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My 2003 GL1800 has just shy of 35000 miles. I did the second spark plug change out for new plugs at 30,000 and just changed them again (with new) at 34,800. I always use the standard NGK BKR6E-11 plug. My memory of the past times was that the plugs looked exactly as expected, first at 14000 and the next ones at 30000. The bike has gotten a little weak and seemed tired. I put new plugs in after only 4800 miles, and it is like new again. I have checked the valve clearance at 30000. I am a little overdue for my second air filter change. Question is - these plugs had a lot of black (dry) carbon deposits, unlike the last two changeouts. I recently traveled to New Brunswick and Nova Scotia and felt some gas fill-ups were not up to our quality, and I changed over to a higher octane for the remainder of that trip. Would higer octane cause carbon builup? Would poor gas cause carbon builup? I know a dirty air filter could make the mixture a bit rich and cause carbon build up. Any other thoughts on the cause?
 

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IMO, I've always thought higher octane gas with out the higher compression it is formulated for will leave carbon deposits. A sufficient cylinder pressure is needed to get a complete burn of the airfuel mixture.

Bradford
 

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Sometimes if you start the bike cold, and just run it for a few seconds and don't let the plugs and head get up to full temperature, then the carbon won't get burned off. If you pull your plugs after just starting and shutting down a cold engine, they will have a thin coating of black on them. It is not something to worry about, as it will burn off once they get hot. The proper way to check plugs is to make sure the bike has been ridden at least 10 miles or more, shut it off and let it cool 4 to 6 hours (or even better, overnight) and then pull the plugs. (Never work on aluminum heads when they are still warm, let them fully cool)

If you have thicker deposits that appear caked on, then you probably have a rich running condition. Could be something restricting the air flow, or a messed up fuel pressure regulator, or possibly bad 02 sensors.
 

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Discussion Starter #4
carbon on plugs

1. I normally use regular gas, but, just in response to what appeared to be bad gas in NB (noticeable pinging), I switched to premium or middle grade for the balance of the trip and have returned to regular since I'm home.

2. re: Fred's answer. I don't usually do short runs (nor start and idle) except for an occsional local errand. Sounds like my mixture may be too rich. Possible air filter restriction (based on plugs' condition after 5000 miles) and having gone over recommended mileage on the current air filter. I think that would be my next attempt.

Thank you both for your responses.
Fred my email is [email protected]. If you could email me so I could send a picture of the plug to you, that would be appreciated.

Chip from Long Island
 

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how about some fuel injector cleaner like techron and run the piss out of it to burn some stuff out of there.
 
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