2002 Honda 400EX keeps stalling?

I have a 2002 400EX and took it out for the first time in months last weekend. It did ok in the beginning, but it would stall if I let off the gas. Then after riding for about an hour it would stall when I would accelerate. I am a newbie and have no idea what is wrong. It is all stock except for a K&N filter. Do I need to rejet it? Desert season is fast approaching so I need to get it fixed ASAP.

Yes, you need to rejet but the gas that has been sitting in your tank may have gone bad. Start with new gas.

X 2 on the fresh gas, you may need to clean the carb too.

* Added year, make, and model, to your thread title.

Fresh Gas, check the air filter. and make sure the carb is clean.