need more then just that for jetting issues
where is it lacking top mid bottom
1/4 turn or less throttle
1/2 throttle
wide open ?

sputering backfire ? what jetting are you running now?

Go on the fmf web set they with tell you what to do they have a hole thng on there page

mid to top sounds like main. go to a feild get into a higher gear hold the throttle mid throttle then pull in clutch and hit kill switch roll to stop and then see what plug looks like then do th same thing at wide open throttle. you want it to be like a brown tan color. If its witeish you are lean if black to rich.

fuel screw. google it. or go to thumper talk and go into the kxf forum ( i know u have a crf but it shouldn't matter they are both kehien fcr carbs only diff is i think the crf is a smaller mm then the kxf.) at the top of the kxf250 forum there is a sticky on jetting READ IT ALL it really helps

you can set fuel screw and find the right pilot by....

start bike warm up. turn the idle down a lil from what you normall have. then start turning the screw out untill you hear the enging stumble or stall out count your turns out and know how many turns out you are starting at . Then go back to your stating point this time turn the screw in untill you hear it stumble or stall.

Now you want to set the screw half way between the values found
ex if you start at 1.5 turns out and you go out two turn and it stalls. your tot out is 3.5 return to 1.5 turns and turn it in one and it stalls or stumbles your turn out is .5 then add the .5 to 3.5 and get 4 then divide by 2 to get 2 so your fuel screw should be two turns out.

all said and done you should be less then 3 turns out if you are more then three you need a bigger pilot if you are less then 1 turn out you need a bigger pilot.

I have a r n d powerbowl on my kawi after you get everything figured out you are going to adjust the leak jet. 55 seems to be good. just twist throttle quick you shouldnt hear it stumble. adjust till hearing crisp.

im sure there is typos wrote fast while watching the race.