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

I know i have a 250F but i need some help from any one on this quick

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:

you sure its hitting, on my weisco high comp piston, the dome is considerably higher........ than the stock piston that is..

Loose rod bearing?

yes it is hitting. I just rebuilt the bike and all the bottom end was rock solid. only had about 10 to 15 hours on the bike prior.

Was the head ever resurfaced?

no sir, 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 mee in the instruction or some where.

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


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


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

I have had one report of the brand "W" having the same problem in SX'ers Ted Cambells race bike.

I am thinking the cylinders are a little inconsistant heights.

I read this incorrectly as this is a 250F in the 450F forum.

I have more than 14:-1 in several 250Fs with no contact

The reference I made was to a 450F

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