It's funny you bring this up. Just yesterday I was yapping with the tech at my local Gander Mtn. in Forest Lake, MN. We know each other well and were just BS'ing. This guy comes up to us and has an 02 500. He said it would start, but as soon as he hit the gas it would die. I asked him when the last time he used/ran the bike was.....9 months. The tech and I looked at each other and smiled. I asked him if he used Sea Foam or other gas stabilizer. He said he used sea foam. I was shocked, and asked him how much he used. He said "A thimbul full"...which is like 1oz for 5 gallons! LOL Told him he needed a lot more than that (like 1/8 bottle) to stabilize the fuel.
We took it into the shop (it's like I work there, but I don't get paid...something here isn't right).

Took the carb off, and it had the yellowish stain in the bowl. All the jets were plugged horrifically. 30 minutes of cleaning, and she fired up like she was brand new off the line!
Just funny that I'm reading this after hearing the same complaint last night from someone with a 500. It could be other things as well, like what freetrapper pointed out. Could be some grit/junk plugging your main jet or something too. Your best bet would be to take the carb out and clean 'er up good.
I run sea foam in every tank as a preventative measure and to keep it clean. I also installed a fuel filter (away from the engine) to keep any grit/sand/crud out of the carbs. Cheap $5 investment.