2007 kxf 250 with weird jetting problems !

Hi all, I've just bought a brand new 2007 kxf 250 (enduro , road legal) ; it was a leftover, a real bargain for about 5000€ !

Aniway, I have some jetting problems with it... Before I say anything, take note that I know fairly well how to jet a bike (even if I'm more experienced with 2-strokes).

The problem is, other that this thing is ridicoulusly sensible to altitude and temperature changes, I can't seem to read the jetting trough the plug color:

My plug is always VERY white in the center, regardless of the jets I put in it...

A few days ago I felt that the bike ran very rich, it sputtered and revved very slowly (jetting was 42 pilot, nhjt needle 4° clip, 185 main), so I took the plug out and expected it to be sooty and dark...WRONG! it was almost white and dry ! However the bike ran definitely rich, so I changed the jetting to 3° clip needle and 178 main and it ran way better.

From that time, i tried to see if the plug got some color many times, but still very white... Float height was fine , tough I tried to lower or raise it with no results. I tried to switch from the stock cr8e plug to a cr9e , as the manual suggests if the plug looks white, but nothing changed...

No air leaks in the carb boots, no air leaks in the exhaust....

Other than the plug color, the bike seems to respond well to jetting changes, but I always fear that its running too lean and that it will blow up in pieces!

I read somewhere that you can't jet a 4-stroke by the lug color, but if it is so, I cant understand why my dr650 has well coloured plugs (white if its lean and black when its rich)...

Do I have a problem on the bike, or should I stop to think about it and just give it some throttle??

Any help will be very apprecieted... thanks!

Stop thinking about it and give it some throttle.

You cannot hurt your bike by being lean. You seem to discovered your bike was rich and you leaned it some and runs better. Perfect jetting is where the bike runs the best. And it sounds like that is where you are now.

Yeah I'm prone to do that ! Plug color cant be more important than the way the engine runs and sounds.... Still I would like to understand why it doesnt get colored the way it is supposed to do...

Unleaded pump gas burns whitish color. The old leaded fuels is what the plug color was based on. Not sure what is applicable for race gas?

Racegas leaves a white residue (lead). Atleast the VP Racing C16 does on my car. O2 sensors hate it.

Note the OP is from Italy, different fuel. I am not sure how it is with plug chops there.

yes I think that the fuel I use is different from yours: I use regular pump gas that here in italy is 95 ron :smirk:

You also do not have the same additives. It is the additives here that make reading a plug on pump fuel basically impossible.

Heck, I bet you do not even have to have ethanol in your fuel!

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