Nov 4, 2004
First off I want to say that I almost feel guilty about putting up another jetting related topic since it has been beat to death here. I have read Ellandoah jetting guide and I have been through the KDX jetting lesson several times, this isn't really a how to but more of why question. First the stats

04 CR250R
FMF Gnarly and Shorty Power Core deuce
Bell Ray 40:1 on 93 Octane fuel
I clean my air filter every ride if it needs it every 3rd if it doesn't.
Main jet 410 down on size from stock
Pilot 30 down one size from stock
Needle on the top clip, as lean as I can move it, one step down from stock.
Approx 400 feet above sea level
Central Arkansas is humid ususally 60-90% any given day
Temp has been 80-95 when I have been riding

Here is the deal. I foul plugs every couple of hours, the only thing is that my bike runs like a scalded ape. Power is instant and crisp, there is no hesitation it just screams. The reason I wonder if it is me is because I have a tendency to bog the bike. I have a tendency to stay out of the power band and lug the bike a gear high because I am a wussy, I admit it, I avoid the power band especially when jumping or turning, basically anything other than a straight stretch intimidates me somewhat although the last time I went riding I did work on taking the simple jumps a gear lower than usual. I wasn't really shocked to find that I went allot father easier, I just had to deal with the arm wrenching acceleration. My buddy wanted to ride my bike so I let him because he absolutely loves it and when he came back it was smoking out the silencer like a mother. Our conclusion was that there was some oil built up in the pipe and what not and since he is a much better rider than me he was just heating it up and "burning it off". He says the jetting is good, I just need to "ride the bike". I am tempted to lean it out a bit more because I still foul the plugs. What do yall think? I haven't done the scientific method of jetting with the quarter, half, three quarter, full throttle runs because I really don't have the room to get a good run. It has been all seat of the pants. ANY input is always appreciated. Sorry this was so long.
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Jan 19, 2004
Well I would at least do the pilot jet test which just involves finding the highest idle point with the air screw and then determining if you need a smaller pilot. You'd be surprised how rich some bikes come delivered especially for you temp/humidity. I have 3 sizes smaller pilot in my bike right now.


Dec 18, 2004
Try a one tooth larger sprocket on the front. That way you can stay down a gear, keep the revs up a bit and not have the hit that the stock gearing would give you.


One leaner pilot and or a leaner needle.

Or train yourself to use 1/2 to 3/4 throttle and stop being such a wuss. hehe

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