I have a 2000 400ex that has been sitting since 2000. It hadn't been started in a few years when I got it. It has been ridden very little. When I added gas and opened the petcock the carb overflowed. I have taken the carb apart and cleaned it. I changed out the float valve, but it still leaks. What else should I do?

 

The gas is coming out the overflo tube? Its either got a hung up float,or too high float, or the needle and seat arent coming together. Check to see if the float moves freely, and that the seat is very clean. When you take off the float bowl, look inside it for particles. If you find any, install an inline filter to catch the rest of them.