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Discussion Starter · #1 ·
My GL650 has always run like a top, until today. I have got a miss on the left cylinder, popping, hesitating etc. The bike starts on just the right cylinder, and I can get the left side to fire by holding the spark plug cap slightly above the plug. As soon as I try to reattach the cap the cylinder goes dead again. Once the bike is warm and I get under way(on one cylinder) the missing settles down a bit, and seems to go away while accelerating. If riding at a steady speed the engine will spit, pop, hesitate and go back to running on one cylinder again. I pulled the plugs before leaving work tonight and the plugs look OK. Tomorrow I am going to try switching sides with the plugs, maybe just a plug going bad. Why does it fire OK when I hold a gap between the cap and plug? Anyone have any ideas?



I posted this just in case someone else has had or is having a similar problem. I will update when I get it running like a top again. This will not stand!
 

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This is not a unusual situation. Why the plug fires when the wire is held away and it has to both jump the gap to the plug and then fire the plug, is a mystery to me. I think it has something to do with the spark being intensified somehow by jumping the first gap. I have explored my theory that the resistors in the plug caps do a similar thing. Everyone says that they are only to stop radio inference, but how would they do that? At one time when radios were an option in autos, if you got a dealer installed radio,(back in the 50's and 60's), they also put capacitors on the distributor, generator, voltage regulator, and several other places to minimize interference. They didn't use any resistors, just caps.



I think that when everything is new and perfect, it may not make much difference. But as things start going downhill, we need all the help we can get.



I have Googled the resistor and the common reason is to cut interference, but there are some suggestions that maybe this is just being perpetuated by the Internet, and that they also provide other functions.
 

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Discussion Starter · #4 ·
I already did the brass rod mod a while ago. Caps test ok for continuity. I am thinking bad plug and will find out later today. My plugs have almost 30,000 miles on them (iridium's) and they don't owe me anything. I will swap them for diagnostic and go from there.. might even spring for a new set!



I will swap out the coils and modules it that order if the plugs aren't it. I have spare sets of those. Lets hope it doesn't come to that since the weather is going to be 60 and sunny today.
 

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How many miles on your bike? By lifting the cap from the plug you delay the spark by a fraction of time. Resistors can also restrict current flow. Depends on what you are doing with them. The resistor plug slows down the current to lessen the over arking. Plugs generaly last longer.

I could be right. Just my thoughts.
 

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Here's another thought. I recently bought a used CDI. Cleaned its contacts, etc. Hooked it up to a known running bike(mine)and the bike only ran on the right cylinder, i.e. no spark to the left one w/the bad CDI. Good Luck.
 

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I had a very similar problem this summer with my GL650. It was running good when I parked it and shut it off. Then when I went to restart after about 30 minutes it would only fire on the right side. Turned out that a new set of plugs fixed the problem.
 

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Discussion Starter · #8 ·
I had a very similar problem this summer with my GL650. It was running good when I parked it and shut it off. Then when I went to restart after about 30 minutes it would only fire on the right side. Turned out that a new set of plugs fixed the problem.


Yes! It was just a bad plug! ( I love it when things are easy to fix) I treated the old hoss with a brand new pair of Iridium's.



I think the plug had been getting worse for the last week or so till it just gave up, because the motor had been running rougher and is very smooth now, like it used to be.
 

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Yes! It was just a bad plug! ( I love it when things are easy to fix) I treated the old hoss with a brand new pair of Iridium's.



I think the plug had been getting worse for the last week or so till it just gave up, because the motor had been running rougher and is very smooth now, like it used to be.


GREAT!! It sure makes you smile all over your face when you've been worrying about about a megabuck repair job, no bike for a month, and then it turns out to be a cheap quick fix.
 
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