I just acquired a 95 Sportsman 400 4x4. I know very little about this atv's past. I do know that it has been sitting for about six years. I have drained the gas tank and checked the fluids and spark plug. I also cleaned up the carb where the gasoline had gummed everything up. The engine is running very rough and will not idle correctly. There is also alot of white smoke in the exhaust. Is this normal? It almost seems like the timing is off. Is this possible? I was driving it yesterday and it backfired and died. Now it wont crank. Also, should I mix two cycle oil in with the fuel? Thanks in advance for any help.