06 kfx 400, I had the same problem, I removed the carb took it completly apart. The needle seat has a small screen and it was plugged only letting a small amout of fuel into the bowl. Most of the jets were clear but I still used music wire and air to clear any blockages. There is a diaphragm in the petcock that should be checked. If it has a pin hole it will not open and let fuel to the carb. You can put it on prime to see if that works too. I also had the valves adjusted and fuel tank cleaned. I bought this from a guy who bought it new in 06 he rode it 3 times and it sat in the garage and the fuel gummed everything up. It runs great now