I have a 2003 WR250F that seems to run well when I have the choke on (less power of course) but falls flat on its face when I put the choke in. The Yamaha shop said that the carb needed to be cleaned, did that but had same problem. I moved the clip up and down and tried every carb adjustment but still no good. I found that the air cut valve diaphram was bad so I replaced it and now I can run it without the choke, but it still falls on its face and dies when I whip open the throttle. Any ideas out there?