Over the last few weeks I've seen posts relating to the YZ250F and it's starting pblms. I think that I may have figured this beast out. I can start this this wonderful machine on the 2nd kick EVER time, warm or cold (if it is warm I need to use the hot start if it will not light-up in two kicks). I've richened the main up so that it pulls VERY well and does not go FLAT at the higher RPM's and I've leaned it out on the bottom with a leaner pilot. The pblm with the bike not starting well (for me at least) was that it was too rich in the pilot circuit. The bike is VERY responsive on the bottom and pulls much better and is very crisp off of idle. Here is the jetting: Pilot - 40 Fuel screw - 2 turns out Needle - Stock (can't remember the number). Main - 182 (the 180 maybe OK but works well for me). I'm ride at 100ft to 2000ft above sea level using 92 Octane pump gas. Hope this helps!!