Maintenance & Technical > KX500 Original
Spark Plugs
Hogwylde:
A hotter or colder plug has nothing to do with how "hot" the spark is. That is a function of your ignition system only.
Sparkplugs have the nose of the center electrode sticking out into the combustion chamber. How long this center electrode (and center insulator) are in relation to the outer shell determines how fast (or slow) it transfers the heat to the cylinder head. With a long path for the heat to flow to the heat (hotter plug) it takes longer for the heat to transfer and the center electrode tends to run at a higher temperature. With a short transfer path for the heat to the head (colder plug), the heat flows to the head quicker and runs cooler.
Now then....how do you know if you need a hotter or colder plug? It's a matter of reading your plugs and a function of what kind of riding you do. Sustained high speed riding puts LOTS of heat into your combustion chamber. This MAY necessitate a cooler plug to avoid overheating the electrode and causing pre-ignition. Running 1st, 2nd gears lugging thru woods and hardly ever getting on the pipe MAY necessitate a hotter plug to keep the electrode temp up high enough to burn off deposits and keep from fouling.
This is a very simplified explination. Go to most major spark plug manufactures and you can get detailed drawings and explanations about spark plug heat ranges.
Sharc:
Thanks Hogwylde. Great info. I found this at NGK.com:
The term "spark plug heat range" refers to the speed with which the plug can transfer heat from the combustion chamber to the engine head. Whether the plug is to be installed in a boat, lawnmower, or racecar, it has been found the optimum combustion chamber temperature for gasoline engines is between 500?C?850?C. When it is within that range it is cool enough to avoid pre-ignition and plug tip overheating (which can cause engine damage), while still hot enough to burn off combustion deposits which cause fouling.
The spark plug can help maintain the optimum combustion chamber temperature. The primary method used to do this is by altering the internal length of the core nose, in addition, the alloy compositions in the electrodes can be changed. This means you may not be able to visually tell a difference between heat ranges. When a spark plug is referred to as a ?cold plug?, it is one that transfers heat rapidly from the firing tip into the engine head, which keeps the firing tip cooler. A ?hot plug? has a much slower rate of heat transfer, which keeps the firing tip hotter.
In identical spark plug types, the difference from one full heat range to the next is the ability to remove 70?C to 100?C from the combustion chamber. The heat range numbers used by spark plug manufacturers are not universal, by that we mean, a 10 heat range in Champion is not the same as a 10 heat range in NGK nor the same in Autolite. Some manufacturers numbering systems are opposite the other, for domestic manufacturers (Champion, Autolite, Splitfire), the higher the number, the hotter the plug. For Japanese manufacturers (NGK, Denso), the higher the number, the colder the plug. When making spark plug heat range changes, it is better to err on the side of too cold a plug. The worst thing that can happen from too cold a plug is a fouled spark plug, too hot a spark plug can cause severe engine damage
Also this about their Iridium spark plugs BR8EIX:
NGK iridium plugs represent the ultimate evolution of spark plug technology and performance. The iridium center electrode is both stronger and harder than platinum. This allows NGK engineers to design an ultra-fine (0.6mm) center electrode reducing the voltage requirement for spark. This allows for a brighter, stronger spark from your existing ignition system. The ground electrode has a tapered cut at the firing end which reduces quenching for better flame core growth and increased ignitability. The combination of fine wire center electrode and tapered cut ground will increase performance, improve acceleration, and fuel efficiency.
Too much info, but interesting.
Sharc :lol:
Rick:
I tested the BR8EIX in the same evironmental conditions (temperature, terrain, fuel, ratio, etc) and motor tuning as the BR8EVX, and found the Iridium more prone to fouling. (Not sure why, as I am just a dumb accountant.) As a result, I stayed with the BR8EVX plug in my bike, as I really did not want to start over and tuning for a different plug.
Just my $.02.
Rick
Paul:
Alan scanned this info sheet in from NGK and was nice enough to post in the Gallery
http://www.pitbull-racing.com/modules.php?set_albumName=album02&id=NGK_Guide&op=modload&name=gallery&file=index&include=view_photo.php
teamgreen500:
B9EVX is what The guys at Kawi put in my bikes for the Best in the Desert series. Actually, I've never had one fail on my trail bikes for that matter.
I've seen some plugs from NGK that just read E-9 or E-10 also used. The bikes don't seem to run any different.
Appaerantly the "R" plugs aren't a neccessity OR our ignitions aren't fragile like, oh, I don't know...maybe...HONDA's!
My motors are Pro-Circuit Top-end/split and I run P/C "MX500" and FMF "Fatty" pipes with stock silencers and/or bolt-on/add-on sparkys (motor doesn't seem to notice 'em).
I run Maxima "SuperM" @ 40:1 with "76" 110 and "76" pump premium 50:50 (Trail bikes...which are really just retired race bikes). At the races I run whatever the Kawi guys are runnin'.
I've NEVER fouled a plug, even when I'm puttin' all day with kids on 50's and 110's and all that goo is dripin' outta my KIPS and my pipe/silencer joint.
I'll find out what my jetting is...I really don't know...but it's spot on for out here in the West. I know it's a 39 w/ some kind of different slide and needle.
Well, that's my $.02...
Manny
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