I just purchased a 1999 kx250 about a month ago. First few time riding it had no problems starting it, now it hit and miss sometimes it will start in a few kicks or i will have to push start it. when running it seems to run very strong. Last time out riding, it did seem to smoke a little, but I was riding trails with my son and was putting around in first and second gear. when I got out in the open I got on it pretty good which seemed to clear up the smoking issue. I figured it was unburned oil in the exhaust. Oil level seems to be goog and not leaking into the cylinder. I have checked the spark plug it's not wet or fouled cleaned the air filter which gave it better throttle response. I plan on rebuilding the top end soon and replacing the reeds at the same time. should I start trouble shooting it at the carb ie (cleaning and new jets) it has stock exhaust and pc silencer and using a 32:1 fuel mixture. I am also questioning the fuel. The station I buy it from says it has no ethanol in it's fuel. From what I have herd ethanol enriched fuel will cause starting problems. So I might try another fuel station.