Hi All. I just purchased a 2004 KX250F at auction. Cheep! Stock pipe, stock everyting. It starts after a few kicks easy enough with the choke on. It idles fine. but no matter how long I run it for, as soon as I push in the choke, it runs like crap. Coughs, pops, backfires and dies. So I removed the carb, opened it up and found some junk in the bottom of the float bowl. I sprayed everything with carb cleaner, brushed and blew out all the port holes with compressed air, put it all back together. I checked the air adjustment screw and found it to be 2-1/4 turns out. and installed it back on the bike. Same thing. Started up fine with choke on. I let it idle for about 10 minutes, pushed in the choke and it popped and backfired and the rpm dropped out and it died. What I didn’t do… I didn't get #'s of any of the jets. When I found the crap in the carb I figured it hasn't been used in a while. The bike looks like ti has maybe 10 hours on it. I guess I’m going to open up the carb again and check the jet #'s. Anyone know what the stock jets are? What I don’t know… It may have had an aftermarket pipe before and the jetting was changed to match the pipe? Perhaps it was taken off the pipe and the stock pipe was installed back on without changing the jetting back? That could possible explain why the jetting is so far out, right? So my questions are these… If the jets are stock and everything looks like it should be, what else could it be? Badly warn valves? I checked them before I installed the carb and they were all within tolerance. It has to be the jetting, right? Your thoughts. Greatly appreciated.