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Still sporadic spark in one cylinder

  • Thread starter Thread starter 1979GS550stl
  • Start date Start date
1

1979GS550stl

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I've been getting sporadic spark to the first cylinder. I've done some amateur diagnostics, and it's not the spark plug, cap, wire or coil.

If it's just one cylinder, what is the next logical step in the diagnostic process? The manual says checking the points, springs, etc. But wouldn't other cylinders be effected if something was wrong there?

Appreciate any and all help. Without the resources I've found on this site, my bike probably would've been dead a long time ago.
 
1979GS550stl said:
I've been getting sporadic spark to the first cylinder. I've done some amateur diagnostics, and it's not the spark plug, cap, wire or coil.

If it's just one cylinder, what is the next logical step in the diagnostic process? The manual says checking the points, springs, etc. But wouldn't other cylinders be effected if something was wrong there?

Appreciate any and all help. Without the resources I've found on this site, my bike probably would've been dead a long time ago.
Click to expand...

How do you know the spark is sporadic? How does the engine run? Does it run good at start up and then start to miss? What are the symptoms?

The first thing to do is probably just switch wires and see if the problem moves to another cylinder. Then switch coils.

I had this problem for a time. Clean, correctly adjusted points, and proper gap are important. Its wierd to just have one cylinder messing up because the coil is firing to both cylinders every time on every stroke, but it happens.

It could be just be a weak spark. Your battery need to be in tip top shape. Also check the voltage from the battery to the orange wires that go to the coils. You shouldn't have much more than about a one volt drop. Check all your grounds and your ignition switch for good connections.

Here's another thing. Sometimes if your plugs have been fouled, even after cleaning they don't fire properly. Put in new plugs and see what happens.

Good luck.
 
Last edited:
Mark, thanks.

The engine runs quite well considering. During decelleration, though, it "pops" and gurgles a bit. And the head pipe from that cylinder never gets hot, even after a good ride.

I removed the cap from the plug and plugged it into a spark tester. When grounded to the engine, it had what I would call weak and VERY sporadic spark. But none of the other cylinders seem to be effected (?????).

First, I swapped caps. Then I cut off the end of the wire and put the cap back on (as someone here suggested). After that, I decided to try to swap wires, but apparently the wires are meant to come out of my coils, and I broke one off in there.

I got a salvage, bench-tested (supposedly) coil at a local shop. I wanted a quick fix to see if it was the problem (and to ride on my day off from work!) I put it on and had the same problem.

Next, I'll try swapping the coils just to make sure the "new" coil/wire are indeed good.

I'm just perplexed why it would only be impacting ONE cylinder. Hopefully it will end up being a bunk coil I got, and a nice new pair of dyna coils will solve all my woes. The battery is good, grounds, connections etc. all seem fine. I haven't gotten into the points (stripped screw from PO), but that's where I'll go next if it's definitely not the coil or a wire.

Anybody try the whole Dyna ignition system? Just curious. Not having to deal with points again would be nice. Hate to drop so much cash, though.

Thanks for listening. I'll keep y'all posted.
 
1979GS550stl said:
After that, I decided to try to swap wires, but apparently the wires are meant to come out of my coils, and I broke one off in there.
Click to expand...

Actually that's what I did finally, went to the Dyna S. Most people end up doing that I think, its a way better way to go.

Anyway your wires are NOT meant to come out of your coils (maybe thats a typo). How did you fix that?
 
Have you thought about it being in the carb on that cylinder.Mine did that after I cleaned the carbs and found out after taking it back apart that there was something stuck on the end of the flow tube the pulls fuel up from the bowl to the carb.Just a thought.Mine was doing exactly what your describing.\if you have points it could also be a condenser.
 
mark said:
Actually that's what I did finally, went to the Dyna S. Most people end up doing that I think, its a way better way to go.

Anyway your wires are NOT meant to come out of your coils (maybe thats a typo). How did you fix that?
Click to expand...

