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Spark Plugs?


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:thinking:What kinda plug is best? What size gap? Can I change the peformance by changing the kind or gap of a plug?

Most people just throw whatever fits in there, right out of the box. I know that in the competative auto or watersports industries that is a big issue. The plug must face the exhaust, be gap'd right, blah, blah, blah.

Moto's???

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most people think that for a PROPERLY jetted two stroke that a B8ES is good enuf and why waste money on anything special. I personally do not feel this way. I like to ride my bikes jetted right for the leanest conditions I will ride, and then just ride it that way for the other riding I do too. Such as a bike jetted for 2000' and then ride it up 10K' with no jetting changes. So, with this in mind I like to use the more expensive plugs like the B8EV, and now the Iridium tips. I have never fouled a plug with a higher grade plug, even with the elev changes I do. But maybe thats cuz the bike is jetted right most of the time and I know when I really do need to change it.

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Mike is right having the right jetting makes all the difference not just elevation but temprature also I have gotten caught with the cold weather needle in warmer temps and the bike gets sluggish on the bottom. I have played with different plugs but never noticed any gains I am back to the plug listed in the manual.

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after having the head milled to proper specs myself, I think having a bike that runs properly has as much to do about proper head set up as the jetting does. I don't worry about spark plugs. There is a good bit of impovement in the tolerances in the head and cyl.

...maybe I should, but I don't.

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the KTM 2st for instance dont always have the best dimensions and shape inside the head to promote the best flame or burn of the fuel. So there are a few guys who seem to know what they are doing in correcting this and the bike then is easier to jet, makes more power and burns cleaner , etc. Not milling where all you do is raise the comp of the motor, but an actual re-shape of the bowl of the head. "Squish" is another aspect of this.

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The combustion chamber is where the power is made. Stock tolerances are somewhat sloppy to allow for varying qualities of gas and differing elevations found throughout the world.

Quote from RB Designs:

Head milling is more than just raising compression, it's a way to help your engine breath, burn more of the fuel mixture and help cool. All of this will give you better snap, rev and torque with great reliability.

The squish band is a very important part of head mods and this is where I spend a lot of time. Just getting the proper squish band without going overboard on the compression will give great results. "HORSE POWER" and "RELIABILITY".

The squish band is the area at the outer edge of the combustion chamber. This is my freshly milled head from MikeS on ktmtalk with increased dome height for better cooling and decreased squish to 1mm.

MikeS_cut_head_(200).jpg

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