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KX 250f 04 JE 13.5:1 piston = Big problem

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Hey guys Check this out my JE 13.5:1 piston is actually tapping the plug and closing the gap to about .10 Inch only under hard acceleration. i regaped the plug and kicked the bike over sevral times and i didnt touch it. i can shine a light in the spark plug hole and see where it is hitting it what the hell is this all about. cosmtic gaskets like oem style and oem plug :applause:

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Check this out i looked on JE's catalog and they refrance their own gasket kit in stead of oem check it out www.jepistons.com/pdf/2006-moto3.pdf check it out on a hi comp piston for say a KX450F the gasket in OEM but for the KX25F hi comp it jists their gasket number ??? if this is the case it would have been nice for the to tell me in the instruction or some where.

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JE's response as follows. will shim the plug.

Victor,

Either use the surface discharge sparkplug or shim the plug with an additional spark plug washer to keep the piston from contacting the head at higher RPM's.

Thank you,

John Noonan

PowerSports Sales & Tech

www.jepistons.com

email jnoonan@jepistons.com

----- Original Message -----

From: Victor Paris

To: jemc@jepistons.com

Sent: Monday, March 05, 2007 7:37 AM

Subject: KX250F 2004 13.5:1 Comp Piston

Hello there I have a slight problem that I would like some input on. I bought your piston in a std. bore 13.5:1 comp for my kx250f 2004 your Part number 243642. The bike had roughly 10 Hrs on it all bearings in bottom end were good I got every thing back together bike idles good but under hard acceleration the piston is nicking the spark plug and closing the gap to about .10 inch I re gap to .30 inch and it dose it again I look down the plug hole in the head and can see where it is hitting the piston and I would like to talk to some one about this and get some clearance information. Please give me a call at the number below or reply with a number for me to call you.

Thank you,

Victor Paris

Senior Draftsman

Power Substations Inc

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I had the same problem with my 05. I bought it used and I had to regap the spark plug every time i rode it. I bought a colder plug and it stopped, Im pretty sure thats the prob. If that does not work than put another spark plug washer in it.

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I had the same problem with my 05. I bought it used and I had to regap the spark plug every time i rode it. I bought a colder plug and it stopped, Im pretty sure thats the prob. If that does not work than put another spark plug washer in it.

Sounds like a hookey fix to me... Adding a spark plug gasket....

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Why would that be a hookey fix. it will seal the same and have the same amount of torque only thing it will do is increase tdc clearance with the sparkplug..

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Because it is... For example... If you had an alcohol drag motor with 16:1 compression built, would they tell you to run a plug with 2 gaskets?... Ah, NO... The distance and heat of the plug is engineered at TDC, you cant just throw a plug in.. If a company is not going to look further into their product, why would you run it?

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Because it is... For example... If you had an alcohol drag motor with 16:1 compression built, would they tell you to run a plug with 2 gaskets?... Ah, NO... The distance and heat of the plug is engineered at TDC, you cant just throw a plug in.. If a company is not going to look further into their product, why would you run it?

wait what??? i think your trying to say that using two plug rings would lower the compression which would defeat the purpose of the high comp piston?? same deal with running JE's head gasket if you get the high comp piston but raise the cylender then it was pointless.

i would go to your dealer and ask for alternative plugs for the plug and measure which one is slightly, not big but slightly, shorter. then buy it. and you really should take the head back off and see just how far your plug is going into the cylinder.

also double check that you actually have a washer on the plug, and the washers will crush too much the more times they are put in and taken out so a fresh plug might solver everything.

sorry that might seem random but im just shootin ideas your way.

hope this helps.

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wait what??? i think your trying to say that using two plug rings would lower the compression which would defeat the purpose of the high comp piston?? same deal with running JE's head gasket if you get the high comp piston but raise the cylender then it was pointless.

i would go to your dealer and ask for alternative plugs for the plug and measure which one is slightly, not big but slightly, shorter. then buy it. and you really should take the head back off and see just how far your plug is going into the cylinder.

also double check that you actually have a washer on the plug, and the washers will crush too much the more times they are put in and taken out so a fresh plug might solver everything.

sorry that might seem random but im just shootin ideas your way.

hope this helps.

agreed, I want to note, JE has been around since what the beginning of time?

They know what they are doing.. and adding a washer I don't think would change the compression ratio.

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agreed, I want to note, JE has been around since what the beginning of time?

They know what they are doing.. and adding a washer I don't think would change the compression ratio.

We also had more cracked turbo buick pistons from JE than Wiseco... FYi...

Adding a washer is a bad fix, most def an after thought....

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i think JE is mostly into the automotive industry. i dont think they spend as much money on the mx dept as they do in the auto dept. but this sounds like its different. was your head ever modified? like milled down or anything? that could cause this. but adding a washer to the plug or using a taller head gasket will lower the compression ratio(youd be surprised at how little they mill off to achieve a higher comp ratio)

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First of all, JE & CP pistons are without a doubt the best pistons on the market. There's a reason companies and engine builders like Pro Circuit & Rom Hamp (RHC) use JE's, PC may sell you a PC piston in their box but just look at the bottom side and you'll see the JE logo plain as day. As far as the idea that adding a spark plug washer is going to lower your compression and defeats the purpose of running a hi compression piston is rediculous. Yes, it will reduce the compression, but it will be so slight you would not be able to tell if you added one or not, it's all about the area, a spark plug is less than a half an inch in diameter, now a thicker head gasket or running two base gaskets is a whole different situation all together, and someone mentioned finding a shorter spark plug but would not use an extra spark plug washer , if you found a 1mm shorter plug or used a 1mm washer what's the difference you're still increasing the volume in the combustion camber which lowers compression. Just run an extra spark plug washer and you'll be fine and you'll be happy with the result.

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the more i think about the more i see that the spark plug length is minute to the comp ratio but still, i would find the correct plug and length rather then adding another washer. thats like the rare breed of people who stiffen their fork springs by throwing a bunch of washers in there. but if JE is so amazing at producing pistons y does this even happen?? ive always gone with wiseco and theyve never done me wrong.

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