Best Spark Plug???

[gandgracing]

I'm sure this has been covered somewhere but thought I would stir it back up. To start things off I run a BR9EIX Iridium plug. All my other buddies think its a waste. But my buddy that has a ESR 350 tried one of my plugs and it ran like crap. We messed with the jetting and had no success. Switched back to a BR9ES with gap at .018 and ran like a beast. Was going to try his plug but ran out of time. What do you guys run??

[Aceman]

The usual BR8ES, seems to work fine for me.

I remember hearing something a while back about running a plug with a thin electrode. Supposedly, if you started running lean/having a meltdown, the plugs electrode will melt off first killing the ignition before you damage the cylinder and piston. I think I read that on Planet Sand, if somebody is interested in looking it up.

[beak7707]

I run the BR9EIX Iridium plug, but its only because Duncan told me I had to in my PC2000 cylinder. He told me I could run other plugs but they would foul like crazy, told me the iridium plug would last me a year.

[gandgracing]

Duncan also told me to run it. And I will have to agree that it does last a long time. I would be willing to run a different plug if I knew of one that performed better.

[beak7707]

I dont understand why Duncans motors have to use them. I have had a couple people from Duncan tell me it wouldnt run very long with a different plug. Haven't tried it yet to see if it would or not.

[wilkin250r]

I'm just going to copy and paste from another one of my posts on the same subject:


Originally posted by wilkin250r
Spark plugs are exposed to heat, fuel, and carbon, and are obviously designed to conduct electricity. As such, they need to be made of an electrically conductive, non-corrosive material.

Along with all the above, Iridium is very hard, which allows for the electrode to be very thin without it breaking, bending, or corroding away.

When something is charged with electricity, the charge will concentrate more in sharp areas, increasing the electric field around sharp corners or points. This means that spark plugs with very small, thin, or fine electrodes will require less voltage to fire. This increases firing efficiency, will ignite leaner fuel/air mixtures, and greatly reduces misfires.

Copper can be made that small, but it is much too soft, and corrodes away much too fast. Platinum is the next best choice, but Iridium is about 8 times harder than platinum. Generally, Iridium plugs will last much longer than a normal copper plug, because the Iridium is much harder and more corrosive resistant.

The problem with gapping them is because the electrode IS so small and so hard. With a normal spark plug, you wedge your gapping tool between the electrode and ground strap, and then pry it open. This won't work with Iridium. If you pry against an Iridium electrode, it is so hard and small it will dig into your gapping tool. (imagine trying to pry open a sewing machine with your thumb by prying on the needle. You won't pry it open, the needle will just stick into your thumb). Now, the electrode is buried inside your gapping tool, if you pull your gapping tool out, it usually breaks the electrode. You have to get a small set of pliers or specialty tool to bend the ground strap, and then check the gap, rather than pry it against the electrode.



Basically, this means that Iridium plugs will fire easier. This means they'll fire better under high compression, better resistance to fouling, and will last longer.

Like the post says, the problem is gapping. You can't gap them normally by prying against the electrode, you'll break it.

[gandgracing]

Real nice write up. What do you gap yours at? I have never gapped mine cause I think I saw something saying not to.

[wilkin250r]

The theory is that a larger spark has more energy, it's hotter. A hotter spark gives you a better start to the combustion process. However, it stands to reason that it requires more energy for a larger gap.

High compression makes things difficult. You have more molecules between the air gap that must get ionized before you can get spark. It requires much higher voltage for high compression. If the gap is too large, and the compression is too high, sometimes the stock 250r ignition doesn't have enough "umph" to get it to spark. This is why you often hear people gapping at 0.018" to cure the problem, because less gap requires less energy to spark.

As I said in the other post, Iridium plugs are supposed to fire better, because the smaller electrode creates a better electric field in the gap.


So, now that I've bored you to tears, I'll answer your question directly. I gap my plug somewhere between .023 and .025

[Iliketogofast]

I used an iridium plug once.

I was idling in the middle of the woods waiting for my buddies to catch up and all of a sudden it just revved to the moon. The tach memory says the highest recorded reading was 15k RPMs. I hit the killswitch immediately but nothing, so I pulled the cap off the plug. It kept on going. It ran at 15k for almost 30 seconds before I figured to just rip the carb off the boot.

What I figure is that the tip was so small that it glowed red hot and the engine just ran like a diesel would. That's why it wouldn't stop - once it got red hot, the heat produced by the RPMs just kept it that way. It would have went on until it blew up.

The motor lasted one more ride after that then the next time I rode it it blew up. I'll never get another one of those pieces of junk. Well I guess I can't really say their pieces of junk since all of you have had no problems, but I'll still never get another.

[MossboysRacing]

I run a BR8EG. It has a smaller electrode then the ES plug. I run it all the time and i get a full season of racing on it with out changing. Its also only like 3 bucks which is nice. Works well for me...

[rustyATV]

I run a B8ES, which omits the resistor. When I changed, it seemed to light off a little better.

[brokenmike]

I run a NGK B8ES in my R,zilla ,Cr80 and I have never had a problem. They are like $1.80 at pepboys

[ERBE]

BR9EIX Iridium or an 8 depending on your fuel and compression, they work, they last, least fouling plug I have ever used .

[rustyATV]

Originally posted by brokenmike
I run a NGK B8ES in my R,zilla ,Cr80 and I have never had a problem. They are like $1.80 at pepboys

Yeah, I like that you can get those just about anywhere.