Yeah, that was a typo. I broke off a wire trying to get it off of the coil, hence the secondhand coil as a temporary solution.

I swapped coils. Turns out, that secondhand coil is bad (from reading posts here I should have known better than to gamble on a used one). Looks like I'll be ordering the dynas, which is what I should have done in the first place.

HOWEVER, I still have a cold head pipe on 1 - so I have another problem, too. Tconroy, I'll be checking fuel flow again because I DID have the carbs off recently to replace the float needle valves/seats because 2 was leaking, but I THINK I did everything right.

After that, I guess it would be time for a compression test. I don't even want to think about that right now.

Thanks again for all the advice. Hopefully I'll have her back on the road soon.
 
Me, too!

Me, too!

I'm gonna 'keep my eye' on this thread because I have exactly the same problem with #4.:cry:
 
Yeah, I ordered ignition, coils, red wires, and a hex-head bolt set from Z1 yesterday based on recommendations from all of you in other threads.

Still perplexed why only ONE cylinder is effected. And its NOT a bunk secondhand coil as I'd previously thought. Battery, wires, caps, plugs, etc. all seem to be fine. Connections and grounds all look clean.

I have the Nipon Denso ignition, so the only other thing I thought it could be was points, condensers, etc. But again, wouldn't TWO cylinders be experiencing sporadic spark? I'm not entirely sure what to look for with the points, condensers, etc. - and I'd rather shell out the bucks and upgrade now rather than hassle with those again.

Going to get feeler gauges tonight to check the valve clearances. Also going to go ahead and order some new tires. Still shopping best sources for those.

It's funny how in a few short days you can spend twice as much money on a bike as you bought it for nine years ago - all for the undying devotion to a machine! :)
 
Up and running again!

Up and running again!

Well, I checked the valves, got the Dyna S on and assembled everything. All four cylinders are running nice and strong! She runs like an absolute dream\\:D/ ! I mean, wow, what a difference.

I can't begin to tell all of you how grateful I am for the advice. Still waiting on a few parts (clutch springs, fork seals, a few gaskets, etc.), but I couldn't wait to see how she ran.

I've changed my avatar to a pic of the bike. Think I'll have to change my screen name as well, because according to suzukicycles.org site, it would appear my machine is actually a 78, even though my title says 79????
 
Just amazing...

Just amazing...

I truely believe the GS series is one of the the few if not the ONLY Japanese bike that deserves its own place on the Web! I have had my GS-1100Gz since new and every time I visit any brand of the dealer, I appreciate my GS even more. I "thought" I was in the market for a 200cc off/on road bike until I saw the $4,000 price tag! Gaaadddss!!

I never ride my 1100 anywhere, but I just hate the thought of not having it. I might trade it for a couple of 73-75 Honda XL-350 singles. That way the wife and I could ride around on the backroads...

Bruce
 
Glad you got it ironed out.
My title says 81 when in fact it is an 80.
 
Highcountry2000 said:
I truely believe the GS series is one of the the few if not the ONLY Japanese bike that deserves its own place on the Web! I have had my GS-1100Gz since new and every time I visit any brand of the dealer, I appreciate my GS even more. I "thought" I was in the market for a 200cc off/on road bike until I saw the $4,000 price tag! Gaaadddss!!

I never ride my 1100 anywhere, but I just hate the thought of not having it. I might trade it for a couple of 73-75 Honda XL-350 singles. That way the wife and I could ride around on the backroads...

Bruce
Click to expand...
WHAT ARE YOU SAYING MAN!!!!!!!!!! Keep the GS and get her one too!!!!
 
Seems a waste...

Seems a waste...

I think I may have put 1,000 miles on my 1100 in the last 5 years. When I get it clean, I hesitate to take it out and get it all dirty again. Back in the 70's, I had a couple of Honda XL-350 singles and we rode those sucker almost every day. Just basic maintenance and off we went. I live in an area with miles of one lane backroads in every direction and it is relaxing to go out and chug along...

Bruce
 
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