250-500cc Fouling Plugs On My Wr250

I thought I would add my experience to this forum. My 2006 WR250 started fouling plugs about a year ago. I have a #15 pilot (yes, not a typo) and 400 main jet. I did every trick I read on this forum, but no success. Until I took the needle valve seat out. The o'ring posed no resistance when I pulled it out. I could hear a leak when I blew through the fuel intake of the carb, even when I pushed the floater closed. Took it apart, replaced the O'ring, and no carb leakage anymore. Took it for a spin, the bike purrs with the new pilot jet #32.5. Hope the fouling issue is over. Will update next time I go for a ride.
Ed

Good advice mate. Thanks for taking the time to share that. My 06 fouls plugs sometimes but opening the airscrew a bit solves the problem every time. Now Im wondering if thats just treating the symptom.

Good post.
What altitude and temps do you ride?
I just my second hand WR250 (2008) and will have to start finding out how to the this bike jetted (it starts and runs, but sputters off from idle if not giving it gas).

I am in toronto an ride from 0-400 m and 0 to 28C.been fiddling with jets and float height and nothing fixes the issue other than keeping my ridiculously small pilot #15. It gets really hard to start on cold days. Let us know what pilot jet you have installed. here is my setup:
Pilot=15
main=400
needle= 6DJ8-61
SLIDE=3.0
IDLE=more than 1.5 turns, but do not remember exactly.

what position, from the top, is the needle clip in?