would produce a black carbon deposit on your plug. If you have a black wet deposit then you have a problem most likely with the piston rings. Sounds However like the plug wire cap if you haven't worked on fuel lines recently.

[Anonymous]

I had a similar problem last year, after re-checking the carbs three times Not counting the problems I created, like dropping a carb on the concrete and having to relpace it) I finally gave up and took it to the dealer. They synched the carbs and did what I was told was a "throttle drop" test, I think that's what they called it. I didn't think to ask what the heck that was, sorry. Somebody more tech savvy might be able to explain it.

[Anonymous]

I decided to swap #1 with #4. After I removed #4, I examined the boot end of the plug wire. It was very loose and a slight tug separated the boot from the wire. I threaded it back on to the wire snugly and then proceeded to swap #1 and #4 wires. I took the bike for a 30 mile ride in 95 degree heat. There was no miss and the bike ran perfectly. These miles were all highway. I then proceeded to take a 3 mile ride in the stop and go traffic in the city. Again the bike ran perfectly. I am not totally convinced that my problem is solved, however I am very pleased at this point. I guess I will not be totally sure that I have fixed the problem until I have logged many more miles. Thanks again to all who replied.

[shaftzuki]

I think I'd go buy some new plug boots, only $3.00 bucks apiece (or so), and replace all of them - one more item you can check off of the "never ending list" 8)

[Anonymous]

swap

swap the one and four wires and see if it does it to the one cylinder if it does your coil is not bad but weak and need replace do the simple stuff before major stuff