Try some Seafoam in the gas. If it's a 2003 and it has sat for any length of time, things could be sticking in the carbs as mentioned above. The 2003's (maybe other years too) had a problem with the paint around the inside of the filler neck on the tank flaking off. It happened on mine, but never caused me any problems. The little filter showed no signs of it, but the carb bowls had a small amount of black stuff in them - the paint, I assume....
You could also take a cap off a spray can, put it under each carb and with the fuel tap off, drain each float bowl and see what comes out. Won't fix anything but may indicate if there's any crap in the carbs....
