First and foremost, I race C class motocross, but I am pretty hard on my bikes. But I baby my bikes, heck, I spend more time working on them than I do riding them. I brought my 1999 YZ400F out for practice last night, but as soon as I unloaded it, I started having problems. First it took forever to start, and when I did get it started, it just coughed and died. I got it started again, after a zillion kicks, then warmed it up and did 1 straight a way, and it just sputtered and died. This was the story of last night, as it would take forever to start, then sputter and die a minute or two later. I checked the plug and it was ok, and I put in all new valve/springs/keepers/seals (Etc), Piston, rings, and cam chain, only about 30 hours ago. I am going to tear apart the carb and clean it, as I am guessing there is a speck of dirt in the pilot jet or something. Any other ideas?