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Misfireing at low idle

  • Thread starter Thread starter Anonymous
  • Start date Start date
A

Anonymous

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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. :(
 
We need more information. Is the bike stock? Did this just start happening? Has the bike been running fine recently? Any other symptoms?
 
Thanks here is more info

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
 
Thanks scotty

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.
 
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?
 
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?
 
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.
 
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.
 
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
 
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?
 
Keith I swapped my spark plug wires around and this still did not help. But I guess it did show me that I do not need a coil. After the swap it still Missed fired from the right side it also misfires when riding and down shifting at very low speed like coming to a stop but then taking off if that info helps. Brad I have not rebuilt the carbs and I have never attempted to rebuild a carb before.
 
No worries. I'd never done it before, either. I followed the carb series on the mainpage. It's easy enough. Otherwise you'd be looking at a minimum of $400 to have a shop do it. Plus you've stumbled upon the best library of knowledge on the web that caters to your bike specifically. :D

Brad tt
 
Ok, went back to the house and checked my manual (duh!), and it says that Suzi switched to electronic ignition starting in '79.

However, when I got to the house, I told my dad what I was about to do, and he said start with the simplest thing first. So, I checked out my plugs again, and found that the stock plug cap was loose inside. I tried tightening it up, but it was spent. I managed to rig up something temporary, and it works great. Looks like I will be visiting the dealership tomorrow, too.
 
ccruit said:
Keith I swapped my spark plug wires around and this still did not help. But I guess it did show me that I do not need a coil. After the swap it still Missed fired from the right side it also misfires when riding and down shifting at very low speed like coming to a stop but then taking off if that info helps.
Click to expand...
OK. If you tested as I said and the problem didn't transfer with the lead, we know it's a carb or cylinder problem. My test would also tell you which carb or cylinder is causing the problem.
Most likely it's the carb. You say the only thing you've checked is the mixture screw adjustments.
I think the carbs need to be cleaned and inspected. Check all o-rings/diaphragms and adjust float levels. Replace manifold o-rings if you have them. Synch the carbs too.
If you're not happy about taking the carbs apart, you may try to synch the carbs and you may be lucky.
 
Ok Keith I was afraid you where going to say that. I have never rebuilt a carb but I will give it a shot. Does any one have a book or drawing I can use?
 
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