[Saki in KY]

Hey all, i have a 2000 Prarie 300 4x4, that is having some issues. The engine is running rough, like it is not getting gas, even with the choke fully open. If I have the choke off, and ride, when I let off of the throttle it back fires. I have changed the plug (fouled), and put in a new tank of gas, any ideas. Someone told me I may have water in the tank, and to run it on reserve to run the bad gas out. Any help would be appreciated.
Thanks
Brian