Spark plug "flameout".

[webbcraft2150]

I have had this issue for years. Hasn't really caused any major problems but it has finally brought up the question, why?. Fired up the rig sunday and knew instantly I was running on three. Hand check of header pipes showed #3 not fireing. I pull the plug cap off about an inch and it bursts to life. It would stay firing as long as I held the cap off the plug, push the cap back on and it would quit fireing. Quick change of the plug and everythings good to go. This issue seems to be exclusive to NGK plugs. They have always done this regardless of the make of bike. Had the "problem" with my 1100 Kawasaki, all of my 2-stroke dirt bikes and even the snortin Norton. Inspection of the plug shows nothing out of the norm. Plugs usually are a few months old or have less than 2k on them. I usually run Bosch plugs in the 11 and they have yet to "flame out". I know, the easiest answer is just don't use NGK plugs, which I usually try to avoid. Just curious why the flame out.

[GNEPIG]

.. i dont think it is called flame out, it sounds more like fouling.

..I only use the NGKs in all of my bikes, even the old Norton.
how a bike reacts to different brand plugs varies: by the heat range of the plugs chosen, the state of tune the bike is in[does the motor burn/use oil, are the carbs jetted correctly, is the air filter clean and so on], by how long the choke is used on start up, by how far the bike is riden[if you live within 5 miles from work, the bike is not getting warmed up enough to keep the plugs clean].. i could keep going but it will only p!ss you off more, so if other brand plugs is what it takes to keep the boat afloat, then i would use them too.
..BTW, what year/ model Norton do you own?

[DiverRay]

I have found that some fuels use additives that can build up and "short out" the spark plugs. I run NGK's, and have no problems with them. If you use Shell Gasoline, that could be part of the "short" problem. I've seen a LOT of carbon buildup with Shell.
just my $0.02
The build up is usually between the tip and the body of the plug, across the porcaline (sp?).
Ray

[prometheus578]

"ooh, ooh... I know this one!"

Yeah, or at least I used to. (it's hell to get old)

I pull the plug cap off about an inch and it bursts to life

Have seen this many times. Now...if I can only 'member why!
Spark jumps the gap and fires the mixture. A strong spark fires the mixture better than a weak spark. A low voltage/weak spark may not jump the gap. A strong spark jumps a gap, or jumps a gap better than a weak spark, etc.
Your plug is producing a weak spark for some reason. Could be electrical in nature, or caused by variences in the fuel/air mixture or situation in the combustion chamber pressures, etc.
(Plugs that you can see spark when held outside against the head may not actually spark when screwed back into the head due to these differences.
Anyway... The closer the plug gap, the easier it is for a spark to jump across. This means that a weaker spark can bridge this gap. A weak spark does not properly fire the mixture.
By holding the plug cap away from the plug tip... you have made a secondary gap that the spark must cross first. This requires a higher voltage for it to be bridged by a spark. This higher voltage spark, once 'that' gap is jumped, travels to the plug gap, and results in a higher voltage spark at that gap, too. Hence a hotter spark and better firing.
Now.... what I can't seem to recall is what the common cause of the weakened spark is. Bad spark plug, Plug cap, bad wires, failing coils, etc.
Personally, I would continue to run the NGK's.

For an interesting read, try the article "Spark plug" in Wikipedia.
http://en.wikipedia.org/wiki/Spark_plug

[prometheus578]

I've seen a LOT of carbon buildup with Shell.

Sorry, Ray... shells are built up with calcium carbonate. Any marine biologist could tell you that.
Hhmmm... And you call yourself a Diver!

(What... oh, I see. Wrong topic, again. Sorry)

[webbcraft2150]

Whats weird is that the plugs do not appear to be fouled. The last plug that "flamed out" was a light brown with no deposits. Like I mentioned, been going on for years and just wondered what could cause it. Its a good thing my DT's/RT's and MX'ers of yore had 2 plugs.

As for the Snortin Norton, it was a '71 Combat Commando with a wealth of Dunstall go fast parts. Meet a untimely death when I lost a return line to the oil tank and siezed a motor. In retrospect, I should have fixed it but the Norton dealer had just become a Laverda dealer and made me a hot smokin deal on a shiney new 750sf. It wasn't near as cool (or fast) as the Norton. I soon moved up to the 1000 Laverdas with the last one being a Jota series.

[trbig]

After reading Pro's post, have you ever tried just gapping the plugs a little wider and see if it makes a hotter spark and makes it run? If you have to hold it an inch above to get it to spark, you may not be able to gap it enough to do this... but maybe worth a shot?
Several years ago in the Nevada desert, I had a YZ250 and my buddy had a YZ460... both same years. If he ever fouled a plug, he couldn't ever re-use it. I could hit his plugs with a wire brush, and they would work just fine in mine. I also have always used strictly NGK. Don't know if this is anything to do with this thread, but just felt like mentioning that... lol.

Tod

[webbcraft2150]

I always gap em to the high side of the spec. Your explanation makes sence, what dosen't is its always a NGK that does it. Have not had the problem with Bosch Platniums, yet, but then again my 31 year old Dodge truck runs like crap on Champions, and thats the brand it came with from the factory. Go figure! (This could start more feedback than an oil or tire thread)
I still have the offending NGK plug, I am gonna widen the gap a little and plug it back in hole and see what happens.

[Ken Talbot]

Try this with a fresh, brand-new-out-of-the-box plug and see if it sparks. Never mind that the existing plug looks clean, just try with one you absolutely know to be clean. Looks might be deceiving...

[prometheus578]

"Plug and Play"

Looks might be deceiving...

and often are. I have run into bad plugs straight from the box. Could have been loopy on the inside... could have had a cracked insulator that I couldn't see, whatever.
If a bike comes in that's running badly and the plugs don't look too bad, I replace them anyway. Nothing's worse than spending several hours cleaning carbs, checking timing and myriad other tasks, just to find out it was a bad sparkplug all along.

[Douglas Money]

I had the same problem on an older Honda that I use to run. Same thing with NGK. I still used them, but had to change when they did this. A friend also had the same problem. The plug actually shorts to ground just slightly. It will ground a weak spark, but the carbon trace cannot handle higher voltage. When you move the wire away you cause the coil voltage to increase to the point that the gap will now fire. In time the trace will get to the point that it can handle the full voltage and the plug ceases to fire completely. I never found a way around changing plugs. Good Luck.

[DiverRay]

prometheus,
If you try to smoke the shell, it will turn to carbon.... Oh, wait, that was the 60's....
Ray

[trbig]

Ray, it's still true today!

Tod

[jeffe]

I'm not a mechanic or anything, but why not try not using the NGK plugs.

[Burly1]

I had a lot of carb issues over the years, and I love NGK plugs. The one thing I did find, was that once I fouled one of them, they were never right again. I don't know if the raw fuel wrecked them inside of the insulator or what exactly happened, but they were junk once fouled. I still use 'em though, because they work well. I tried others, but they're just not as good. Burl