you need to purge after you get done riding for the day.
I bought a nitro r/c car fuel bottle and fill it about half full of gas, then I undo the line at my petcock and insert the tip of the fuel bottle in it. Fire it up and work the throttle to keep it running.
If you don't purge after you get done riding, you run the risk of attracting moidture not only into the fule bowl of your carbs, but also in the crankcase, which will make your bearings rust.
also make sure to keep any extra alky you have in a sealed gas can. DO NOT leave the little vent cap open. And if you leave it in the tank, make sure you seal the vent tube that comes off the gas cap. I just use a little screw. Works great and fits in my pocket so I don't lose it.