Misfireing at low idle

[Anonymous]

I have a GS550 1985 it is Misfireing at low idle I need direction on how to troubl shoot this. I put new plugs still misfireing.

[Jethro]

We need more information. Is the bike stock? Did this just start happening? Has the bike been running fine recently? Any other symptoms?

[Anonymous]

Thanks here is more info

Long story but I bought the bike from a friend the battery was dead and the new one would not keep a charge this turn out to be the reg/rec. However, the Misfiring has always been happing when I am starting out from a stop or only while idling. I think bike should have allot more power to it I have to double clutch from a dead stop. The bike is stock. 8O

[scotty]

Read your plugs and do you have a vacume operated petcock??

[Anonymous]

Thanks scotty

I will look to see what kind of vacume hookup I do not recall. When you say read your plug what do you mean. I am a little new at this and I do not have allot of money to put in to the bike. It has been years and I finely talk the wife into letting me get this one.

[Anonymous]

The right side is the side misfiring.

[KEITH KRAUSE]

Try the basics.
Be sure the plug is gapped correctly.
Check the connections at the plug cap, and the plug lead where it connects to the coil. Any lead cracks? The spark should be similar to the other(s).
Try adjusting the mixture screw to the same turns out as the other mixture screw(s). It may be way off. Be careful and use a good fitting tool because the mixture screws can be stiff.
The air filter is clean?

[Anonymous]

The gap is the same on all plugs. I have adjusted all the mixture screws to 1 ? out and I still have the same results I removed the air cleaner no luck it misfires a bought every 2 to 3 min while sitting. I think it might be the coil. I saw one at jcwhitney part number ZX013085X for 29.98 but it did not look like the wires where connected and I think the one on my bike are built into the coil. Will this one work?

[KEITH KRAUSE]

You have to know what ohm resistance your stock coils are. (ex: 3 ohm.)
When you say "the right side", this would mean cylinder 3 and/or 4. If your # 1 and 2 seem fine, then it's not a coil issue. One coil feeds 1 and 4, and the other coil feeds 2 and 3. You would have to have the same problem on 1 and 4, or 2 and 3.
You need to find out which "right side" cylinder is not firing right. For safety, mark #1 and 4 caps/leads with electrical tape. ONLY SWAP LEADS THAT BOTH HAVE TAPE OR BOTH HAVE NO TAPE.
The bike should run on 3 cylinders, especially if you turn up the idle a little. So pull either 3 or 4 cap off until the missfiring stops.
After you know which cylinder/plug lead it is, then swap that lead with the other lead from the same coil, to see if the missfiring moves with the swap.
(EX: if #3 is missfiring, then swap its lead with #2.
If #4 is the one missfiring, then swap it with #1.)
To see if the missfiring is moving because of a bad coil lead, now lift the lead that was involved with the missfiring cylinder. If the missfiring stops, then it's a bad lead. If the missfiring continues, then the missfiring cause is the carb or cylinder that was missfiring when you started this check. We can go from there.
PS: just another thought, if you have to use the little aluminum screw on connector at the end of the spark plug, make sure you tightened them with pliers.

[Anonymous]

Thanks Keith I will give this a try.

[jhw84]

I am having a similar problem, and a young mechanic told me to check the points. I have yet to do this, but after spending 5 hours on the fuel system, Im almost sure its electrical.

[Anonymous]

I believe it is electronic ignition so there would be no points?

[KEITH KRAUSE]

I believe it is electronic ignition so there would be no points?

Right. No points.

[bradleymaynar]

Just out of curiosity, have you rebuilt the carbs? When I picked up my bike from it's previous owner, it ran real rough. It would just about die when idling. Seemed like it was running atleast one cylinder short. During the carb rebuild I discovered that one carb was "dead". Meaning that the float needle had frozen so that that carb was getting no fuel. Since the rebuild it's ran great, I just need to sync the carbs now.

Brad tt

[jhw84]

What are those doodads under the right engine cover, in the round part that sticks out? Signal generator contact something or others?

Or are they on my bike and not his b/c mines older?