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hi I have an 03 400ex with 11:1 compression, full curtis sparks exhaust, air box removed with k&n filter, 152 main jet and 42 pilot.

the bike rides great and beats bikes with more stuff done. but when I race it, It gets so hot that I have to stop every 10 minutes and let it cool down for an hour. I'm thinking that the main jet isn't big enough and is causing it to lean out at wot. The spark plug shows great tuning but it has no power on top end.

could the spark plug not show that its running lean at wot because I spend more time playing around half - quarter throttle?
 

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152 main is too small. atleast a 165 or 170 would be better. like blowfish stated run a plug test that will determine how lean or rich it may be running, but from your description you are way too lean.
 
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