450 not running smooth

HAve a problem with my 03 wr 450.. It doesen`t run smooth unless I have over 50% throttle or riding uphill or high speed. Feels like it fails to ignite every 5-10 sec.. I have a high comp piston and new jetts.. The spark plugg have a nice milkchocolate color when I ride it hard, but it gets very dark and seems it gets to much gas when I keep to the speedlimits..

Where is the problem?

Sounds like your float level maybe off. Or you may have too big of a pilot jet. Its getting rich and loading up at low rpms?? right?

Think Ive fixed it! I just tok the needle out and remounted it one notch down.. So now it seems to run perfectly, but Im stilll thinking about putting inn the 170 main jet..

...so, you moved the needle up ?

No.. I Moved it dovn so that the engine get less fuel from 1/8 to about 1/2 throttle.. I first i took it for a ride.. hard riding gave the sparkplug the right colour, the same when ideling, so then when i tried it for slow riding the plug got al black.. so the engine got to much fuel at this throttle range.. Still aint perfect at the low end so i have to work a litle on the mixture screw..

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